METHOD AND APPARATUS FOR AFFECTING OR CHANGING THE LIQUID CONTENT IN A SOIL STRATUM

Abstract: Method and apparatus for affecting or changing the liquid content in a soil stratum, either by draining or by infiltration. A liquid conductor provided with slots is driven down into the soil stratum, whereafter it is filled via supply means with a material under pressure such that the material is pressed out of the conductor through the slots towards the stratum to form radial cracks therein, these cracks being simultaneously filled with the material in question. The material, which is a multicomponent material, is taken in component form through the supply means, whereafter the components are mixed, and under the action of the water in the soil stratum go over to solid form with open cells or ducts.

Description: METHOD AND APPARATUS FOR AFFECTING OR CHANGING THE LIQUID CONTENT IN A SOIL STRATUM The present invention relates to a method and apparatus for affecting or changing the liquid content in a soil stratum, either by draining or by infiltration. Many attempts have already been made to drain soil strata, especially fine-grained soils such as silt or clay with very low permeability. In connection with the foundation of most building structures there is a risk of settlement in the ground even a long period after the structure has been finished, and in many cases this can lead to damage to the building. Settlement depends primarily on changed loading conditions. For effecting a remedy to this problem, draining and pre-loading of the soil strata therefore take place before construction begins. In an already known drainage method, it is prescribed that vertical, cylindrical holes in the ground are filled with sand, so called sand drains, with the aid of which drainage is facilitated in the lower soil strata. A number of such vertical sand drains are arranged at a given mutual spacing so that effective drainage will be obtained. The ground is then subjected to a large load, which may be larger than the load from the finished building (the pre¬ loading method). With the aid αf this extraneous load and the sand drains the ground will be drained in due time. The method works, but is time-consuming and expensive, since a large number of drains is required to make drainage effective. There is also the risk that the drains sludge up, which reduces the draining effect. An alternative to the sand drains are web-like drains thrust into the ground, and consisting of sacking, unoiled paper, defibratεd wood or other water-permeable porous or fibrous ' material, for leading the pore water from the ground upwards, Different plastics materials have also been used more recently as drains. In the Swedish published specification 7415474-1 (publication number 407.598) there is described a method of consolidating a ground area containing layers of clay. Drains are installed first, after which the ground is pre-loaded to promote water run-off. The drains are installed by infiltrating into the ground an agent that reacts with, or physically co-operates with one or more of the components in the natural soil. The agents that have been suggested are organic and inorganic calcium compounds, magnesium compounds etc. A disadvantage with the method is that continuous, effective drains cannot be achieved in practice. An important factor in draining the soil strata is that the drains ace implemented such that their effective draining area is as large as possible. For natural reasons, it is unfeasible to make sand drains a nd web-like drains too large. With a previously known drain, it has been made so that it has a substantially star-shaped cross section. This increases the effective draining area somewhat, but seldom sufficiently. The intention of the invention is to provide a method and apparatus for affecting or changing the liquid content in a soil stratum, either by draining or by infiltration, the disadvantages with previously known methods and apparatus having been eliminated. This has been achieved by the method and apparatus in accordance with the invention having been given the distinguishing features disclosed in the accompanying claims. The present invention thus relates to a new method and a new apparatus far draining, al ernatively infiltrating, of liquid from, alternativel into, a soil stratum. In accordance with the invention, there is thus described a method of draining/ infiltrating liquid from/into soil strata using a slotted pipe pressed down into the earth to a predetermined depth. A multi- component material, e.g. liquids, is taken into the central, hollow part of the pipe via mutually separated conduits for each of its different components and in their predetermined proportions. Simultaneously as the components are pressed out of the conduits into the pipe and out via the slots, which have formed groove-like regions during their passage through the soil strata along the vertical, cylindrical soil wall, the components are mixed with each other and react with the water in the soil to form a material, the properties of which are described later on. The pressure, which does not need to be great, at which the material is pressed out of the slots results in that the ground cracks up, and substantially vertical cracks, up to a length in the order of magnitude of 5 meters are formed. At the same time the cracks are filled with the material, which solidifies in contact with the water in the soil, is warmed up and expands. The cracks will generally be in a radial direction outwards from the centre of the pipe. The number of cracks is dependent on the number of slots in the pipe. In order that cracks will be formed and filled in at different levels, the pipe may be formed with a number of slots or openings along the entire generatrix of the pipe. The openings do not need to be uniformly oriented about the circumference of the pipe, and their positions may be suited to the desired directions of the cracks. It is also possible within the scope of the invention to drive down two coaxial pipes, of which the outer functions to form the drainage hole in the ground and to provide the groove-like markings along the walls of the hole, after which this pipe is removed and the inner pipe provided with the openings serves to form the vertical cracks under the action of the filling material. A suitable material to use for the formation of the cracks and drainage/infiltration is a multicompαnent material. This material is usually formed with closed cells, which is not desirable, since it then lacks liquid conducting properties. With the right mixing ratios of the components included in the material there is, however, obtained a material that after hardening in contact with water consists of open cells or ducts. Very advantageous drainage and/or infiltration pro- perties are obtained with such a material. Simultaneously as the material hardens in contact with water, and the open pores or cells are formed, there is a heavy expansion and generation of heat in the material. Expansion time, hardening time and pore size may be controlled by the selection of suitable mixing proportions. For example, the multico pαnent material may comprise polyurethane foam or the like. Other types of multicompαnent material can also be utilized. Both the expansion and heat generation affect drainage positively. The expansion results in an increased horizontal pressure in the soil strata, and this pressure can resemble the extraneous load necessary in other draining methods for consolidating the soil. The pressure from the expanding material will be more effective than a pressure arranged at ground level, since the pressure can be applied directly at the area to be drained, the water being pressed out sideways into the filled cracks in the ground, from where it is led through the open cells or ducts in the material to the ver¬ tical drain and up to the ground surface. On its part, the heat generation results in that the soil strata nearest the drain and the filled cracks are dried out, also resulting in that these regions also obtain liquid-absorbing properties, which further accelerates drainage. The solidified filter material has considerably hiqher strength than the surrounding fine-grained soil, and thus increases the stability and stiffness of the soil mass, e.g. with respect to embankment stability problems. Filling the pipe with the multicα pαnent material may take place in stages, beginning at the lower end of the pipe. The pipe is then provided with a movable plunger or a diaphragm separating the remainder of the pipe from the section to be filled. By the use of this method, material having different properties and different pressures may be supplied to the drain hole, which is desirable, e.g. when the soil is in strata having different compositions or when varying pressure is needed to produce cracks of varying dimensions. An important characteristic of the present invention is the formation of the generally radially extending cracks, which positively contribute to increasing the effective area of the drain, and filling these with a material to form open cells or ducts. The number of drains may be reduced considerably, using the method in accordance with the invention, compared with the necessary number of sand drains or web-like drains, while the liquid is drained off more rapidly. As previously mentioned, the drains may also be used to increase the liquid content in the soil strata. This is necessary in the case where the ground-water level has been lowered for some reason or another, so that settlement in the ground occurs. The water may be led downwards through the multicomponent material with its open pores in the drain and out into the horizontal cracks, from whence it is effectively absorbed by the dried-out soil strata.

Claims: CLAIMS 1. Method of changing the liquid content in a soil strata comprising one or more layers with the aid of one or more liquid conductors with outlets arranged in the soil stratum, c h a r a c t e r i z e d in that each liquid conductor is partly or entirely filled with a material at a pressure such that cracks are formed in said stratum, said cracks being directed generally radially outwards in relation to the liquid conductor and are simul aneously filled with the material, whereafter liquid may be led in any direction via said cracks and said liquid conductor. 2. Method as claimed in claim 1, c h a r a c t e r i z e d in that filling takes place in stages such that a part of the liqttid conductor is made to form a closed first chamber, which is provided with said material for the formation of the cracks and their filling, whereafter a second chamber adjacent the first is closed off and filled with said material for the formation and filling of further cracks, whereafter further chambers are closed off and filled until the major part of the liquid conductor is filled with the ma e i l . 3. Method as claimed in either of the preceding claims, c h a r c t e i z e d in that the material is supplied to the liquid conductor and cracks in liquid form, subsequent to which it goes over to solid form while forming open cells or ducts. 4. Method as claimed in any one of the preceding claims, c h a r a c t e r i z e d in that the material is a multi- component material and that it is supplied to the liquid conductor in component form, and in that the components are mixed at the same time as they fill the liquid conductor as well as the cracks that are formed. 5. Apparatus for carrying out the method according to claim 1 for changing the liquid content in a soil stratum comprising one or more layers, c h a r a c t e r i z e d in that the apparatus includes at least one liquid conductor which may be driven down into the soil stratum and which is provided with slots or openings, supply means and a material supplied under pressure to the interior of the liquid con¬ ductor via the supply means, and in that the material is pressed out through the slots or openings towards the soil stratum to form longitudinal cracks in the stratum that are filled with said material. 6. Apparatus as claimed in claim 5, c h a r a c t e r i z e d in that at least one edge on each slot or opening is provided with a radial projection to form groove-like markings on the soil stratum wall formed by the liquid conductor. 7. Apparatus as claimed in claim 6, c h a r a c t e r i z e d in that the liquid conductor is provided with slots or openings in both the circum¬ ferential and longitudinal directions, such that in relation to the longitudinal axis of the conductor sub¬ stantially radially oriented cracks are formed in the soil stratum at different levels when the material is pressed out through the slots or openings in the region of the groove-like markings. δ. Apparatus as claimed in any one of claims 5-7, c h a c t e r i z e d in that the material is a mul icσmponent material, which is taken in component form through separate supply means tα the region of the slots or ODeninαs, 9. Apparatus as claimed in claim 8, c h a r a c t e r i z e d in that the material in contact with the ground water solidifies and forms ooen cells or ducts.

Inventors: MASSARSCH KARL RAINER, MASSARSCH, KARL, RAINER
Applicants: FRANKI INTERNATIONAL, MASSARSCH KARL RAINER, MASSARSCH, KARL, RAINER
Application year: 1985
Main classification: E02D3
IPC codes: E02D3