Woven geosynthetic fabric with differential wicking capability

Descriptive Report on the Invention Patent for: "GEOTEXTILE FABRIC ABSORBING FABRIC AND ABSORBENT DRAINAGE SYSTEM".

DESCRIPTION

CROSS REFERENCE TO RELATED ORDER

This application claims the benefit of US Patent Application Serial No. 12 / 359,876 filed on January 26, 2009, which is incorporated herein by reference in its entirety.

TECHNICAL FIELD OF THE INVENTION

The present invention generally relates to woven fabrics. More specifically, the present invention relates to geosynthetic absorbent fabrics and floor structures employing them.

BACKGROUND OF THE INVENTION

Elevation of the ground due to frost and weakening due to thawing can damage pavement structures, such as parking areas, highways, airfields, etc., in northern regions. The formation of ice lenses in the pavement structure is a significant contributor to such damage, as illustrated in FIGURE 1. Three elements are necessary for ice lenses, and thus elevation of the ground due to frost, to form. These are: (1) frost-susceptible soil, (2) sub-cooling temperatures, and (3) water. Often, water is available from the groundwater level, infiltration, an aquifer, or retained within the fine-grained soil voids. By removing any of the three elements above, the elevation of the ground due to frost and the weakening by thawing can at least be minimized or eliminated altogether.

Techniques were developed to mitigate the damage to pavement structures caused by elevation of the ground due to frost and weakening by thawing. This method involves removing soils susceptible to frost and replacing them with soils not susceptible to frost. Frost-free soil is placed in a suitable thickness to reduce the stress on frost-susceptible soil layers below an acceptable level. Other methods include the use of insulation to reduce the depth of freezing and thawing. In areas where removing soils susceptible to frost and reducing the subcooling temperature is difficult and expensive, removing water can save construction costs by reducing the formation of ice lenses. By breaking the capillary flow path, the frost action may be less severe.

A capillary barrier is a coarse-grained or geosynthetic soil layer in a fine-grained soil that (i) reduces upward capillary flow of water from the soil due to the suction gradient generated by evaporation or freezing, and (or) (ii) reduces or prevents water from infiltrating unsaturated soil from fine pores overlying the soil

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2/32 under the capillary barrier. In the latter case, if the capillary barrier is declined, the water that infiltrates flows down the thin soil along the interface with the capillary barrier. It has been discovered that geosynthetic (geogrid) drainage networks serve as capillary barriers because of their large pore sizes. The performance of non-woven geotextiles as a capillary barrier appears to be compromised by soil intrusion into the interior, decreasing the pore size and increasing the material's affinity for water. In addition, as reported by Henry (1998), The use of geosynthetics to mitigate frost heave in soils. Doctoral dissertation, Department of Civil Engineering, University of Washington, Seattle, hydrophobic geotextiles were more effective in reducing soil elevation due to frost than hydrophilic geotextiles.

The capillary barriers mentioned above attempt to cut the capillary flow of water by generating a horizontal layer with very low unsaturated permeability under suction. The entire structure is permeable for descending rainwater infiltration. This type of capillary barrier requires that the barrier thickness exceeds the height of the capillary water rise in it. In addition, it provides adequate conditions for the flow of water vapor because of its high porosity and comparatively low degrees of saturation balance.

Thus, there remains a need for a geosynthetic woven fabric with differential absorbent capacity that reduces or eliminates soil elevation due to frost in soils. Consequently, it is to address this and other needs that the present invention is addressed.

SUMMARY OF THE INVENTION

The present invention is directed to an absorbent geotextile fabric. The absorbent fabric comprises a polymeric thread disposed on one axis of the fabric and a plurality of absorbent fibers disposed substantially parallel to each other and woven with the polymeric thread on another axis of the fabric. The absorbent fiber comprises a non-round or non-oval cross section and has a surface factor of approximately 100 cc / g / hr to approximately 250 cc / g / hr. In one aspect of the present invention, the cross-sectional shape of the absorbent fiber is multi-channel, three-lobed, or pad.

In another aspect of the present invention, an absorbent drainage system is disclosed. The absorbent drainage system comprises a layer of absorbent tissue arranged on a layer of soil susceptible to frost. A layer of soil not susceptible to frost is placed on the absorbent tissue. Optionally, a base layer to support asphalt and / or concrete is placed on the soil not susceptible to frost. The absorbent drainage system may further comprise an impermeable hydrophobic geomembrane disposed under the absorbent tissue. In addition, the absorbent fabric can be tilted with respect to the water table level and / or the

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3/32 asphalt and / or concrete being supported by the absorbent drainage system.

In yet another aspect of the present invention, an absorbent drainage system comprises a layer of absorbent tissue arranged on a first layer of soil susceptible to frost. A second layer of soil susceptible to frost is placed on the layer of absorbent tissue. Located on the second layer of soil susceptible to frost is a geotextile layer. A layer of soil not susceptible to frost is placed on the geotextile layer. Optionally, a base layer to support asphalt or concrete is placed on the soil not susceptible to frost. The geotextile layer may be another layer of absorbent fabric.

It is to be understood that the phraseology and terminology used in this document are for the purpose of description and should not be considered as limiting. As such, those skilled in the art will appreciate that the design, upon which this specification is based, can readily be used as a basis for the design of other structures, methods, and systems for carrying out the present invention.

Other advantages and capabilities of the invention will become apparent from the following description taken in conjunction with the accompanying drawings showing the modalities and aspects of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and the objects above as well as objects other than those indicated above will become apparent when consideration is given to the following detailed description of them. This description refers to the attached drawings in which:

FIGURE 1 is an illustration of the formation of ice lenses on a pavement structure;

FIGURE 2 is an illustration of cross sections of absorbent fiber employed in the present invention;

FIGURE 3 is an illustration of an absorbent drainage system according to the present invention;

FIGURE 4 is an illustration of another aspect of the absorbent drainage system according to the present invention;

FIGURE 5 is an illustration of yet another aspect of the absorbent drainage system according to the present invention;

FIGURE 6 is an illustration of yet another aspect of the absorbent drainage system according to the present invention;

FIGURE 7 is a graph illustrating the granulometric analysis of silt taken from the CRREL permafrost tunnel;

FIGURE 8 is a graph illustrating the particle size analysis of D1 material in

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4/32

Fairbanks;

FIGURE 9 is a graph illustrating results of compacting tests for silts from the CRREL permafrost tunnel;

FIGURE 10 is a graph illustrating compaction test results for Fairbanks D1 material with 10% fines; and

FIGURE 11 is the comparison of gravimetric water content in relation to the matrix suction for Fairbanks material D1.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to an absorbent mesh fabric that optimizes capillary tension substantially on a single axis to improve dewatering around the fabric protected area versus conventional fabrics. For example, US Patent No. 6,152,653, which is incorporated herein by reference in its entirety, describes a geocomposite capillary drain (GCBD) for displacing water from under the floor. The GCBD system employs a transport layer, a capillary barrier and a separating layer. Specifically, the GCBD transport layer uses the capillary properties of a fiberglass fabric to move water away from the paved surface. In accordance with the present invention, the innovative canvas fabric described below can be incorporated into the GCBD system by replacing the fiberglass fabric. In addition, the innovative canvas fabric of the present invention can be used to completely replace the GCBD system.

According to the present invention, an absorbent geotextile fabric comprises a conventional yarn or filament on one axis and an absorbent fiber fabric with the yarn or filament on another axis to form the fabric. For example, the absorbent fiber can be woven into the absorbent fabric in the directions of the warp or weft. The absorbent fiber has a non-round or non-oval cross section with a surface factor between approximately 1.5 and approximately 3.3. In another aspect, the absorbent fiber has a flow range of approximately 100 cc / g / hr to approximately 250 cc / g / hr. In yet another aspect, the absorbent fiber maintains at least approximately 80% flow up to 60,000 ft-lb / ft³. In yet another aspect, the absorbent fiber maintains unsaturated hydraulic conductivity in environments that have saturation between 100% and 17%. As indicated above, the fabric of the present invention finds use in civil engineering applications. The polymers described below can be used to make conventional yarn or filament.

In one aspect of the present invention, the absorbent fabric has a specific surface area of ​​3,650 cm²/ g and a permeability of 0.55 cm / s, which is equivalent to a flow rate of 1,385 l / min / m². In addition, the absorbent tissue of the present invention can maintain saturation in a water infiltration test after being exposed to

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5/32 evaporation for three days.

The absorbent tissue of the present invention can either drain water out of the soil from below or from the top of the soil when water accumulates. This aspect of the invention deals with the rapid drainage of water in thaws with the arrival of spring. In addition, absorbent tissue can be used to reduce soil moisture content and improve soil shear resistance. Absorbent fibers

In one aspect of the present invention, the absorbent fibers are woven into an absorbent fabric substantially parallel to each other. As a result, a fluid, such as water, is carried along with the absorbent fibers to the periphery of the fabric of the present invention. That is, the absorbent fibers move the fluid substantially along a single axis. The absorbent fibers employed in the present invention have a high surface factor of less than 1.5 compared to a round cross section fiber of the same denier which has a high surface factor of 1.0. Such absorbent fibers generate increased capillary action on the fibers of the round cross section of the same denier. Several types of fibers can be used in the present invention and are described below.

US Patent No. 5,200,248, which is incorporated herein by reference in its entirety, describes polymeric capillary channel fibers that can be employed in the present invention. Such fibers store and transport liquids and have non-round cross-sectional shapes that include relatively long thin portions. The cross-sectional shapes are substantially the same along the length of the fiber. In addition, these capillary channel fibers can be coated with materials that provide a water bond strength of at least 25 dynes / cm.

US Patent No. 5,268,229, which is incorporated herein by reference in its entirety, describes fibers that can be employed in the present invention. These fibers have non-round cross-section shapes, specifically E-shaped cross sections with stabilizing legs. In addition, these fibers are spontaneously wetted fibers and have cross sections that are substantially the same along the length of the fiber.

US Patent No. 5,977,429, which is incorporated herein by reference in its entirety, describes fibers that have a distorted H shape, a distorted Y shape, a distorted + shape, a distorted U shape, and a distorted form of a spun fiber which is referred to as 4DG. Such fibers can be used in the present invention.

US Patent No. 6,103,376, which is incorporated herein by reference in its entirety, describes a bundle of synthetic fibers for carrying fluids

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6/32 that can be employed in the present invention. The bundle comprises at least two fibers which, by acting as individual fibers, are poor fluid carriers, even when in a bundle the fibers provide a bundle which is an effective fluid carrier. As described, the bundle has a Specific Volume greater than 4.0 cubic centimeters per gram (cc / gm), an average inter-fiber capillary width from 25 to 400 micrometers, and a length greater than one centimeter (cm). At least one of the two fibers has a non-round cross section, an Individual Fiber Mass Factor greater than 4.0, a Specific Capillary Volume less than 2.0 cc / gm or a Specific Capillary Surface Area less than 2000 cc / gm, and more than 70% of intra-fiber channels that have a capillary channel width greater than 300 micrometer.

The absorbent fibers employed in the present invention are made from the main melt-roll groups. These groups include polyesters, nylons, polyolefins, and cellulose esters. Poly (ethylene terephthalate) and polypropylene fibers are useful in the present invention at least because of their fabricability and wide range of applications. The denier of each fiber is between approximately 15 and approximately 250, or between approximately 30 and approximately 170.

In addition, absorbent fibers can be formed from other polymers that shrink significantly when heated, such as polystyrene or foamed polystyrene. The shrinkage step introduces distortion in the fiber that increases long-range distortion factor (LRDF) and short-range distortion factor (SRDF). The relatively large values ​​of LRDF and / or SRDF of the fibers described in US Patent No. 5,977,429 provide their utility in absorbent products. Shrinkage occurs for oriented amorphous polymer fibers when the fibers are heated above their glass transition temperature. Shrinkage occurs before or in the absence of substantial crystallization.

As indicated above, the absorbent fibers of the present invention can be made of any polymeric material that is insoluble in the fluid that is to be contacted with the capillary channel structures. For example, the polymer used can be a thermoplastic polymer, which can be extruded and dragged via an extrusion process to form the final product. Examples of suitable polymeric materials, in addition to polyester, polystyrene and polyolefins such as polyethylene and polypropylene, include polyamides, chemical cellulose-based polymers such as viscose and di- or tri-ace-, Co-, ter-, etc. polymers and grafted polymers can also be used. One type of thermoplastic polymer that can be employed in the present invention are polyesters and copolymers of dicarboxylic acids or esters thereof and glycols. The ester and dicarboxylic acid compounds used in the production of polyester copolymers are well known to those skilled in the art. Include terephthalic acid, isophthalic acid, p-acid, Petition 870190077378, from 08/09/2019, p. 14/45

7/32 diphenyldicarboxylic, p, p'-dicarboxydiphenyl ethane, p, p'-dicarboxydiphenyl hexane, p, p'dicarboxydiphenyl ether, p, p'-dicarboxyphenoxy ethane, and the like, and the dialkylesters thereof containing from 1 to approximately 5 carbon atoms in their alkyl groups.

Aliphatic glycols useful for the production of polyesters and copolyesters are aliphatic acrylic and alicyclic glycols that have from 2 to 10 carbon atoms, such as ethylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, and decamethylene glycol.

It is additionally contemplated to use graft copolymers or copolymers, terpolymers, chemically modified polymers, and the like, which are permanently high surface hydrophilicity and do not require the use of wetting agents, which can wash away from the structure surface upon contact with fluids. Modified polymers that can exhibit permanent hydrophilicity include chemical cellulose polymers such as cellulose acetates. In addition, one can also include pigments, dyes or optical brightening agents by known procedures and in known amounts.

One type of polyester that can be used in the present invention is glycol modified poly (ethylene terephthalnelate) copolyester (pETG). Suitable PETG is available from Eastman Chemical Products, Inc. (Kingsport, Tenn., USA), under the name KODAR TM 6763, with a glass transition temperature of approximately 81 ° C.

Another factor that affects the choice of polymer is receptivity to chemical modification of its surface to increase, for example, hydrophilicity. Thus, for capillary channel structures intended to absorb and / or transport aqueous based solutions, it may be advantageous to use a polyester-based polymer instead of, for example, a polypropylene. However, this selection option does not mean that it limits the scope of the invention. Also, depending on the intended use of the structures, it may be desirable that the polymer material used is flexible at the temperatures at which the structures are intended to be used. Due to the relatively thin bases and walls of their structures, even relatively high modulus polymers can be used to make structures that are both flexible and smooth, yet retain surprisingly high resistance to collapse. Flexibility will depend on such factors as the thickness and dimensions of the base and capillary channel walls, as well as the modulus of elasticity. Thus, the choice of polymer in this regard will be highly subject to the intended use and temperature conditions. Choosing such a suitable polymer material is well within the skill of a person skilled in the art.

Depending on the intended use, capillary channel structures can be made from polymers that are hydrophilic or oleophilic, or can be treated to be hydrophilic or oleophilic.

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8/32

The surface hydrophilicity of polymers used to make the capillary channel structures of the present invention can be increased to make the capillary channel walls more wetted with water or aqueous solutions by treatment with surfactants or other hydrophilic compounds (hereinafter, collectively in this document) hydrophilizing agents) known to those skilled in the art. Hydrophilizing agents include wetting agents such as polyethylene glycol monolaurates (e.g., PEGOSPERSE.TM. 200ML, a polyethylene glycol monolaurate 200 available from Lonza, Inc., Williamsport, Pa., USA), and ethoxylated oleyl alcohols (for example , VOLPO.TM.-3, available from Croda, Inc., New York, NI, USA). Other types of hydrophilizing agents and techniques can also be used, including those well known to those skilled in the fields of fibers and textiles to increase absorbent performance, improving soil release properties, etc. These include, for example, polyacrylic acid surface graft. Suitable commercially available hydrophilizing agents include ZELCON.TM. soil release agent, a nonionic hydrophilic available from DuPont Co., Wilmington, Del. (USA) and Milease T.TM., comfort finish available from ICI Americas, Inc., Wilmington, Del., USA. In addition, ERGASURF, ceramic microspheres and vinyl pyrrolidone can be used as hydrophilic or hygroscopic additives.

The capillary channel structures of the absorbent fibers have an axial base and at least two walls extending from the base, whereby the base and walls define at least one capillary channel. Certain such fibers have at least five walls and at least four capillary channels. Others may have at least six walls and at least five capillary channels. There is no maximum theoretical number of capillary channels that their structure can have, such a maximum number of capillary channels being governed more by the need for such structures and the practicality of making them. In one aspect of the present invention, the capillary channels are substantially parallel to each other and an open cross section along at least approximately 20% of its length, along at least approximately 50% of its length or and along from at least 90% to 100% of its length.

The absorbent fibers of the present invention provide flexible and collapse-resistant capillary channel structures, which comprise a polymer composition and which have at least one capillary infrastructure channel, wherein the structures have an axial base and at least two extending walls from the base, typically (but not necessarily) along substantially the entire length of the base element, by means of which the base element and the walls define the said capillary channel (s). In general, the walls should extend from the base by a distance in the axial direction from the base by at least approximately 0.2 cm. In another aspect of

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In the present invention, the walls extend from the base by a distance in the axial direction of the base by at least approximately 1.0 cm. The actual length of the structure is limited only by practical concerns. Although their capillary channel structures may have a capillary channel or a plurality of capillary channels, for convenience the plural form channels is used with the intention that it refers to a single channel in structures that have only that channel or a plurality of channels in structures that have more than one channel. The structures are further characterized in that the capillary channels are open over a substantial length such that the fluid can be received from outside the channel as a result of such an open construction. In general, structures will typically have a Specific Capillary Volume (SCV) of at least approximately 2.0 cc / g, at least approximately 2.5 cc / g or at least approximately 4.0 cc / g, and a Surface Area Specific Capillary (SCSA) of at least approximately 2000 cm²/ g, at least approximately 3000 cm²/ g or at least approximately 4000 cm²/ g. The procedures to be used to measure SCV and SCSA are provided in at least one of the patents incorporated above.

The absorbent fibers of the present invention have a surface composition that is hydrophilic, which can be inherent due to the nature of the material used to make the fibers or can be manufactured by applying surface finishes. Hydrophilic surface finishes provide structures whose surfaces have high adhesion stress (ie, which attract strongly) with aqueous liquids and are therefore preferred for applications involving aqueous liquids such as those discussed below for temporary acquisition / distribution structures and permanent storage structures. In one aspect, the hydrophilic surface has an adhesion stress with distilled water greater than 25 dynes / cm as measured on a flat surface that has the same composition and finish as the fiber surface. Some of the finishes / lubricants useful for providing high adhesion stresses to aqueous liquids are described or referenced in US Patent No. 5,611,981, which is incorporated by reference in this document in its entirety. Surface finishes are well known in the art.

As discussed above, absorbent fibers have channels on their surface that can be useful in the distribution or storage of liquids when the appropriate surface energizers exist on the surface of the fibers, such as when the fibers satisfy the above equation in relation to surface forces specific. Surface energetics determine the adhesion tension between the surface and any liquid that is in contact with the surface. The higher the adhesion tension, the stronger the attraction force between the liquid and the surface. Adhesion stress is a factor in capillary forces acting on liquid in a channel. Another factor that affects the capillary forces that act

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10/32 in a liquid in a channel is the length of the channel's perimeter. When the channel widths are small, the capillary forces are relatively strong compared to the gravity force on the liquid, since the gravity force on the liquid in a channel is proportional to the channel area.

FIGURE 2 illustrates cross sections of multi-channel absorbent fiber, three lobes, and pad that can be employed in the present invention. However, as indicated in the patent discussed above, other forms can be employed in the present invention. The multichannel is also referred to as the 4DG form.

In one aspect of the present invention, an absorbent fabric made from nylon has high wettability similar to fiberglass. The absorbent fabric has a high specific surface area of ​​3650 cm²/ g and high permeability of 0.55 cm / s (equivalent to a flow rate of 1385 l / min / m²).

Weaving

Weavings that can be employed in the present invention include, but are not limited to, flat weaving, twill, specialty, 3-D, satin, satin, alveoli, gauze, basketwork, oxfords, or panama. FIGURE 2 is a photomicrograph of a geosynthetic tissue of the present invention.

Absorbent drainage system

With reference to FIGURE 3, in accordance with the present invention, an absorbent drainage system 10 comprises an absorbent fabric 20, a layer of soil not susceptible to frost 30 arranged on the absorbent fabric, and a base layer 40, such as a asphalt-treated base, arranged on the soil layer 30. The asphalt and / or concrete 50 are arranged on the base layer 40. The absorbent fabric 20 is arranged on the soil bed susceptible to frost 60. The frost-susceptible soil bed 60 is raised above the water table level to form side drains 70 that facilitate water drainage. The thickness of the frost-sensitive soil bed 60 is conventional. For example, the soil bed 60 can be 40 inches above the water table level. The soil layer not susceptible to frost 30, like the D1 material with 10% of fines content described below, should be of sufficient thickness to allow drainage from the water of the base layer 40 to the absorbent tissue 20 In one aspect of the present invention, the thickness of the frost-free soil layer 30 is approximately 13 inches. However, the thickness can be varied as needed depending on the soil conditions.

In another aspect of the present invention, the absorbent drainage system comprises an impermeable hydrophobic geomembrane (not shown) disposed under the absorbent tissue 20. The absorbent tissue 20 allows water from the overlying soil to pass through the absorbent tissue 20 when the overlying soil is saturated and transports

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11/32 water laterally to side drains 70. When the overlying soil is unsaturated, the absorbent tissue can absorb water from the overlying unsaturated soil and transport it in the lateral directions. The waterproof hydrophobic geomembrane can repel water and completely cut the capillary rise of groundwater from below. In another aspect of the present invention, the geomembrane can be a one-way valve geotextile.

In an alternative design, the absorbent drainage system comprises the arrangement as shown in FIGURES 4-6. When installed on the floor structure, the absorbent fabric 20 is sloped down a slope of 5-10% so that the water that infiltrates will flow downward. In addition, there should be no wrinkles of any significance that would cause water to be dammed at the top of the impermeable layer. FIGURE 4 illustrates the absorbent drainage system 10 of FIGURE 3 with the inclined arrangement.

As illustrated in FIGURE 5, a second layer of absorbent tissue 20 is employed in the absorbent drainage system 10. Disposed between the respective layers of absorbent tissue 20 is a layer of soil susceptible to frost. In another aspect of the present invention, as illustrated in FIGURE 6, the absorbent fabric 20 is disposed on a frost-susceptible soil layer 60. In addition, another layer of frost-susceptible soil 60 is disposed on the absorbent fabric 20. A geotextile separation layer 80 is arranged over the second frost-susceptible soil layer 60, and a frost-susceptible soil layer 30 is arranged over the geotextile separation layer 80.

The overall effect of the absorbent drainage system is to cut the upward capillary water flow and drain most of the infiltrated water out of the pavement structure through the drainage network tilted by the absorbent tissue. The downward force for the water flow in the drainage network is gravity and the downward forces for the water flow in the absorbent tissue are gravity and suction generated by evaporation and freezing.

EXAMPLES

Example 1: Particle size analysis and gradation curves for two typical soils in Alaska

Two typical soils used in Alaska pavements were collected. These soils were Fairbanks silt obtained from the CRREL permafrost tunnel and D1 material obtained from University Ready Mix Company. Silt is frost-prone soil and is typically used as a subgrade for Alaska pavements. CRREL's permafrost tunnel silt was sieved to remove organic material. A granulometric analysis was performed on the silt and is shown in FIGURE 7.

The D1 material was a typical frost-free material that is typically

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12/32 employed as basic courses in Alaska pavements. To be qualified as a D1 material, the fines content must be less than 4%. In this example, the particle size analysis was done for Fairbanks' D1 material and fines with grain size less than 0.075 mm were added to make a new material susceptible to frost with 10% fines content. Gradation curves for original and manufactured D1 materials are shown in FIGURE 8.

Example 2: Modified Proctor Compaction Tests

Fairbanks silt and D1 material with 10% fines content were compacted according to ASTM D1557 in order to simulate the compaction process in the field. The results of the compaction test are as shown in FIGURES 9 and 10.

Example 3: Soil Water Characteristic Curve

Pressure plate tests according to ASTM D2325-68 were used to obtain the characteristic water retention curve in the range from 0 to 1500 kPa. Salt concentration tests were used to measure the soil water characteristic curve for suction values ​​greater than 1,500 kPa. FIGURE 11 shows the test results for Fairbanks Material D1.

Example 4: Soil Column Tests

Using the D-1 material with 10% fines and in the optimum moisture content, cylinders were built. The cylinders were compacted in five layers, 52 strokes for each layer. Geosynthetic materials were placed above the second layer. 13 different cylinders were made by testing 5 different geosynthetic materials ((Nylon Absorbent Fabric, Glass Fabric, HP570, FW402, and HIPS plate). 5 cylinders were made with the geosynthetic material being the same size as the cylinder and 5 cylinders were made with the appropriate geosynthetic material that protrudes outward in order to understand the effects and advantages of drainage capabilities for each geosynthetic material. A membrane was placed around each cylinder in order to retain moisture inside the cylinder. Baths were configured to allow water to seep into the bottom of the cylinder. Evaporation within the room in which the water baths were placed was measured by filling a full glass of water and measuring the weight of the glass of water each day for a week. Water was added to the water baths throughout the week.

Example 5: Laboratory Capillary Rise Tests and Soil Water Characteristic Curves for Different Geosynthetics

The performance of six different geosynthetics in three different locations of layered pavement systems was tested through two groups of capillary testing in the laboratory. The three locations are in the basic course, between the basic course and the subgrade, and in the subgrade. The D1 material with 10% Fairbanks fines and silt content was used to represent the base course layer and the subgrade of the

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13/32 floor, respectively. In the first group of tests, all geosynthetics were involved in the membrane, which is referred to as non-draining in the following discussion. In the second group of tests, only the top and bottom halves of the soil specimens were wrapped in the membrane while geosynthetic specimens were larger (approximately 6 inches in diameter) and partially exposed to air to increase evaporation, which is referred to as with drainage in the following discussion. Six different geosynthetics were tested and 36 tests in total were carried out for three different locations. For each location, a soil test reference was included, six soil columns with geosynthetics inside, but without drainage, and six soil columns with geosynthetics inside and with drainage. The purposes of the two test groups were (1) to investigate whether geosynthetics can cut the capillary rise, and (2) to investigate the influence of evaporation on the water content distribution of the pavement structure. The first group of tests was used to simulate the geosynthetic in the center of the pavement structure, while the second group of tests is used to simulate the performance in the rebound of the pavement structure. For each test group, there was also a reference soil column with no geosynthetics inside. The geosynthetic specimens used in the tests, where specimens 1 through 6 were Mirafi® FW402, Drainage Compounds of the Mirafi® G series, Glass Fabric, Mirafi® HP570, Mirafi Nylon Absorbent Fabric, and Imp, respectively.

The specimens were compacted in three layers, 25 strokes for each layer. Twenty-six specimens in total were compacted. Each was 4.5 inches tall. After the specimens were made, a capillary barrier was placed on top of a specimen. Another specimen was placed on top of the capillary barrier. A plastic membrane was placed around each specimen to control humidity. The top of the silt specimens that were placed on top of the capillary barriers was sealed to eliminate evaporation. In total, 13 soil columns were made. The soil columns were then placed on a tray and water was periodically poured into the tray to maintain a height of approximately 0.5 inches to wet the soil from the bottom. After two weeks the specimens were removed from their water baths in order to measure the moisture content at various times. The specimens were separated and the capillary barrier was removed. A ruler was used to measure the appropriate width for each section. Each section was 1.5 inches wide. Both the top and bottom of the specimens were cut into three equal sections. A knife was used to cut each section. Once each section was removed, its weight was weighed on a capillary barrier type scale and its section height was recorded and the section was placed on a tray that corresponded to that particular specimen. This was done for each specimen. After that, the trays were placed in the oven and weighed again 24

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14/32 hours later in order to obtain the dry weights.

Example 6: Salt Concentration Test and Pressure Plate Test

The salt concentration tests that were used to measure the soil water characteristic curve for suction values ​​are greater than 1,500 kPa. Specimens 2 and 3 show reasonable curves as shown in Figs 44 and 45, but the curve for specimen 5 looks a little strange as shown in Fig. 46. For this reason, the results are currently being redone. The results may have been interpreted by a number of things. The first of which is material handling. Although gloves were used and precautions were taken to prevent moisture from escaping from the capillary barrier, this may have been a source of error. This may be responsible for the extremely low content of moisture levels that has been found. Another reason may be that the salt concentration levels inside the test containers are out. One reason for this may be because of the adhesive tape that was used that was not adhering to the glass container as one might expect. The results of the next test should prove to be helpful in determining where the error is coming from.

Pressure plate tests according to ASTM D2325-68 were used to obtain the characteristic water retention curve in the range from 0 to 1500 kPa. Data is currently being collected for the Pressure Plate Test. After the data is collected, the specimens need to be dried in order to determine their dry weight which is used to determine the moisture content. Once the moisture content is determined, the specimens will be saturated and returned to the pressure plate apparatus in a different suction.

Example 7: Floor section configuration

Preliminary numerical simulations of absorbent tissue performance in expansive soils were performed assuming the material properties of the absorbent tissue. Fig. 47 shows an example of a typical configuration of the studied floor section, and the conditions of mechanical limits are also shown.

In the example, the concrete slab was 0.25 meter (10-in) thick. Those concretes were made with gravel aggregates from Victoria, Texas, with a ratio of 0.45 water-cemented (w / cm). The concrete has a Young Modulus of E = 2x10⁷ kPa, Poisson ratio v = 0.15, and hydraulic conductivity of K = 1x10^-12 m / s. Due to the symmetry of the pavement structure, a 5 meter (16.4-ft) wide one was chosen. The suction at a depth of 6.0 m was constant and assumed to be equal to 10 kPa, which is just above the water table level.

The suction at the soil surface was assumed to be 1000 kPa for the first approach. For the left and right sides of the structure, only vertical displacements were allowed due to symmetry.

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Example 8: Simulation of Soil-Structure Interaction

The joined thermo-mechanical elements (contact) coupled in ABAQUS / Padrão (2002) are used to simulate the interaction in the interface between the soil and the concrete slab. The top side of the contact element is the bottom surface of the concrete slab and the bottom side is the surface of the ground where the concrete slab is resting. The bottom face of the concrete slab is assigned to be the primary surface and the soil surface is assigned to be the secondary surface. Namely, concrete may penetrate the soil while the soil may not penetrate concrete (ABAQUS / Padrão 2002).

The ABAQUS hard contact ratio is used to simulate normal behavior at the soil-slab interface. During the simulation, the program will calculate the thickness of the contact elements in the normal direction to the soil-structure interface. When the soil and the slab foundation are in contact (the thickness of the contact element is zero), any compressive load can be transferred from the slab to the ground. When the ground and the foundation are not in contact (the thickness of the contact element is greater than zero), no load can be transferred from the slab to the ground.

The basic Coulomb friction model is used to simulate the tangential behavior in the soil-structure interaction in which the two contact surfaces can carry shear stresses up to a certain magnitude through their interfaces before starting relative sliding.

It is also assumed that no water is allowed to flow through the soil-slab interface. This condition is idealized by defining a very low space conductance to the joined elements. The space conductance of the contact elements is assumed to be 10^-30 s^-1 when the slab and the ground are in contact with each other. The space conductance of the contact elements is assumed to be 0 when the slab and the ground are separated.

Example 9: Discussion of Simulation Results

The absorbent fabric was installed at a depth of 1.0 m under the concrete slab. The absorbent tissue was assumed to be under high compression with a mass factor of 1. It had an ability to transport water at a rate of 1.48 gal / hour / yard. This corresponds to a horizontal permeability ability of 2x10^-3m / s (for an absorbent fabric with a thickness of 1 mm, transmissivity is 2x10^-6m²/s). Three different absorbent tissues were considered as follows:

1. The ability of the absorbent fabric to carry water is limited so that the absorbent fabric works as a reinforcement only as a geotextile. This case is referred to as reinforcement only in the following discussions;

. The absorbent fabric is highly permeable in all directions. This case is referred to as single-layer absorbent tissue in the following discussions; and

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3. The absorbent fabric is highly permeable in the direction out of the floor only and impermeable in the other two directions. This case is referred to as an absorbent fabric with an impermeable layer in the following discussions. It was used to simulate the absorbent drain plate proposed in the previous progress report.

Two different conditions were considered. One is that the concrete slab is integrated and there is no form of leakage from the slab to the subgrade, and the other is that there was a leak in the center of the slab, which caused the suction in the 1.0 meter interval under the center line equal to 10 kPa (field capacity).

In order to investigate the influence of the absorbent tissue on the performance of the pavement structure, the conditions when there is no inclusion of absorbent tissue were also considered. In total, eight simulations were performed as shown in Table 3.

Table 3 SUMMARY OF NUMERIC SIMULATION

<td colspan="3">Case</td><td>Voltage of Von Mises Max. (KPa)</td><td>Unsupported Slab Length (m)</td>

<td rowspan="4">No Leakage</td><td> 1</td><td>No Geosynthetic</td><td> 2399</td><td> 1,1</td>

<td> 3</td><td>Reinforcement Only</td><td> 2668</td><td> 1,1</td>

<td> 5</td><td>Single layer absorbent fabric</td><td> 517,6</td><td> 0,162</td>

<td> 7</td><td>Absorbent fabric with Waterproof layer</td><td> 517,6</td><td> 0,162</td>

<td rowspan="4">Leaking</td><td> 2</td><td>No Geosynthetic</td><td> 3597</td><td> 1,4</td>

<td> 4</td><td>Reinforcement Only</td><td> 3600</td><td> 1,4</td>

<td> 6</td><td>Single layer absorbent fabric</td><td> 3527</td><td> 1,26</td>

<td> 8</td><td>Absorbent fabric with Waterproof layer</td><td> 1425</td><td> 0,079</td>

The simulations were carried out under stationary conditions. Two parameters were used to assess the performance of the pavement structure. The first was the length of the unsupported slab, which is the length of the slab that was not supported by the subgrade soils. This parameter refers to the differential settlements caused by expansive soils under certain weather conditions.

The second parameter was Von Mises' tensions. A Von Mises stress is an invariant stress used in performance criteria. It is calculated independently of the coordinate reference system, it does not carry directional stress information such as shear and normal stresses, but it carries enough information to identify points

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Hot 17/32 where failure could occur. The higher the Von Mises tensions, the greater the possibility of damage exists.

In the simulation of a pavement structure built on expansive soils with no absorbent fabric and no leakage, the expansive soils under the concrete pavements are covered by the concrete slab so that there is no water evaporation while the soils outside the slab concrete are subject to evaporation. As a result, the soils under the concrete slab have lower suction values, which correspond to a higher moisture content. While the soil outside the slab has high suctions and less water content (dryness). The difference in moisture content due to the covering of the concrete slab can cause large differential settlements. The soils on the ledge of concrete pavements shrink more than the soils under the slab, which causes a phenomenon called bounce rotation or if the edge falls. The differential settlement can be so large that part of the concrete slab loses support from the subgrade soils and makes the concrete slab a cantilever. This will cause very large bending moments in the concrete slab, which can result in damage to the slab. The maximum Von Mises stress for this case is 2399 kPa, which is occurring in the center of the slab. The slab and soils separated at the edge of the slab and the separation length is 1.1 m for a 5.0 m concrete slab as shown in Table 3.

Case 2: No absorbent fabric, leaking

In the simulation of the pavement structure built on expansive soils with leakage and without absorbent tissue, there is a leak under the center of the slab, which makes the soil more humid than the previous case. Outside the slab, the soils were still dry due to evaporation. As a result, the differential movements are greater than in the previous case. The length of the unsupported slab is approximately 1.4 m and the maximum Von Mises tension is 3597 kPa, approximately 50% higher than in the previous case. In conclusion, the leak in the pavement structure will make the differential settlements more severe and more likely to result in damage to the pavement structure. Cases 1 and 2 were used as references to demonstrate the influence of absorbent tissue on the performance of the pavement structure.

Case 3: With Reinforced Geotextile, Without Leakage

In this case, a geotextile was included in the pavement structure at a depth of 1.0 m under the concrete pavement. The geotextile was assumed to have the same permeability as that for soils because it is relatively thin. Its Young's Modulus was assumed to be 200,000 kPa, which is much stronger than expansive soils. In the simulation of the pavement structure built on expansive soils with geotextile reinforcement and without leakage, the inclusion of geotextile reinforcement had no influence on the suction distribution. Although the length of the unsupported slab was

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1.1 m (the same as that for case 1), the maximum Von Mises voltage was 2668 kPa, 11% higher than when there is no reinforcement. This case indicates that the inclusion of a reinforcement does not cause any benefit to the pavement structure for the differential settlement caused by expansive soils.

Case 4: With geotextile reinforcement, with leakage

In this case, there is a leak under the center of the concrete slab. As a result, suction was 10 kPa in the 1.0 m range under the concrete slab. Just like case 2, the leak significantly increases differential settlements in subgrade soils. As a result, the length of the unsupported slab is 1.4 m and the maximum Von Mises stress is 3600 kPa, which is basically the same as those in the case

2. Again, this case indicates that the inclusion of a geotextile reinforcement does not reduce the differential settlements caused by expansive soils.

Case 5: With a single layer of absorbent tissue, without leakage

This case is used to simulate the case when the absorbent fabric is installed on a floor structure. In the simulation of pavement structure built on expansive soils with a single layer of absorbent and leak-free fabric, due to the high ability of the absorbent fabric to carry water, the absorbent fabric significantly increases the suction under the concrete slab and suction distributions in the structure of pavement are more evenly distributed with depth. As a result, the differential seating on the pavement structure is very small.

The length of the unsupported slab is only 0.162 m, which is mainly limited to a very small range close to the edge of the slab. Due to the fact that most of the slab rests on subgrade floors and the difference in suction under the slab is small, the stress on the slab is small (if the differential settlements are zero, the stress on the slab will be the lowest).

The maximum voltage of Von Mises is only 517.5 kPa, less than 22% of the maximum voltage of Von Mises for case 1 when there is no absorbent tissue. This case indicates that the inclusion of the absorbent fabric can significantly improve the performance of the pavement and the pavement is much less likely to damage compared to the case

1.

Case 6: With a single layer of leaking absorbent tissue

The difference between cases 6 and 5 is that there is a leak under the center line of the concrete slab. Due to the leak, the soil under the center line of the slab is very moist with a suction of 10 kPa, while the outside still remains 1000 kPa. The difference in suction is big. As a result, the differential settlements are very large. The leak not only causes swelling to the soil above the absorbent tissue, but also causes swelling of the soil under the absorbent tissue. O

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19/32 final length of unsupported slab is 1.26 m, and the maximum Von Mises tension is 3527 kPa. Compared to cases 2 and 4, the inclusion of the absorbent fabric only slightly improves the performance of the pavement structure when there is leakage. It is noteworthy that case 6 is a stationary simulation in which the leak is assumed to be lasting for a significant period of time. Under a real situation, a rain event only lasts for a short period of time. Therefore, the actual improvement made including an absorbent tissue could be superior to the simulation. This case was performed for comparison purposes only.

Case 7: Absorbent fabric with waterproof layer, without leakage

This case simulates the situation in which the absorbent drainage board discussed above is installed in a pavement structure. In this simulation of a pavement structure built on expansive soils with the installation of the absorbent and leak-free drain plate, the absorbent drain plate significantly increases the suction under the concrete slab and suction distributions in the pavement structure are more evenly distributed with depth as in case 5. Differential seating on the pavement structure is very small. The length of the unsupported slab is only 0.162 m and the maximum Von Mises stress is only 517.5 kPa. The results obtained are like those obtained in case 5. This case indicates that the inclusion of an absorbent drainage board can significantly improve the performance of the pavement.

Unlike case 7, in case 8 there is a leak under the center line of the slab. The leak causes increased suction under the slab, resulting in a significant difference between the center line and the outside of the slab. However, because the absorbent drainage plate is impermeable in the vertical direction, soil wetting is limited between the concrete slab and the absorbent drainage plate. Also, because the drain plate is permeable on both sides, the bottom side can still drain water out of the floor structure even when there is a leak at the top. As a result, the soil on the center line is still dried under the absorbent drainage plate.

Moistening the soil above the absorbent drainage plate causes the soil to swell, while dryness of the soil under the absorbent drainage plate causes the soil to shrink. These two effects counterbalance and reduce the differential settlement even when there is a leak in the center of the slab. In case 8, the slab and the soils are in good contact with an unsupported slab length of 0.079 m. Consequently, the maximum Von Mises stress is 1425 kPa, approximately 60% and 40% of the maximum Von Mises stresses in cases 1 and 6, respectively. The maximum Von Mises stresses and unsupported slab length in cases 7 and 8 are very

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20/32 smaller than those under similar situations. It is concluded that the inclusion of absorbent drainage board can significantly improve the performance of pavement structure.

Example 10: Performance Under Rainy Weather Conditions

The study of the performance of different geosynthetics under rainy weather conditions was investigated using two different sets of tests. First, the performance of different geosynthetics placed between D1 material completely saturated with 10% fines and Fairbanks silt. Second, the performance of different geosynthetics placed between material D1 completely saturated with 10% fines and material D1. The geosynthetics tested were Mirafi® FW402, Drainage Compounds of the Mirafi® G series, Mirafi® HP570, and an Absorbent Nylon Fabric made in accordance with the present invention.

The interface is where each geosynthetic was placed. The material above the interface needed to be completely saturated as well as the geosynthetic itself in order to accurately understand the effects of rain on the performance of the geosynthetics. The membranes were wrapped around the outside of the compacted materials in order to control moisture loss due to exposure. Tests in which geosynthetics have been wrapped in a membrane are termed as non-draining. Tests in which geosynthetics have been partially exposed to air are termed as having drainage.

D1 material was prepared and allowed to set without exposure to air. This allowed the moisture to be able to distribute throughout the sample. The prepared materials were then compacted in a plastic cylinder mold in 3 layers at 25 strokes per layer. After the material was compacted, the surface was smoothed out and removed from the mold. Holes were cut in the bottom of plastic molds to allow water to infiltrate. Plastic molds were also raised using spacers to serve this same purpose. To avoid material loss during extraction, a cut was made along the length of the mold, which allowed the mold to be carefully fitted around the compacted D1 material. Once the mold was in place, adhesive tape was used to seal the cut that was made and to hold the compacted D1 material firmly in place. The filter paper was placed between the compacted D1 material and the holes that were cut in the plastic molds in order to prevent material loss. As the water level inside the bath water increased, the water level inside each cylinder would also rise.

The performance of the absorbent nylon fabric under rainy weather conditions was evaluated. For both water infiltration tests with D-1 / D-1 and D1 / Silte drainage, the absorbent nylon fabric gives better results than the others because it has the

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21/32 smaller distributions of moisture content both above and below the interface. For the water infiltration test without D-1 / D-1 drainage, the absorbent nylon fabric gives better results than the others because it has the lowest distributions of moisture content both above and below the interface. The absorbent nylon fabric has been shown to be effective in both drainage and non-drainage applications.

Example 11: Performance Under Rainy Weather Conditions

Example 11 was conducted like Example 10 except that:

1. Instead of using D1 material, uniform sand was used to represent the thick base material. This can significantly increase the uniformity of soil specimens while the hydraulic properties of the two soils are similar.

2. Rather than using compact soil specimens, soil slurry was employed to make soil specimens that can approximate the uniformity of soil specimens. Other reasons why soil slurry was used instead of compact soils are as follows:

(i) soils compacted to the optimum moisture content usually have good mechanical properties and are less likely to cause problems for the pavement structure, while soil with a high moisture content does. After the elevation of the soil due to frost, when the soil thaws, the moisture content in the soil is as high as or even greater than the soil slurry. If the use of absorbent fabric can reduce the moisture content of soils with a high moisture content in the pavement structure, it will be highly beneficial for the performance of the pavement structure.

(ii) high moisture content in soil specimens means high unsaturated permeabilities, which can lead to reduced experimental time for testing.

3. Instead of placing geosynthetics in the center of the soil columns, the geosynthetics were placed on the bottom of the soil specimens (8 inches high). Two different soils were used: Fairbanks silts and uniform medium sand. The experiment can be used to investigate the impact of geosynthetics on soils above them after rain infiltrations.

4. In order to investigate the influence of geosynthetics on the soil under it, a series of tests was also carried out. To facilitate the discussion, this group of tests is referred to as Rain / Top Infiltration Test in the following sections. Tests for the modified laboratory rain infiltration soil column tests were performed using silt and medium sand. In order to measure the effectiveness of the geosynthetic under conditions of saturated soil due to the climate, slurries were prepared from Fairbanks silt.

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After the slurry was prepared, it was placed in a cylindrical plastic mold. The plastic mold was filled with the slurry and the upper part was leveled. To densify the soil, light blows were made on the side of the plastic mold. An initially saturated geosynthetic and impermeable membrane were placed under the slurry. The waterproof membrane was placed directly under the geosynthetic and the geosynthetic was placed directly under the soil slurry.

Hammer holes were made at the top of each plastic mold using a hammer and a sharp metal object. The reason for the orifices was to decrease the suction caused by draining water that would otherwise inhibit the flow of moisture through the soil slurry. The holes were made after the experiment was completely configured. The water was allowed to drain for 3 days. Initially, all geosynthetic materials were saturated and remained saturated. Some excess water was drained off due to gravity and the amount of water flow reduced rapidly over time in the first several minutes. There were 2 tests performed for each geosynthetic. The geosynthetic materials used in the experiment were periodically checked to see if the geosynthetic was still saturated.

It was found that in the interval where the soil slurry columns settled, in the direction of the absorbent nylon fabric, the nylon absorbent fabric remained wet after more than three days of testing, while outside the interval where the soil slurry columns were wet. soil were settling, the absorbent nylon fabric quickly dried in less than a day.

Outside the range where soil slurry columns are settling, Mirafi® G-Series Drainage Compounds remained relatively wet after three days, while Mirafi® FW402 and Mirafi® HP570 quickly dried in less than a day.

After 3 days, the molds were removed. The soil was then cut into 6 equal layers. The initial weight of each layer was recorded and each layer was put in the oven to dry for 24 hours. After 24 hours, each layer was removed from the oven and the final weight was obtained. Using the initial and final weights, the moisture content was found for each layer.

The rain / top infiltration tests were performed at a moisture content of 28% using sand. There were 2 test configurations for each geosynthetic. First, the sand and water were mixed together to obtain the correct moisture content. The sand slurry was poured into a plastic mold at a height that would leave 1.33 inches at the top. A geosynthetic was placed in the mold at this point. The ends of each geosynthetic were cut so that they remained below the 1.33 inch mark along the outside of the mold.

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23/32 plastic throughout the test. Each geosynthetic that was used in the test was initially saturated. After the geosynthetic is firmly in place, the rest of the sand slurry was placed on top of the geosynthetic and filled to the top of the plastic mold. An aluminum sheet was used to cover the soil slurry above the geosynthetic in order not to allow moisture inside the slurry to evaporate. After the upper parts of the molds were covered, the experiment was left to settle for 5 days. After 5 days, the moisture distribution for each test was recorded.

The same observations were made during the rain / top infiltration test as the modified laboratory rain infiltration soil column tests. The Drainage Compounds of the Mirafi® G Series and Mirafi Nylon Absorbent Fabric remained saturated for a longer period of time than Mirafi® FW40 2 and Mirafi® HP570.

There were two series of tests performed for each geosynthetic. The average moisture distribution was found between the series of tests for each geosynthetic. The average moisture content throughout each of the averaged moisture distribution was also found. The data that was recorded in preliminary tests was not used in data analysis due to different original moisture content.

For the silt water infiltration test using Mirafi nylon absorbent tissue, the moisture content near the top of the specimen shifted to the left and was slightly lower than the moisture content near the bottom. This observation may be due to the influence of gravity. The moisture distribution for each test series is relatively stable in that the moisture distribution trend does not change dramatically. In three days, the average moisture content decreased from 53% to approximately 40%.

For moisture distributions for the silt water infiltration test using Mirafi® HP570, the moisture content near the top of the specimen shifted to the left and was slightly lower than the moisture content near the bottom. There was also a slight curve in the moisture distribution for each series of tests. In three days, the average moisture content decreased from 53% to approximately 43.35%.

The moisture distributions for the silt water infiltration test using Mirafi® G-Series Drainage Compounds show a lower moisture content at the top, a slight curve in the middle, and a sloping moisture content at the bottom. In three days, the average moisture content decreased from 53% to approximately 43.54%.

For moisture distributions for the silt water infiltration test using Mirafi® FW402, more moisture was allocated in the central area of ​​the cylinder. The smaller

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24/32 moisture content is at the bottom instead of the top. In three days, the average moisture content decreased from 53% to approximately 42.09%.

Of the average moisture distributions for Mirafi® nylon absorbent fabric, Mirafi® HP570, Mirafi® FW402, and Mirafi® G series drainage compounds, Mirafi nylon absorbent fabric has the lowest moisture distribution. The average moisture distribution was found by taking the average of the results for the first and second series of water infiltration tests. The average moisture content throughout each calculated moisture distribution shows that the Mirafi nylon absorbent fabric removed most of the moisture from the silt slurry and the difference in moisture content ranged from 2% to 3.5% . It is known that the resistance to undrained shear of fine grained soils can increase approximately 20% to 1% reduction in moisture content. This means by using the absorbent fabric, the resistance to undrained shear of soil slurry can be 45% to 90% higher compared to soil treated with other geosynthetics.

The results of the above tests have some important implications for the use of the absorbent fabric of the present invention in a floor structure. Usually, after a pavement structure is built, the moisture content in the pavement structure will increase due to the following reasons:

1. evaporation is prevented in the vertical direction by the asphalt pavement;

2. accumulation of rain infiltration from cracks in the pavement, and

3. capillary water rise induced by elevation of the ground due to frost and other reasons.

As a result, there could be excess water in the pavement structure that would be much higher than the optimum moisture content when the soil was originally compacted. Consequently, there will be an increasing differential increase and reduced resistance to soil shear. From the results of the tests above, it can be concluded that the inclusion of absorbent tissue in a pavement structure can lead to reduced moisture content, increased resistance to shearing the soil, and reduced different settlement. All of this is expected to significantly improve the performance of the pavement structure and service life.

The rain infiltration tests for medium sand really simulated the situations when there is a traditional drainage layer of gravel in the pavement structure. In Alaska, a thick 4-inch material D1 is usually used for drainage purposes as well as to prevent soil elevation due to frost and weakening by thawing. Its characteristic is similar to the sand used in rain infiltration tests. When there is rain infiltration, a considerable amount of water can be captured in this layer and cannot be removed by draining the structure

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25/32 of pavement. The sand is close to saturation, when it is exposed to air, water cannot be removed by drainage below due to the same small negative suction. The moisture content is approximately 25%. Under this situation, the inclusion of Mirafi® FW402 and Mirafi® HP570 may not help drain water, while absorbent fabric can help reduce the moisture content by transporting water out of the floor structure.

When rain has infiltrated from the top of a pavement structure, a considerable amount of water will be captured in both the drainage layer and the silt soil layer. Under humidity, the relative humidity in the air is less than 90%, which corresponds to a suction value of 10 MPa. As a result, soil exposed to air will dry quickly and become almost impermeable under negative pore water pressure (suction). The soils on the ledge work like a large plastic mold. With a geosynthetic reinforcement layer such as Mirafi® FW402 and Mirafi® HP570, the differential settlement would still be large, as none of the Mirafi® FW402 and Mirafi® HP570 can carry water under negative pore water pressure (suction). Drainage compounds of the G Mirafi® series cannot work very well since it is designed to transport water under positive pore water pressure conditions. There is a high concentration of stress in the pavement structure.

Conversely, when there is a layer of the absorbent fabric made in accordance with the present invention on the floor structure that has a high ability to transport water under negative pore water pressure in the transverse direction, the water content will be more evenly distributed in the structure of pavement along the absorbent tissue as any difference in suction can lead to water flow. As the suction value on the ledge is higher, it can (1) reduce the moisture in the pavement structure, and (2) make the moisture content to be more evenly distributed in the top layer of soil in the transverse direction. Both effects are beneficial for improving pavement performance and life. When there is less water in the pavement structure, it is also expected that there is less chance of soil elevation due to frost during the winter. The absorbent fabric made in accordance with the present invention helps in reducing the moisture content in the soil. In the summer season when the soils are completely defrosted, the suction in the center of the pavement structure is low, which corresponds to a high relative humidity (usually above 99.9%). The relative humidity in the air under most situations is less than 90%, which corresponds to very high suction. Once installed on the pavement structure, the absorbent fabric can provide a good water transport channel under unsaturated conditions, the soil on both sides of the absorbent fabric tends to be as dry as the soil near the shoulders of the pavement structure in order to maintain a balance in the matrix suction (or relative humidity). This

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26/32 way, it can generate an area with low water content and consequently low unsaturated permeability. This zone can work as a capillary barrier when winter comes due to the reduced unsaturated permeability of the soil. In addition, since there is less water in situ, there is less elevation of the ground due to frost, as well.

During the winter, the absorbent fabric in the pavement structure can help prevent soil from rising due to frost. The freezing process starts from the outside towards the inside of the floor structure. When the soil along the ledge freezes, the free water in the soil becomes ice, which reduces the thawed water content in the soil and increases the suction in the soil at the ledge. The soil in the core of the pavement structure normally has a higher moisture content and low suction value. As a result, water flows from the core to the shoulder of the pavement structure, which also generates an area with less moisture content than it would have had the absorbent fabric not existed. As the freezing front brings the absorbent fabric closer to the top, it will have less elevation from the ground due to frost.

From the results of the rain / top infiltration test, it is concluded that the inclusion of the absorbent fabric in the pavement structure also helps to improve the performance of the pavement structure during thawing seasons. When defrosting occurs, it starts from the outside towards the inside. The defrosting process may not be uniform and cause water to accumulate on the pavement structure since frozen soils are usually impermeable. From the results of the rain / top infiltration test, it is found that the absorbent tissue drains water from the top, which is of great help in reducing water.

The following conclusions can be drawn from the above analysis:

1. The traditional granular drainage layer cannot drain water out of the pavement structure under low suction value. The granular material can hold a considerable amount of water in the field capacity.

2. Mirafi® HP570, Mirafi® FW402, and Mirafi® G Series Drainage Compounds cannot drain water out of the ground under unsaturated situations. These geosynthetics have been found to dry out quickly when exposed to air. When these geosynthetics are dry, they are impervious to the unsaturated water flow.

3. The absorbent fabric of the present invention can remain wet and work as a very good channel for transporting water under high suction values. All test results indicated that the absorbent tissue effectively helps to reduce water in the soil under negative pore water pressure.

4. The analysis indicates that if properly designed, the inclusion of absorbent tissue in a pavement structure can effectively reduce the content of

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27/32 moisture in the pavement structure in all seasons.

Example 12: Moisture Migration

Two tests were carried out to investigate the performance of different geosynthetics during the process of elevating the soil due to frost: tests of migration of outside and inside moisture. In the tests of migration of the external humidity, the upper halves of each soil specimen were surrounded by a geosynthetic and an impermeable layer that was wrapped around the geosynthetic. In the tests of migration of indoor humidity, each geosynthetic was placed vertically inside each specimen of soil. The material that was used was silt soil taken from CRREL's Fairbanks permafrost tunnel. The geosynthetic materials that were used in the tests included Mirafi® FW402, Mirafi® G Series Drainage Compounds, Mirafi® HP570, and Mirafi nylon absorbent fabric. At least one reference was also made for each set of tests. The main purpose of the two test groups was to evaluate the moisture migration performance of each geosynthetic.

In the preliminary tests, water was allowed to seep into the soil from a water bath inside the soil elevation apparatus due to frost. A hammer was used in the preliminary tests as well. The soil was prepared at a moisture content of 25%. The soil specimens are then installed on the soil elevation apparatus due to frost for testing ground elevation due to frost. During soil elevation tests due to frost, the soils were frozen down with the temperature maintained at 7 ° C at the top of the specimen and 1 ° C at the bottom. The soil specimens were surrounded by insulating materials on the side to ensure that the freezing process is one-dimensional. During the freezing process, temperatures in the five different locations of the specimens were measured to monitor the freezing process. The elevation of the soil due to frost is measured at the top of soil specimens using LVDTs. Usually, the tests lasted for at least three days until the soil specimens were completely frozen.

The tests that followed the preliminary tests were performed differently in the following way. First, in the vertical vertical moisture migration tests, water was not allowed to seep into the soil. Second, the soil was not compacted using a hammer. Instead, light pats were made on the sides of the plastic molds to eliminate voids and / or air bubbles inside the soil. Third, the moisture content has been increased up to 40%. The amount of soil elevation due to frost over time was also shown in this set of tests.

After the soil elevation test due to frost, each specimen was removed and cut into six approximately equal portions along the height. All six portions

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28/32 were then placed in the oven and the moisture content was determined. From 0 to 4 inches, the moisture distribution of Mirafi® FW402 remains relatively constant and centered on the original moisture content of 25%. From 4 to 8 inches, moisture has migrated towards the top. Rather than a constant moisture distribution as seen in the 0 to 4 inch portion, the moisture distribution from 4 to 8 inches shows a higher moisture content at the top and lower moisture content at the bottom.

There is a slight increase in moisture content just before the 4 inch mark. This is due to the fact that the impermeable layer prevents water migration, which resulted in a slight construction of ice lenses. Although this is an open system, the moisture distribution under the 4 inch mark achieves a constant moisture distribution that is slightly higher than the original moisture content, indicating that there is a little water migration in the soil.

From 0 to 4 inches, the moisture distribution of G Series Mirafi® Drainage Compounds has increased from 25% to 28%. From 4 to 8 inches, moisture has migrated towards the top. The moisture content at the top of the soil specimens reached 32.8%, 7.8% higher than the original moisture content of 25%. At the 6-inch mark, the moisture content was 21.9%, 3.1% lower than the original moisture content. The bottom had a moisture content of 23%, 2% less than the original moisture content. It was also found that at the top of the interface, the soil is relatively dry. All of this indicated that there was a water migration in the range from 4 to 8 inches.

For the Mirafi® HP570, from 0 to 2 inches, the moisture distribution remains relatively constant and centered on the original moisture content of 25%. From 2 to 4 inches, the moisture content has increased from 25% to 28.1% due to water absorption in this open system. The waterproof layer prevents water migration, and a construction on the moisture content at the 4-inch mark below the interface is expected. From 4 to 8 inches, moisture has migrated towards the top. Instead of a relatively constant moisture distribution as seen in the 0 to 4 inch portion, the moisture distribution from 4 to 8 inches shows a higher moisture content at the top and lower moisture content at the bottom. The moisture content at the top was as high as 30.7%, 5.7% higher than the original moisture content while at the bottom it was 18.8%, 6.2% lower than the original moisture content. These results as well as the previous result clearly showed that the moisture migrated during the freezing process. Since the upper part was a closed system, the overall moisture content should be kept the same.

The moisture distribution of the Mirafi nylon absorbent fabric was determined

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29/32 averaging the results of two different tests performed with Mirafi nylon absorbent fabric under the same conditions. From 0 to 4 inches, the moisture distribution of Mirafi nylon absorbent fabric has increased slightly. From 4 to 8 inches, moisture has migrated towards the top. Instead of a relatively constant moisture distribution as seen in the 0 to 4 inch portion, the moisture distribution from 4 to 8 inches shows a higher moisture content at the top and lower moisture content at the bottom. The moisture content at the top was as high as 30.6%, 5.6% higher than the original moisture content while at the bottom it was 15.8%, 9.2% lower than the original moisture content. These results, as well as the previous result, clearly showed that moisture migrated during the freezing process. Since the upper part was a closed system, the overall moisture content should be kept the same.

With respect to a reference soil specimen, the difference between the reference soil specimen and the previous one is that there are no geosynthetics in the reference soil specimen. The trend of moisture distributions is similar to that with geosynthetics. From 0 to 4 inches, there is a slight increase in moisture content due to water absorption and the average moisture content has increased from 25% to approximately 26% with a relatively constant distribution. From 4 to 8 inches, the moisture distribution increased linearly with height with 15.2% at the bottom, 22.9% in the middle and 29.6% at the top. This distribution indicated that there was water migration from the end to the top during the elevation of the soil due to frost.

In the outdoor moisture migration test, the original moisture content of the soil was 40% in order to simulate the situation when there is excess water in the pavement structure.

For soil specimens with Mirafi® FW402, the bottom (0 to 4 inches) has water migration during the freezing process. Above the 3-inch height, the moisture content of the soil specimen is higher than the original moisture content of 40%, indicating water absorption. Under the height of 3 inches, the moisture content is less than 40%, indicating that the soil is drying out. The moisture content at the bottom of the soil specimen was considered to be the initial moisture content due to free access to water. These test results indicated that for this specific soil, when the initial moisture content in the soil is high, the water migration in the soil specimen is sufficient to correspond to the freezing process at the same time as the water absorption from the water is very small.

This can be verified by the results obtained from the top (4 to 8 inches), the central part of the soil specimen at 6 inches basically had the

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30/32 same moisture content as the initial moisture content. Above 6 inches, the moisture content is over 40%, indicating that there was water absorption. Below 6 inches, the moisture content is less than 40%, indicating that water has been lost. The upper half is a closed system and the total humidity has been kept constant.

For soil specimens including Mirafi® G Series Drainage Compounds, the bottom (0 to 4 inches) has water migration during the freezing process. Above the 3-inch height, the moisture content of the soil specimen is higher than the original moisture content of 40%, indicating that there is water absorption. Below the 3-inch height, the moisture content is less than 40%, indicating that the soil is drying out. These test results indicated that for this specific configuration, when the initial moisture content in the soil is high, the water migration in the soil specimen is sufficient to correspond to the freezing process at the same time as the water absorption from the bath. water is very small.

For the upper part (4 to 8 inches), the central part of the 6-inch soil specimen basically had the same moisture content as the initial moisture content. Above 6 inches, the moisture content is over 40%, indicating that there was water absorption. Below 6 inches, the moisture content is less than 40%, indicating that there was water loss. The upper half is a closed system and the total humidity has been kept constant.

The test results for soil specimens including Mirafi® HP570 were different. For the bottom (0 to 4 inches), the moisture content was lower than the initial moisture content. In addition, the moisture content was relatively evenly distributed, which was not consistent with the results of the other tests in this group. However, the result was similar to the results in the preliminary tests of migration of outside moisture. That is, when the initial moisture content was low, the moisture content in the lower halves of the soil specimens was relatively evenly distributed.

For the upper part (4 to 8 inches), the central part of the 6-inch soil specimen basically had a moisture content of 35.1%, below the target 40%. The moisture content above the 7 inch mark is 45.1%, higher than the target 40%. The moisture distribution content shows the migration of moisture during the freezing process.

The test results for soil specimens with the inclusion of Mirafi nylon absorbent tissue and the soil specimen without the inclusion of geosynthetics, respectively, were similar to those with Mirafi® FW402 inclusions and Mirafi® G Series Drainage Compounds. Both the top and the bottom indicated water migration from the bottom to the top.

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The moisture content for the soils in the upper halves of the specimens in this group basically had similar declined distributions, indicating that there is migration of moisture during the freezing process. The differences in moisture distributions between different geosynthetics were insignificant except for the Drainage Compounds of the Mirafi® G Series. The excess moisture content in the soil specimen with the inclusion of the Mirafi® G Drain Compost was due to the fact that the G Mirafi® Drain Compound was initially moistened and contained more water. For the lower parts, there should be no differences in the content of moisture distributions since all soil specimens had the same configuration and access to water absorption.

The vertical vertical moisture migration test used soil that had an original soil moisture content of 40%. Except for the reference soil specimens, different geosynthetics were included vertically in the center of the soil specimens. Both ends of all soil specimens were sealed without access to water. All soil specimens were frozen from the bottom with a constant temperature of -7 ° C on the top and 1 ° C on the bottom.

For Mirafi® FW402, the moisture distribution content below the 6 inch mark was basically uniform with a moisture content ranging from 37.0% to 37.5%. Above the 6-inch mark, the moisture content increased to 48.4% at an approximate height of 7 inches. The results indicated that there was a significant migration of water at the very beginning of the freezing process. As the front of the freeze moved down, the water migration speed slowed. This was demonstrated by the decrease in moisture content with height. The water migration gradually matched the moving freeze front and resulted in an approximately uniform moisture distribution below the 6 inch mark.

For the Mirafi® G Series Drainage Compounds, the moisture distribution content below the 3-inch mark was basically uniform with a moisture content ranging from 36.6% to 36.8%. Above the 6-inch mark, the moisture content increased to 36.7% at the 3.5-inch mark to 52.9% at the approximately 7-inch mark. In comparison to the previous soil specimen with the inclusion of Mirafi® FW402, the declined moisture distribution occurred at a depth greater than 3.7 inches. The moisture content below the 3.7 inch mark was also less than that in the previous specimen of soil with inclusion of Mirafi® FW402.

The moisture distribution for Mirafi® HP570 had the same pattern as that of the soil specimen with the inclusion of Mirafi® G Series Drainage Compounds. The difference was that the declined moisture distribution was only in the range above the 5 inch mark and the moisture content below the 5 inch mark was basically

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32/32 uniform.

For the Mirafi Nylon Absorbent Fabric, the moisture content was the highest at the top (46.5%). It decreased to 35.9% up to the 3 inch mark and then slightly increased to 36.3% and remained relatively uniform below that. This was a closed system and the initial moisture content was 40% anywhere, it is evident that the migration of moisture was induced by frost.

The experimental results for the reference soil specimen were similar to those above, except that the reference soil carried more water to the upper part.

It can be concluded that when there is Free access to water, Mirafi Nylon Absorbent Fabric can transport water better compared to other geosynthetics. Through the above test groups, several conclusions can be made: During the freezing process, capillary forces (suction) can be generated due to freezing of free water. When the soil is under the influence of suction, the soil is unsaturated and there is still water migration. Water migration due to the freezing process is the reason for the elevation of the soil due to frost. In these group tests, it is shown that Mirafi Nylon Absorbent Fabric, an absorbent fabric made in accordance with the present invention, has high transmissivity under unsaturated conditions. Such a property, when properly used, can be used to prevent elevation of the soil due to pavement frost in cold regions.

With respect to the above description then, it is to be idealized that the optimal dimensional relationships for the parts of the invention, to include variations in size, materials, shape, mode, function and manner of operation, assembly and use, are readily apparent and obvious. to a person skilled in the art, and all relationships equivalent to those illustrated in the drawings and described in the specification are intended to be covered by the present invention.