JP6546720B2 - Liquefaction countermeasure method by ground consolidation using injection method - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a liquefaction countermeasure method by the solidification of the ground using a pouring method. In particular, in the case of loose sandy land where liquefaction is a concern, when taking measures against liquefaction against the existing embankment and foundations of bridges etc., it is simple and economical to solidify the ground by the chemical injection method. It is about the liquefaction measures construction method.

  Conventionally, the following method is employed.

(1) Technique for injecting a drug solution in a pulse form (dynamic injection method) (see the following patent documents 1 to 3 and the following non-patent document 1)
As a method for 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 perform high quality infiltration injection into sand ground, and in viscous soil and rock foundation, it is intended to inject water into water and cracks, etc. It will be done.

  On the other hand, a vein improvement method is also under development at Light Industries Co., Ltd., which enables the soil to be made solid with a low injection amount for sandy land.

(2) Countermeasures against liquefaction by chemical solution injection method As a countermeasure method against liquefaction ground by chemical solution injection up to now, seepage / solidification method in which a chemical solution is infiltrated into saturated ground and replaced with water to solidify liquefied ground. Be In addition, there are deep layer mixing treatment method and high pressure jet agitation method, which improve the rigidity and strength of the ground by mixing the target ground with chemical solution and cement. However, in these cases, measures are taken by improving the ground to be liquefied by 100%, so the effect of the measures to be obtained is large, but the cost is correspondingly high.

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

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

  In the above-described method, the ground can be improved in a grid form, and the cost can be reduced. However, the construction machine is large, and it is difficult to construct the narrow structure for the existing structure.

  Next, there is also a patent (patent 2) of a liquefaction preventing construction method of forming a solidified injection material in the ground by splitting and injecting a chemical solution while forming a split in the liquefied ground. Although this patent ideally wants to carry out osmosis injection to the sand ground where there is concern about liquefaction, in fact it may become split injection due to non-uniformity of the ground, mixing of fine particles, etc. Since the content is large, it is intended to form a large number of split-like injection-solidified materials, thereby increasing the rigidity of the ground by its restraint and increasing the liquefaction resistance. Therefore, in order to obtain a predetermined liquefaction countermeasure effect, the injection amount becomes relatively large, and accordingly, the cost becomes high. In addition, when the split-like injection-solidified body is damaged due to the deformation of the ground due to the earthquake, the improvement effect of the ground rigidity decreases.

(3) Countermeasures against liquefaction through consolidation Realization On the other hand, static or dynamic sand compaction pile methods (SCP method: sand compaction pile method) and press-fit clamps as existing liquefaction countermeasure methods through consolidation of ground The compaction method (CPG method: compaction grouting method), the rod compaction method which applies vibration to compact the ground, and the weight drop compaction method can be mentioned, but all of these require a large-sized machine, and for construction at narrow places Not suitable. In addition, there are problems such as high cost in order to obtain a predetermined liquefaction countermeasure effect. In addition, since noise and vibration during construction and ground displacement are large, it is unsuitable for construction at locations where displacement restrictions are severe, such as railways.

Patent No. 3731189 gazette Patent No. 3709505 gazette Patent No. 3757400

Dynamic injection method, dynamic injection method association compilation, brochure

in this way,
(1) The ground improvement method, which has been applied as a liquefaction countermeasure method, is expensive because it is based on improving the ground to be liquefied by 100%.

 (2) A method is also proposed for placing the injection-solidified material in the form of splits, but in order to increase the rigidity of the ground solely by the injected-solidified material, there is still a high improvement rate. Therefore, drastic cost reduction can not be realized.

 (3) The conventional liquefaction prevention methods by dense realization all require large machines, noise, vibration and deformation during construction are also large, and displacement restrictions such as railways are severe and noises such as locations and urban areas It is difficult to construct in places where vibration is limited and where construction space is narrow.

  In view of the above situation, the present invention provides a liquefaction countermeasure method by the consolidation of the ground using the injection method, which aims to make the sand ground compact and enable a simple and economical liquefaction countermeasure. The purpose is

The present invention achieves the above object by
[1] In liquefaction countermeasure method according dense Mika Ground Using grouting, the tip of the injection tube in a state of closing, Tatekomi the injection tube and static or blow penetration, then the chemical, maximum By injecting dynamically so that the injection rate fluctuates at an amplitude where the value becomes larger than the limit injection rate of the ground, split veins are positively generated also in sand ground, and this split vein is made in the orthogonal direction It is characterized in that it spreads out and achieves unification of the uninjected ground sandwiched between this split vein and this split vein.

  [2] In the method for preventing liquefaction by solidification of the ground using the injection method according to the above-mentioned [1], in the injection method, the injection pipe is made to exist and the connectivity between the split veins is made using the injection pipe as a trunk It is characterized by raising.

  [3] A liquefaction preventing construction method based on the consolidation of the ground using the injection method according to the above [1], characterized in that the injection pipe is replaced with mortar or the like when it is pulled out.

  [4] In the method for preventing liquefaction by solidification of the ground using the injection method according to the above [3], after the injection pipe is drawn out and replaced with mortar, a reinforcing body such as a reinforcing bar is left in the mortar It is characterized by

  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 measures based on the injection rate (about 20 to 50%) of the conventional osmotic injection method Also high. In addition, since the construction machine is small, it is also excellent in construction at narrow places.

   (2) Basically, it is a countermeasure against liquefaction due to the consolidation of the ground, but by injecting it into the ground, a relative drop in permeability can be expected compared to the uninjected ground, so excessive pore water pressure during the earthquake This effect also contributes to reducing the degree of liquefaction of the ground.

   (3) In addition, the effect of suppressing shear deformation can also be expected by constructing a trunk (presence of injection pipe, mortar and reinforcing bar, ground improvement pile, etc.) that does not break due to shear deformation during an earthquake.

It is a schematic diagram of the consolidation by injection pipe standing-up by the Example of this invention. It is a schematic diagram which shows the effect of the desalination by the spreading of the split vein according to the Example of this invention. It is a schematic diagram which shows the inhibitory effect of the shear deformation by the connection of the injection pipe which kept only the improved vein, and the split vein. It is a schematic diagram which shows the alternative plan of the injection pipe by mortar etc. It is a drawing substitute photograph which shows the vein-like body (third time) which shows the Example of this invention. It is a figure which shows the mini-ram test result before and behind a vein improvement object construction. It is a figure of a confirmation experiment model. It is a figure which shows an experimental result. It is a application schematic diagram of the vein ground improvement construction method which shows the example of the present invention. It is a schematic diagram of the method (TOFT method) which ground-refines in a grid | lattice form with a mechanical stirring mixing method etc., and reduces cost.

In the liquefaction prevention method by the consolidation of the ground using the injection method, the injection pipe is erected by static or impact penetration in a state where the tip of the injection pipe is closed, and then the chemical injection rate is the limit injection speed of the ground. by dynamically injected with a larger amplitude, thereby also generate actively dividing裂脈in sand, spread the split裂脈in orthogonal directions, the split裂脈and unimplanted sandwiched between the split裂脈We aim to make the ground a reality.

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

  FIG. 1 is a schematic view of the solidification by injection pipe stand-up according to the embodiment of the present invention.

  In this figure, 1 indicates an injection pipe, 2 indicates an increase in density around the injection pipe 1, and the injection pipe 1 is compacted by erecting. At that time, drilling may be carried out using a conventional small boring machine, but if, for example, static or impact penetration is performed in a state where the tip of the injection pipe is closed, the ground can be compacted at penetration of the injection pipe. Furthermore, at that time, by injecting dynamically with an amplitude larger than the limit injection rate of the ground, a split vein is positively generated even in the sand ground, and the split vein is expanded in the orthogonal direction, and the split vein and the split vein are It is possible to achieve the realization of the uninjected ground sandwiched between.

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

  In this figure, 11 indicates an injection tube, 12 indicates a modified vein (split vein), and 13 indicates a solid part due to spreading of the modified vein 12. That is, the injection is performed dynamically with an amplitude larger than the limit injection rate of the ground. Here, the conventional dynamic injection method (the above-mentioned patent documents 1-3) aimed at performing penetration injection into sand ground with higher quality, but according to the method of the present invention, even in sand ground, it splits positively. The veins are generated, and the split veins try to spread in the orthogonal direction to achieve effective consolidation of the ground. By setting the injection method, injection agent, gel time, etc. for the purpose of efficiently solidifying the ground with a low injection amount, solidity of uninjected ground sandwiched between split veins and split veins Can be implemented. According to indoor experiments and soil layer experiments, the desired consolidation can be obtained with an injection rate of 2.5% to 5%, but although it is necessary to also expect some loss in actual ground, it is still about 5 to 10% The injection rate can be expected to improve the relative density Dr of the ground by 10% or more, thereby increasing the liquefaction resistance of the ground.

  FIG. 3 is a schematic view showing an effect of suppressing shear deformation by connection of an injection pipe and split veins which are kept only with improved veins, and FIG. 4 is a schematic view showing an alternative of the injection pipe by mortar or the like.

  The split vein can be expected to actually suppress the shear deformation of the ground during the earthquake, but there is concern that the split vein will break and become discontinuous when the ground is sheared during the earthquake, The suppression effect of shear deformation seems to be small. Therefore, in the injection method of the present invention, as shown in FIG. 3 (a), the injection pipe is generally withdrawn from the split vein 21, but in the present invention, it is also possible to leave the injection pipe. As a result, as shown in FIG. 3 (b), the connectivity between the split veins is enhanced with the injection pipe as the trunk, so the effect of suppressing the shear deformation of the ground and the supporting force improvement effect of the existing structure (fill or foundation) Can also be expected.

  Alternatively, as shown in FIG. 4, the injection tube 33 in which the split vein 31 and the solid portion 32 are formed may be replaced with mortar 34 or the like, and the rebar 35 or the like may be left, as shown in FIG. An effect is obtained. Here, the reinforcing bars 35 are provided to prevent breakage of the mortar 34 due to tension or bending. Further, similar effects can be obtained even if the ground is improved in a pile shape (improvement rate of about 5 to 10%) by a jet agitation method or a mechanical agitation method having sufficient strength in a process separate from injection.

  As described above, in the liquefaction prevention method by the consolidation of the ground using the injection method of the present invention, the injection pipe is used as the injection pipe, and the connection between the split veins is enhanced by using the injection pipe as a trunk. be able to.

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

  FIG. 5 is a drawing-substituting photograph showing a vein-shaped improved body (third time) showing an example of the present invention. FIG. 6 is a diagram showing the results of the mini ram test before and after construction of the vein-shaped improved body.

Pulsed chemical solution injection was carried out using a 5.0 m long x 4.0 m wide x 4.0 m deep earth tank, and the evaluation of the finished shape and the ground improvement effect by mini-ram sounding were evaluated.

  As shown in FIG. 5, it has been confirmed that dynamic improvement is possible by pulse injection. Further, as shown in FIG. 6, an increase in N value can be confirmed before and after the injection.

  Using the medium-sized shaking table test equipment owned by the National Railways Research Institute, we confirmed the effectiveness of the measures against liquefaction by the vein ground improvement method (Figure 7 and Figure 8). FIG. 7 is a view of a confirmation experimental model, FIG. 7 (a) is a view of an unmodified ground, and FIG. 7 (b) is a view of an improved ground (improvement rate 2.5%).

  In FIG. 7, 41 is a crushed stone layer (filter sand layer), 42 is a water pressure gauge (100 kPa), 43 is a water pressure gauge (50 kPa), 44 is an accelerometer, 45 is an inlet, 46 is a seal, 47 is a pulse reformer is there.

  FIG. 8 shows experimental results, and FIG. 8 (a) shows the elapsed time (seconds) for the input acceleration (gal), and FIG. 8 (b) shows the elapsed time (seconds) for the amount of settlement (mm). c) is the elapsed time (seconds) for the excess pore water pressure (kPa).

  By configuring in this manner, the relative density increases by 12% at a target improvement rate of 10%. As a result, the liquefaction resistance is increased, and the ground displacement after vibration is reduced to 10% or less.

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

  In this figure, 51 is a liquefaction layer, 52 is an improved vein ground (vein improvement body), 53 is an embankment, 54 is a railway track built on the embankment 53, 55 is a road of a car, 56 is a road A house (building), 57 is a sliding surface, and 58 is a sliding resistance by the trunk.

  Thus, the liquefaction layer 51 can be widely improved at low cost with the improved veined ground (vein improved body) 52.

  The present invention is not limited to the above-described embodiments, and various modifications can be made based on the spirit of the present invention, 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 achieves the solidification of the sand ground and enables the simple and economical measures against the liquefaction. It can be used as a liquefaction countermeasure method by realization.

1,11,33 Injection tube 2 Increase in density around the injection tube 12,21,31 Improved vein (split vein)
13, 32 solid part 34 mortar 35 rebar 41 crushed stone layer 42 water pressure gauge (100 kPa)
43 water pressure gauge (50 kPa)
44 accelerometer 45 inlet 46 seal 47 pulse modifier 51 liquefaction layer 52 modified pulse ground (pulse modifier)
53 embankment 54 railway track built on embankment 55 automobile road 56 residence (building)
57 Slip surface 58 Slip resistance by the stem

Claims (4)

(A) With the end of the injection pipe closed, insert the injection pipe up by static or impact penetration.
(B) Next, by actively injecting the chemical solution so that the injection rate fluctuates with an amplitude at which the maximum value is larger than the limit injection rate of the ground, the veins are actively split even in the sand ground. Raises, the split裂脈flaring in orthogonal direction, said split裂脈and the split of unimplanted ground sandwiched between裂脈the ground the grouting method used, characterized in that to achieve tight Mika dense Mika Liquefaction measures construction method.   In the liquefaction countermeasure method according to the solidification of the ground using the injection method according to claim 1, the injection method comprises allowing the injection pipe to be kept, and using the injection pipe as a trunk to improve the connectivity between the split veins. The liquefaction prevention method by the consolidation of the ground using the injection method.   In the liquefaction countermeasure method by solidification of the ground using the injection method according to claim 1, the liquid by solidification of the ground using the injection method characterized in that the injection pipe is replaced with mortar or the like when the injection pipe is pulled out. Measures against   In the liquefaction preventing construction method by solidification of the ground using the pouring construction method according to claim 3, the pouring pipe is drawn out and replaced with mortar, and then a reinforcement body such as a reinforcing bar is left in the mortar. The liquefaction prevention method by the soil consolidation of the ground using the construction method.

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