Method of laying subsoil membranes

A METHOD OR״ LAZING SUBSOIL MEMBRANES

The invention relates to the separation of upper eoil layers from the subsoil by laying a membrane of a preferably impervious material at a predetermined depth below the soil surface. This separation by underground films or membranes is done for various purposes:- to produce impermeable panda, dam levees _ror reservoirs for water or other.liquids. Impermeable membrane« are being used in the building of roads, runways, subgrades, Sidewalks and road margins. More recently, impermeable membranes have been Tnntalled in aCTicuItural^fielils at several decimetres below the surface Qth^the purpash-of-reduclng^leakage of rain or irrigation water below the root zone and thus to increase the yield.

Several methods of preparing an impermeable underground layer are known. In one of these methods the soil is excavated to the necessary depth, the surface smoothed and compacted and the impermeable layer is brought up on this surface by either laying prefabricated sheeting or by spraying a suitable plastic or liquid material. The excavated soil is then returned on to the top of the membrane. The drawbacks of this method are that the costs of smoothing and compacting after removal of the top layer are very high, that the thickness and strength of the membrane must be sufficient to sustain the stresses imposed on it by the heavy earthmoving equipment used in replacing the previously removed soil, as otherwise there may be the danger of tearing, punctures and imperfect cover.

An. improved method has been suggested wherein a subsoil blade is dragged through the soil parallel to the surface ^jd^iwyoualy^a suitable material is ejected and sprayed from the rear edge of this blade formIng an impervious mombrano after hardening, In this manner excavation and replacing of the soil, as well as manual or mechanical laying of a membrane are avoided and combined in one continuous operation. The main drawback of this method is the high cost of the material destined to form the membrane, since th®, requirement of producing a perfect continuous membrane demands the spraying of a relatively thick layer. As an example, the use of asphalt calls for a thickness of several millimetres. In addition, production of this type of membrane is limited to soils having no rough clods or aggregates and permit smooth penetration of the blade, *t is also required that the soil is compatible with tie sprayed material to allow perfect spraying and bonding.

It is, therefore, the object of the present invention to improve on the lastmentioned method by laying and inserting into״the.ground.a prefabricated film or membrane־^f^S^determined pMgerties by means of special equipment suitable for laying this.membrane without the need of a previous excavation. Furthermore, the use of this equipment should :j iiwwm, jw'-i«¹;..wirw permit to lay such membrane in other configurations than flat and in parallel to the soil surface.

Another object of the invention is to lay a membrane of a prefabricated material which can be produced to a wide range of properties thus allowing various applications. Still another object is to make the membrane of a very thin an inexpensive plastic material in order to iave costs.

The method consists of dragging a hollow cutting blade having a straight or otherwise formed cutting edge, an upwardly sloping front portion and a downwardly sloping rear portion ending at about the sane height as the front edge, through the soil at a predetermined depth by means of a traction vehicle, providing for the supply of prefabricated thin sheeting of a pliable material to the interior of the blade and for the feeding of the said sheet material from the interior of the blade parallel to the rear edge thereof, at the velocity of the progress of the blade through the soil. The feeding is automatic in that the sheet material is held back by the soil falling on to its upper surface after having been raised by the passing blade.

In a preferred embodiment of the invention the blade possesses a straight front edge and a straight hollow body of the said configuration, a flat bottom portion open at its rear, with a roll of the sheet material positioned rotatably in the blade interior in parallel to the front edge, the membrane being formed by the sheet material unrolling from the said roll through the said bottom opening into the cut made by the blade underneath the rear edge of the latter.

The method may also include the laying of pipes, cables or wires on top and adjacent to the sheet material forming the membrane by feeding these materials into the soil by any method known to the art.

Figure 1 illustrates a vertical cross section througha hollow blade serving to carry out the method according to the invention. Figure 2 is a perspective view of the blade illustrated in Figurel, shoving attachment means to a traction vehicle.

Figure 3 is a perspective view of the interior of the blade illustrated in Figures 1 and 2,

Figure 4 is a cross section through a blade together with equipment suitable for laying piping adjacent to the sheet membrane, and Figure 5 illustrates six different ways of placing membranes by the iiethod described.

Referring now to Figures 1, 2 and 3 of the drawings, the equipment: for carrying out the operation consists of a blade of the required width that is carried «at beneath a vehicle and is dragged through the soil at a predetermined depth, with the front edge cutting through the a.

soil. Its bottom portion 5 forms a release angle with the cut soil so as to prevent friction between the.bottom and the soil surface. The top portion of the blade 3 is sloped in an upward direction at an angle b for the purpose of pushing the soil above the blade, terminating in a aiihat.ftnt.-ΐnlly horizontal centre portion 10. The rear portion 4 of tho blade is arranged at a rearward and downward slope with its rear edge 11 and!ng at a height slightly above the height of the front edge. The two side shields 12 close the hollow space formed between the top and.the bottom of the blade. The blade is attached to a traction vehicle above ground by means of .two substantially vertical arms or shanks 13 which are standard equipment with earthmoving equipment.

A pipe 7 carrying a roil 8 of a thin sheet material of a width commensurate with the width of the interior space is positioned within the space And׳ carried at its ends on spaced rollers 16 attached to the end shields permitting its free rotation about its axis. The free end 9 of the material is shown to have unrolled off the roll and to be kept pressed between tho stationary and the raised and replaced soil layers respectively.

All pivots of the abovenentioned rollers 16 are secured in the walls of a special tray 14 which is hinged to the end shield 12 by simple hinges that allow it to drop below the whole structure to facilitate »ויזanH.ing and reloading of the film rolls. Wen the tray is lifted to a working position it is automatically locked there by free.-falling hooks 15.

This arrangement is not essential but exemplifies a specific .design that has been built and field tried for reliance and simplicity of operation.

Wider or narrowerblades and film strips may be used, depending on the type of soil, specific use, tractor available etc. Other dimensions of the implement may also be changed due to the end uses and well-known laws of soil mechanics.

Various modifications and alterations may be carried out to the implement and to the method by a person skilled in the art, however within the limits of the invention and the scope of the appended claims.

The underground laying of prefabricated films may be combined with underground spraying by means of the same tool in the same pass. Thus any liquid may be injected by spraying for different purposes, such as softening the ground, introducing fertilizer,fumigation or any other end use. _____

The tool edge may be implemented with special teeth, chisels, and vibrating parts to reduce the necessary forces in some heavier soils or in soils with some cohesive strength*

The tool edge may be straight, slightly curved or V-shaped, so that the cross section of the finished membrane is straight, curved or V-shaped* This is necessary to obtain special effects. (Fig.5).

The implement is equipped with standard aids as are common in earthwork machines and agricultural machinery, but are not part of this invention. They are, for example, edge markers to aid in exact performance, depth indicators, depth wheels and/or automatic depth controlling sensors to indicate the flow of the unrolled film and even to essay its length.

Of special importance is the possible combination of prefabric— ated membrane and underground pipes. The techniques of laying underground pipes or wires is well known. An implement is dragged through the soil while a pipe, a wire or a cable is unrolled trough a special conduit in the implement straight into a mole hole which has been formed in the soil. The combination of a^ prefabricated membrane and such an underground piping and wiring is claimed here to be of unique advantage,

There may be regular pipes, perforated pipes, heat conducting pipes, stripped or insulated wires. The pipes may be laid below the membrane or above the first~casej^the־־pipentin־־l'ai'dbefore the_____ membrane. In the second case, the pipe laying implement is a part of the ^^Sn~6Igg°anaj£hB^ pipe is laid afterihd membrane, Fig 4 shows such a combination; In addition to the described in Fig,1 it contains a pipe conduit 18 through which the pipe or wire or cable 20 is!fed;

The pipes may be laid at the seams between neighbouring membrane strips; The invention thus includes the combination in one implement of both installations of prefabricated . membrane and piping or wiring!

The abovementioned implement is usually dragged through the soil by a proper tractor or any other vehicle that has the necessary drawbar pull for the specific blade in the specific soil; However, it may also be dragged by a vehicle specially built for the purpose in which the knife is not dragged behind; but is anchored underneath the vehicle in a form that allows various degrees of freedom such as depth, tilt; angle etc! This last arrangement <inay be similar to a-motograder.