Apparatus for solidifying and improving fragile ground

[57] ABSTRACT

An apparatus for solidifying and improving moist, soft, clayey and/or industrially polluted soils to make them available for land construction works. The apparatus is divided into ground-type equipment and underground-type equipment, each type of equipment comprises a sucking unit for absorbing the soils, a mixing unit for mixing the soils with stabilizer, and a pressure feeding unit for pressure feeding the mixture of soils and stabilizer to the desired location. The apparatus is characterized by the incorporation of a nonmotorized pipeline mixer into the mixing unit and a powerful pump capable of transferring highly viscous material or clay with a high water content.

Claims, 18 Drawing Figures

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U.S. Patent sept. 30,1975

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U.S. Patent sept. 30,1975

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U.S. Patent Sept. 30,1975 sheet 6 of 6 3,908,387

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3,908,387

APPARATUS FOR SOLIDIFYING AND IMPROVING FRAGILE GROUND

The present invention relates to an apparatus for solidifying and improving the quality of moist, soft, clayey and/or industrially polluted soils by means of mixing them with different kinds of stabilizers, thereby producing a mixture of soils and stabilizer to be put into practical use for different kinds of land construction works.

Conventionally, the mixing of stabilizer with unimproved soil has been conducted either by means of putting the stabilizer into a hollow cylinder, the hollow cyclinder penetrating into a sedimentary layer of unimproved soil with a stirring blade attached at the lower portion thereof for mixing the stabilizer with the unimproved soil, or by means of inserting a rod into a prebored longitudinal hole, then jetting stabilizer under high pressure into a layer of unimproved soil through a jet nozzle on the rod at the forward tip thereof.

These conventional means, however, have such defects as: in the former method, the stabilizer is limited to a solid, even mixing is difficult and the mixing condition is difficult to examine before the completion of the mixing; in the latter method, the stabilizer must be liquid as opposed to solid, even mixing is also difficult, the mixing condition is also difficult to examine before the mixing comes to a halt, and the scope of mixing is liable to change in accordance with the quality of the unimproved soil to a great degree.

A first object of the present invention is to obviate the afore-mentioned defects of the conventional means by using an apparatus operable either above ground or underground, thereby enabling the even mixing of stabilizer with unimproved soil in disregard of the mixing ratio between the stabilizer and the unimproved soil, and also enabling constant comprehension of the operating condition of the apparatus by installing a flow meter, a pressure meter and the like in the apparatus at various points therein. The apparatus when functioning will suck a pile of unimproved soil in for an effective mixing of the unimproved soil with the said stabilizer and discharge a mixture of the unimproved soil and stabilizer as wanted.

A second object of the present invention is to dispense with the selection of stabilizer for getting a required effect of mixing, and for lowering the cost of land construction by using the mixture produced in the present invention, owing to the availability on the general market of the stabilizer to be used in the present invention.

A third object of the present invention is to produce a mass of solid soil for land construction work as required in size or shape by way of controlling the amount of unimproved soil to sucked into the apparatus, or to dispose improved soil required to be removed from a spot. In this underground or “within soil” mixing operation, the solidification of unimproved soil is effective for preventing harmful components, if any, of the unimproved from filtering out into underground water.

The above and further objects of the present invention will be apparent from the following descriptions in reference to the annexed drawings

FIG. 1 is an illustration of the apparatus in the first practical operation.

FIG. 2 is a horizontal view of an above-ground equipment of the apparatus in a practical use.

FIG. 3 and FIG. 4 are magnified sectional views of units, pressure feeding the unimproved soil, in operation as shown in FIG. 1.

FIG. 5 is a sectional view of the units described in FIGS. 3 and 4 with an indication of the order of the mixing work.

FIGS. 6, 7 and 8 show the apparatus, shown in FIG. 1, in practical use, respectively.

FIG. 9 is an illustration of the equipment in the second practical operation.

FIG. 10 is a longitudinal sectional view of the abovedescribed equipment in concrete shape.

FIG. 11 is a magnified horizontal view of a stirring grid used in the foregoing operation.

FIG. 12 is a sectional view of the equipment described in FIG. 10 with an indication of the order of the mixing process.

FIGS. 13, 14 and 15 show examples of practices for improving unimproved ground.

FIG. 16 is a longitudinal front sectional view of part of the unit described in FIG. 3 in practical operation.

FIG. 17 is a sectional view of the abovementioned unit with an indication of the order of operation.

FIG. 18 is a graph showing the relationship between the number of days elapsed after the practice of the mixing operation and the strength of the mixture produced during the mixing.

FIG. 1 shows an unimproved soil suction pipe 11 inserted into a pile of unimproved soil 13, a pipe 12 for pressure feeding the mixture of unimproved soil and stabilizer, both pipes 11, 12 being connected to unimproved soil sucking unit 14, and unimproved soil discharging unit 15 incorporated into ground level-type equipment A.

The ground level-type equipment A comprises a stabilizer feeding unit 16 and a mixing unit 17. The unimproved soil 13 which is sucked in by a pump placed in the unimproved soil sucking unit 14 or the unimproved soil sucking pipe 11 is sent to the mixing unit 17 via the stabilizer feeding unit 16. Then stabilizer fed from the feeding unit 16 through a stabilizer feeding pipe 18 is supplied to the mixing unit 17, whereby the mixture 19 of the stabilizer and the unimproved soil is discharged into the unimproved soil 13 via the pressure feeding pipe 12 under the power of the pressure feeding unit 15 or a pressure feeding pump.

In FIG. 2, which is a horizontal view of the said ground-type equipment A, are shown a spring feeder 20, a liquid tub 21, a pump 22 for watering a fixed volume of water, supplier 23 of a fixed volume of powder, and a mixer 24 for adjusting stabilizer.

A fixed volume of powdered stabilizer supplied from the spring feeder 20 is fed into the mixer 24 by the supplier 23; the powdered stabilizer becomes a slurry by way of mixing with water which is sent into the mixer 24 from the liquid tub 21 by the pump 22; and the slurry stabilizer is fed into a pipeline mixer 26 which plays the main role of a mixing unit, whereby the slurry stabilizer is mixed with unimproved soil sucked into the mixing unit 26 by the sucking pipe 11 and the mixture is discharged into the pressure feeding pipe 12 by a injection pump 27 which plays the main role of a pressure feeding unit.

In FIG. 3, a screen 28 in the shape of a perforated panel for the screening of foreign substances is pro3,908,387 vided at the unimproved soil sucking pipe 11 at the lower opening thereof, and a cylindrical separator 29 of a large diameter is provided at the pressure feeding pipe 12 at the lower portion thereof so that the foregoing mixture discharged from the pressure feeding pipe 12 may not be sucked again into the Hcdoro sucking pipe 11.

In FIG. 4, a casing 30 of a large diameter is shown with a separator 31 in the shape of a flange provided at the unimproved soil sucking pipe 11 at the lower portion thereof, the separator 31 going up and down inside the casing 30, the pressure feeding pipe 12 piercing through a hole bored on the separator 31, and another separator 32 in the shape of a flange provided on the pipe 12 at the lower portion thereof also traveling up and down inside the casing 30.

In this case, the casing 30 is put upright on the unimproved soil 13, as shown in numeral I of FIG. 5, and the pressure feeding pipe 12 pierces deep into the unimproved soil 13 at first, as shown in numeral II of FIG. 5, then the casing 30 pierces into the unimproved soil 13 and is filled with unimproved soil. The separator 32 is inserted into the casing 30, and another separator 31 is placed thereabove, also in the casing 30. In this state, unimproved soil is sucked from the upper portion of the casing 30 into the sucking pipe 11 and sent to the ground-type equipment A whereby the unimproved soil is mixed with stabilizer. The mixture is then pressure fed into the casing 30 to the lower portion thereof via the pressure feeding pipe 12, resulting in the gradual elevation of the pressure feeding pipe 12 together with the separator 32 when the casing 30 is filled with the mixture 19, as shown in numeral V of FIG. 5, the casing 30 is pulled out of the unimproved soil 13, resulting in the production of a solid mixture in the shape of a pillar. In this case, the separator 31 should be fixed at the upper portion of the casing 30.

In FIG. 6, the unimproved soil 13 brought by a conveyor 34 from a factory 33 is stored in a storing unit 35 from which it is removed by the sucking pipe 11 to be mixed with the stabilizer by the ground-type equipment A. The mixture produced thereby is then conveyed by a truck 36 to land construction sites and used for various ground improving works.

In FIG. 7, the mixture discharged from the pressure feeding pipe 12 is put into a molder 37 to be formed into blocks to use for road construction, land reclamation and the like.

In FIG. 8, the storing unit 35 is divided into two partitions by a panel, and the unimproved soil 13 in one of the said partitions is fed into the ground-type equipment A and mixed with the stabilizer, the produced mixture thereby getting back to the storing unit 35 to enter in the other of the said partitions.

Contrary to the above showing examples of mixing by the ground-type equipment A after absorption of the unimproved soil into the equipment, FIG. 9 shows examples of mixing by underground-type equipment B penetrating into the unimproved soil.

In the underground equipment B shown in FIG. 9, is shown a sucking and pressure feeding unit 51 having an inlet 52 and an outlet 53. The outlet 53 is communicated with a supply unit 55 located above a mixing unit 54; an outlet 56 of the ixing unit 54 opens downward at a position below the inlet 52 of the sucking and pressure feeding unit 51. Also, a pipe 58 for supplying stabilizer is linked to the supply unit 55 at the upper portion thereof. The unimproved soil 59 sucked in by the sucking and pressure feeding unit 51 through the inlet 52 is discharged from the outlet 53 thereof and fed to the mixing unit 54 via the supply unit 55, thereby being 5 mixed with the stabilizer fed from the said pipe 58 via the supply unit 55 into the mixing unit 54. The produced mixture 60 leaves the mixing unit 54 through an outlet 56 thereof.

FIG. 10 which is an embodiment of the underground 10 equipment B, shows a pump 61 which is an integral part of the sucking and pressure feeding unit 51, the pump adopted in this experiment being of a unique system called “MOHNO-system”.

The said MOHNO-system pump is characterized in 15 its pumping function by its ability to shift shifting the capacity of inlet side and outlet side, the two sides being completely separated by a seal, with the transfer of a line of contact between a female screw inside a stator 62 and a male screw at the periphery of a rotor 63, 20 the rotor 63 being brought into rotation by a motor 65 via a connection rod 64, and the rotor 63 being inserted into the elastic stator 62 incorporated in the cylindrical pump casing. The pump has a capacity of: sucking pressure—700-750 mm H g; feeding pressure—10-24 25 kg/cm square, and is capable of transferring even highly glutinous material with ease, and is also capable of transferring clay ranging from 70% to 80% in water content. The pump is equipped with a water proof motor 65, operated by either electric power or hydrau³⁰ lie pressure. Thus, the MOHNO-system pump is quite fit for the suction and pressure feeding of unimproved soil, but other kinds of pumps could be used also for the same purpose.

The pump 61, with the inlet 66 directed downward, ³⁵ is fitted vertically to the penetrating pipe 67 at the lower terminal therof, the pipe 67 being equipped with a penetrating device 68 at the upper terminal thereof, and is lifted by a crane 79.

An outlet 69 at the upper side of the pump 61 is com⁴⁰ municating with the upper inlet of the supply unit 71 at the upper terminal of the mixer 70 which plays the main role of a mixing unit. The pipe line mixer 70 is an unmotorized system with a plurality of divided elements 72 incorporated into a hollow cylinder. The sup⁴⁵ ply unit 71 of the mixer 70 is connected to a flexible and pressure-endurable pipe 73 for pressure feeding of the stabilizer, the pipe 73 also being connected with equipment 74 on the ground for pressure feeding the stabilizer. The equipment 74, consisting of an injection ⁵⁰ pump, a motor and the like, uses the pump 61 for pressure feeding the stabilizer to the supply unit 71 via the pipe 73.

Therefore, the pressure of the stabilizer fed through the pipe 73 to the supply unit 71 flows through the ele'' ments 72 in the mixer 70 together with unimproved soil discharged from the outlet 69 of the pump 61, thus the stabilizer and the unimproved soil mix into a complete mixture before leaving the mixer 70 at the lower outlet thereof. A motorized continuous system mixer or kneeder can also be used for the above process.

The mixer 70 has a separator 75 at the outlet of the lower terminal thereof to prevent the mixture discharged from the mixer 70 from being sucked into the inlet 66 of the pump 61. When there is no separator 75, a stirring grid 76 is fitted at a point between the pump and the mixer 70. The grid 76 has holes 77 and 78 for the pump 61 and the mixer 70 to fit therein and

3,908,387 makes easier the suction of unimproved soil near around the inlet 66 of the pump 61 by stirring it.

The foregoing underground-type equipment B, installed on unimproved soil 59, as shown in FIG. 12, penetrates into the unimproved soil to a depth as required by the operation of the penetrating device 68, as shown in II and III of FIG. 12, with simultaneous starting of the pump 61 and the equipment 74 for pressure feeding the stabilizer into the supply unit 71 via the pressure feeding pipe 73. Also, the unimproved soil sucked into the pump 61 is discharged from the outlet 69 and pressure fed into supply unit 71, thereby mixing with the stabilizer while flowing through the elements 72 to become a nearly complete mixture before being discharged into the unimproved soil from the separator 75 at the lower portion thereof, and thereby enabling the formation of the mixture into a solid pillar 80 by way of gradual elevation of the underground equipment B as shown in IV of FIG. 12.

Accordingly, a solid pillar 80 of the mixture which reaches the ground level is made in the process of elevating the underground equipment B until it reaches the ground level as shown in V of FIG. 12. The underground-type equipment B, as a matter of course, need not use the penetrating device 68 when the unimproved soil 59 is so soft as to admit the penetration of the underground-type equipment B by its own weight.

In the foregoing process, the volume of mixture and mixing ratio of Hedoro to stabilizer can be confirmed on the ground by means of waterproof electromagnetic flow meters, one each at the inlet of the mixer 70 and the outlet of the pressure feeding equipment 74. Also, the resistance of the ground can be estimated by means of measuring the discharging pressure at the outlet of the mixer 70. Furthermore, penetration depth of the underground type equipment B can be confirmed and, also, recorded by the utilization of a depth indicator with the rotation of self synchronizing motor, the motor revolving in proportion to the depth of the penetration, and a pulley block links the said motor to a wire, one end of which is firmly connected to the penetrating device 68 and the like. Also, the solid pillar 80 of the mixture is transformable into circular or square or any other shape by changing the form of the separator 75 horizontally as required.

A plurality of the solid pillars 80 produced in the foregoing process are put side by side with intervals in between each other, as shown in FIG. 13, or in close contact with each other, as shown in FIG. 14. Also, an artificial ground supporter 81 can be produced by means of unifying a number of the solid pillars with limited length formed in the unimproved soil 59 at the lower portion therein.

In FIG. 16 as the embodiment of the third practising example, a sucking and pressure feeding apparatus C is shown, the apparatus C consists of a MOHNO-system pump 82, a motor 83 and a slide panel 84. The MOHNO-system 82 and the motor 83 are equivalent to the MOHNO-system pump 61 and the motor 65 described in the second practising example, respectively, the pump 82 having a screen 85 for screening foreign substances at the lower terminal thereof. The slide panel 84, available in any shape horizontally, has a hole 86 in the center thereof for the cylindrical casing of the pump 82 to fit through.

In FIG. 17, numeral I shows the undergroundtype equipment C set on the unimproved soil 87 with the slide panel 84 placed on the unimproved soil 87, numeral II shows the pump 82 penetrating deep into the unimproved soil 87, the pump 82 sucking the unimproved soil 87 into the inlet at the lower terminal thereof with the start of the motor 83 and pressure feeding the unimproved soil 87 through the outlet 88 into the ground level equipment A, as shown in FIG. 1, where the unimproved soil 87 is mixed with stabilizer and the produced mixture is brought into various uses as described above: At the time of the foregoing suction of the unimproved soil, the slide panel 84 plunges along the cylindrical casing of the pump 82 and accomplishes a nearly complete suction of unimproved soil at the lower portion of the slide panel 84, the slide panel 84 having a weight appropriate for applying a pressure downward as required. The weight of the slide panel 84 enables the slide panel 84 to descend as the unimproved soil around the lower portion of the pump 82 is sucked in by the pump 82 to prevent the bottom of the pump 82 from becoming a cave, and as the result, contributes to the full suction of the unimproved soil by the pump 82. The slide panel 84 can also be installed on the vertical portion of the sucking pipe 11 as shown in FIG. 1.

As for the stabilizer lime cement, water glass, and high polymer material are applied as the stabilizer for the foregoing practice, provided that they are used in a state of slurry.

Stabilizers are divided into following groups:

1. Cement group slurry (at a weight ratio of 2 to 1 between cement and water)

2. Lime group slurry

3. Water granulated slag with alkalic irritant slurry 4. Grout material of water glass group

5. Grout material of lignin group

6. Grout material of high polymer group

7. Others.

The foregoing groups of stabilizer should be used distinctively with each other in accordance with the condition or character of the unimproved soil, the predetermined usage of the mixture, and the circumstance where the mixture is to be used, and the like. The mixing ratio of the stabilizer to the unimproved soil is then determined.

The graph in FIG. 18 shows the results of experimental usage of the mixture produced in the process by the present invention. The vertical axis shows uni-axial compression strength and the horizontal axis shows the number of days elapsed after the day when the experiment is conducted.

Curves in the said graph show various ratios as following:

Curve 91 (in case of bentonite muddy water): Water content (weight ratio) 437%; stabilizer (weight ratio) cement:water=2:1; mixing ratio (weight %) 10%

Curve 92 (in case of soft, clayey soil): Water content (weight ratio) 113%; stabilizer (weight ratio) cement:water glass:water=2:0.1:1; mixing ratio (weight ratio) 20%

Curve 93 (in case of waste acid neutralized sludge): Water content (weight ratio) 333%; stabilizer (weight ratio) cement:water granulated slag:water=l: 1:1; mixing ratio (weight ratio) 30%.