JP2001294857A - Method for ground improving - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for ground improving capable of improving the properties of an easily fluidizable sand ground including a ground having an existing structure, at a low cost and reliably by enabling a solidification material to be filled in spaces of sand particles in the ground while penetrating homogeneously and widely. SOLUTION: In this method, solidifies the ground 4 is solidified by naturally penetrating a liquid solidification material comprising an acidic silica colloid having viscosity close to water and gelling/solidifying after a predetermined time course, from a ditch 6 formed on the surface of the ground, naturally penetrating in the ground 4 from a hollow tube 7 inserted into the ground 4, filling the liquid into the space of the sand particles and mutually bonding the sand particles to solidify the ground 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ground improvement method, and more particularly, to a method of filling a liquid solidifying material into voids of sand particles in the ground, thereby binding the sand particles to each other, thereby liquefying the sand particles. The present invention relates to a soil improvement method for improving the properties of a ground by solidifying a sandy ground which is easy to use.

[0002]

2. Description of the Related Art Conventionally, when improving the ground of a sandy ground which is liable to be liquefied, the ground is hardened by using a solidifying material such as a liquid, a slurry or a powder to improve the properties of the ground. .

[0003] When the ground is improved using such a solidified material, the solidified material is placed in the voids of the sand particles in the ground due to the viscosity of the solidified material itself and the effect of water existing in the voids of the sand particles. Because it is difficult to fill the material while it is homogeneous and widespread, it is generally necessary to inject the solidified material itself under pressure through a hollow pipe inserted into the ground, or to solidify the material with compressed air or water. Injecting has been done.

[0004]

However, even with these ground improvement methods, it is difficult to fill the solidified material uniformly and widely in the voids of the sand particles in the ground, so that the solidified material is difficult to fill. In order to improve the ground over, it is necessary to drill holes in the ground at a number of positions and inject the solidifying material through hollow pipes, which, combined with the need for dedicated construction equipment, There was a problem that construction costs increased. For the same reason, when making improvements to the ground where existing structures such as oil tanks exist,
Ground improvement could only be performed around the existing structure, and there was a problem in reliability.

The present invention has been made in view of the above-mentioned problems of the conventional ground improvement method, and has set the solidified material in the voids of sand particles in the ground.
By making it possible to fill while infiltrating homogeneously and widely, the sandy ground that is easily liquefied, including the ground where the existing structure exists, is solidified, and the properties of the ground at low cost.
It is another object of the present invention to provide a ground improvement method that can be improved with reliability.

[0006]

In order to achieve the above object, the soil improvement method of the present invention has a viscosity equivalent to that of water, and gels and solidifies after a predetermined time has elapsed.
The liquid solidifying material composed of acidic silica colloid naturally penetrates into the ground, and is filled in the voids of the sand particles in the ground, thereby bonding the sand particles to each other to solidify the sand ground. . Here, “viscosity comparable to water”
It means a viscosity not more than three times the viscosity of water.

In this ground improvement method, a liquid solidified material made of an acidic silica colloid, which has a viscosity equivalent to that of water and gels and solidifies after a predetermined period of time, naturally penetrates into the ground, By filling the sand particles in the voids to bind the sand particles together to solidify the sand ground, the solidified material penetrates uniformly and widely into the voids of the sand particles in the ground It can be filled while being made.

[0008] In this case, when the liquid solidified material naturally penetrates into the ground, the groundwater level can be lowered below the ground improvement range by draining free water.

As a result, natural penetration and filling of the sand particles in the ground of the liquid solidified material into the voids can be promoted,
Ground improvement can be performed with higher reliability.

Further, the liquid solidified material can be made to naturally penetrate into the ground through a groove formed on the ground surface, or can be made to naturally penetrate into the ground through a hollow tube inserted into the ground.

As a result, the ground can be improved in accordance with the properties of the target ground.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the ground improvement method of the present invention will be described below.

According to the soil improvement method of the present invention, a liquid solidified material comprising an acidic silica colloid, which has a viscosity approximately equal to that of water and gels and solidifies after a predetermined time has elapsed, is allowed to naturally penetrate into the ground. By filling the inside of the voids of the sand particles in the ground, the sand particles are connected to each other to solidify the sand ground.

The liquid solidifying material composed of acidic silica colloid used in this soil improvement method has a viscosity similar to that of water (generally 3.0 mPa · s (25 ° C.) or less, preferably 1.5 mPa · s (25 ° C.)).
The properties and the like are not particularly limited as long as they are made of an acidic silica colloid having mPa · s (25 ° C. or less), but in terms of adjusting the gel time to 1 hour to 14 days, Preferably, pH 1.0 to 6.5 and S
An iO ₂ concentration of 2 to 6% by weight is preferred. pH and S
Since the gelation time becomes shorter as the iO ₂ concentration increases, the gelation time can be adjusted to a desired gelation time by appropriately combining these conditions. When the storage temperature or the temperature at the time of use exceeds 40 ° C., the stability of the liquid solidification material deteriorates or rapid gelation occurs. C. or less is preferred. The acidic silica colloid giving such a liquid solidified material can be obtained by a conventionally known method. As an example, if necessary, an acid (preferably an acid (preferably (Inorganic acid) to adjust the pH. When the SiO ₂ concentration in the obtained acidic silica colloid exceeds the above, it may be diluted with water. The particle size of the colloidal particles (silica particles) in the acidic silica colloid is not particularly limited as long as it is stable as a colloid, but may be generally 3 to 6 nm, preferably 4 to 6 nm.

Since the liquid solidified material composed of the acidic silica colloid has low viscosity, the liquid solidified material naturally penetrates into the ground, and is filled into the voids of the sand particles in the ground, whereby the sand particles are reduced. Because they are connected to each other to solidify the sand ground, the solidified material is inserted into the voids of the sand particles in the ground,
In addition to the feature that it can be filled while penetrating uniformly and widely, as shown in FIG. 1, it has gelled compared to water glass that has been conventionally used as a liquid solidifying material in ground improvement methods and the like. Since the leaching rate of silica at that time is extremely low, the solidification performance of the ground whose ground has been improved can be stably maintained over a long period of time.

When the liquid solidifying material comprising the acidic silica colloid has, for example, a SiO ₂ concentration of 2% by weight, a sand gel uniaxial compressive strength using Toyoura standard sand is 0.1%.
It can provide a strength of about 1 MN / m ² .

When the liquid solidified material naturally penetrates into the ground, deep water and well points are used in combination to drain free water and lower the groundwater level to below the ground improvement range. Natural penetration and filling of the sand particles in the ground of the liquid solidified material into the voids can be promoted, and ground improvement can be performed with higher reliability.

When the ground improvement method is performed, it is desirable to surround the ground to be improved with a water impervious wall so that the liquid solidified material does not leak out of the ground to be improved.

Next, when the ground improvement method of the present invention is applied to an existing structure, specifically, a sand ground 3 having an oil tank 1 as an existing structure, as a measure for preventing liquefaction of the sand ground. An example will be described.

First, a water impervious wall 2 is constructed around the ground 4 to be improved of the sand ground 3 where the oil tank 1 is present by a known method, and a liquid solidified material made of an acidic silica colloid is used as the ground 4 to be improved. Avoid leakage outside. Next, before or while allowing the liquid solidified material to naturally penetrate into the ground 4 to be improved, the free water is drained from the deep well 5 provided at an appropriate position on the ground 4 to be improved to lower the groundwater level. In order to promote the natural permeation and filling of the sand particles of the liquid solidification material into the voids by reducing the voids of the sand particles in the ground 4 to be improved to an unsaturated state. I do. In this case, in causing the liquid solidified material to naturally penetrate into the ground 4 to be improved,
Depending on the properties of the ground, the liquid solidifying material is allowed to naturally penetrate into the ground 4 through the grooves 6 formed on the ground surface,
The hollow pipe 7 inserted into the ground 4 allows the soil to naturally penetrate into the ground 4, or these can be used in combination, whereby the ground can be appropriately and reliably improved with higher reliability. Become. Then, the liquid solidified material that has uniformly and widely penetrated into the ground 4 to be improved is filled in the voids of the sand particles in the ground 4, gels after a predetermined time has elapsed, and the sand particles are mutually bonded. , Oil tank 1
The solidified ground 4 including the lower part of the ground is surely solidified, whereby the liquefaction of the sand ground can be prevented.

In FIG. 4, assuming a 2,000 kiloliter oil tank, under the conditions of FIG. 3 and Table 1, as a liquid solidifying material composed of acidic silica colloid, the SiO ₂ concentration is 4.0% by weight, The coefficient η is 1.2 mPa · s (25
C) and the results of analyzing the state of penetration of the solidified material into the ground when the liquid solidified material was used for a gelation time of 5 days.
In FIGS. 3 and 4, one cell indicates 1 m,
In FIG. 4, hatching is applied to a portion where the liquid solidifying material has penetrated.

[0022]

[Table 1]

As is apparent from FIG. 4, according to the ground improvement method of the present invention, depending on the properties of the ground 4 to be improved, etc.
The liquid solidified material composed of an acidic silica colloid is allowed to naturally penetrate into the ground 4 through the groove 6 formed on the ground surface, or is naturally penetrated into the ground 4 from the hollow tube 7 inserted into the ground 4. Or by using these together
It has been found that the ground improvement can be appropriately performed with high reliability only by allowing the liquid solidifying material to naturally penetrate.

[0024]

According to the soil improvement method of the present invention, a liquid solidified material comprising an acidic silica colloid, which has a viscosity approximately equal to that of water and gels and solidifies after a predetermined time has elapsed, is placed in the ground. By infiltrating naturally and filling the voids of the sand particles in the ground, the sand particles are mutually bonded to solidify the sand ground, so the solidified material is placed in the voids of the sand particles in the ground. It can be filled while being infiltrated homogeneously and over a wide area.For example, even in the ground where the existing structure exists, the entire liquefiable sand ground including the lower part of the existing structure is surely solidified, Properties can be improved at low cost and with reliability.

Further, when the liquid solidified material naturally penetrates into the ground, free water is drained to lower the groundwater level below the ground improvement range, whereby the sand particles in the ground of the liquid solidified material are removed. Can be spontaneously permeated and filled into the voids, and the ground can be improved with higher reliability.

Further, according to the properties of the target ground, etc.,
The liquid solidification material can be allowed to naturally penetrate into the ground through grooves formed on the ground surface, or can be made to naturally penetrate into the ground through hollow pipes inserted into the ground. Can be appropriately performed with higher reliability.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing the leaching rate of silica from a gelled product.

FIG. 2 is an explanatory diagram showing a relationship between a liquid solidifying material and a gelation time.

FIG. 3 is an explanatory view showing an example in which the ground improvement method of the present invention is applied to the ground where an oil tank exists.

FIG. 4 is an analysis diagram showing a state of penetration of a liquid solidified material into the ground.

[Explanation of symbols]

 Reference Signs List 1 oil tank (existing structure) 2 impermeable wall 3 sand ground 4 ground to be improved 5 deep well 6 groove 7 hollow pipe

Claims (4)

[Claims] 1. A liquid solidifying material comprising an acidic silica colloid, which has a viscosity equivalent to that of water and gels and solidifies after a lapse of a predetermined time, naturally penetrates the ground,
A ground improvement method characterized in that sand particles are bonded to each other to solidify the sand ground by filling the voids of the sand particles in the ground. 2. The soil improvement method according to claim 1, wherein, when the liquid solidified material naturally penetrates into the ground, the groundwater level is reduced to a level below the soil improvement range by draining free water. 3. The ground improvement method according to claim 1, wherein the liquid solidified material is allowed to naturally penetrate into the ground through a groove formed on the ground surface. 4. The soil improvement method according to claim 1, wherein the liquid solidified material naturally penetrates into the ground from a hollow tube inserted into the ground.