JPH06336721A - Prevention of displacement of ground - Google Patents

Abstract

PURPOSE:To absorb stresses of frost heaving, settlement, etc., on freezing and thawing and securely prevent displacement of ground, by constructing balloon- like bodies at the upper and side faces of an improved body against freezing to be constructed and managing the inner pressure. CONSTITUTION:A casing pipe 1 is inserted to a specified depth of the upper face and the side faces of an improved body A against freezing to be constructed. Next, a stabilizing solution 24 is poured while extremely high pressure jet 21 is ejected from a triple-tube 20 for jet grouting inserted into the easing pipe 1 to construct a cavity 23 for absorbing an expansion pressure. Next, an antifreeze solution pipe 2 is inserted and a balloon-like body BS folded to form a thin diameter is pushed in. Subsequently, an antifreeze solution 24 is poured into the balloon-like body BS and the balloon-like body is pressurized to contact the wall face of the cavity 23 and form balloon like bodies B1-B13. And a freezing agent is poured from a freezing agent pipe P to construct the improved body A against freezing. At this time, the inner pressure of the balloon-like bodies B1-B13 is managed to absorb the expansion pressure EP due to freezing. Thereafter, after the ground has beer stabilized, a hardening agent is infected in the balloon-like bodies B1-B13 to solidify the ground.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing ground displacement when constructing a freezing improver.

[0002]

2. Description of the Related Art A freezing process for injecting a freezing material into a cohesive ground to form a freezing improver to improve the cohesive ground is well known.

[0003]

In this freezing method, the phenomenon of frost heaving during freezing and the phenomenon of subsidence upon thawing occur,
A secondary disaster will occur due to the improvement. In addition, the ground other than the soil to be frozen will freeze even on the ground around the freezing pipe, causing a problem.

An object of the present invention is to provide a ground displacement preventing method for preventing the displacement of the ground by absorbing stress such as freezing and subsidence during freezing and thawing in the freezing method.

[0005]

The method according to the present invention comprises a step of inserting a casing pipe by drilling holes on the upper surface and the side surface of a freeze improver to be formed to a predetermined depth and inserting the casing pipe to a predetermined depth. Inserting the triple pipe for jet grout and inserting the triple pipe for jet grout to pull up the casing pipe to a predetermined depth, and jetting the ultrahigh pressure jet of the stable liquid from the triple pipe for jet grout and injecting the stable liquid Expanding the triple pipe and excavating the ground to create a cavity for expansion pressure absorption, and a step for creating a cavity for expansion pressure absorption, collecting the triple pipe for jet grout on the ground, and inserting an antifreeze pipe to the bottom of the cavity An antifreeze pipe inserting step to perform, and a balloon-shaped body building step of building a balloon-shaped body folded into a thin diameter that can be inserted into the casing pipe, A balloon-shaped body adhering step of injecting an antifreeze liquid into the balloon-shaped body and pressurizing and adhering to the inner wall of the cavity, an expansion pressure absorbing step of managing the internal pressure of the balloon-shaped body to absorb the freezing expansion pressure during freezing, After the completion, the pressure in the balloon-shaped body is controlled, and after the ground is contracted and stabilized, a hardening material injecting and hardening step of injecting and hardening the hardening material in the balloon-shaped object is characterized.

The hole diameter is preferably 150 mm, for example.

Further, it is preferable to select, as the material for the balloon-shaped material, a material having a large expansivity that is not damaged by a sharp blade-shaped material such as a tool shell in cohesive soil.

[0008]

In the method of the present invention, the pressure in the balloon is controlled to be close to the fresh water pressure, and when the freeze expansion pressure is generated, it is absorbed by the balloon.

When the freezing process is completed, the pressure inside the balloon-shaped body is controlled, and after the ground material has contracted and stabilized while measuring the time-dependent contraction of the ground material, a hardening material is injected into the balloon-shaped material.

Therefore, ground displacement due to frost heave phenomenon during freezing and thaw subsidence phenomenon during thawing can be prevented.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, a freezing pipe P is inserted from the upper layer to the sand layer c in the ground of the fine sand layer a, the clay layer b and the sand layer c. Then, a freezing material is injected from the freezing pipe P to construct the freezing improver A from the cohesive soil layer b to the sand layer c.

In order to prevent displacement of the ground due to freezing up and subsidence due to the formation of the freezing improver A to be built, the present invention is carried out so as to contact the upper surface of the freezing improver A and the side surface located in the clay layer b. A plurality of balloons B1 and B
2 ..., B9, B10 ... (the reference numeral B is used when collectively referred to below) are formed by the antifreeze pipes 2a, 2b ...

FIG. 2 shows another example of the arrangement of balloons. In this example, balloon-like bodies B1 to B3 are formed by antifreeze pipes 2a to 2c on the upper surface of the freeze improvers A1 to A4 formed by overlapping the freeze pipes P1 to P4.

FIG. 3 shows an example of an apparatus for carrying out the present invention.

A drain pipe 3 is connected to the upper portion of the antifreeze pipe 2 housed in the casing pipe 1, and the drain pipe 3 is provided with a pressure sensor 4 and a drain control solenoid valve 5. In addition, the antifreeze pipe 2 has an injection pipe 6 which also serves as a drain pipe.
Has been inserted. The injection pipe 6 is connected to the discharge side of the injection pump 9 via the injection speed adjusting solenoid valve 7 and the injection control solenoid valve 8, and the suction side of the injection pump 9 is connected to the antifreeze tank 10. There is. Furthermore, the injection pipe 6 is connected to the relief valve 11. A level meter 12 is provided on the surface of the earth, and a plurality of pressure sensors 13 are provided below the bottom surface of the balloon B. Then, these devices 4, 5, 7, 8, 9, 11, 13 and the underground displacement sensor 15
The ground level sensor 16 (FIG. 7) is connected to the pressure management recording device 14, respectively.

Next, the mode of preventing ground displacement will be described with reference to FIGS. 4 to 6 by taking the balloon-shaped body B1 on the upper surface of the freezing improver A as an example.

(1) Casing pipe insertion step For example, a boring hole of 150 mm is formed in the ground at a predetermined depth H.
The holes are drilled up to (Fig. 1) and the casing pipe 1 is inserted (Fig. 4).

(2) Jet grouting triple pipe inserting step The jet grouting triple pipe 20 is inserted to a predetermined depth of the casing pipe 1, that is, to the bottom, and the casing pipe 1 is pulled up to a predetermined depth H1 (FIG. 4).

(3) Process of creating cavity for expansion pressure absorption Ultra high pressure jet 2 of stabilizing liquid from upper nozzle of triple pipe 20
While ejecting No. 1, the stable liquid is injected 22 from the lower nozzle to pull up the triple pipe 20, and the clay soil layer b is excavated to form the expansion pressure absorbing cavity 23. Then, the cavity 23 is filled with the stabilizing solution 24 so that the cavity wall does not collapse (FIG. 4).

(4) Antifreeze Pipe Inserting Step After the triple pipe 20 is collected on the ground, the antifreeze pipe 2 is inserted into the cavity 2
Insert to depth H1 of 3 (Fig. 5).

(5) Balloon-shaped object building step At the bottom of the antifreeze tube 2, a balloon-shaped object BS folded into a small diameter that can be inserted is installed (FIG. 5).

(6) Balloon-shaped body adhering step In the folded balloon-shaped body BS, the injection pump 9 is operated to inject and pressurize the antifreeze liquid 25, and the balloon-shaped body Bs is expanded to adhere to the wall surface of the cavity 23. Then, the balloon B1 is formed (FIG. 6). At this time, the injection pressure is the hydrostatic pressure plus soil pressure obtained from the preliminary study. Further, the stabilizing liquid 24 is discharged from the upper end of the casing pipe 1.

(7) Expansion pressure absorption step In this state, the frozen material is injected from the freezing pipe P to obtain the freeze-improved body A.
(Fig. 1). At the time of this freezing, the internal pressure of the balloon B1 is controlled as described later, and the expansion pressure E
Absorbs P (FIG. 1) (FIG. 6).

(8) Hardening material injecting and solidifying step After freezing is completed, the internal pressure of the balloon-shaped body B1 is controlled as described later, and after the ground material shrinks and stabilizes while measuring the time-dependent shrinkage of the ground material, The balloon B1 filled with the antifreeze solution 25 is filled with a hardening material that develops strength similar to the ground strength, and is solidified.

Next, the manner of managing the internal pressure of the balloon B1 will be described with reference to FIG.

The pressure management recording device 14 includes the pressure sensor 1
3. Based on the detection signals from the underground displacement sensor 15 and the underground level sensor 16, it is judged whether or not the set allowable value of the internal pressure is held (step S1). If YES, the setting allowable value is held (step S7), recorded and managed (step S8).

If step S1 is NO, it is judged whether or not the fluctuations in pressure and level are increasing (step S).
2). If YES, open the electromagnetic valve 5 for drainage control (step S3), drain and depressurize (step S4), NO
In the case of, the injection pump 9 is operated (step S5), and the antifreeze solution is replenished and pressurized (step S6).

[0029]

As described above, according to the present invention, it is possible to manage the internal pressure of a balloon and reliably prevent the ground displacement due to the frost heave phenomenon during freezing and the sinking phenomenon during thawing.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing an example of the arrangement of balloons with respect to a freeze improver.

FIG. 2 is a plan view showing another example of the arrangement of the balloon-shaped bodies with respect to the freeze improver.

FIG. 3 is an overall configuration diagram showing an example of an apparatus for implementing the present invention.

FIG. 4 is a vertical cross-sectional view for explaining the steps from the casing pipe insertion step to the expansion pressure absorbing cavity formation step.

FIG. 5 is a vertical cross-sectional view illustrating an antifreeze pipe inserting step and a balloon-like body arranging step.

FIG. 6 is a vertical cross-sectional view illustrating a balloon-shaped body contacting step and an expansion pressure absorbing step.

FIG. 7 is a control flowchart of a balloon-shaped body pressure management.

[Explanation of symbols]

 A Freeze improver B Balloon EP Inflation pressure P Freezing pipe a Fine sand layer b Cohesive soil layer c Sand layer 1 Casing pipe 2 Antifreeze pipe 3 Drain pipe 4 Pressure sensor 5 Drainage control solenoid valve 6 Injection pipe 7 Electromagnetic for injection speed control Valve 8 Solenoid valve for injection control 9 Injection pump 10 Antifreeze tank 11 Relief valve 12 Level gauge 13 Pressure sensor 14 Management recording device 15 Underground displacement sensor 16 Underground level sensor 20 Triple pipe for jet grout 21 Super high pressure jet 23 Expansion pressure absorption Cavity 24 Stabilizer 25 Curing material

Claims (1)

[Claims] 1. A casing pipe inserting step of drilling holes on a top surface and side surfaces of a formed freeze improver to a predetermined depth and inserting a casing pipe, and inserting a triple pipe for jet grout to a predetermined depth of the casing pipe, and Jet grouting triple pipe insertion step of pulling up the casing pipe to a predetermined depth, and jetting a stabilizing liquid ultra-high pressure jet from the jet grouting triple pipe and injecting stabilizing liquid to pull up the triple pipe and excavate the ground An expansion pressure absorbing cavity forming step to form an expansion pressure absorbing cavity, an antifreeze tube inserting step of inserting the antifreeze tube to the bottom of the cavity while collecting the triple pipe for jet grout on the ground, and the casing pipe A step of constructing a balloon-shaped body that is folded into a small diameter so that it can be inserted into the inside, and an antifreeze liquid is injected into the balloon-shaped body to form the cavity A balloon-shaped body contacting step in which the balloon-shaped body is adhered under pressure to the inner wall, an inflation pressure absorption step in which the pressure in the balloon-shaped body is absorbed during freezing to absorb the freezing expansion pressure, and a pressure in the balloon-shaped body is managed after completion of freezing. A method for preventing ground displacement, which comprises a step of injecting and hardening a hardening material into the balloon-shaped body after the ground material contracts and stabilizes.