JP6493834B2 - Ground liquefaction countermeasure method - Google Patents

Description

  The present invention builds an injection pipe in the ground and repeats a chemical injection operation for injecting a chemical (grouting) into the ground through the injection pipe, thereby suppressing or preventing liquefaction of the ground. It relates to the construction method.

  As a liquefaction countermeasure method for the ground, there is a method in which an injection pipe is built in the ground, and a chemical liquid injection operation for repeatedly injecting the chemical liquid into the ground through the injection pipe is performed. However, since this liquefaction countermeasure method is a method using a large amount of chemical solution, it has a problem that the construction cost becomes high.

  Therefore, as a construction method for reducing the usage amount of the chemical solution and thereby reducing the construction cost, a construction method in which unimproved portions are intentionally scattered has been proposed (see Patent Document 1). In this method, a solidified body of a predetermined volume is formed by injecting a chemical solution from an injection pipe inserted into the sand ground to be improved, and this solidified body is overlapped in the vertical and horizontal directions and the front-rear direction to form the improved ground. An unmodified part having the same volume as the solidified body is formed in the improved ground without injecting a chemical solution from the injection tube, and two or more unimproved parts are not continuous, and the solidified body surrounds the top, bottom, left, right, and front and back. ".

  However, since this method is intended to form an unimproved portion having the same volume as the solidified body made of an osmotic solidified product, the amount of chemical used can only be reduced to about half. Therefore, the proposal of the liquefaction countermeasure construction method which can further reduce the usage-amount of a chemical | medical solution is anticipated.

JP 2007-217979 A

  The main problem to be solved by the present invention is to provide a ground liquefaction countermeasure method capable of remarkably reducing the amount of chemical used.

The present invention for solving this problem is as follows.
[Invention of Claim 1]

A ground liquefaction countermeasure construction method in which an injection pipe is built in the ground, and a chemical liquid injection work for injecting a chemical liquid into the ground through the injection pipe is repeated,
The chemical solution is injected by split injection and by dynamic injection that periodically changes the injection pressure,
Erection of the injection pipe is performed at predetermined intervals in the left-right direction and the front-rear direction of the ground, and so as to satisfy the following conditions (A) and (B):
The ground liquefaction countermeasure method characterized by this .
(A) With respect to the left-right direction and the front-rear direction of the ground, the work area and the non-work area are adjacent to each other.
(B) Regarding the oblique direction of the ground, the work area is continuous.
Here, the work area refers to an area surrounded by a virtual square whose four sides pass through a position that is a quarter of the predetermined distance from the position where the injection pipe is built. The non-work area is an area that does not correspond to the work area.

[Invention of Claim 2 ]
The predetermined interval is set so that the injection rate of the chemical solution is 2% to 15%.
The ground liquefaction countermeasure construction method according to claim 1 .
Here, the injection rate of the chemical solution is “the injection amount of the chemical solution (L) / the volume of the ground to be countermeasured (m ³ ) × 100”.

[Invention of Claim 3 ]
The chemical solution injection operation is performed by a single-phase double tube strainer method.
The ground liquefaction countermeasure construction method according to claim 1 or claim 2 .

[Invention of Claim 4 ]
The dynamic injection of the chemical solution is performed so that the amplitude of the flow waveform is at least one of a sine wave and a pulse wave of 30% to 100%.
The ground liquefaction countermeasure construction method according to any one of claims 1 to 3 .

[Invention of Claim 5 ]
Dynamic injection of the chemical solution is performed so that the frequency is 0.01 Hz to 0.5 Hz.
The ground liquefaction countermeasure construction method according to any one of claims 1 to 4 .

[Invention of Claim 6 ]
As the drug solution, a drug solution whose gel time corresponds to 0.1 cycle to 3 cycles of the dynamic injection is used.
The ground liquefaction countermeasure construction method according to any one of claims 1 to 5 .

[Invention of Claim 7 ]
As the chemical solution, a chemical solution having a gel time of 2.5 to 40 sec is used.
The ground liquefaction countermeasure construction method according to any one of claims 1 to 5 .

[ Reference invention]
As the chemical solution, a chemical solution whose gel time corresponds to an injection time of the chemical solution 0.5L to 5L (L indicates an injection amount of the chemical solution) is used.
The ground liquefaction countermeasure construction method according to any one of claims 1 to 5 .

[Invention of Claim 8 ]
As the chemical solution, a mixed type chemical solution in which two or more liquids are mixed, and a chemical solution having a viscosity at the time of mixing of 1 mPa · s to 100 mPa · s, is used.
The ground liquefaction countermeasure construction method according to any one of claims 1 to 7 .

[ Reference invention]
As the chemical, a suspension-type chemical and particulate concentration of the above median diameter 1μm to use chemical ^{200kg / m 3 ~760kg / m 3} ,
The ground liquefaction countermeasure construction method according to any one of claims 1 to 8 .

[Invention of Claim 9 ]
The chemical solution is
(1) A blast furnace slag or a cement containing the blast furnace slag and a first liquid mainly composed of slaked lime (2) a second liquid mainly composed of water glass are brought into contact with each other.
The ground liquefaction countermeasure construction method according to any one of claims 1 to 8 .

[Invention of Claim 10 ]
The ground liquefaction countermeasure construction method according to claim 1, wherein the drilling water is discharged at a rate of 10 L / min or more in the ground drilling performed before the injection pipe is built in the ground.

[Invention of Claim 11 ]
A part of the chemical solution injection work is performed instead of the high-pressure jet stirring work.
The ground liquefaction countermeasure construction method according to claim 1.
Here, the high-pressure jet agitation operation refers to an operation in which a rotating rod is built in the ground instead of the injection pipe, and a hardened material is injected while rotating the rotating rod to form a columnar improvement body.

[Invention of Claim 12 ]
After at least one of the chemical solution injection operation and the high-pressure jet stirring operation, the hole formed by the operation is replaced and filled with at least one of mortar, cement milk, and chemical solution.
The ground liquefaction countermeasure method according to claim 11 .
Here, the chemical solution is
(1) A blast furnace slag or a cement containing the blast furnace slag and a first liquid mainly composed of slaked lime (2) a second liquid mainly composed of water glass are brought into contact with each other.

  According to the present invention, it is a ground liquefaction countermeasure method that can significantly reduce the amount of chemical used.

It is a conceptual diagram for demonstrating the installation position of an injection tube, and the breadth of a vein-like solidified substance. A conceptual plan view (1) for explaining the erected position of the injection pipe according to the first example, a conceptual plan view (2) for explaining the erected position of the injection pipe according to the second example, and the first It is a conceptual top view (3) for demonstrating the construction position of the injection pipe and rotation rod which concern on the example of 3. FIG. Conceptual sectional view (1) for explaining the erected position of the injection pipe according to the second example, and conceptual sectional view (2) for explaining the erected position of the injection pipe and the rotating rod according to the third example ). It is the graph which showed the N value of the ground before a liquefaction countermeasure, and the ground after a liquefaction countermeasure. It is the graph which showed the N value of the ground before a liquefaction countermeasure, and the ground after a liquefaction countermeasure.

Next, modes for carrying out the invention will be described.
In the ground liquefaction countermeasure method according to this embodiment, as shown in FIG. 1, the injection pipe 10 is built in the ground G, and the chemical solution is injected into the ground G through the injection pipe 10. This chemical injection is performed by split injection and by dynamic injection that periodically changes the injection pressure. Here, the split injection refers to an injection form in which the ground is split by the injection pressure, the injected material enters into it to form a chemical solution pulse, and the pulse extends into the ground.

  In the conventional construction method, since the chemical solution is injected by osmotic injection, the amount of the chemical solution used cannot be reduced sufficiently. That is, in the osmotic injection, since it is necessary to replace the entire ground gap with the chemical solution, an injection rate of about 40% of the volume of the ground to be improved is required. On the other hand, in the construction method of the present embodiment, the non-penetrating chemical solution is intentionally split and injected (injected in a pulse shape or in a planar shape while forming a tear in a weak portion of the ground G). Increase density and improve liquefaction performance. Therefore, the required amount of the chemical solution is about 10% of the volume of the ground to be improved, and the amount of the chemical solution can be reduced as compared with the osmotic injection.

In addition, when the chemical solution is injected by split injection, a vein-like solid (homgel) S is formed. The strength of this vein-like solid S is, for example, 2000 kN / m ² or more at 28 days of age. Can be increased to. Therefore, according to the construction method of the present embodiment, so-called a state where tree branches extend in the ground G or a state where a lattice is assembled, the liquefaction resistance of the ground G can be improved. In addition, the ground G is consolidated with the split injection of the chemical solution, and the strength of the ground G itself is improved, so that the liquefaction resistance of the ground G is further improved. In addition, the intensity | strength of the osmosis | solidification solid body (sand gel) formed by the conventional osmotic injection | pouring is about 100 kN / m < ² >.

  Furthermore, in the construction method of this embodiment, since the chemical solution is injected by dynamic injection, the chemical solution injected into the ground G progresses when the injection pressure is lowered. Then, when the injection pressure increases thereafter, the injected chemical liquid collides with the chemical liquid that has been gelled. Therefore, when split injection is performed by dynamic injection as in this embodiment, the pulse that was initially split is blocked, and a new pulse is formed by a new split, so that the pulse is formed. The vein-like solid object S comes to draw a very complicated locus. As a result, so-called tree branches are densely distributed in the ground G, and the liquefaction resistance of the ground G is further improved.

  In the construction method of this embodiment, the chemical solution injection operation using the injection tube 10 is repeated while changing the position where the injection tube 10 is installed. For example, as shown in FIG. 2 (1) as the first example, the injection pipe 10 is erected at predetermined intervals L in the left-right direction and the front-rear direction of the ground G. The predetermined interval L can be set in consideration of, for example, how much the liquefaction resistance of the ground G is improved.

  At present, there is no detailed agreement on how much to improve the liquefaction resistance of the ground G. However, in the future, considering the use of the ground G, for example, whether there are buildings on the ground G, whether roads and tracks are laid, runways exist, or are only vacant land, etc. It is expected to be determined as appropriate.

  Also in the embodiment shown in FIG. 2 (1) and the like, the effect of performing the injection of the chemical solution by split injection and dynamic injection is exhibited. However, from the viewpoint of uniformly improving the liquefaction resistance over the entire ground G to be constructed, as shown in FIG. Is preferably performed so as to satisfy the following conditions (A) and (B).

(A) Regarding the left-right direction and the front-rear direction of the ground G, the work area X and the non-work area Y are adjacent to each other.
(B) Regarding the oblique direction of the ground G, the work area X is continuous.
Here, as shown in FIG. 1, the work area X is an area surrounded by a virtual square D whose four sides pass through a position that is a quarter of the predetermined distance L from the position where the injection tube 10 is built. . The non-work area Y is an area that does not correspond to the work area X. In addition, the said left-right direction, the front-back direction, and the diagonal direction do not mean a specific direction, but are relative directions along the surface of the ground G.

  In the former form (form (1) of FIG. 2 etc.) that does not satisfy these conditions (A) and (B), there is a complete non-work area Y1 in which the non-work area Y continues in the left-right direction and the front-back direction. Will do. Even in such a form, as described above, the minimum operation and effect due to split injection and dynamic injection can be obtained, but the liquefaction resistance of the completely unworked region Y1 portion becomes relatively weak. . Therefore, it is more preferable to use the latter form (form (2) of FIG. 2) that satisfies the above conditions (A) and (B).

  Further, according to the latter form satisfying the above conditions (A) and (B), as shown in (1) of FIG. The vein-like consolidated portions S injected through the injection pipes 10 adjacent to each other in the oblique direction of G can be in an intertwined state (the portion where this vein-like consolidated matter S is intertwined is indicated by the symbol W. .) Therefore, according to the latter form, the liquefaction resistance of the ground G can be further improved.

  As is clear from this example, there is a possibility that the work area X and the chemical solution injection area (or the area where the pulmonary solid S is formed) are different areas. The work area X is merely an area defined as described above. Similarly, there is a possibility that the non-work area Y and the area where the chemical solution is not injected (or the area where the pulmonary solid S is not formed) are different areas.

  In the liquefaction countermeasure method of this embodiment, there is no particular limitation on how much the predetermined interval L is set. However, it is preferable to set the predetermined interval L so that the injection rate of the chemical solution is 2% to 15%, and it is more preferable to set the predetermined interval L so as to be 10%.

The injection rate of the chemical solution is “the injection amount of the chemical solution (L) / the volume of the ground to be countermeasured (m ³ ) × 100”. Therefore, the injection rate of the chemical solution can be changed by changing the predetermined interval L, and can also be changed by changing the injection amount of the chemical solution for each installation position of the injection tube 10. That is, if the predetermined interval L is increased or the injection amount of the chemical solution at each erection position is decreased, the injection rate is lowered. On the other hand, when the predetermined interval L is shortened or the injection amount of the chemical solution at each erection position is increased, the injection rate is increased.

  The inventors set the predetermined interval L to 1.5 m, and performed a chemical injection test with a chemical injection rate of 10% for the entire ground to be tested. As a result of this test, it was confirmed that the N value of the ground increased. Further, when this ground was subjected to a simple liquefaction test using vibro, no liquefaction phenomenon occurred.

(Chemical solution (grouting))
As a chemical solution to be injected into the ground G, a chemical solution in which a curing agent (A solution) and a reactive agent (B solution) are mixed can be used. As the curing agent, for example, cement slurry, cement bentonite slurry, slag slurry, slag cement slurry and the like can be used. Moreover, as a reactive agent, a water glass solution, an aluminum salt solution, etc. can be used, for example.

  However, as the chemical solution of this embodiment for splitting and dynamic injection, it is preferable to use a mixed type chemical solution or a suspension type chemical solution in which two or more liquids are mixed. Slag cement slurry (A solution) and water glass It is more preferable to use an instant-sustaining suspension type plastic grout mixed with the solution (liquid B). This plastic grout is a chemical solution that hardens when an alkali reacts with slag, and has plasticity and durability. Therefore, the effect by dynamic injection is fully exhibited, and the vein-like solidified substance can be formed in a complicated manner.

  The mixed chemical solution preferably has a viscosity at the time of mixing of 1 mPa · s to 100 mPa · s. If the viscosity at the time of mixing is too high, the resistance applied at the time of injection becomes too high, and the injection pressure and splitting force become too high, making it unsuitable for forming a complex pulse. Note that if the viscosity at the time of mixing is too low, the particle concentration will be lowered, and there is a risk of penetration injection rather than split injection.

Further, suspension type of chemical is preferably particle concentration relative to the median size 1μm or more of the particles is ^{200kg / m 3 ~760kg / m 3} . If the particle concentration is too high, a mud film will be formed in the sand layer near the injection port of the chemical solution, and the ground G will not be split and the entire ground G will be pushed, so the consolidated product will be spherical or thick plate-like There is a risk that it will not become a pulse.

The median diameter (“median diameter”) is determined using, for example, the following method. More specifically, when the particle size is 500 microns or more, screening is performed according to the method described in JIS M 8801 Coal Testing Method, and the screening result is expressed as a Rosin-Rammler distribution, and the integrated mass (on the screen) corresponds to 50%. The particle diameter at the time is defined as the median diameter (D ₅₀ ). When the particle size of the dehydrated product is less than 500 microns, the particle size distribution is measured using a laser diffraction type particle size distribution measuring device (for example, trade name SALD-3100, manufactured by Shimadzu Corporation), and the cumulative volume is 50%. Is defined as the median diameter (D ₅₀ ). In addition, the dispersion medium used when calculating | requiring a median diameter is IPA, and it disperse | distributes using an ultrasonic wave.

  In addition, additives, such as a dispersing agent, a strength accelerator, and a thickener, can also be mix | blended with a chemical | medical solution as needed.

  By the way, as described above, according to the dynamic injection, when the injection pressure is lowered, the chemical solution injected into the ground G progresses, and the injected chemical solution collides with the chemical solution that has advanced the gelation. For this reason, the vein-like solidified substance S comes to draw a very complicated locus. However, when the gel time (gelation time) of the chemical solution is too long, the gelation of the chemical solution does not proceed sufficiently and is not suitable for complicating the pulmonary solid S. Moreover, the improvement range of the ground cannot be limited. Furthermore, the thickness of the vein-like consolidated product S is thin, and the consolidation effect is not excellent. On the other hand, if the gel time is too short, the influence of displacement on the ground tends to increase. Further, the vein-like solid S is difficult to spread, and the vein-like solid S is difficult to be formed. Furthermore, there is a problem that the chemical solution stays in the vicinity of the injection port and tends to become a spherical or thick plate-like consolidated product.

  From the above, as a chemical solution, a gel solution having a gel time corresponding to 0.1 cycle to 3 cycles of dynamic injection (for example, a drug solution having a gel time of 2 seconds to 1 minute when one cycle is 20 seconds), or It is preferable to use a chemical solution whose gel time corresponds to the injection time of 0.5 L to 5 L of the chemical solution (in the case of 10 L / min, the gel time is 3 to 18 seconds).

In the dynamic injection, the energy at the time of maximum discharge is high, and the pulmonary solid S is formed at the time of this maximum discharge. Assuming that a plate-like vein-like solid S having a width of 10 cm to 50 cm and a thickness of 0.2 cm to 1 cm is formed by discharging the chemical solution once, the reach distance of the vein-like solid S is: It can be represented by the following formula (1).
(Formula 1)
Reach distance (cm) = chemical solution gel time (sec) × maximum discharge flow rate (L / min) × 1-2

  In order to improve the ground uniformly, the interval (pitch) between adjacent injection pipes 10 is preferably 1 to 4 m. Accordingly, the required reach distance of the vein-like consolidated object is 50 cm to 200 cm.

  Further, the maximum discharge amount is preferably set to 5 to 20 L / min in order to suppress the cost of the chemical solution and to suppress the sudden displacement of the ground.

  Therefore, by substituting the values of the pulse solidified object reach distance and the maximum discharge amount into the formula 1, a preferable gel time of the chemical solution is required to be 2.5 to 40 sec.

  In addition, when the strength of the chemical solution is rapidly developed, after forming one vein-like solid S, another new vein-like solid S is formed after the gel time. However, since the chemical solution used in the present invention has a slow strength development, it undergoes plastic deformation after the gel time and continues to be pushed by the same vein-like solid S for several cycles, so that the thickness of the vein-like solid S increases. If the vein-like solid S is too thick, it will lead to ground displacement, but if the thickness of the vein-like solid S is several centimeters, the consolidation effect will be high and the liquefaction suppression effect will be high. Therefore, from the viewpoint of strength development, the gel time is preferably 2.5 to 20 sec.

  In addition, the instantaneous setting chemical | medical solution whose gel time is shorter than 2.5 sec forms many vein-like solidified substances S around an injection hole, and it becomes a lump. And since the ground is largely displaced near the injection hole, it is not preferable.

(Injection method)
The chemical solution injection operation is preferably performed by a single-phase double tube strainer method in which holes are drilled with a double tube rod and the chemical solution is injected using the double tube rod. In the conventional liquefaction countermeasure construction method, the penetration of the chemical solution is performed as described above, and the double pipe double packer construction method has been generally adopted. However, the chemical solution injection operation in this embodiment can be performed by a single-phase double pipe strainer method because the chemical solution is injected by split injection. According to the double pipe strainer method, the construction cost can be greatly reduced as compared with the case of the double pipe double packer method.

  In injecting the chemical solution into the ground G, the liquid A such as slag cement slurry and the liquid B such as a water glass solution are separately fed into the double pipe and merged at the tip of the double pipe (2 Shot method) or at the mouth of a double pipe (1.5 shot method).

  The injection pressure of the chemical liquid can be changed, for example, in the range of 0.1 to 3.0 MPa. Moreover, the injection | pouring speed | rate of a chemical | medical solution can be 1 L / min-18 L / min. If the injection pressure of the chemical solution is extremely weak or the injection speed is extremely slow, the chemical solution will solidify in the vicinity of the injection hole, causing significant ground displacement such as the ground near the injection hole rising, and measures against liquefaction The effect may be reduced. Moreover, there is a possibility that the amount of the chemical used needs to be increased.

(Dynamic injection)
The liquefaction countermeasure method of this embodiment performs dynamic injection of a chemical solution, but it is not always necessary to change the injection pressure. For example, the injection pressure can be temporarily fixed at an injection start stage, an injection end stage, or the like. Moreover, what is necessary is just to change injection | pouring pressure periodically about each of 2 liquids, when using the chemical | medical solution of the type which mixes 2 liquids (A liquid and B liquid). Furthermore, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2008-231907, the chemical solution is injected with a fluctuation in the injection pressure in which the periodic fluctuation in the short wave injection pressure is superimposed on the periodic fluctuation in the long wave injection pressure. You can also.

  Moreover, the waveform of the flow rate in the dynamic injection of the chemical solution is not particularly limited, and can be, for example, a sine wave or a pulse wave. However, in the case of a sine wave, it is a mild increase in energy in the process of increasing the flow rate, and has effects such as little influence on the structure or the like. In addition, when the pulse wave is used, the energy is instantaneously amplified in the process of increasing the flow rate, and there are effects such as easy splitting.

  The amplitude of the injection pressure is preferably 30% to 100%. By increasing the amplitude in this way, a dense and complicated pulse can be formed. In addition, this amplitude means (flow rate lower limit / flow rate upper limit) × 100.

  Furthermore, the dynamic injection is preferably performed so that the frequency is 0.01 Hz to 0.5 Hz.

(High-pressure jet stirring)
By the way, as described above, how much the liquefaction resistance of the ground G is improved is appropriately determined in consideration of the use of the ground G and the like. Therefore, depending on the use of the ground G, there are cases where it is necessary to significantly improve the liquefaction resistance. Therefore, in such a case, it is preferable to take measures against liquefaction by replacing a part of the above-described chemical solution injection operation with the high-pressure jet stirring operation.

  As shown in FIG. 2 (3) and FIG. 3 (2), this high-pressure jet agitation operation (construction method) is a construction in which a rotating rod 20 is installed in the ground G in place of the injection tube 10, and the rotating rod 20 The column-shaped improvement body T is created by spraying a hardener such as cement milk while rotating. In this respect, according to the chemical injection method (work) of the present embodiment, it has been described above that a tree branch extends into the ground G. However, according to the embodiment in which this high-pressure jet stirring operation is used together, the improved body T is From this trunk, a vein-like solidified substance S, which is a tree branch, extends. Therefore, the liquefaction resistance of the ground G is greatly improved.

  This high-pressure jet stirring operation can be performed in the same procedure as in the CCP method, for example.

  The injection pressure of the curing material can be, for example, 5 MPa to 50 MPa, preferably 40 MPa. The pulling speed of the rotating rod 20 can be set to, for example, 30 seconds / m to 6 minutes / m, preferably 1 minute / m to 3 minutes / m. By performing the high-pressure jet stirring operation at such jet pressure and pulling speed, for example, an improved body T having a diameter of 600 mm to 1000 mm can be created. In the general CCP method, the injection pressure of the curing material is 20 MPa, the pulling speed of the rotating rod is 2 minutes / m to 6 minutes / m, and an improved body having a diameter of 300 mm to 500 mm is created. . In addition, the rotational speed of the rotating rod 20 can be 10 rpm-40 rpm, for example.

  It is not particularly limited which of the chemical solution injection operation (formation of the vein-like solid S) and the high-pressure injection operation (formation of the improved body T) is performed first, but it is preferable to perform the high-pressure injection operation first. Since the improved body T is formed by performing the high-pressure jetting operation first, and then the chemical solution injection operation is performed, the improved body T and the pulmonary solid S are integrated, and a synergistic effect of the liquefaction suppression effect is obtained. It is. Moreover, it is because it can prevent that the pulse-like solidified substance S by chemical | medical solution injection | pouring is destroyed by the cutting force of high pressure injection.

  Further, the work just under an existing structure or the like is more suitable by a chemical liquid injection work that facilitates an oblique work. Therefore, it is preferable to set the erection positions of the injection tube 10 and the rotating rod 20 on the assumption that the chemical solution injection operation is performed around the structure.

(Drilling)
In the liquefaction countermeasure method according to the present invention, first, the ground is drilled, and an injection pipe is built into the drilled hole. In this drilling operation, it is preferable to set the discharge amount of drilling water to 10 L / min or more. By making it 10 L / min or more, the ground can be split with the drilling water before the chemical solution is injected. As a result, when the chemical solution is injected later, the pulmonary solid S is easily formed.

  Further, at the time of drilling, the instantaneous discharge pressure of the drilling water when the rod is pushed downward is preferably 0.2 MPa or more. By setting it to 0.2 MPa or more, it is possible to obtain the same effect as when the discharge amount of drilling water is 10 L / min or more.

(Replacement filling)
In the present embodiment, it is more preferable to replace and fill at least one of mortar, cement milk and chemical liquid into the hole formed by the work after the above chemical liquid injection work or high-pressure jet stirring work. . In addition, the said chemical | medical solution makes both liquids of (1) the 1st liquid mainly composed of blast furnace slag or the cement containing the said blast furnace slag, and (2) 2nd liquid mainly composed of water glass contact. It is a thing. Next, replacement filling will be described.

  Usually, after a chemical solution injection operation or a high-pressure jet agitation operation, a process such as solidification of a hole formed by the operation is not performed. However, in this embodiment, the hole is replaced and filled with mortar or cement milk, and the solidified body formed by this replacement filling is a “stem” that is continuous with the pulmonary solidified body existing in the previously formed ground. The resistance to shear deformation due to seismic waves can be increased.

  In addition, when replacing with at least any one of mortar, cement milk, and the said chemical | medical solution, if a structure, such as a reinforcing bar and H steel, is inserted in a drilling hole, stronger shear deformation resistance can be obtained.

Next, examples and comparative examples will be shown to explain the effects of the present invention.
(Chemical solution test)
A comparison test between the chemical solution used in the present invention and a conventional chemical solution was performed.
First, as Example 1 of this invention, the A liquid and B liquid of following Table 1 were mixed within the beaker, and it was made to gelatinize. The gel time of this mixed drug solution is 5 to 8 seconds.

Next, as Example 2 of this invention, the C liquid and D liquid of following Table 2 were mixed within the beaker, and it was made to gelatinize. The gel time of this mixed drug solution is 8 seconds to 12 seconds.

And as a comparative example, E liquid and F liquid of following Table 3 were mixed within the beaker, and it was made to gelatinize. The gel time of this mixed drug solution is 40 seconds to 50 seconds.

Table 4 shows the vane shear strength and the converted uniaxial strength of each board in Examples 1, 2 and Comparative Examples. Here, the vane shear strength was performed based on the “In-situ Vane Shear Test Method” of the Geotechnical Society Standard (JGS 1411-2003).

  In Example 1 and Example 2, it can be seen that the vane shear strength gradually increases with time. Since the increase in strength is gradual, it is possible to spread the vein-like solid S for split injection over a wide range.

  On the other hand, the comparative example has a problem that the chemical solution does not solidify in about 30 seconds and the packing effect is weak.

  In addition, the vane shear strength rapidly increases from 1 minute to 3 minutes. When such rapid development of strength occurs, there is a problem that the chemical solution is solidified around the injection port and the pulmonary solid S is difficult to spread. Furthermore, there is a problem that the ground around the injection port is raised and the ground is deformed.

  From the above results, it can be understood that a form in which slaked lime or an admixture is included in the liquid A is preferable.

(Piezo Drive Cone Test)
In addition, a piezo drive cone test was performed on the ground subjected to liquefaction countermeasures according to the present invention. Details of this test are described below. The Piezo Drive Cone (also referred to as “PDC”) test is a ground survey method that measures the penetration resistance (N value) of the ground and estimates the fine particle content (FC) in situ. is there.

  In the liquefaction countermeasure, the dynamic injection conditions were an amplitude of 50% and a period of 20 seconds.

  4 and 5 show the N values of the ground before the liquefaction countermeasure and the ground after the liquefaction countermeasure. In addition, the area | region which improved the ground is depth 3m-6m. Note that the measured values are shown averaged for every 0.5 m depth. Moreover, the space | interval (pitch) of the injection pipe 10 adjacent to the front-back direction or the left-right direction is 1.5 m in FIG. 4, and 2.0 m in FIG. Further, A1 and B1 indicate positions that are a quarter of the predetermined distance L, and A2 and B2 indicate midpoints of the injection tubes that are adjacent in the oblique direction.

  The ground with liquefaction countermeasures was able to confirm that the converted N value increased overall compared to before the countermeasures.

  The present invention is applied as a ground liquefaction countermeasure method that suppresses or prevents liquefaction of the ground by repeatedly performing a chemical liquid injection operation in which an injection pipe is built in the ground and a chemical liquid is injected into the ground through the injection pipe. Is possible.

  DESCRIPTION OF SYMBOLS 10 ... Injection pipe | tube, 20 ... Rotating rod, G ... Ground, S ... Pulse-shaped solidified substance, T ... Improvement body, X ... Working area | region, Y ... Non-working area | region.

Claims (12)

A ground liquefaction countermeasure construction method in which an injection pipe is built in the ground, and a chemical liquid injection work for injecting a chemical liquid into the ground through the injection pipe is repeated,
The chemical solution is injected by split injection and by dynamic injection that periodically changes the injection pressure,
Erection of the injection pipe is performed at predetermined intervals in the left-right direction and the front-rear direction of the ground, and so as to satisfy the following conditions (A) and (B):
The ground liquefaction countermeasure method characterized by this .
(A) With respect to the left-right direction and the front-rear direction of the ground, the work area and the non-work area are adjacent to each other.
(B) Regarding the oblique direction of the ground, the work area is continuous.
Here, the work area refers to an area surrounded by a virtual square whose four sides pass through a position that is a quarter of the predetermined distance from the position where the injection pipe is built. The non-work area is an area that does not correspond to the work area. The predetermined interval is set so that the injection rate of the chemical solution is 2% to 15%.
The ground liquefaction countermeasure construction method according to claim 1 .
Here, the injection rate of the chemical solution is “the injection amount of the chemical solution (L) / the volume of the ground to be countermeasured (m ³ ) × 100”. The chemical solution injection operation is performed by a single-phase double tube strainer method.
The ground liquefaction countermeasure construction method according to claim 1 or claim 2 . The dynamic injection of the chemical solution is performed so that the amplitude of the flow waveform is at least one of a sine wave and a pulse wave of 30% to 100%.
The ground liquefaction countermeasure construction method according to any one of claims 1 to 3 . Dynamic injection of the chemical solution is performed so that the frequency is 0.01 Hz to 0.5 Hz.
The ground liquefaction countermeasure construction method according to any one of claims 1 to 4 . As the drug solution, a drug solution whose gel time corresponds to 0.1 cycle to 3 cycles of the dynamic injection is used.
The ground liquefaction countermeasure construction method according to any one of claims 1 to 5 . As the chemical solution, a chemical solution having a gel time of 2.5 to 40 sec is used.
The ground liquefaction countermeasure construction method according to any one of claims 1 to 5 . As the chemical solution, a mixed type chemical solution in which two or more liquids are mixed, and a chemical solution having a viscosity at the time of mixing of 1 mPa · s to 100 mPa · s, is used.
The ground liquefaction countermeasure construction method according to any one of claims 1 to 7 . The chemical solution is
(1) A blast furnace slag or a cement containing the blast furnace slag and a first liquid mainly composed of slaked lime (2) a second liquid mainly composed of water glass are brought into contact with each other.
The ground liquefaction countermeasure construction method according to any one of claims 1 to 8 .   The ground liquefaction countermeasure construction method according to claim 1, wherein the drilling water is discharged at a rate of 10 L / min or more in the ground drilling performed before the injection pipe is built in the ground. A part of the chemical solution injection work is performed instead of the high-pressure jet stirring work.
The ground liquefaction countermeasure construction method according to claim 1.
Here, the high-pressure jet agitation operation refers to an operation in which a rotating rod is built in the ground instead of the injection pipe, and a hardened material is injected while rotating the rotating rod to form a columnar improvement body. After at least one of the chemical solution injection operation and the high-pressure jet stirring operation, the hole formed by the operation is replaced and filled with at least one of mortar, cement milk, and chemical solution.
The ground liquefaction countermeasure method according to claim 11 .
Here, the chemical solution is
(1) A blast furnace slag or a cement containing the blast furnace slag and a first liquid mainly composed of slaked lime (2) a second liquid mainly composed of water glass are brought into contact with each other.

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