JP2010180633A - Method of filling up gap part produced by land subsidence - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of filling a gap part produced by land subsidence which can prevent the strength of a pile foundation from being lowered by forming a filling hole in a footing and filling up the gap part with a liquefied stabilized soil through the filling hole. <P>SOLUTION: In this method of filling up the gap part 4 produced, by land subsidence, between the bottom surface of the existing footing 2 supported by support piles 1 and a ground 3 with the liquefied stabilized soil 5, the filling hole 6 extending from the upper surface of the footing 2 to the gap part 4 through the footing 2 is bored at one position by core boring. The highly liquefied stabilized soil 5 which meets the quality requirements comprising a liquidity of 180-300 mm in flow value, a specific gravity of 1.35-1.6 t/m<SP>3</SP>, a material separation resistance of less than 1% in bleeding rate, and a uniaxial compression strength of 13-55 N/cm2 in 28 days age is filled up into the gap part 4 through the filling hole 6. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention is a structure having a pile foundation constructed on soft ground such as a landfill, and has high fluidity as a filler in a gap formed between the bottom of the footing (concrete foundation) and the ground due to ground subsidence. The present invention belongs to a technical field of a construction method for filling fluidized soil, and more specifically, relates to a technique for preventing a decrease in yield strength of a pile foundation by filling the voids with fluidized soil.

When ground subsidence occurs in a structure having a pile foundation constructed on soft ground such as a landfill, a void is generated between the bottom of the footing supported by the support pile and the ground. If voids occur around the pile head, the resistance to horizontal forces such as earthquakes will decrease, and the ultimate bearing capacity of the piles in the vertical direction will decrease, which will greatly reduce the strength of the pile foundation of the structure. It has been known. Therefore, it is necessary to fill the voids, particularly the voids around the pile head periphery, with a filler to prevent a decrease in the yield strength of the pile foundation.
Conventionally, various methods for preventing a decrease in the yield strength of a pile foundation by filling the voids around the pile head with a filler have been publicly known (see, for example, Patent Documents 1 to 3).

  Patent Document 1 discloses that at the time of pile foundation work, at least two through holes (through holes) 1 reaching the ground contacting the bottom surface of the concrete foundation 4 through the concrete foundation 4 from the upper end portion of the concrete foundation 4 in advance. A pipe is embedded in the surface, and the presence or absence of a gap between the bottom surface of the concrete foundation 4 and the ground is monitored by using the through hole 1. An invention is disclosed in which a filler (flowable solidified substance) is injected through 1 to fill the void 8 (see the claims and drawings).

  In Patent Document 2, when a gap 4 is generated between the bottom of the structure 1 and the ground 3, a plurality of filler injection holes 5 and air vent holes 6 are formed in a balanced manner at the bottom of the structure 1. An invention in which a filler (hydraulic composition mortar) is filled through a filler injection hole 5 and cured by leaving a slight gap, and then the remaining void is filled with a fluid expandable filler. Is disclosed (see claims and drawings).

  In Patent Document 3, in the case of pile foundation work, a supply path that can be filled with a filler between the bottom of the footing and the ground is formed in the center of the footing in advance, and between the bottom of the footing and the ground due to ground subsidence. An invention is disclosed in which the voids are prevented from occurring by continuously filling the voids generated through the supply path with a filler that has fluidity and is difficult to consolidate over a long period of time. (See claims and FIGS. 1-3).

Japanese Patent Laid-Open No. 51-94611 Japanese Patent Publication No.55-30087 JP-A-62-78321

In the invention according to Patent Document 1, at the time of pile foundation work, at least two through holes (through holes) are formed in advance using a pipe. Therefore, there is a possibility that the pipe 1 may be damaged due to, for example, a horizontal force acting on the concrete foundation 4 at the time of an earthquake, and this may not be used when a gap portion is actually generated. Also, until the actual filling operation is started, maintenance such as covering the upper end of the pipe 1 is necessary, which is very troublesome. That is, the significance of providing the through holes in advance before the voids are generated is unavoidable in view of the cost effectiveness (hereinafter referred to as the first problem).
Further, this type of through hole (through hole) is generally provided with at least two holes for filling and air venting so that the filler is densely filled in the gap. Even if it can be filled with no gaps, considering the fact that voids are generated due to land subsidence over time, the significance of providing a plurality of holes for solid filling is not much considering the cost effectiveness. I can't help but say. The purpose of filling the gap with the filler is to prevent a decrease in the yield strength of the pile foundation, and if the pile foundation is given rigidity that can withstand horizontal forces such as earthquakes, the objective is achieved. It can be said that there is little need to completely and completely fill the part. Furthermore, considering the influence of the number of through holes on the rigidity of the concrete foundation 4, it is desirable that the number is as small as possible (hereinafter referred to as the second problem).

In the invention according to Patent Document 2, when a gap 4 is generated between the bottom of the structure 1 and the ground 3, a plurality of filling injection holes 5 and air vent holes 6 are formed afterwards. The problem does not occur.
However, since the plurality of filling injection holes 5 and air vent holes 6 are formed, the second problem is not solved at all. Therefore, it is uneconomical and there is concern about the effect on the rigidity of the bottom of the structure. In addition, since the gap portion is divided into two stages and used with different fillers, the filling operation is troublesome and the workability is poor, which is very uneconomical.

  Since Patent Document 3 is implemented in advance by forming a complicated supply path in the center of the footing, the first and second problems are not solved at all. Further, since the filler that has fluidity and is difficult to consolidate over a long period of time is continuously filled through the supply path, its control and maintenance are very troublesome, costly, and very uneconomical.

  In short, various methods for filling the voids according to the prior art with the filler have been disclosed, and the effects thereof have been recognized for some time, but there is still room for improvement in consideration of economy and practicality.

An object of the present invention is to provide a filling method in which the above first and second problems are solved, that is, a single injection hole is formed in the footing afterwards, and a void is filled with a filler (fluidized soil) through the injection hole. Provide a construction method that fills the gap caused by ground subsidence with a simple structure that can prevent the deterioration of the strength of the pile foundation by filling the area. That is.
The next object of the present invention is to provide an economical and rational ground subsidence that can fill a void portion even with a single injection hole using fluidized soil with high fluidity that satisfies a predetermined quality standard. It is to provide a method of filling the voids generated by the above.

As a means for solving the problems of the background art, a method of filling a void portion caused by ground subsidence according to the invention described in claim 1,
This is a method of filling fluidized soil, which is a mixture of construction residual soil, solidification material, and water or mud water, into the gap between the existing footing bottom and the ground supported by support piles due to ground subsidence. And
The injection hole which penetrates the footing from the upper surface of the footing and reaches the gap is drilled at one location by core boring, the fluidity is a flow value of 180 to 300 mm, and the specific gravity is 1.35 to 1.6 t / m ³ . The fluidized soil with high fluidity satisfying the quality standard of material separation resistance of less than 1% breathing rate and uniaxial compressive strength of 13 to 55 N / cm ² at the age of 28 days is passed through the injection hole. It is characterized by being injected and filled in.

  The invention described in claim 2 is characterized in that, in the method of filling a void portion generated by ground subsidence described in claim 1, the diameter of the injection hole is 80 to 100 mm.

  According to a third aspect of the present invention, in the method of filling a void portion generated by ground subsidence according to the first or second aspect, before the fluidized soil is injected, the water stored in the void portion is injected into the injection hole. It is characterized by draining through.

The construction method for filling the voids generated by the ground settlement according to the present invention has the following effects.
1) Since the filling operation can be started simply by drilling one injection hole in the vertical direction in the footing, the cost required for the drilling operation can be drastically reduced and there is no possibility of adversely affecting the rigidity of the footing. . Therefore, since it can be implemented with a simple configuration and the construction period can be shortened, it is very excellent in economic efficiency and workability.
2) Since fluidized soil is press-fitted directly under the footing through a vertical injection hole from above the footing, the filling property is excellent. Therefore, it is possible to fill the gap portion densely.
3) Since an inexpensive fluidized soil is used as a filler for filling the voids, it is possible to contribute to cost reduction and to set fluidity and strength flexibly.
4) Filling work is performed using fluidized soil that has the proper fluidity and satisfies the quality standards necessary for curing at the appropriate time, so only one injection hole is used for filling. Even if it performs, the space | gap part around a pile head can be filled densely. Therefore, it is rational and economical and is highly effective.

A is an elevation view showing an implementation point of a method for filling a void portion caused by ground subsidence according to the present invention, and B is a plan view thereof. It is the elevational view which showed the state which filled the space | gap part around the pile head produced by the ground subsidence concerning this invention densely with the fluidization processing soil.

Below, the Example of the construction method with which the space | gap part produced by the ground subsidence which concerns on this invention is filled is demonstrated based on drawing.
As shown in FIG. 1 and FIG. 2, the present invention has the construction residual soil and the solidified material in the gap portion 4 formed between the bottom surface of the existing footing 2 supported by the support pile 1 and the ground 3 due to ground subsidence. This is a method of filling fluidized soil 5 formed by mixing water or muddy water, and the injection hole 6 that penetrates the footing 2 from the upper surface of the footing 2 and reaches the gap 4 is drilled at one location by core boring. The fluidity is a flow value of 180 to 300 mm, the specific gravity (density) is 1.35 to 1.6 t / m ³ , the material separation resistance is less than 1%, and the uniaxial compressive strength is 28 days. A fluidized soil 5 having high fluidity that satisfies a quality standard of 13 to 55 N / cm ² is injected and filled into the gap 4 through the injection hole 6.

1 and 2 show one pillar 8 as a part of the structure and a footing 2, a mat slab 7, and four support piles 1 supporting the pillar as main parts of the present invention. Other pillars and the like are omitted for convenience of illustration. In FIG. 1B, the mat slab 7 is omitted for convenience of illustration.
Incidentally, reference numerals 9 to 12 in the figure are instruments for injecting (press-fitting) the fluidized soil 5 through the injection hole 6, reference numeral 9 is an elbow, reference numeral 10 is a union, reference numeral 11 is an electromagnetic flowmeter, reference numeral 12 Indicates an injection hose.
Hereinafter, the procedure of the construction method for filling the gap 4 according to the present invention will be specifically described.

(Detection of void 4)
There are various methods for detecting the gap 4 due to ground subsidence. In this embodiment, the presence or absence of the gap 4 between the bottom surface of the footing 2 and the ground 3 is predicted to some extent from the ground subsidence around the structure, and the pile head When it is determined that the required depth of the gap 4 around the part is inappropriate for the structural strength of the support pile 1, a drilling operation for forming the injection hole 6 in the footing 2 is started. And a fiberscope and a rod-shaped member are inserted in the formed injection hole 6, and the required depth of the cavity 4 around the pile head is measured. Incidentally, the filling operation into the gap 4 is effective and economical when the required depth of the gap 4 around the pile head reaches about 1.0 to 1.5 times the pile diameter to be used. Is.

(Punching footing 2)
The footing 2 is drilled in the vertical direction to form one injection hole 6 penetrating the footing 2 in the vertical direction. The site where the injection hole 6 is formed in the footing 2 is a place that does not interfere with the reinforcement of the footing 2 and the column 8 by referring to the structural design drawing, and the place that does not adversely affect the rigidity of the footing 2. Furthermore, it is set considering the place where the core boring machine can be installed without hindrance. Incidentally, the injection hole 6 according to the present embodiment is formed by forming one in the vicinity of the corner portion when the footing 2 is seen in the plane direction (see FIG. 1B).
There are various methods for drilling the footing 2 in the vertical direction. In this embodiment, the baby mall propulsion device installed on the upper surface of the footing 2 is used to carry out the so-called baby mall (cutting) construction method. ) Is made of a highly rigid steel pipe. Of course, the method of drilling the footing 2 in the vertical direction is not limited to this, and a core boring method using a known core boring machine can be similarly implemented.
Moreover, it is preferable to implement the aperture diameter of the said injection hole 6 with a small aperture of 80-100 mm. This is because if it is less than 80 mm, the cost of core boring increases because it is necessary to use a special propulsion device, and if it exceeds 100 mm, the rigidity of the footing 2 may be adversely affected. For reference, the injection hole 6 according to the present embodiment is formed of an 80A steel pipe having an outer diameter of 89.1 mm, and the tip thereof is positioned about 100 mm away from the bottom surface of the gap portion 4.

(Drained water)
As a result of detecting the situation in the gap 4 around the pile head using the injection hole 6, the work cannot be properly cured when filling the fluidized soil 5. This is carried out when there is enough accumulated water that will hinder the filling operation. The means for discharging the accumulated water is not particularly new, and the accumulated water in the gap 4 is drained through the injection hole 6 by a drain pump.

(Filling fluidized soil 5)
Thus, after the injection hole 6 is formed in the footing 2 and equipment necessary for filling work such as the electromagnetic flow meter 11 and the injection hose 12 is installed, the fluidized soil 5 supplied from the injection pump to the injection hose 12 is added to the footing 2. It fills by injecting (pressing) into the gap 4 through the injection hole 6.
The amount of fluidized soil 5 required to fill the gap 4 around the pile head was calculated using a fiberscope inserted from the ground into the injection hole 6 based on the structural design drawing. The design is appropriately changed according to the volume of the gap 4 around the pile head.
Control means such as the filling speed and the filling amount of the fluidized soil 5 are well known and controlled by the electromagnetic flow meter 11 or the like to confirm that the fluidized soil 5 overflows from the upper part of the injection hole 6. Finish the filling operation. The injection hole 6 is finally closed by floor treatment.
By the way, the fluidized soil 5 according to the present embodiment has an appropriate fluidity in the space 4 around the pile head using only one small-diameter injection hole 6 and an appropriate time. In order to harden, fluidized soil 5 that satisfies the following quality standards is used based on the results of various experiments conducted by the present applicant.

(Quality standard of fluidized soil 5)
The fluidity is set within a flow value range of 180 to 300 mm. If the flow value is less than 180 mm, the fluidity of the fluidized soil 5 is impaired, resulting in a problem of hardening before the gap 4 around the pile head is densely filled, and if the flow value exceeds 300 mm. This is because other quality standards such as density and uniaxial compressive strength are not satisfied.
The specific gravity (density) is 1.35 to 1.6 t / m ³ . This is because if the specific gravity is 1.35 t / m ³ , the fluidized soil 5 is not properly cured, and if it exceeds 1.6 t / m ³ , there is a possibility of promoting ground settlement due to its own weight.
The material separation resistance is less than 1% breathing rate. This is because if the breathing rate is 1% or more, the amount of water increases, and as a result, it does not cure properly.
The uniaxial compressive strength is 13 to 55 N / cm ² at 28 days of material age. This is because if the uniaxial compressive strength is less than 13 N / cm ² , it is impossible to effectively prevent a decrease in the yield strength of the pile foundation, and if it exceeds 13 N / cm ² , other quality standards such as a flow value cannot be satisfied.
The above is the main quality standard of the fluidized soil 5 that has appropriate fluidity in the void 4 around the pile head and hardens at an appropriate time.

(Manufacture of fluidized soil 5)
In order to contribute to environmental conservation, the fluidized soil 5 that satisfies such quality standards is generally added to the locally generated soil that is treated as industrial waste, and is added to the mixer truck and stirred to obtain a flow value (180 ˜300 mm) and specific gravity (1.35 to 1.6 t / m ³ ), a cement-based solidified material (in this example, blast furnace cement B) is further added and kneaded as the solidified material 3, and the necessary uniaxial It is manufactured so as to obtain a compressive strength (13 to 55 N / cm ² at 28 days of material age).
Incidentally, the strength characteristics of the fluidized soil 5 are governed by the adjusted mud specific gravity and the amount of solidified material, provided that the muddy water has a sufficient fine grain content and is a product satisfying a breathing rate of less than 1%. The Therefore, strength management may be performed by adjusting mud water specific gravity and solidifying material addition amount, and the implementation composition is as follows.
[Formulation 1] Formulation per 1 m ^{3 of} product (kg) {1,300 kg of 1 m ³ of adjusted mud water, 120 kg of cement (external split)}, product specific gravity 1.36 t / m ³
[Composition 2] Composition per 1 m ³ product (kg) {1,300 kg with 1 m ³ of adjusted mud water, 140 kg of cement (outer division)}, product specific gravity 1.37 t / m ³

As described above, according to the present invention, the method of filling the void portion caused by the land subsidence is performed by core boring the injection hole 6 that penetrates the footing 2 vertically from the upper surface of the footing 2 and reaches the void portion 4. (In this embodiment, baby mall construction method) drilled at one place, as shown in FIGS. 1 and 2, the fluidized soil 5 satisfying the above-mentioned quality standards, through the injection hole 6 around the pile head Therefore, the following effects can be obtained.
1) Since the filling operation can be started simply by drilling one small-diameter injection hole 6 in the vertical direction in the footing 2, the cost required for the drilling operation can be drastically reduced and the rigidity of the footing 2 can be increased. There is no risk of adverse effects. Therefore, since it can be implemented with a simple configuration and the construction period can be shortened, it is very excellent in economic efficiency and workability.
2) Since the fluidized soil 5 is pressed into the footing 2 directly from the footing 2 through the vertical injection hole 6, the filling property is excellent. Therefore, the gap 4 can be filled with solidity.
3) Since the low-cost fluidized soil 5 is used as the filler for filling the gap portion 4, it contributes to cost reduction, and the fluidity and strength can be set flexibly. 4) Since the filling operation is performed using the fluid-treated soil 5 having the proper fluidity and satisfying the quality standard necessary for curing at the appropriate time, only one injection hole 6 is used. Even if the filling operation is performed, the gap 4 around the pile head can be filled with solidity. Therefore, it is rational and economical and is highly effective.

  The embodiments have been described with reference to the drawings. However, the present invention is not limited to the illustrated examples, and includes a range of design changes and application variations that are usually made by those skilled in the art without departing from the technical idea thereof. I will mention that just in case.

DESCRIPTION OF SYMBOLS 1 Support pile 2 Footing 3 Ground 4 Cavity part 5 Fluidization processing soil 6 Injection hole 7 Mat slab 8 Column 9 Elbow 10 Union 11 Electromagnetic flowmeter 12 Injection hose

Claims (3)

This is a method of filling fluidized soil, which is a mixture of construction residual soil, solidification material, and water or mud water, into the gap between the existing footing bottom and the ground supported by support piles due to ground subsidence. And
The injection hole which penetrates the footing from the upper surface of the footing and reaches the gap is drilled at one location by core boring, the fluidity is a flow value of 180 to 300 mm, and the specific gravity is 1.35 to 1.6 t / m ³ . The fluidized soil with high fluidity satisfying the quality standard of material separation resistance of less than 1% breathing rate and uniaxial compressive strength of 13 to 55 N / cm ² at the age of 28 days is passed through the injection hole. A method of filling voids caused by ground subsidence, characterized by being injected into the ground.   The method for filling a void portion caused by ground subsidence according to claim 1, wherein a diameter of the injection hole is 80 to 100 mm.   3. The method of filling a void produced by ground subsidence according to claim 1 or 2, wherein the water stored in the void is drained through an injection hole before injecting the fluidized soil.

Images