JP4555977B2 - Ground improvement method - Google Patents

Description

  The present invention relates to a ground improvement method by chemical injection mainly for the purpose of preventing liquefaction of sandy ground.

  Conventionally, as a method of preventing liquefaction of sandy ground in the event of an earthquake, a vertically permeable sand pile is formed in the ground at regular intervals, and sand soil pore water released by an earthquake is passed through the sand pile. Using a sand compaction pile method that prevents liquefaction of the ground by discharging, a ground agitator equipped with a stirring blade on the outer periphery of the rotating shaft and capable of discharging a solidified material such as cement milk from the stirring blade, The ground agitator is inserted into the ground while being rotated vertically, and the solidified material is mixed into the ground by injecting the solidified material while stirring the ground. There is a ground improvement method (a method called a deep mixing method) using a mechanical agitation method to form a layer.

  When these methods are applied to the ground under existing structures, existing buildings often have to be removed. There is a problem that is large. In addition, the equipment used and the solidifying agent require a large amount of money, and there are significant problems for economic reasons.

  In order to solve these problems, in recent years, a solution-type chemical solution injection method (also referred to as an osmotic solidification treatment method) has been developed in which a solid chemical solution is infiltrated into a soil gap to increase the strength of the ground. This method is a method of injecting and solidifying a silica-based solution-type chemical into the ground, and a method of solidifying the ground by injecting the chemical through a strainer inserted into the ground.

  In this chemical injection method, drilling machines can be used to drill not only vertically but also in the inclined direction, the horizontal direction, and the direction in which they are interwoven. There is an advantage that construction can be carried out without stopping the sharing of existing facilities even for ground such as under complicated oil storage facilities (for example, Non-Patent Document 1).

  In addition, in this chemical solution injection method, a method for solidifying the ground more uniformly (for example, Patent Document 1) and a method for performing necessary ground improvement by reducing the amount of chemical solution to be used (for example, Patent Document 2). Has been developed.

As shown in FIG. 8, the method of reducing the amount of the chemical solution used disclosed in Patent Document 2 uses the strainer 2 from each of a plurality of chemical solution injection points a set at predetermined intervals in the ground improvement planned ground 1. By injecting the chemical solution, the chemical solution is infiltrated in a spherical shape around each injection point to form a large number of spherical solid bodies 3, 3... Is adjusted to bring the solidified solid bodies 3 and 3 into contact with each other to form a stable solidified ground. 9 (a) to 9 (d) show the improvement rate due to the difference in the injection amount, (a) is when the improvement rate is 100%, (b) is when the improvement rate is 70%, (c ) Shows the case where the improvement rate is 50%, and (d) shows the case where the improvement rate is 30%. When a chemical solution of 50% or more relative to the amount of void between soils when groundwater in the ground is removed is injected, the spherical solidified bodies 3 and 3 come into contact with each other as shown in FIG. The ground is formed.
Issued in March 1999, “Foundation Works Vol. 27, 1999-3”, pages 27-29 “Liquefaction countermeasures directly under existing structures” Kentaro Hayashi Hiroyuki Yamazaki Japanese Patent No. 3193950 Japanese Patent Laid-Open No. 11-131467

  In the method for reducing the amount of chemical used in the conventional chemical injection method described above, the amount of chemical used is reduced by leaving an unimproved portion between the spherical solidified bodies. When the amount is small, the unimproved portion remaining in the ground is in a continuous state. For this reason, as shown in FIG. 10, the excess soil pore water pressure generated by liquefaction occurring outside the improved range at the time of the earthquake is improved. There is a problem that the unmodified portion between the spherical solidified bodies is liquefied.

  In view of such problems, the present invention has been made for the purpose of providing a ground improvement method by injecting a chemical solution that can more effectively prevent liquefaction even when the amount of the chemical solution used is less than the space between soils.

In order to solve the above-mentioned conventional problems and achieve the intended object, the features of the invention described in claim 1 are many in the sandy ground to be improved at intervals in the vertical and horizontal directions. The chemical solution injects into the ground around each chemical injection position by injecting the solution type chemical solution for solidification into each chemical injection position and penetrating it into the space between soils in the ground. And forming a solidified body in which the surrounding permeation liquid permeation areas are continuous by forming the permeation areas of the medicinal liquid permeation areas that are formed outside the adjacent chemical liquid injection positions. In the ground improvement method by chemical injection,
After injecting a predetermined amount of the chemical solution for solidification at each chemical solution injection position, water for injecting the chemical solution in the injected ground formed previously is injected from the chemical solution injection position to to each chemical penetration region by infiltrating into the ground to form a water-permeable zone solidified body and which is sequencing outer peripheral portion of each liquid chemical penetration range has been extended by forming the water penetration zone continuous with each other There is to do.

Invention features of claim 2, in addition to the configuration of claim 1, wherein the injection of water into the drug solution penetrate the region, the liquid chemical to the state does not remain liquid medicine unimplanted portion between chemical penetration zone adjacent to each other The purpose is to expand the outer periphery of the infiltration area .

The invention feature of claim 3 is that, in addition to the configuration of claim 1 or 2, the injection work hole is drilled by a drilling machine in the ground to be improved, and a strainer is inserted into the injection work hole. It is to inject | pour in order the chemical | medical solution and the water for chemical | medical solution osmosis | permeation area expansion using the formed same injection nozzle.

In addition to the structure of the first, second, or third aspect, the invention feature of the fourth aspect is characterized in that packers that are expanded by water injection are installed at two locations above and below the position of the liquid injection nozzle of the strainer. After inserting the strainer into the hole to a predetermined depth, the packer is expanded to fill the gap between the strainer and the inner surface of the injection hole formed in the ground above and below the liquid injection nozzle in a watertight state. The purpose is to inject the chemical solution and water for expanding the chemical solution permeation area.

  The invention feature of claim 5 is that, in addition to the structure of claims 1 to 3 or 4 described above, a silica-based aqueous solution type chemical solution is used as the chemical solution for solidifying the ground.

In the ground improvement method by chemical solution injection according to the present invention, a number of chemical solution injection positions are set in the ground to be improved as in claim 1 at intervals in the vertical and horizontal directions, and each of these chemical solution injection positions is set. By injecting the chemical solution for solidification into the soil, the chemical solution penetrates into the inter-soil gap in the ground, and the outer peripheral part of the chemical solution infiltration area formed at the adjacent chemical solution injection position is continuous in the ground. When forming the solidified body, after injecting a predetermined amount of the chemical solution at each of the chemical solution injection positions, a liquid for extending the chemical solution infiltration area that spreads the chemical solution infiltration area into the ground in the chemical solution infiltration area from each of the chemical solution injection positions. By injecting and expanding each chemical solution permeation area, the peripheral part of each chemical solution permeation area is made continuous to form a continuous solidified body. Filled Because the is the shell-like integral with adjacent ones being expanded spherical amount of expensive chemical solution decreases. In particular, since water is used for expansion of the chemical solution permeation area, the material used is inexpensive and the cost is further reduced.

In addition, as described in claim 2, by injecting the liquid for expanding the chemical solution infiltration area, the chemical solution infiltration area is expanded to a state where no chemical solution injecting portion remains between the adjacent chemical solution infiltration areas, thereby improving the ground. Within the range, the whole was solidified by the chemical solution, and the expansion liquid infiltration area was scattered in the ground independently with a certain interval, and was pressurized by free water outside the ground improvement range at the time of earthquake However, this does not flow into the improved portion, and liquefaction is more completely prevented.

  Furthermore, as in claim 3, an injection work hole is drilled in the ground to be improved by a drilling machine, a strainer is inserted into the injection work hole, and the same liquid injection nozzle formed in the strainer is used to make a chemical solution. And by inject | pouring the liquid for chemical | medical solution penetration area | region expansion in order, a chemical | medical solution and the liquid for chemical | medical solution penetration area | region expansion are inject | poured efficiently.

Furthermore, after the packer which expand | swells by water injection is installed in the upper and lower two places which pinch | interpose the liquid injection nozzle position of a strainer like Claim 4, after inserting a strainer into the injection | pouring operation hole to predetermined depth, the said packer By injecting the chemical solution and the liquid for expanding the chemical solution penetration region in a state where the gap between the strainer and the inner surface of the injection work hole opened in the ground is filled in a watertight state above and below the liquid injection nozzle, The injection surface with respect to the ground can be increased by widening the space between both packers, and the entire circumference of the strainer can be injected into the ground, resulting in high injection efficiency .

  Further, as described in claim 5, by using a silica-based aqueous solution as the chemical for solidifying the ground, a highly stable solidified ground can be formed.

  Next, embodiments of the present invention will be described based on the examples shown in FIGS. FIG. 1 shows a state of liquid injection using a strainer. In FIG. 1, 10 is a ground to be improved, 11 is an injection work hole preceding the ground surface by a drilling machine, and 12 is a strainer inserted into the injection work hole. , 13 is a pressurized liquid feeding device that pumps the injected liquid to the strainer 12. In the strainer 12, an injection liquid flow path 14 is formed in the central portion, and a liquid to be injected is supplied from the pressurized liquid feeding device 13 from the upper end thereof.

  The strainer 12 is provided with a liquid injection nozzle 15 communicating with the injection liquid flow path 14 at a predetermined position on the outer periphery, and packers 16 and 16 are provided at upper and lower positions sandwiching the liquid injection nozzle 15. The packers 16 and 16 expand by injecting a liquid such as water into the inside thereof, and close the gap between the outer periphery of the strainer 12 and the inner peripheral surface of the injection work hole 11 in a liquid-tight state. After the strainer 12 is inserted so that the position becomes a predetermined injection position height, the packers 16 and 16 are filled with water and expanded, and the strainer outer peripheral gap above and below the nozzle is closed. Inject liquid. As a result, the injected liquid permeates radially from the entire inner peripheral surface of the injection work hole between the packers 16 and 16 into the ground 10 around the injection position a, and a spherical liquid infiltration region M is formed. Is done.

  Similarly, as shown in FIG. 2, a large number of injection work holes 11, 11... A liquid injection operation is performed for each of the injection operation holes 11, 11.

  Further, as shown in FIG. 3, the injection position a is set at a predetermined interval in each injection work hole 11, and liquid injection work is sequentially performed at regular intervals over the entire depth of the ground to be improved 10. As shown in the schematic diagram shown in FIG. 4, the liquid permeation areas M, M... Are formed at substantially equal intervals in the upper, lower, left, and right directions so that their periphery is continuous with adjacent ones.

At each injection position a, first, a predetermined amount of a solution-type chemical solution for ground solidification (hereinafter simply referred to as a chemical solution) is injected. As a result, as shown in FIG. 5A, a chemical solution permeation region M1 in which the chemical solution penetrates in a spherical shape with the injection position a as the center is formed in the ground. Next, the same strainer 12 is used to inject a solution for expanding a chemical solution permeation area using water (hereinafter simply referred to as an expanding solution). As a result, as shown in FIG. 5 (b), the expansion liquid infiltration area W is formed around the injection position a, and the expansion liquid moves the chemical liquid radially outward in the ground, so that the chemical liquid infiltration area M1. Is formed into a spherical shell-shaped chemical solution permeation region M2 that is expanded in the radial direction .

In this way, a spherical shell-shaped medicinal solution permeation area M2 having an expansion liquid permeation area W at the center is formed for each injection position a, a..., And adjacent medicinal liquid penetration areas M2 are continuous with each other. Then, the chemical solution and the expansion solution are sequentially injected. In this way, by injecting the chemical solution over the entire area of the planned improved ground, an improved ground is formed in which the chemical solution infiltration regions M2, M2,... The

  By adjusting the injection amount of the chemical liquid and the expansion liquid at each injection position a, as shown in FIG. 6, the non-permeation areas S, S... Surrounded by the adjacent chemical liquid infiltration areas M2, M2,. ..., the shape where each non-penetrated area communicates with each other, or the shape where the medicinal solution and expansion liquid penetrated the entire ground to be improved so that no non-penetrated area remains. Select according to need.

  In the case where the adjacent chemical solution permeation areas M2, M2... Are continuously connected with the non-permeation areas S, S. The total amount may be 50% of the amount of voids between soils. In this case, when the amount ratio between the amount of the chemical solution and the expansion solution is, for example, about 2: 1, the amount of the chemical solution used is 2 in the conventional example described above. / 3 can be reduced.

  In addition, the improved ground in the case where the chemical solution penetration areas M2, M2,... Are solidified so that no non-penetration area remains is the only solution liquid penetration area W for expansion. Compared to the conventional technology that penetrates the chemical solution throughout the entire area, it is dispersed in the improved ground in a state separated into a single state by M2 ....... The expansion liquid infiltration area that can save chemicals and is dispersed is completely isolated from the surroundings, so it does not flow out in the event of an earthquake, and the excess soil pore water pressure around the improved ground is improved. Even if it acts on the ground, liquefaction does not occur.

In addition, a silica-based solution type chemical solution can be used for the above-described chemical solution, and Na2O / nSiO2 or K2O / nSiO2 that is a raw material for manufacturing a so-called “water glass” and an inorganic salt, an organic salt, or a metal oxide that is a curing agent thereof. , Metal hydroxides, inorganic acids, organic acids, acidic salts, basic salts and the like, as well as silica fine particles and curing agents such as Permalock NS (trademark) manufactured by Asahi Denka Kogyo Co., Ltd. Broadly divided into those prepared in combination. Both are slightly different in the constituent materials of the chemical solution and the solidification principle, but the principle of the present invention can be applied to either case.

Moreover, although water is used for the expansion liquid, this water may be water whose viscosity is adjusted so that it is difficult to mix with the chemical liquid, for example.

It is a longitudinal cross-sectional view which shows an example of the chemical | medical solution injection | pouring state in the ground improvement construction method which concerns on this invention. It is a top view which shows arrangement | positioning of the injection | pouring work hole of the ground improvement construction method in this invention. It is a longitudinal cross-sectional view same as the above. It is a schematic diagram which shows an example of the chemical | medical solution injection | pouring state of the ground improvement construction method in this invention. It is a longitudinal cross-sectional view which shows the osmosis | permeation state to the ground of the chemical | medical solution and expansion liquid in the method of this invention. It is a longitudinal cross-sectional view which shows an example of the improved ground in this invention method. It is a longitudinal cross-sectional view which shows the other example. It is a longitudinal cross-sectional view which shows the chemical | medical solution injection | pouring state in a conventional construction method. It is a schematic diagram which shows the example at the time of changing the improvement rate same as the above. It is explanatory drawing for showing the excess soil pore water pressure from the circumference at the time of the earthquake in the construction method same as the above.

10 Ground Improvement Planned Ground 11 Injection Work Hole 12 Strainer 13 Pressurized Liquid Feeding Device 14 Injection Liquid Channel 15 Injection Liquid 16 Packer a Injection Position M Liquid Infiltration Area M1 M2 Chemical Infiltration Area W Expansion Liquid Infiltration Area

Claims (5)

A large number of chemical solution injection positions are set in the sandy ground to be improved at intervals in the vertical direction and the horizontal direction, and a solution type chemical solution for solidification is injected into each of the chemical solution injection positions. By infiltrating into the gap, a chemical solution infiltration area where the chemical solution penetrates into the ground around each chemical injection position is formed, and the outer peripheral parts of the chemical solution penetration area formed outside the adjacent chemical injection positions are continuous with each other In the ground improvement method by injecting the chemical solution in which the solidified body in which each of the peripheral solution infiltrating areas is continuously formed is formed,
After injecting a predetermined amount of the chemical solution for solidification at each chemical solution injection position, water for injecting the chemical solution in the injected ground formed previously is injected from the chemical solution injection position to to each chemical penetration region by infiltrating into the ground to form a water-permeable zone solidified body and which is sequencing outer peripheral portion of each liquid chemical penetration range has been extended by forming the water penetration zone continuous with each other Ground improvement method by chemical injection, which is characterized by 2. The outer peripheral portion of each chemical solution permeation region is expanded to a state where no chemical solution non-injection portion remains between the chemical solution penetration regions adjacent to each other by injection of water into each chemical solution penetration region . Ground improvement by chemical injection. Drilling an injection work hole in the ground to be improved by a drilling machine, inserting a strainer into the injection work hole, and using the same injection nozzle formed in the strainer, the chemical solution and the water for expanding the chemical solution infiltration area are supplied . The ground improvement construction method by chemical | medical solution injection | pouring of Claim 1 or 2 inject | poured in order. Packers that expand by water injection are installed in two places above and below the strainer injection nozzle position, and after inserting the strainer into the injection work hole to a predetermined depth, the packer is expanded and the injection nozzle The said chemical | medical solution and the water for chemical | medical solution penetration area expansion are inject | poured in the state which filled the clearance gap between this strainer and the inner surface of the injection | pouring operation hole opened in the ground in the watertight state in the upper and lower sides of Claim 1, 2 or 3 Ground improvement by chemical injection.   The ground improvement construction method by chemical | medical solution injection | pouring of Claims 1-3 or 4 which uses a silica type aqueous solution type chemical | medical solution as a solution type chemical | medical solution for ground solidification.

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