JP2015203243A - Liquefaction countermeasure method of foundation by means of solidification using an injection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquefaction countermeasure method of foundation by means of solidification using an injection method capable of easily performing liquefaction countermeasure at a low cost while improving solidification of sand foundation.SOLUTION: The liquefaction countermeasure method solidifies the foundation by using an injection method. A filling pipe with the front end sealed is inserted into the foundation with a static manner or hitting manner. Subsequently, an injection material is dynamically injected with vibration amplitude larger limit infusion rate of the foundation to thereby positively generate cleavage veins in a sand foundation. Non-injected foundation between the cleavage veins is solidified by expanding the cleavage vein in orthogonal directions.

Description

  The present invention relates to a liquefaction countermeasure method by the solidification of the ground using an injection method. In particular, in the case of loose sandy ground where liquefaction is a concern, when taking measures against liquefaction on existing embankments or bridge foundations, a simple and economical way to solidify the ground using a chemical injection method. It relates to the liquefaction countermeasure method.

  Conventionally, the following construction methods have been adopted.

(1) Technology for injecting a chemical solution in a pulse shape (dynamic injection method) (see Patent Documents 1 to 3 and Non-Patent Document 1 below)
As a method of injecting a chemical solution to the ground, a technique for dynamically injecting a chemical solution has been proposed. The purpose of this method is to inject high quality osmotic injection into sand ground, and to inject into water veins and cracks in the form of veins for viscous or rocky ground. Is to be done.

(2) Liquefaction countermeasures by chemical solution injection method The conventional liquefaction countermeasures method by injecting chemical solution includes infiltration solidification method in which chemical solution is infused into saturated ground to replace water and solidify the liquefied ground. It is done. In addition, there are a deep mixing method and a high-pressure jet agitation method that increase the rigidity and strength of the ground by mixing the target ground with chemicals and cement. However, in these cases, since countermeasures are to be taken by improving the liquefaction target ground by 100%, the countermeasure effect obtained is great, but the cost is correspondingly increased.

  FIG. 10 is a schematic diagram showing an example of a conventional grid-like ground improvement.

  In this figure, 101 is a non-liquefied layer, 102 is a liquefied layer, 103 is a pile, and there is also an example in which a grid-like ground improvement is performed.

  In the above construction method, the ground can be improved in a lattice shape and the cost can be reduced. However, the construction machine is large, and it is difficult to perform construction in a narrow area targeting an existing structure.

  Next, there is also a patent for a liquefaction countermeasure method (Patent 2) that forms an injection solidified product in the ground by splitting and injecting a chemical solution while forming a tear in the liquefied ground. This patent ideally wants to infiltrate sand ground where liquefaction is a concern, but in reality, it may cause split injection due to ground inhomogeneity or inclusion of fine particles. Since there are many, it aims at the effect of forming many split-like injection | pouring solidified substances, increasing the rigidity of a ground by the restraint, and increasing liquefaction resistance. Therefore, in order to obtain a predetermined liquefaction countermeasure effect, the injection amount becomes relatively large, and the cost is correspondingly increased. Further, when the split solidified solidified body is damaged due to the deformation of the ground due to the earthquake, the effect of improving the ground rigidity is lowered.

(3) Measures against liquefaction due to solidification On the other hand, existing liquefaction countermeasures due to solidification of the ground include static or dynamic sand compaction pile method (SCP method: sand compaction pile method) and press-fit type tightening method. The compaction method (CPG method: compaction grouting method), the rod compaction method that applies vibration and compacts the ground, and the weight drop compaction method are all mentioned. Not suitable. In addition, there are problems such as high costs in order to obtain a predetermined liquefaction countermeasure effect. In addition, noise, vibration, and ground displacement during construction are large, making it unsuitable for construction in places where displacement restrictions are severe, such as railways.

Japanese Patent No. 3731189 Japanese Patent No. 3709505 Japanese Patent No. 3757400

Dynamic injection method, edited by Dynamic Injection Method Association, pamphlet

in this way,
(1) The ground improvement method that has been applied as a liquefaction countermeasure method so far is based on improving the liquefaction target ground by 100% and is therefore expensive.

 (2) A method of arranging the injected solidified material in a split shape has also been proposed, but in order to increase the rigidity of the ground only by the injected solidified material, the improvement rate is still high. For this reason, drastic cost reduction cannot be realized.

 (3) The conventional liquefaction countermeasure methods by solidification all require large machines, large noise, vibration and deformation during construction, severe displacement restrictions such as railways, noise in urban areas, etc. Construction in places where vibration is restricted and construction space is narrow is difficult.

  In view of the above situation, the present invention provides a liquefaction countermeasure method by solidification of the ground using an injection method, which makes it possible to solidify the sand ground and enable a simple and economical liquefaction countermeasure. For the purpose.

In order to achieve the above object, the present invention provides
[1] In the liquefaction countermeasure method by the solidification of the ground using the injection method, with the injection tube closed, the injection tube is set up by static or impact penetration, and then the limit injection of the ground By dynamically injecting with an amplitude larger than the velocity, the split ground is actively generated even in the sand ground, and the split vein is pushed in the orthogonal direction, and the uninjected ground sandwiched between the split vein and the split vein It is characterized by achieving solidification.

  [2] In the liquefaction countermeasure method by the solidification of the ground using the injection method described in [1] above, in the injection method, the injection tube is allowed to remain, and the connectivity between the splitting veins is established using the injection tube as a trunk. It is characterized by increasing.

  [3] In the liquefaction countermeasure method by the solidification of the ground using the injection method described in [1] above, when the injection tube is pulled out, it is replaced with mortar or the like.

  [4] In the liquefaction countermeasure method by the solidification of the ground using the injection method described in [3] above, after the injection tube is pulled out and replaced with mortar, a reinforcing body such as a reinforcing bar is placed in the mortar. It is characterized by.

  [5] A ground improvement pile is used in the liquefaction countermeasure method by the solidification of the ground using the injection method described in [1] above.

  According to the present invention, the following effects can be achieved.

   (1) Since the injection method of the present invention has an injection rate of about 5 to 10%, it is more economical than the liquefaction countermeasure by the injection rate (about 20 to 50%) of the normal osmotic injection method, and the construction speed Is also expensive. Moreover, since the construction machine is small, it is excellent in workability in a narrow space.

   (2) Basically, it is a countermeasure against liquefaction due to the solidification of the ground, but when injected into the ground, it can be expected that the water permeability will be relatively lower than that of the unfilled ground. The rise of the soil can also be suppressed, and this effect also contributes to reducing the degree of ground liquefaction.

   (3) In addition, the effect of suppressing shear deformation can be expected by constructing a trunk that does not break due to shear deformation during an earthquake (such as the existence of injection pipes, mortar and reinforcing bars, ground improvement piles, etc.).

It is a schematic diagram of the realization by injection pipe standing by the Example of this invention. It is a schematic diagram which shows the effect of solidification by the expansion of the split vein by the Example of this invention. It is a schematic diagram which shows the suppression effect of the shear deformation by the connection of the injection pipe and the split vein which existed only with the improved vein. It is a schematic diagram which shows the alternative of the injection tube by mortar etc. It is a drawing substitute photograph which shows the pulse improvement body (3rd time) which shows the Example of this invention. It is a figure which shows the miniram test result before and behind construction of a vein improvement body. It is a figure of a confirmation experiment model. It is a figure which shows an experimental result. It is an application schematic diagram of the vein ground improvement method which shows the Example of this invention. It is a schematic diagram of a method (TOFT method) for improving the ground in a lattice shape by a mechanical stirring and mixing method or the like and reducing the cost.

  The liquefaction countermeasure method by the solidification of the ground using the injection method is a method in which the injection tube is set up by static or impact penetration with the tip of the injection tube blocked, and then larger than the limit injection rate of the ground. By dynamically injecting with amplitude, split fissures are actively generated even in sand ground, and the split fissures are spread in the perpendicular direction, and the solidity of the uninjected ground sandwiched between the split fissures and split fissures Plan.

  Hereinafter, embodiments of the present invention will be described in detail.

  FIG. 1 is a schematic diagram of realization by setting up an injection pipe according to an embodiment of the present invention.

  In this figure, 1 indicates an injection tube, 2 indicates an increase in density around the injection tube 1, and the injection tube 1 is made dense by standing. At that time, a hole drilling by a normal small boring machine may be used. However, for example, if the injection tube is statically or hammered while the tip of the injection tube is closed, the ground can be solidified when the injection tube penetrates. Furthermore, at that time, by dynamically injecting with an amplitude larger than the limit injection speed of the ground, the split vein is actively generated even in the sand ground, and the split vein is pushed in the orthogonal direction, and the split vein and split vein are The solidity of the uninjected ground sandwiched between them can be achieved.

  FIG. 2 is a schematic diagram showing the effect of realization by the spreading of the split vein according to the embodiment of the present invention.

  In this figure, 11 indicates an injection tube, 12 indicates an improved pulse (split pulse), and 13 indicates a solid part due to expansion of the improved pulse 12. That is, the injection is dynamically performed with an amplitude larger than the limit injection speed of the ground. Here, the conventional dynamic injection method (the above Patent Documents 1 to 3) was intended to infiltrate the sand ground with higher quality, but the method of the present invention also actively splits the sand ground. The ground is generated efficiently by generating the veins and trying to spread the split veins in the orthogonal direction. By setting the injection method, injection agent, gel time, etc. for the purpose of efficiently solidifying the ground with a low injection volume, the solidity of the uninjected ground sandwiched between the split veins and the split veins Can be achieved. According to laboratory experiments and soil layer experiments, the specified solidification can be obtained at an injection rate of 2.5% to 5%, but it is still necessary to expect some loss in the actual ground, but still about 5-10% With the injection rate, an improvement effect of 10% or more of the relative density Dr of the ground can be expected, thereby increasing the liquefaction resistance of the ground.

  FIG. 3 is a schematic diagram showing the effect of suppressing shear deformation by the connection between an injection tube having only an improved vein and a split vein, and FIG. 4 is a schematic diagram showing an alternative to the injection tube by mortar or the like.

  The splitting vein can actually be expected to suppress the shear deformation of the ground during the earthquake, but when the ground undergoes shear deformation during the earthquake, there is a concern that the splitting vein breaks and becomes discontinuous, It seems that the effect of suppressing shear deformation is small. Therefore, in the injection method of the present invention, as shown in FIG. 3A, generally, the injection tube is pulled out from the splitting vein 21, but in the present invention, it is also possible to leave the injection tube. As a result, as shown in FIG. 3 (b), the connectivity between the split veins is enhanced with the injection tube as a trunk, so that the effect of suppressing shear deformation of the ground and the effect of improving the bearing capacity of existing structures (banking and foundation) are improved. Can also be expected.

  Alternatively, in place of the infusion tube, as shown in FIG. 4, when the infusion tube 33 in which the split vein 31 and the solid portion 32 are formed is pulled out, it is replaced with a mortar 34 or the like, and the rebar 35 or the like is also present. An effect is obtained. Here, the reinforcing bar 35 is installed in order to prevent the mortar 34 from being broken by pulling or bending. In addition, the same effect can be obtained even if the ground is improved into a pile shape (an improvement rate of about 5 to 10%) by a jet stirring method or a mechanical stirring method having sufficient strength in a separate process from the injection.

  In this way, in the liquefaction countermeasure method by the solidification of the ground using the injection method of the present invention, by connecting the injection tube in the injection method, the connectivity between the split veins is improved with the injection tube as a trunk. be able to.

  Further, when the injection tube is pulled out, it may be replaced with mortar or the like. Further, the injection tube may be pulled out and a reinforcing body such as a reinforcing bar may be placed. Furthermore, a ground improvement pile may be used.

  FIG. 5 is a drawing-substituting photograph showing a vein-like improvement body (third time) showing an example of the present invention. FIG. 6 is a diagram showing the miniram test results before and after the execution of the vein improvement body.

  A pulsed chemical solution was injected using a soil tank of 5.0 mm in length, 4.0 m in width, and 4.0 m in depth, and the shape improvement and the ground improvement effect by mini-ram sounding were evaluated.

  As shown in FIG. 5, it has been confirmed that the pulse shape can be improved by dynamic injection. Moreover, as shown in FIG. 6, the increase of N value has been confirmed before and after injection | pouring.

  The effect of liquefaction countermeasures by the vein-shaped ground improvement method was confirmed using the medium-sized shaking table test equipment owned by Railway Research Institute (Figs. 7 and 8). FIG. 7 is a diagram of a confirmed experimental model, FIG. 7A is a diagram of an unimproved ground, and FIG. 7B is a diagram of an improved ground (an improvement rate of 2.5%).

  In FIG. 7, 41 is a crushed stone layer (filter sand layer), 42 is a water pressure meter (100 kPa), 43 is a water pressure meter (50 kPa), 44 is an accelerometer, 45 is an inlet, 46 is a seal, 47 is a vein-like improvement body. is there.

  8A and 8B are diagrams showing experimental results. FIG. 8A shows the elapsed time (seconds) with respect to the input acceleration (gal), FIG. 8B shows the elapsed time (seconds) with respect to the sinking amount (mm), and FIG. c) is the elapsed time (seconds) relative to the excess pore water pressure (kPa).

  With this configuration, the relative density increased by 12% at a target improvement rate of 10%. As a result, the liquefaction resistance increased, and the ground displacement after vibration was reduced to 10% or less.

  FIG. 9 is a schematic view of application of the vein-like ground improvement method showing an embodiment of the present invention.

  In this figure, 51 is a liquefied layer, 52 is an improved vein ground (a vein improvement body), 53 is embankment, 54 is a railroad track constructed on the embankment 53, 55 is an automobile road, 56 is A residence (building), 57 is a slip surface, and 58 is a slip resistance by a trunk.

  Thus, the liquefied layer 51 can be improved over a wide range at a low cost by the improved vein ground (vein improvement body) 52.

  In addition, this invention is not limited to the said Example, Based on the meaning of this invention, a various deformation | transformation is possible and these are not excluded from the scope of the present invention.

  The liquefaction countermeasure method by the solidification of the ground using the injection method of the present invention is intended to solidify the sand ground and enable a simple and economical liquefaction countermeasure. It can be used as a liquefaction countermeasure method by actualization.

1,11,33 Injection tube 2 Increase in density around the injection tube 12,21,31 Improved pulse (split pulse)
13, 32 Dense part 34 Mortar 35 Reinforcement 41 Crushed stone layer 42 Water pressure gauge (100 kPa)
43 Water pressure gauge (50kPa)
44 Accelerometer 45 Inlet 46 Seal 47 Vein improvement 51 Liquefaction layer 52 Improved vein ground (vein improvement)
53 Embankment 54 Railroad track built on embankment 55 Car road 56 Dwelling (building)
57 Sliding surface 58 Slip resistance by stem

Claims (5)

(A) In a state where the tip of the injection tube is closed, the injection tube is stowed by static or impact penetration,
(B) Next, by dynamically injecting with an amplitude larger than the limit injection speed of the ground, a split vein is actively generated even in the sand ground, and the split vein is expanded in the orthogonal direction. A liquefaction countermeasure method by solidification of the ground using an injection method characterized by solidification of the uninjected ground sandwiched between the two.   In the liquefaction countermeasure method by the solidification of the ground using the injection method according to claim 1, in the injection method, the injection tube is allowed to remain, and the connectivity between the split veins is enhanced with the injection tube as a trunk. The liquefaction countermeasure method by the solidification of the ground using the injection method.   In the liquefaction countermeasure method by the solidification of the ground using the pouring method according to claim 1, the liquid by the solidification of the ground using the pouring method, wherein the mortar is replaced when the pouring pipe is pulled out. Chemical countermeasure construction method.   In the liquefaction countermeasure construction method by the solidification of the ground using the injection construction method according to claim 3, after the injection pipe is pulled out and replaced with mortar, a reinforcing body such as a reinforcing bar is placed in the mortar. The liquefaction countermeasure method by the solidification of the ground using the method.   The liquefaction countermeasure construction method by the solidification of the ground using the injection construction method characterized by using a ground improvement pile in the liquefaction countermeasure construction method by the solidification of the ground using the injection construction method according to claim 1.

Images