JP2006233627A - Method of restraining liquefaction of lower ground of existing structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of restraining liquefaction of the lower ground of an existing structure allowing even a drain material with comparatively low tension proof stress to be laid without using a casing. <P>SOLUTION: The method of restraining liquefaction generated to the lower ground of the existing structure includes processes of forming an excavated hole which crosses the lower ground of the existing structure, by an induction type boring device, and leading in a drain pipe while jetting a pressure liquid in the excavated hole and applying vibration to perform enlarging excavation. Stiffening members are fixed at predetermined spaces to the drain pipe, and a linear material such as a steel wire is connected between the stiffening members. The linear material bears at least a part of tensile force in the drain pipe lead-in process. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for suppressing liquefaction that occurs in the lower ground of an existing structure during an earthquake.

  Soft ground such as sand may cause liquefaction during an earthquake, and when an existing structure such as an oil tank is built on such soft ground, drainage material such as a drain pipe is placed directly on the ground. There has been proposed a method for suppressing the liquefaction of the ground.

  As such a ground liquefaction suppression method, for example, in Japanese Patent Application Laid-Open No. 2003-119768 (Patent Document 1), a hole is obliquely drilled from the periphery of an existing structure toward the target ground, and the stratum is formed from the oblique hole. It is described that a structure for preventing liquefaction in soft sand ground is constructed by excavating holes parallel to each other and press-fitting a water-permeable material into these oblique holes and parallel holes. However, in such a reinforcing method, there is a concern that when the water-permeable material is press-fitted into the oblique holes and the parallel holes, ground deformation occurs, and the existing structure is adversely affected.

Japanese Patent Laid-Open No. 2000-290989 (Patent Document 2) discloses a case in which a curved burial hole is provided in a direct base plate of an existing structure by steerable boring, and a drain material is laid in the curved burial hole, and then the casing length A method has been proposed in which the gap between the drain material and the ground is filled with a water-permeable filler.
In such a construction method, when a low-cost synthetic resin pipe is used as a drain material, if the pipe itself is pulled in by a boring device, the synthetic resin pipe has a low tensile strength and breaks in the ground. Probability is high. Therefore, Patent Document 2 describes a method of using a casing, but it is not so easy to fill the gap formed between the drain material and the ground with the water-permeable filler by pulling out the casing. Not that.
JP 2003-119768 A JP 2000-290989 A

  An object of the present invention is to provide an existing structure capable of laying a drain material on a soft ground without adversely affecting the ground and the existing structure and without generating a gap between the drain material and the ground. It is to provide a liquefaction suppression method for the lower ground.

  Another problem of the present invention is that it is possible to lay without using a casing into which a drain material is inserted even when a drain material made of a material other than metal and having a relatively small tensile strength is used. It is providing the liquefaction suppression construction method of the lower ground of a structure.

  Another object of the present invention is to lay drain material on soft ground, so that even when a casing (sheath tube) is used, it is possible to save labor in the casing pull-out operation. It is an object of the present invention to provide a method for suppressing liquefaction of the lower ground of an existing structure that can prevent the occurrence of a gap between the drain material and the ground later.

In the present invention, a drain pipe is provided in the lower ground of the existing structure, and the excess pore water pressure generated during the earthquake is transmitted to the drain pipe, thereby suppressing the liquefaction during the earthquake of the lower ground. Forming a drilling hole that crosses the lower ground by an induction boring device, and ejecting a pressure fluid in the drilling hole and applying vibration to draw a drain pipe while expanding and drilling, A ground comprising fixing stiffening members at predetermined intervals, connecting a tensile reinforcing material between the stiffening members, and causing the tensile reinforcing material to bear at least a part of the tensile force in the drawing process of the drain pipe. A liquefaction suppression method is provided.
Here, a linear material such as a steel wire or a small diameter pipe can be used as the tensile reinforcing material.
In the ground liquefaction suppression method according to the present invention, stiffening members are fixed to the drain pipe at predetermined intervals, and the stiffening members are connected by a tensile reinforcing material such as a steel wire, and the tensile force is applied to these tensile reinforcing materials. Therefore, even if the drain tube has a relatively small tensile strength (for example, a tube formed of a material other than a metal having a peripheral surface with an opening ratio of 20% or more) It is now possible to draw in the ground without using a casing (sheath tube). As a result, it is possible to prevent the gap between the drain material and the ground, which has conventionally been generated when the casing is extracted, and to prevent adverse effects on the ground and existing structures. In addition, since the drain pipe can be constructed even if it has a relatively small tensile strength, the material cost can be greatly reduced compared to the conventional method using a conventional steel pipe having a peripheral surface with a high opening ratio. became.

In the present invention, a drain pipe is provided in the lower ground of the existing structure, and the excess pore water pressure generated during the earthquake is transmitted to the drain pipe, thereby suppressing the liquefaction during the earthquake of the lower ground. A step of forming an excavation hole crossing the lower ground by an induction boring device, a step of ejecting a pressure fluid in the excavation hole and pulling the sheath pipe and the drain pipe while expanding the excavation by applying vibration, and the drawing step And detaching the sheath tube at a predetermined position when the drain tube reaches a planned laying position, leaving the drain tube in the ground, and pulling one of the sheath tubes to the predetermined position while applying vibration to the ground. The ground liquefaction suppression construction method characterized by this is provided.
In the ground liquefaction suppression method according to the present invention, in the step of drawing the sheath pipe and drain pipe into the ground, when the drain pipe reaches the planned laying position, the sheath pipe (casing) is separated at a predetermined position, and the ground is vibrated. Since one of the sheath pipes is pulled out to a predetermined position while being added, and the drain pipe is left in the ground, it is possible to construct so that no gap is generated between the drain pipe and the ground. Further, in the ground liquefaction suppression method according to the present invention, it is possible to lay the drain pipe without applying a large tensile force, so that the drain pipe having a relatively small tensile strength (for example, a circumference having an opening ratio of 20% or more). It has become possible to use a tube formed of a material other than a metal having a surface.
Further, in the present invention, the drain pipe is laid only in the required section of the lower ground of the existing structure, and the other sections are adjusted by adjusting the separation position of the sheath pipe as appropriate and adjusting the distance to move the sheath pipe appropriately. It is possible to make up with a sheath tube, which makes it possible to save labor in the extraction of the sheath tube.

In the present invention, a drain pipe is provided in the lower ground of the existing structure, and the excess pore water pressure generated during the earthquake is transmitted to the drain pipe, thereby suppressing the liquefaction during the earthquake of the lower ground. A step of forming an excavation hole crossing the lower ground with an induction boring device, a step of ejecting a pressure fluid in the excavation hole and drawing a sheath pipe and a drain pipe while expanding the excavation by applying vibration; and There is provided a ground liquefaction suppression method characterized by including a step of leaving the soil in the ground and pulling out the entire length of the sheath tube while applying vibration to the ground from within the drain tube.
In the ground liquefaction suppression method of the present invention, after pulling the drain pipe to the planned laying position, only the sheath pipe is pulled out full length while applying vibration to the ground depending on the ground condition. It has become possible to construct so that no gaps are generated.

In the present invention, the drain pipe can be installed without adversely affecting the ground and the existing structure and without generating a gap between the drain pipe and the ground.
In the present invention, a drain pipe having a relatively small tensile strength can be laid in the ground without using a casing. On the other hand, even when a casing is used, the drain pipe and the ground after the casing is pulled out can be used. It is possible to prevent the generation of a gap between the casing and the labor of pulling out the casing.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited thereto.

<First embodiment>
The present invention provides a drain pipe that crosses the lower ground of an existing structure in soft ground that may cause liquefaction during an earthquake, and the excess pore water pressure generated during an earthquake is transferred to the ground space (atmosphere) via the drain pipe. ) To prevent liquefaction occurring in the lower ground, and the main process includes a guide pipe laying process and a drain pipe laying process.

[Details of drain pipe]
In the ground liquefaction suppression method according to the present invention, prior to the drain pipe laying process or in parallel with the drain pipe laying process, additional work such as fixing required members to the drain pipe is performed. First, the drain pipe and accompanying work will be described.
FIG. 1A is a view showing a drain pipe 10, other members and an apparatus.
The drain tube 10 uses a tube formed of a material other than a metal having a peripheral surface with an aperture ratio of 20% or more. As such a drain tube 10, for example, a mesh-shaped split made of high-density polyethylene is used. It is possible to use a tube in which a tube 11 is formed of fibers, and reinforcing ribs 12 are spirally provided on the outer periphery thereof. For example, Max Drain manufactured by Taiyo Kogyo Co., Ltd. can be used.

The drain pipe 10 having the above-described configuration has a relatively high resistance to compressive force, and is not crushed even when buried in the ground, and can maintain the internal space of the pipe body. Compared with a steel pipe whose surface is formed in a screen shape), there is an advantage that the material cost is low, but there is a weakness that the resistance to tensile force and frictional force in the axial direction of the tube body is relatively small. Therefore, the cap 13, the stiffening member 14 and the wire 15 (tensile reinforcing material) are attached to the drain pipe 10 without using the casing, as shown in FIG. 1 (a) or 2 (a). .
That is, the cap 13 is attached to one end of the drain tube 10, the tubular stiffening member 14 is fixed at a predetermined interval, and the wire 15 is connected between the stiffening members 14. The cap 13 protects the drain pipe 10 from the frictional force of the ground and supplements the tensile rigidity. The stiffening member 14 is for attaching the wire 15 and for supplementing the tensile rigidity. The stiffening member 14 can also be used as a joint at a connection portion between the drain pipes 10. Further, the stiffening member 14 is formed so as to hold the hole wall in the laying process of the drain pipe 10 so that the hole wall is not collapsed and to be able to push sand toward the outside so that the drain pipe 10 does not bear a frictional resistance. Is. Since the tip cap 13 and the stiffening member 14 are connected by the wire 15, the tensile force acting in the laying process of the drain pipe 10 is hardly transmitted to the drain pipe 10, and the tip cap 13, the stiffening member 14 and the wire 15 are not transmitted. And will be paid.

The joint between the stiffening member 14 and the wire 15 can be configured as shown in FIG. 1B or FIGS. 2A to 2C.
1B, a hook 15a is provided at the end of the wire 15, a hole 14a is formed in the stiffening member 14, and the hook 15a is hooked on the hole 14a.
2 (a) to 2 (c), the stopper 15b is provided at a predetermined position of the continuous wire 15, the overhanging portion 14b (see FIG. 2 (c)) is provided in the stiffening member 14, and the overhanging portion. The stopper 15b is hooked on 14b. The projecting portion 14b is composed of two members fixed to the outer peripheral surface of the stiffening member 14, and includes a slit 14c through which the wire 15 is passed between the two members, and the stopper 15b is hooked on the end portion 14d. By configuring the stopper 15b and the overhanging portion 14b in this manner, the tensile force can be transmitted from the wire 15 to the stiffening member 14 in the pull-in direction of the drain tube 10, but conversely, the wire 15 is moved backward. When pulled, it can be easily pulled out from the overhanging portion 14b.

  Furthermore, it is desirable to install vibration devices (not shown) at a plurality of locations in advance inside the drain pipe 10. That is, a wire (not shown) is extended from the cap 13, a vibration device (not shown) is fixed to a plurality of locations of the wire, and each vibration device is arranged inside each stiffening member 14. The vibration device is activated when the drain tube 10 is drawn into the liquefied layer 21.

[Guide laying process]
Next, FIG. 3 (a) (b) is the figure which showed each process by the liquefaction suppression construction method of the ground of this invention.
In FIG. 3A, a liquefied layer 21 and a support layer 22 exist below the existing structure 20, and the direction of the liquefied layer 21 is controlled by a conventional induction boring device (not shown). However, the liquefied layer 21 is drilled so as to cross the lower part of the existing structure 20 substantially in parallel. This hole is provided in a planned laying path of the drain pipe 10, and a guide pipe 23 having a diameter of about 60 mm is laid in this hole.

[Drain pipe laying process]
Next, the tip portion of the guide tube 23 protruding to the ground surface is removed, and an enlarged reamer 24 (see FIG. 1A) is attached thereto, and a diameter of about 250 to 260 mm is connected to the enlarged reamer 24 via a universal joint 25. A drain tube 10 is attached. The reaming reamer 24 is an application of a vibratory vibrator, and is intended to reduce the amount of discharged soil by expanding and excavating only the required hole diameter while compacting the hole wall while making it easier to pull in by loosening the sand ground ahead. Is.
While pulling the expanded reamer 24 with the guide tube 23, the hole excavated by the above process is expanded with the expanded reamer 24, and the drain tube 10 with the cap 13 is pulled in, so that the drain tube 10 is liquefied. 21.
Although not shown, a lubricant supply tube is inserted into the drain pipe 10 and the lubricant is ejected from the enlarged reamer 24 or the front surface of the cap 13 through the lubricant supply tube to reduce the tensile resistance. It is possible to lay the drain pipe 10. In this case, as the lubricant, it is possible to use a biodegradable solution mainly composed of water, air, or natural vegetable oil, and the biodegradable solution disappears with the lapse of time. It does not affect the dissipation of excess pore water pressure.
Furthermore, when pulling the drain pipe 10 into the liquefied layer 21, by applying vibration to the liquefied layer 21 with the above-described vibration device, the rear drain pipe 10 can be easily pulled in, and after removing the cap 13, By pulling out while vibrating, the gap between the drain tube 10 and the liquefied layer 21 can be reduced.
When the expanding reamer 24 reaches the opposite side of the existing structure 20 while drawing the drain pipe 10 into the liquefied layer 21 as described above, the cap 13 at the tip is then removed, and the wire 15 (the form of FIG. 2) is also used. If pulled out from the rear, these members can be used repeatedly.

<Second Embodiment>
In the second embodiment, a drain pipe is laid only on the ground directly under the existing structure, and pipe bodies (sheath pipes) are connected to both ends of the drain pipe to extend to the ground surface. It is a construction method that suppresses the liquefaction that occurs in the lower ground by transmitting it to the ground space (in the atmosphere) via the drain pipe and the sheath pipe, and as its main processes, the guide pipe laying process and the drain pipe laying process Are provided.

[Details of drain pipes, etc.]
FIGS. 4A to 4C are views showing the drain tube 10, the sheath tube 30 and other devices used in the second embodiment. First, these configurations will be described.
The drain pipe 10 is the same as that of the first embodiment, that is, a pipe 11 made of high-density polyethylene mesh-like split fibers and a reinforcing rib 12, and the length thereof is shown in FIG. As shown in (c), the excess pore water pressure in the section immediately below the existing structure 20 in the liquefied layer 21 is made so as to be absorbed. Further, a wire (not shown) in which a vibration device (not shown) is fixed at a plurality of locations is extended inside the drain tube 10, and the end of the wire is fixed to the tip of the sheath tube 30. The vibration device is for starting the drain pipe 10 when drawing it into the liquefied layer 21 and transmitting vibration to the liquefied layer 21.
In the first embodiment, the stiffening member 14 and the wire 15 (tensile reinforcement) are provided in order to compensate for the weakness of the drain pipe 10 that the resistance to tensile force and frictional force is relatively small. Then, this weak point is compensated by inserting the drain pipe 10 into the sheath pipe 30 and performing the laying operation.
As such a sheath tube 30, a flexible and inexpensive material such as a vinyl chloride tube or a polyethylene tube can be used while having tensile strength.
The sheath tube 30 is formed so as to be separable into a first sheath tube 30a and a second sheath tube 30b, and a cap 30c is screwed to the tip. The first sheath tube 30a and the second sheath tube 30b are formed so as to be able to be inserted into each other, and a locking tool 31 is pivotally attached to the inner peripheral surface of the first sheath tube 30a at the insertion portion. A recess 32 is provided on the inner peripheral surface of the tube 30b, and an urging means such as a spring 33 is provided so that the state where the locking tool 31 is locked to the recess 32 as shown in FIG. As shown in (c), the lock release means such as the wire 34 is connected to the lock 31 in order to release the locked state by operating the lock 31 opposite to the urging direction.

[Guide laying process]
In the second embodiment, the laying process of the guide pipe 23 is performed in the same manner as in the first embodiment using a conventional induction boring device as shown in FIG.

[Drain pipe laying process]
Next, the distal end portion of the guide tube 23 protruding to the ground surface is removed, and an enlarged reamer 24 is attached thereto, and the sheath tube 30 is attached to the enlarged reamer 24 via the universal joint 25. The drain tube 10 is inserted into the sheath tube 30 and simultaneously pulled into the ground as shown in FIG. 5 (b). At this time, by means of the reaming reamer 24 using a vibration vibrator, the sand sand in front is loosened and easily pulled in, and only the necessary hole diameter is expanded while the hole wall is compacted, thereby reducing the discharged sediment.
Until reaching the planned laying position of the drain pipe 10, the lubricant is fed through the sheath pipe 30 to reduce the pull-in resistance of the sheath pipe. As this lubricant, it is possible to use a biodegradable solution mainly composed of water, air, or natural vegetable oil.
When the drain pipe 10 reaches the laying planned position, the sheath pipe 30 is cut in the soil, and only the second sheath pipe 30b is pulled out. In this drawing process, the vibration device arranged inside the drain pipe 10 is activated, and the liquefied layer 21 is compacted by vibration while moving the apparatus, so that there is no gap between the drain pipe 10 and the liquefied layer 21. Like that. The rear end of the drain pipe 10 is connected to the first sheath pipe 30a that has been cut and left in the soil, and is left in the ground. When the second sheath pipe 30b on the drawing side reaches the ground surface, the excavation by the expanding reamer 24 is finished, and further, the second length of the drain pipe is exposed to the ground at the necessary position until the second pipe is exposed to the ground. The drawing process of the sheath tube 30b is continued.
As described above, in the present invention, since the drain pipe 10 is laid only in the section immediately below the existing structure 20 and the first sheath pipe 30a and the second sheath pipe 30b are connected to both ends of the drain pipe 10, Thus, since the drawing length is shorter than the method of drawing the full length of the sheath tube from the ground, the drawing resistance can be reduced and the work period can be shortened.

<Third embodiment>
In the third embodiment, a drain pipe is provided so as to cross the lower ground of the existing structure, and the excess pore water pressure generated during the earthquake is transmitted to the ground space (in the atmosphere) via the drain pipe. The main method includes a guide pipe laying process, a drain pipe laying process, and a sheath pipe full length drawing process as its main processes.

[Details of drain pipes, etc.]
In the third embodiment, illustration is omitted, and description will be made with reference to the first and second embodiments.
The drain tube is the same as in the first and second embodiments. A plurality of vibration devices connected by wires are installed inside the drain tube, and the end of the wire is connected to the cap of the drain tube. In addition, the sheath tube uses a flexible and inexpensive vinyl chloride tube, polyethylene tube or the like while having tensile strength as in the second embodiment, but unlike the second embodiment, an intermediate portion is used. Use a continuous joint with a joint.

[Guide laying process]
In the third embodiment, the guide pipe laying step is performed in the same manner as in the first and second embodiments using a conventional induction boring device.

[Drain pipe laying process]
Next, as in the second embodiment, an enlarged reamer is attached to the tip of the guide pipe protruding to the ground surface, and a sheath pipe is attached to the enlarged reamer via a universal joint. A drain pipe is inserted inside the sheath pipe, and the sheath pipe and the drain pipe are simultaneously drawn toward the ground surface on the opposite side of the existing structure while the liquefied layer is expanded and excavated by the expanding reamer. When the sheath tube and drain tube reach the ground surface, the expansion reamer is removed.

[Drawing process of sheath tube]
When the reamer is removed, only the sheath tube is pulled out, leaving the drain tube in the liquefied layer. In this drawing process, the vibration device arranged in the drain pipe is activated, and the vibration is transferred to the liquefied layer through the drain pipe and the sheath pipe while moving the apparatus, thereby the liquefied layer is compacted, Suppresses the gap between the tube and the liquefied layer.
As described above, in the third embodiment, the entire length of the sheath tube is pulled out from the ground while transmitting vibrations to both the liquefied layer and the sheath tube, so that the pulling resistance can be reduced along with the suppression of the gap with the ground. It became possible.

(A) is the figure which showed the drain pipe used in 1st embodiment, another member, and an apparatus, (b) is the figure which showed the wire and the stiffening member. (A)-(c) is the figure which showed the drain pipe | tube and other members different from FIG. (A) (b) is the figure which showed each process in 1st embodiment. (A) is the figure which showed the drain tube used in 2nd embodiment, a sheath tube, and another apparatus, (b) (c) is the connection state of a 1st sheath tube and a 2nd sheath tube. It is the figure which showed the means to cancel. (A)-(c) is the figure which showed each process in 2nd embodiment.

Explanation of symbols

10 Drain pipe 14 Stiffening member 15 Wire (tensile reinforcement)
DESCRIPTION OF SYMBOLS 20 Existing structure 21 Liquefaction layer 23 Guide pipe 24 Enlarged reamer 30 Sheath pipe 30a First sheath pipe 30b Second sheath pipe

Claims (3)

It is a construction method that suppresses liquefaction during an earthquake in the lower ground by providing a drain pipe in the lower ground of the existing structure and transmitting the excess pore water pressure generated during the earthquake to the drain pipe.
Forming a drilling hole that crosses the lower ground of an existing structure with an induction boring device, and ejecting a drain pipe while expanding and excavating pressure fluid in the drilling hole and applying vibration, Fixing a stiffening member to the drain pipe at a predetermined interval, connecting a tensile reinforcing material between the stiffening members, and causing the tensile reinforcing material to bear at least a part of the tensile force in the drawing process of the drain pipe. A characteristic ground liquefaction suppression method. It is a construction method that suppresses liquefaction during an earthquake in the lower ground by providing a drain pipe in the lower ground of the existing structure and transmitting the excess pore water pressure generated during the earthquake to the drain pipe.
A step of forming an excavation hole crossing the lower ground of an existing structure by an induction boring device, and a step of ejecting a sheath pipe and a drain pipe while expanding the excavation by injecting a pressure fluid in the excavation hole and applying vibration. In the drawing step, when the drain pipe reaches the planned laying position, the sheath pipe is cut off at a predetermined position, the drain pipe is left in the ground, and one of the sheath pipes is pulled to the predetermined position while applying vibration to the ground. The ground liquefaction suppression construction method characterized by including a process. It is a construction method that suppresses liquefaction during an earthquake in the lower ground by providing a drain pipe in the lower ground of the existing structure and transmitting the excess pore water pressure generated during the earthquake to the drain pipe.
A step of forming an excavation hole crossing the lower ground of an existing structure by an induction boring device, and a step of ejecting a sheath pipe and a drain pipe while expanding the excavation by injecting a pressure fluid in the excavation hole and applying vibration. A method for suppressing liquefaction of the ground, comprising a step of leaving the drain pipe in the ground and extracting the full length of the sheath pipe while applying vibration to the ground from the drain pipe.

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