JP4787111B2 - How to prevent sucking out backfill soil - Google Patents

Description

  The present invention relates to a method for preventing suction of backfilled soil on the back of a structure facing the sea such as a caisson, etc., and the backfilled soil capable of quickly forming a suction preventive layer in a necessary range while reducing the number of work steps. The present invention relates to a method for preventing the sucking of water.

  If the permeation-preventing sheet, such as long-fiber polyester-based non-woven fabric laid on the backside of a caisson or other structure facing the sea, does not pass through the backfill stone, the backfill soil is Since it is sucked into the sea in front of the structure, various methods for preventing such sucking of the backfill soil have been proposed (see, for example, Patent Document 1).

In Patent Document 1, the suction of the backfilling soil is stopped by injecting an instantaneous setting liquid into the backfilling soil in and around the place where the suction is generated to form a temporary suction prevention layer, In addition, a method for forming a permanent suck-out preventing layer by injecting a slow-set permeation solidification solution has been proposed. However, in this proposed method, two types of solidifying liquids, a slow-setting solidified liquid and a quick-setting solidified liquid with many restrictions on handling, are required, and the process of forming the suction prevention layer is repeated twice. There is a problem that the number of work steps increases, the work becomes complicated, and cost reduction becomes difficult.
JP 2003-13437 A

  An object of the present invention is to provide a method for preventing the backfill soil from being sucked out, which can reduce the work man-hours and can form the suction prevention layer for preventing the backfill soil from being sucked out quickly within a necessary range.

  In order to achieve the above object, the method of preventing sucking of backfilling soil according to the present invention comprises forming a sucking prevention layer on the backfilling soil on the back side of the structure facing the sea to the front of the structure of the backfilling soil. A method for preventing suction of backfilling soil to prevent sucking, wherein a slow-setting solidification liquid forming the suction-preventing layer is injected into the backfilling soil, and the structure is more than the injection position of the slow-setting solidification liquid. The solidification accelerating liquid of the slow-setting solidified liquid is injected into the backside soil on the object side.

  Here, the solidification accelerating liquid can also be injected into the backfill soil later than the slow-setting solidification liquid, and the slow-setting solidification liquid and the solidification-promoting liquid are independently provided for each predetermined injection depth. It is also possible to inject into the backfill using an injection tube and an injection pump. In addition, the slow-setting solidification liquid and the solidification promoting liquid can be poured into the backfill soil along the inclined back surface of the backfill stone provided immediately after the back surface of the structure. Further, for example, the slow-setting solidified liquid is an alkaline solidified liquid, and the solidification promoting liquid is carbon dioxide gas or carbonated water.

  According to the method for preventing suction of backfill soil of the present invention, a slow-setting solidified liquid for forming a suction-preventing layer is injected into the back-filled soil on the back side of the structure facing the sea. Since the solidification accelerating liquid of this slow-setting solidified liquid is injected into the backfill soil on the structure side from the injection position, the injected solidifying solidified liquid is reacted with the solidification-promoting liquid in the range on the structure side. The outflow of the slow-setting solidified liquid that has been rapidly solidified and injected can be quickly stopped. On the other hand, in the range where the injected solidifying solid solution is on the opposite side of the structure, it will solidify slowly with the original properties of the slow solidifying liquid, so it spreads to the necessary range of backfilling soil and backfilling It is possible to form an anti-suction layer that prevents the soil from being sucked out.

  In this way, using the slow-setting solidification liquid and the solidification-promoting liquid, which are easier to handle than the quick-setting solidification liquid, a layer sufficient for the necessary range can be quickly obtained by performing the process of forming the suction prevention layer once. A permanent anti-suction layer having a thickness can be formed.

Hereinafter, the method for preventing suction of backfill soil according to the present invention will be described based on the embodiments shown in the drawings.
As illustrated in FIG. 1, a backfilling stone 3 is arranged immediately after the back of the caisson 1 facing the sea, and a backfilling soil 4 is backed on the back of the backfilling stone 3. Since the gap between the backfilling stones 3 is large and has high water permeability, the suction of the soil particles is prevented by the suction prevention sheet 5 made of a long-fiber polyester nonwoven fabric laid on the inclined back surface of the backfilling stones 3. A part of the suction preventing sheet 5 is broken and the backfill soil 4 is sucked from the damaged portion B to the sea in front of the caisson 1.

  Therefore, the suction prevention method of the present invention is implemented to prevent the backfill soil 4 from being sucked out from the damaged portion B. First, a hole is drilled along the inclined back surface of the backfilling stone 3, and the solidifying liquid pipe 6 and the accelerating liquid pipe 8 are installed in the backfilling soil 4. At that time, the accelerating liquid pipe 8 is installed closer to the caisson 1 than the solidified liquid pipe 6. Each of the solidifying liquid pipe 6 and the accelerating liquid pipe 8 has a double pipe structure in which an inner pipe provided with a packer is provided, and the outer pipe is provided with a large number of injection holes 6a and 8a, respectively. The liquid can be injected by a so-called double pipe double packer system.

  Further, the solidification liquid pipe 6 is connected to a supply tank for the slow-setting solidification liquid C, and an injection pump 7 is installed in the middle thereof. The accelerating liquid pipe 8 is connected to a supply tank of the solidification accelerating liquid P, and an injection pump 9 is installed in the middle thereof.

  As the slow-setting solidified liquid C, a permanent suction-preventing layer L can be formed, and various alkaline solidified liquids and acidic solidified liquids (silica sol, etc.) of water glass chemicals are mainly used. The solidification time from liquid to solidification (gelation) is, for example, about one day. The solidification accelerating liquid P is for accelerating solidification by increasing the solidification speed of the slow-setting solidified liquid C to be used. For example, the solidification time is about 5 to 30 seconds. The solidification accelerating liquid P neutralizes the slow-setting solidified liquid C. In the case of the alkaline slow-setting solidified liquid C, an acidic component is used, and in the case of the acidic slow-setting solidified liquid C, an alkaline component is used. It is done.

  When an alkaline solidification liquid such as colloidal silica is adopted as the slow-setting solidification liquid C, and carbon dioxide or carbonated water is adopted as the solidification promoting liquid P, a great cost reduction effect can be obtained.

  Next, as illustrated in FIG. 2, the injection pump 7 is operated, and a predetermined amount of the loose solidification liquid C is backfilled from the injection hole 6 a below the solidification liquid pipe 6 by the double pipe double packer system. 4 and sequentially injects the solidified solidified liquid C from the upper injection hole 6a. The injected slow-setting solid solution C penetrates into the backfill soil 4 in the order of injection and spreads around.

  Next, as illustrated in FIG. 3, after the start of the injection of the slow-setting solidified liquid C, the injection pump 9 is operated with a predetermined time difference, and the double pipe double packer system is used. A predetermined amount of the solidification promoting material P is injected into the backfill soil 4 from the injection hole 8a, and the solidification promotion liquid P is sequentially injected from the upper injection hole 8a in the same manner. The injected solidification accelerating liquid P penetrates into the backfill soil 4 in the order of injection, and the accelerating liquid pipe 8 is in a range where it mixes with the slow-setting solidified liquid C that has been infiltrated and spread earlier. In the peripheral region, the slow-setting solidified liquid C rapidly solidifies due to the neutralization reaction between the two. On the other hand, in the vicinity of the solidification liquid pipe 6 and the area on the opposite side of the solidification liquid pipe 6 from the promotion liquid pipe 8 in a range where the slow solidification liquid C and the solidification promotion liquid P do not mix with each other. Since the solidification of C is not promoted, the slow-setting solidified liquid C continues to permeate into the backfill soil 4 and solidifies slowly according to the original characteristics.

  As a result, the suction preventing layer L is formed along the inclined back surface of the backfill stone 3 as illustrated in FIG. The sucking prevention layer L is formed of only the quick setting layer L1 formed by the reaction of the slow setting solid solution C and the solidification promoting liquid P, and only the slow setting solid solution C along the back surface of the quick setting layer L1. And a loosened layer L2.

  Thus, the process of forming the suction prevention layer L using the slow-setting solidification liquid C and the solidification-promoting liquid P, which are instantly solidified and have better handling than the quick-setting solidification liquid with many restrictions on handling. The quick-coupling layer L1 that closes the damaged portion B of the suction preventing sheet 5 is quickly formed and the loose-coupling layer L2 is formed in a necessary range on the opposite side of the caisson 1 of the instantaneous connection layer L1. A permanent suck-out preventing layer L having a sufficient layer thickness can be formed.

  Since the quick setting layer L1 is formed quickly, the injected slow solidifying liquid C is prevented from flowing out from the damaged portion B, and the slow solidifying liquid C is not used wastefully. Further, it is not necessary to perform the step of forming the suction preventing layer L twice as in the prior art, and the number of work steps can be greatly reduced, so that a great cost reduction effect can be obtained.

  The injection timing of the slow-setting solid solution C and the solidification accelerating solution P differs depending on the injection conditions such as the soil conditions and the injection amount of the backfilling soil 4, and the solidification promoting solution P Although it is possible to inject prior to or simultaneously with the slow-setting solidification liquid C, it is preferable to inject the solidification promoting liquid P into the backfill soil 4 later than the slow-setting solidification liquid C. By injecting the solidification accelerating liquid P with a relative delay, the minimum amount of the slow solidification liquid C necessary for closing the damaged portion B is solidified, and the remaining amount of the slow solidification liquid C is solidified immediately. This is because it is easy to form the loosened layer L2 having a sufficient thickness by infiltrating the necessary range of the backfilling soil 4 without any problem.

The injection timing of the slow-setting solidification liquid C and the solidification promoting liquid P can be calculated by, for example, the following formulas (1) and (2).
t = μ × t ₀ (1)
t ₀ = (πλr ² h) / q (2)

Here, t is the time (s) from the start of injection of the slow-setting solidified liquid C to the injection of the solidification accelerating liquid P, and μ is the injection time coefficient of the solidification accelerating liquid P (0.5 depending on the soil quality of the backfilling soil 4). ˜1.0), t ₀ is the arrival time (s) of the slow solidification liquid C from the injection hole 6a of the slow solidification liquid C to the injection hole 8a of the solidification promoting liquid P, and λ is the injection rate (= α × n / 100%), α is the filling rate of the slow-setting solidified liquid C (approximately 0.9 depending on the soil quality of the backfill soil 4), and n is the porosity (%) of the backfill soil 4. r is a radius (m) from the injection hole 6a of the slow-setting solidified liquid C to penetrate, and h is a thickness (m) into which the slow-setting solidified liquid C to be penetrated is injected. q is the flow rate (m ³ / S) of the slow-setting solidified liquid C.

  The above-described coefficients are obtained by collecting the backfilling soil 4 forming the suction preventing layer L as a test sample and performing an experiment with the test sample, or using an empirical value. .

  FIG. 5 illustrates another embodiment. In this embodiment, a solidification liquid pipe 6 and an accelerating liquid pipe 8 are erected substantially vertically at the caisson side of the solidification liquid pipe 6 for each predetermined injection depth near the inclined back surface of the backfill stone 3. Then, the solidifying solid C is injected into the backfill soil 4 from the injection hole 6 a at the tip of each solidification liquid pipe 6, and the solidification promotion liquid P is injected from the injection hole 8 a at the tip of each promotion liquid pipe 8.

  Independent injection pumps 7 and 9 are installed in each of the solidified liquid pipe 6 and the accelerating liquid pipe 8, so that the injection timing, injection speed, injection amount, etc. can be freely set for each injection depth. It is easy to form the suction preventing layer L according to the required specifications. The solidification liquid pipe 6 and the accelerating liquid pipe 8 may be provided with injection holes 6a and 8a at positions other than the tips, respectively.

  As described above, according to the present invention, in any of the embodiments, the slow-setting solidification liquid C and the solidification promoting liquid P are injected into the backfill soil 4 using an independent injection pipe and injection pump at each predetermined injection depth. can do.

  FIG. 6 illustrates still another embodiment. In this embodiment, a single pipe solidification liquid pipe 6 is disposed along the inclined back surface of the backfilling stone 3, and a single pipe accelerating liquid pipe 8 is disposed at a predetermined deepest position on the caisson 1 side of the solidification liquid pipe 6. Until the solidified liquid pipe 6 and the accelerating liquid are injected into the backfill soil 4 while injecting the slow-setting solidified liquid C and the solidifying accelerating liquid P from the injection holes 6a and 8a at the respective ends. The pipe 8 is lifted upward. Even if this method is used, the same suction prevention layer L illustrated in FIG. 4 can be formed.

  According to this embodiment, the slow-setting solidification liquid C and the solidification accelerating liquid P can be injected into the backfilling soil 4 along the inclined back surface of the backfilling stone 3 accurately and quickly. It becomes easy to form the suction preventing layer L having a uniform layer thickness along the inclined back surface.

  Here, when the slow solidifying liquid C injected from the injection hole 6a of the solidifying liquid pipe 6 penetrates the backfill soil 4 and reaches the vicinity of the accelerating liquid pipe 8, the slow solidifying liquid C The injection hole 6a at the tip of the solidification liquid pipe 6 is positioned above the injection hole 8a at the tip of the promotion liquid pipe 8 so that the injection hole 8a through which the solidification promotion liquid P is injected passes through the region where C has penetrated. Thus, it is preferable that the solidifying liquid pipe 6 and the accelerating liquid pipe 8 are lifted.

  The present invention can be applied not only to the caisson 1 but also to the suction prevention of the backfill soil 4 on the back of various structures facing the sea, and can also be applied to the case where there is no backfill stone 3. For example, as in the embodiment illustrated in FIG. 7, it is applied to prevent the backfill soil 4 from being sucked out from the back side of the steel sheet pile 10 that is erected from the sea in parallel in the width direction facing the sea. Can do. The parallel steel sheet piles 10 are erected by tie rods 12 or tie wires connected to piles 11 embedded in the backfill soil 4 behind, and the joints of the parallel steel sheet piles 10 and 10 are sealed with a water stop material. Has been. When this water stop material is damaged, the backfill soil 4 may be sucked into the sea in front of the steel sheet pile 10.

  In order to prevent this suction, the slow-setting solidified liquid C is backed up from the injection hole 6a of the outer pipe of the solid pipe 6 having a double pipe structure by the double pipe double packer system as in the above embodiment. The solidification promoting liquid P is injected into the soil 4 and from the injection hole 8a of the outer pipe of the double pipe structure promoting pipe 8 to the backfilling earth 4 on the steel sheet pile 10 side from the injection position of the slow solidifying liquid C. Inject. Thereby, the instantaneous linking layer L1 immediately after the back surface of the steel sheet pile 10 is formed, the slow linking layer L2 is formed on the back surface of the instantaneous linking layer L1, and the suction preventing layer L similar to the example of FIG. 4 is formed. Can do.

  Also in this embodiment, the same method illustrated in FIG. 6 can be applied, and the single solidification liquid pipe 6 and the accelerating liquid pipe 8 are drawn upward along the steel sheet pile 10, The slow-setting solidification liquid C and the solidification promoting liquid P can be injected into the backfill soil 4 from the injection holes 6a and 8a.

  In the present invention, not only the double tube double packer method but also the super multi-point method or double tube strainer method is used for injecting the slow-setting solidification liquid C and the solidification promoting liquid P into the backfill soil 4. You can also.

  Further, the present invention can also be applied to prevent the backfill soil 4 from being sucked on the back of a structure facing not only the sea but also a lake or a river if the backfill soil 4 is sucked out.

It is a longitudinal cross-sectional view which illustrates the first process of the suction prevention method of this invention. FIG. 2 is a longitudinal sectional view illustrating the next process of FIG. 1. FIG. 3 is a longitudinal sectional view illustrating the next step of FIG. 2. It is a longitudinal cross-sectional view which illustrates the suction prevention layer formed after the process of FIG. It is a longitudinal cross-sectional view which illustrates another embodiment of the suction prevention method of this invention. It is a longitudinal cross-sectional view which illustrates another embodiment of the suction prevention method of this invention. It is a longitudinal cross-sectional view which illustrates another embodiment of the suction prevention method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Caisson 2 Foundation mound 3 Backfill stone 4 Backfill soil 5 Suction prevention sheet 6 Solidification pipe 6a Injection hole 7 Injection pump 8 Accelerating liquid pipe 7a Injection hole 9 Injection pump 10 Steel sheet pile 11 Pile 12 Tie rod C Looseness Solidification liquid P Solidification promoting liquid L Suction prevention layer L1 Instant tie layer L2 Slow tie layer

Claims (5)

  A method for preventing the backfill soil from sucking out the backfill soil by forming a suction prevention layer on the backfill soil on the back of the structure facing the sea. Injecting a slow-setting solidification liquid that forms a layer into the backfill soil, and a solidification-promoting liquid for the slow-setting solidification liquid to the backfill soil on the structure side from the injection position of the slow-setting solidification liquid How to prevent sucking out backfill soil.   The method of preventing suction of backfilling soil according to claim 1, wherein the solidification promoting liquid is injected into the backfilling soil after being delayed from the slow-setting solidifying liquid.   The suction of the backfilling soil according to claim 1 or 2, wherein the slow-setting solidification liquid and the solidification accelerating liquid are injected into the backfilling soil using an independent injection pipe and injection pump at each predetermined injection depth. Prevention method. The backfilling soil according to claim 1 or 2 , wherein the slow-setting solidification liquid and the solidification promoting liquid are respectively injected into the backfilling soil along the backside of a backfilling stone provided immediately after the back of the structure. How to prevent sucking out.   The method for preventing the backfill soil from being sucked out according to any one of claims 1 to 4, wherein the slow-setting solidified liquid is an alkaline solidified liquid and the solidification accelerating liquid is carbon dioxide gas or carbonated water.

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