JPS61229012A - Method of consolidating and improving soft ground - Google Patents

Abstract

PURPOSE:To facilitate a construction work, by a method wherein plural holes are excavated in a soft ground at intervals, and after the holes are respectively filled with a water absorption swelling high molecular material, the inlet part of each of the holes is sealed. CONSTITUTION:Plural boring holes 12 are excavated in a soft ground 10 at intervals, and after the holes 12 are respectively filled with a granular water absorption swelling high molecular material 14, the inlet part of each of the holes 12 is sealed with a space filler 16. The water absorption swelling high molecular material 14 absorbs a moisture content contained in the soft ground 10 for gradual swelling, and a pressure F is exerted on a hole wall to consolidate the ground.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for improving the consolidation of soft ground, which improves the strength of the ground by consolidating the ground using a water-absorbing and expanding polymeric material filled in the soft ground. It is something.

[Prior art] When constructing a civil engineering building structure, it is not always possible to select a good ground, and some ground may be insufficient to directly support the structure being constructed in terms of bearing capacity and settlement. There are many cases.

An example of such ground is soft ground made of clay or organic material. In such soft ground, it is necessary to improve the ground so that it can withstand high loads by using some construction method to reduce the amount of groundwater it contains and artificially induce consolidation subsidence.

Typical examples of conventional consolidation improvement methods for soft ground include the sand pile method and T! There is the 754-1-7E method.

The sand pile construction method involves drilling a number of poling holes in the ground to be improved, filling them with sand (sand pile), then embanking the entire top of the ground to carry the load, and consolidating the ground using the loading pressure. This method also improves the ground by draining water through sand piles. In addition, the Chemi-colime construction method involves filling a hole drilled in the ground with quicklime, and causing it to absorb water and expand through the following reaction with water: CaO+H20→Ca(OH)2, which absorbs surrounding groundwater and compresses soft soil due to the pressure generated. This is a construction method that improves the ground by combining the following.

[Problems to be Solved by the Invention] In the sand pile construction method, it is necessary to apply a large loading pressure in order to consolidate the ground and discharge the groundwater contained therein. Therefore, it is necessary to carry out a large amount of embankment over the entire ground to be improved, and once the ground improvement work is completed, it is necessary to transport all or most of the used earth and sand. The transportation of such large amounts of earth and sand is
This results in huge economic and time losses.

On the other hand, in the 1-tarime construction method, the amount of water absorbed is small (stoichiometrically about 115 times the amount of quicklime used) and the amount of expansion is small. Therefore, a large number of chemico piles must be installed close to each other, and a large amount of quicklime is used, which inevitably leads to high costs. Furthermore, since quicklime is a strong alkaline agent, it may cause groundwater contamination, so it is not very desirable from the viewpoint of pollution prevention.

The purpose of the present invention is to eliminate the drawbacks of the prior art as described above, and to eliminate the need for embankment as in the sand pile method or the need to form a large number of excavated holes as in the Chemi-colime method. To provide a method for improving the consolidation of soft ground, which can be extremely easily constructed by simply filling a specified material and sealing the entrance part, and is completely free from the risk of causing pollution.

[Means for Solving the Problems] The present invention, which can achieve the above objects, utilizes the extremely large water absorption and expansion ability of water-absorbing and swelling polymer materials to water-absorb and consolidate the ground to increase its strength. This is a method to improve the consolidation of soft ground.

That is, the present invention involves drilling a plurality of holes in soft ground at appropriate intervals, filling the holes with a water-swelling polymeric material, and then sealing the entrance portion of the hole. The polymer material is configured to absorb groundwater and expand under pressure, which consolidates the ground in the direction of the hole wall, and also absorbs and removes groundwater from the ground to increase the strength of the ground.

The hole drilled into the ground here may be a normal poling hole, a trench, or the like. Various known materials can be used as water-absorbing and swelling polymer materials to be filled in the pores, but they are stable without being decomposed in the soil, and do not cause toxicity or other problems if mixed into groundwater. Materials are selected that do not cause pollution problems. This type of material may be granular or shaped. In the case of filling the polling hole, a rod-shaped material can be used, and in the case of storing it in a trench, a sheet-shaped material can be used.

[Operation] The water-absorbing and swelling polymeric material filled in the hole expands while absorbing groundwater contained in the ground, thereby compressing the ground in the direction of the hole wall. As a result, the ground is consolidated, and moisture in the ground is removed by water absorption, so the synergistic effect of these actions increases the strength of the ground.

The reason for sealing the entrance of the hole is that if it were not sealed, the expanded material would bulge out to the surface, making it impossible to apply sufficient pressure to the hole wall. The amount of deformation of the hole and the effect on the surrounding ground are determined by the volume of the hole, the material and amount of water-swellable polymer material used to fill it, and by drilling holes at appropriate intervals,
A uniform and good ground can be created over a wide area.

[Example] Hereinafter, the present invention will be explained in more detail based on the drawings. FIGS. 1 and 2 show an embodiment of the construction method of the present invention. As described above, a plurality of poling holes 12 are drilled at intervals in the soft ground 10, and the poling holes 1
After filling granular water-absorbing and swelling polymer material 14 into 2,
The entrance portion of the polling hole 12 is sealed with a filler 16 to prevent the poling hole from rising.

The water-swelling polymeric material used here may be the water-swelling polymer compound itself, or it may be a composite compounded with a material such as a soft resin or rubber, or a mixture thereof. A water-swelling polymer compound refers to a substance that absorbs water and expands from several times to 1,000 times its own weight, but does not dissolve in water. It may be of any type, such as acrylic type or acrylic type. For example, acrylic acid
Examples include, but are not limited to, vinyl alcohol copolymers, sodium acrylate copolymers, sodium acrylate/acrylamide copolymers, and starch polyacrylic acid copolymers. Further, as a material for sealing the entrance portion of the polling hole 12, cement, concrete, or the like can be used.

When the construction is carried out as shown in FIG.
It gradually expands by absorbing the moisture contained in it. The situation is shown in Figure 2. A pressure F is applied in the direction of the pore wall by the water-absorbing and swelling polymer material that expands in this manner. Water absorption amount and expansion amount per unit weight of water-absorbing and swelling polymer materials,
Since the expansion pressure generated is an order of magnitude greater than that of quicklime, soft ground is absorbed and consolidated, increasing its strength and improving the ground over a wide area.

As the water-absorbing and swelling polymeric material, for example, a material made of a composite of saponified vinyl acetate/acrylic acid ester copolymer and styrene/butadiene rubber, which expands by absorbing 50 times its own weight of water, is suitable. Water absorption capacity of this material (
= Weight after water absorption/Weight before water absorption) and the generated pressure
As shown in the figure. As is clear from the figure, a pressure of about 9 kg/d is generated when the same amount of water as its own weight is absorbed.

Consolidation of the ground is only possible when the water moves through consolidation, as the soil and water in the ground are incompressible substances. In the present invention, since there is a water-absorbing and swelling polymer material in the ground that absorbs a large amount of water, the water in the ground moves and is absorbed more quickly, and the pressure and expansion generated thereby promotes consolidation. This is a major feature of the present invention.

In the present invention, the radius of the poling hole to be drilled into soft ground, the amount of water-swelling polymer material filled inside the poling hole, the spacing between adjacent poling holes, etc. are determined based on the consolidation characteristics of the ground based on soil tests, etc. It can be determined from the physical properties of the water-swelling polymer material used, etc. The spacing between adjacent poling holes is such that the area where the compaction effect of the water-absorbing and swelling polymer material filled inside the holes is sufficiently matched.
Moreover, the conditions may be set such that the material is consolidated to a predetermined pressure or higher.

If the thickness of a water-swellable polymeric material increases in the direction in which water infiltrates, the penetration of water into the interior of the material may deteriorate and the rate of expansion may become slow. In such a case, as shown in FIG. 4, a water-permeable substance 18 such as sand is sandwiched in the water-absorbing and swelling polymeric material 14 in the form of a sandwich, thereby promoting water permeation into the interior. Just do it.

In yet another embodiment of the present invention, instead of the poling hole, a trench 20 is dug as shown in FIG. 5, and the interior thereof is filled with water-swellable polymeric material 14.

In that case, it is also possible to insert a sheet-shaped material. The basic idea is exactly the same as the case of filling the polling holes. The spacing between the trenches 20 may be narrower than the pressure at which the ground can be compacted to achieve the compacted state required by soil testing or the like.

[Effects of the Invention] The present invention is a method for improving the consolidation of soft ground constructed as described above, and since it is a method for improving the consolidation of the ground by filling it with a water-absorbing and expanding polymer material, it is different from the conventional sand pile method. In comparison, there is no need to bring in and take out embankment materials to apply loading pressure, making the work simple and economically superior.In addition, the amount of expansion is extremely large compared to the Chemi-Colime method, making it difficult to drill holes. There is no need for a small number of them, and a small one is sufficient, which has the effect of being excellent in economical efficiency.

Furthermore, since the materials used have been proven to be safe, there is no risk of causing pollution.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram showing an example of the consolidation improvement method for soft ground according to the present invention immediately after construction, Fig. 2 is an explanatory diagram showing the state after a certain period of time, and Fig. 3 is an explanatory diagram showing an example of the method for improving consolidation of soft ground according to the present invention. FIGS. 4 and 5 are explanatory diagrams showing other embodiments of the present invention, respectively, and FIGS. 4 and 5 are characteristic diagrams of Kerr absorption capacity for generated pressure of an example of a water-absorbing and swelling polymeric material suitable for use. 10... Soft ground, 12... Poling hole, 14.
...Water-absorbing and swelling polymer material, 16...Filling for sealing the entrance portion of the poling hole, IL...Water-permeable material, 20
...trench.

Claims (1)

[Claims] 1. After drilling a plurality of holes at intervals in the soft ground and filling the holes with a water-swelling polymer material, the entrance of the hole is sealed, and the water-swelling polymer material absorbs groundwater. A method for improving the consolidation of soft ground, which is characterized by increasing the strength of the ground by consolidating the ground in the direction of the hole wall by absorbing and expanding pressure.