JP2014092020A - Grout injection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a grout injection method capable of surely gelling injected grout and preventing the appearance of a future water channel in the case of injecting a slow-setting grout (chemical liquid) formed mainly of acid silica sol, with a sandy soil layer containing a cohesive soil layer, a gravel layer, a shell layer, etc. as a target.SOLUTION: In a grout injection method for injecting a slow-setting grout containing acid silica sol into a subgrade 1, the slow-setting grout containing acid silica sol is injected into the subgrade 1 after water containing salt is injected into the subgrade 1 in advance.

Description

  The present invention relates to a grout injection method in which a solution-type slow-growing grout containing an acidic silica sol is injected into the ground and neutralized for the purpose of water stopping and strengthening of the soft ground. .

  Conventionally, acidic silica sol grout, which is stabilized by adding acid such as dilute sulfuric acid to water glass to make it in an acidic state at the site of grout placement, has improved urban ground as a solution-type grout with excellent permeability. It is used as a countermeasure against liquefaction in coastal areas (for example, see Patent Documents 1 and 2).

  When the acidic silica sol is used as a slow-growing grout material, as shown in FIG. 3, the acidic silica sol permeated into the sandy ground through the injection hole without adding a curing accelerator to the chemical solution, It is expected to gel by reacting with alkali ions such as Na and Ca ions present on the surface of sand particles. This effect is obtained because the acidic silica sol uniformly permeates into the skeleton structure of the sand, thereby sufficiently contacting the sand particles.

  However, when injected into the viscous ground, unlike the infiltration injection in the sandy ground as described above, as shown in FIG. There is a concern that the contact area with the surface of the cohesive soil is not sufficient, and the alkali ions on the surface of the cohesive soil and the acidic silica sol do not sufficiently react and do not gel.

  Also, in the case of injection into a gravel layer or shell layer having a large particle size, as shown in FIG. 5, when the gravel or shell is sandwiched thinly, these sandwich layers are injected. Since it is difficult to exclude from the target, it will be improved with the sandy soil layer. However, since gravel and shells have a large particle size and a small specific surface area, the contact area between the injected acidic silica sol and gravel and shells may be small and may not be sufficiently gelled. If the acidic silica sol injected into the sandwich layer does not gel and remains in an unconsolidated state, there is a high possibility that the injection site becomes a water channel and a sufficient water stop effect cannot be obtained. Moreover, unconsolidated acidic silica sol becomes a weak point in strength during excavation, and there is a high possibility that the excavated surface will be destroyed.

JP 2012-112157 A Japanese Patent No. 5017620

  The present invention has been made in view of the above, and is intended for a sandy soil layer ground where a viscous soil layer, a gravel layer, a shell layer, etc. are present, and a slow-grouting grout (based on acidic silica sol ( An object of the present invention is to provide a method for injecting grout that can reliably cause gelation of the injected grout and prevent future water channels and weak points in strength.

  In order to solve the above-described problems and achieve the object, a grout injection method according to the present invention is a grout injection method for injecting a slow-growing grout containing an acidic silica sol into the ground, and water containing salt is added in advance. After injecting into the ground, a slow-growing grout containing the acidic silica sol is injected into the ground.

  Further, according to another grout injection method according to the present invention, in the above-described invention, after grasping the hydraulic characteristics of the ground by injecting salt-containing water into the ground in advance, the grasped hydraulic of the ground is obtained. According to characteristics, a slow-growing grout containing the acidic silica sol is injected into the ground.

  According to another grout injection method according to the present invention, in the above-described invention, the ground includes a sandy soil layer including at least one of a viscous soil layer, a gravel layer, and a shell layer.

  According to the present invention, there is provided a grouting method for injecting a slow-growing grout containing an acidic silica sol into the ground, wherein water containing a salt content is previously injected into the ground and then the slow-growing grout containing the acidic silica sol. Is injected into the ground, so that salt (alkaline ions such as Na and Ca ions) is supplied into the target ground prior to the grouting.

  The acidic silica sol injected into the ground after injecting water containing salt can be surely gelled by reacting with the salt (alkali ions such as Na and Ca ions) supplied into the ground. . Therefore, in the case of injecting slow-grouting grout (chemical solution) mainly composed of acidic silica sol to sandy soil layer ground where viscous soil layer, gravel layer, shell layer, etc. exist, There exists an effect that generation | occurrence | production can be prevented.

FIG. 1 is a diagram of step 1 showing an embodiment of a grout injection method according to the present invention. FIG. 2 is a diagram of step 2 showing an embodiment of the grout injection method according to the present invention. FIG. 3 is a conceptual diagram of acidic silica sol permeation injection in a conventional sand ground. FIG. 4 is an explanatory diagram of a layer (viscous soil layer) existing in a sandy soil layer in which there is a concern about insufficient gelation of a conventional acidic silica sol. FIG. 5 is an explanatory diagram of layers (gravel layer, shell layer) existing in a sandy soil layer where there is a concern that the conventional acidic silica sol is insufficiently gelled.

  Embodiments of a grouting method according to the present invention will be described below in detail with reference to the drawings. In the present invention, there is a viscous soil layer having a certain thickness in the sandy soil layer, and when the grout is injected while splitting, the gravel layer and the shell layer are thinly interposed in the sand layer, and the grout It is assumed that two types of injections are applied. In the case where a cohesive soil layer is present, a case of alternating layers of sand and clay is also assumed. Note that the present invention is not limited to the embodiments.

  A grouting method according to the present invention is a grouting method for injecting a solution-type slow-growing grout containing acidic silica sol (hereinafter sometimes referred to as acidic silica sol grouting) into the ground, and containing salt-containing water. It has the process 1 which inject | pours in a ground previously, and the process 2 which inject | pours an acidic silica sol grout into a ground after the process 1. FIG.

FIG. 1 illustrates the situation in step 1 of the present embodiment, and FIG. 2 illustrates the situation in step 2.
As shown in FIG. 1, in a sandy ground 1 (sandy soil layer ground) as a target ground into which acidic silica sol grout is injected, a substantially horizontal layered viscous soil layer 2 and the like exist. Here, the viscous soil layer 2 or the like is configured to correspond to a stratum composed of at least one of a viscous soil layer, a gravel layer, a shell layer, or a combination thereof.

  In addition, a small-diameter injection hole 3 is drilled in advance in the sandy ground 1 from the ground toward the inside of the sandy ground 1. A pipe (not shown) for feeding the acidic silica sol grout and salt water in the present embodiment is inserted into the injection hole 3. In addition, although the injection hole 3 in this Embodiment has shown about the case of the structure extended in the substantially perpendicular direction from the ground surface, and penetrated the viscous soil layer 2 etc. up and down, it does not restrict to this. For example, it is possible to adopt a structure extending from the sandy ground 1 in the lateral direction or the oblique direction.

  First, in step 1 of the present embodiment, prior to grouting, salt water (water containing salt) is separated by a packer 4 in the sandy ground 1 through a pipe (not shown) passed through the injection hole 3. It inject | pours into the injection | pouring object area 5 made. In this case, salt water is also injected into the viscous soil layer 2 and the like existing in the sandy ground 1. Here, when the cohesive soil layer 2 is cohesive soil, salt adheres to the split part, and when the cohesive soil layer 2 is a gravel layer, shell layer, etc., the salt adheres to the entire layer. By doing so, salt (alkaline ions such as Na and Ca ions) is supplied into the target ground prior to the grouting.

  Next, as shown in step 2 of FIG. 2, acidic silica sol grout is injected into the injection target section 5 divided by the packer 4 in the sandy ground 1 through a pipe (not shown) passed through the same injection hole 3. To do. Here, the acidic silica sol grout is injected also into the viscous soil layer 2 and the like existing in the sandy ground 1 by the injection route similar to the step 1. The injected acidic silica sol grout reacts with the salt (alkali ions such as Na and Ca ions) supplied in the sandy ground 1 and the cohesive soil layer 2 in the step 1. Here, when the cohesive soil layer 2 is a cohesive soil, the salt content attached to the split part reacts with the acidic silica sol, and when the cohesive soil layer 2 is a gravel layer, a shell layer, etc., the entire layer The salt adhering to the surface reacts with the acidic silica sol. By doing so, the acidic silica sol grout can be reliably gelled. Thereby, generation | occurrence | production of the future water path in the cohesive soil layer 2 etc. can be suppressed.

  In other words, in the conventional grouting method, the contact area between the injected acidic silica sol grouting and the constituent particles such as the viscous soil layer, gravel layer, and shell layer is small and there is a possibility that the gel does not sufficiently gel. Furthermore, if the acidic silica sol injected into such a layer does not gel and remains in an unconsolidated state, the injection location may become a water drainage and a sufficient water-stopping effect may not be obtained, or it may be a weakness in strength. was there. However, according to the grout injection method of the present embodiment, the acidic silica sol grout injected in step 2 is supplied into the viscous soil layer 2 (viscous soil layer, gravel layer, shell layer, etc.) in step 1. By reacting with the salt content (alkaline ions such as Na and Ca ions), this can be gelled reliably.

  Therefore, according to the present invention, in the case of injecting a slow-growing grout mainly composed of acidic silica sol to sandy soil layer ground where viscous soil layer, gravel layer, shell layer, etc. are present, The generation of water can be prevented.

  In the above embodiment, the case where salt water is simply used as the water containing salt in the present invention has been described as an example. However, the present invention is not limited to this. For example, sea water or spring water containing salt may be used. I do not care.

  Further, in the above embodiment, as equipment for injecting acidic silica sol grout and salt water into the ground, a structure similar to the equipment in the conventional grout injection method, for example, an acidic silica sol grout tank provided on the ground part, It can be composed of fresh water or salt water tank, salt storage tank, injection pipe, pressure gauge, flow meter, pump and the like. In this configuration, equipment for adjusting the amount of salt in the salt water to be injected may be provided.

  Moreover, in said embodiment, the water pushing test before acidic silica sol grout injection | pouring operation was performed by inject | pouring salt water into the sandy ground 1, and the hydraulic characteristic which this sandy ground 1 has was grasped | ascertained. Thereafter, grout design may be performed according to the grasped hydraulic characteristics of the sand ground 1, and the acidic silica sol grout may be injected into the sand ground 1 based on the grout design.

  The water push test before the acidic silica sol grout injection operation is performed, for example, for the water permeability test for the grout plan such as the Lugion test, and for the evaluation of the ground for the grout design in the subsequent acidic silica sol grout injection operation. In the test, for example, it is possible to set the salt water injection pressure state at several stages at the time of pressure increase and decrease, measure the injection amount when stabilized at each pressure, and obtain the Luzione value and the limit pressure. Here, based on the result of this water pushing test, the suitable injection speed and maximum injection pressure of the acidic silica sol grout are determined. The acidic silica sol grout may be injected by a plurality of grout injection operations such as primary injection and secondary injection each having different specifications.

  In this way, for example, when a pre-boring survey is conducted, it is expected that a viscous soil layer, gravel layer, shell layer, etc. exist in the sandy ground that is the target of chemical injection. Prior to the grouting, the water injection test by injecting salt water as described above is carried out to supply salt (alkaline ions such as Na and Ca ions) into the target ground, while the hydraulic characteristics of the target ground through the water injection test. To figure out. A grout design for the subsequent process is performed based on the hydraulic characteristics, and an acidic silica sol grout is injected into the sandy ground based on the grout design. In this way, the acidic silica sol injected with an appropriate grout design after the salt water injection test reacts with the salt (alkaline ions such as Na and Ca ions) supplied to the ground. It is possible to make it gel, and it is possible to prevent the generation of future water channels and weak parts on strength.

  As described above, according to the present invention, there is provided a grouting method for injecting a slow-growing grout containing an acidic silica sol into the ground, wherein the acidic silica sol is previously injected into the ground with salt-containing water. Is injected into the ground, so that salt (alkaline ions such as Na and Ca ions) is supplied into the target ground prior to the injection of the grout.

  The acidic silica sol injected into the ground after injecting water containing salt can be surely gelled by reacting with the salt (alkali ions such as Na and Ca ions) supplied into the ground. . Therefore, in the case of sandy soil layer ground where viscous soil layer, gravel layer, shell layer, etc. are present, when injecting loose-grouting grits composed mainly of acidic silica sol, Generation of weak parts can be prevented.

  As described above, the grout injecting method according to the present invention injects solution-type slow-growing grout containing acidic silica sol into the ground and neutralizes it for the purpose of water stopping and ground strengthening of the soft ground. This method is useful for the grout injection method, especially for sandy soil layers where viscous soil layers, gravel layers, shell layers, etc. are present, and injecting slow-grouting grouts mainly composed of acidic silica sol. In this case, it is suitable for preventing the occurrence of future water paths and weak parts on strength.

1 Sandy ground (ground)
2 Cohesive soil layer, etc. 3 Injection hole 4 Packer 5 Injection target section

Claims (3)

A grout injection method for injecting a slow setting grout containing an acidic silica sol into the ground,
A method for injecting grout, wherein water containing salt is injected into the ground in advance, and then a slow-growing grout containing the acidic silica sol is injected into the ground.   After grasping the hydraulic characteristics of the ground by injecting salt-containing water into the ground beforehand, a slow-growing grout containing the acidic silica sol is added to the ground according to the grasped hydraulic characteristics of the ground. The grouting method according to claim 1, wherein the grouting method is performed.   The grouting method according to claim 1 or 2, wherein the ground includes a sandy soil layer including at least one of a viscous soil layer, a gravel layer, and a shell layer.

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