JPH11217837A - Soil improvement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a ground efficiently particularly to the bearing ground of an existing structure. SOLUTION: A pilot hole 12 is drilled into a ground to be improved by the excavation of a drilling machine by using the drilling machine 5 capable of forming a drilled hole into the ground by an arbitrary locus from a ground surface, and drilling, in which the diameter of the pilot hole is expanded by the drilling machine, is conducted. A columnar soil improvement body 13 is formed by injecting a liquefied solidifying material into the pilot hole and agitating and mixing soil and sand generated by diameter-expanding drilling and the liquefied solidifying material at that time, and a large number of the soil improvement bodies are formed to the whole ground to be improved at regular intervals. When the soil-improvement method is applied to the bearing ground of an existing structure, the pilot hole may be drilled under an approximately horizontal state. When drilling is conducted by the drilling machine using an excavation fluid, the liquefied solidifying material such as cement milk is employed as the excavation fluid when the pilot hole is drilled while the diameter is expanded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soil improvement method implemented as a measure for preventing liquefaction and the like, and more particularly to a soil improvement method suitable for application to a ground supporting an existing structure.

[0002]

2. Description of the Related Art As is well known, liquefaction of the ground caused by an earthquake causes great damage, and it is necessary to improve the ground as a countermeasure against the ground where liquefaction is likely to occur. . In particular, it is new to remember that many structures, including seawall structures at ports and harbors, were damaged by liquefaction in the previous great earthquake, so it is not only memorable that new structures need to be built, but also to existing structures. It is said that it is urgently necessary to improve the ground for the supporting ground as a measure for seismic reinforcement.

[0003] By the way, various methods such as displacement method, compaction method, drainage method, consolidation method and the like have been put into practical use as a soil improvement method as a measure for preventing liquefaction. It is assumed that it will be carried out on the ground in the condition, so it can be carried out without hindrance to the vacant ground when constructing a new structure. It is usually difficult to carry out as it is on the existing ground.

[0004] Therefore, as a construction method for improving the ground supporting the existing structure, a shaft is provided around the existing structure so as to reach the depth of the ground to be improved, and the ground is erected from the bottom of the shaft. A method of performing horizontal boring and injecting a chemical solution is being studied.

[0005]

However, the above-mentioned construction method requires a large-scale shaft, so that the construction period is long and the construction cost is high. In addition, when the installation space of the shaft cannot be secured, Is, of course, something that cannot be implemented. For this reason, it has been urgently required to develop an effective construction method that can easily and inexpensively improve the ground for the supporting ground as an anti-seismic reinforcement measure for existing structures and that is not restricted by the location conditions.

[0006]

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide an effective ground improvement method which can be applied particularly to a ground supporting an existing structure. After drilling a pilot hole in the ground to be improved by drilling using a drill machine capable of forming a hole in the ground on an arbitrary track from the ground surface, expanding the pilot hole with the drill machine. At the same time as drilling, by injecting the liquid solidifying material into the pilot hole, the earth and sand generated by the diameter drilling and the liquid solidifying material are stirred and mixed to form a columnar ground improvement body. It is to improve the ground by forming a large number of ground improvement bodies at predetermined intervals over the entire area of the target ground.

When the ground improvement method of the present invention is applied to the ground for supporting an existing structure, the above-described drilling machine excavates from the vicinity of the existing structure toward the ground below the existing structure, so that the ground is improved in the ground to be improved. The pilot hole may be drilled in a substantially horizontal state.

Further, it is reasonable to adopt a drilling machine of the type drilling using a drilling fluid, and to use the liquid solidified material as the drilling fluid when drilling the pilot hole with a large diameter. It is.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the present embodiment is for improving the ground as a measure for preventing liquefaction on the ground supported by the revetment structure 1 which is an existing structure.
The revetment structure 1 in the illustrated example is constructed by placing a caisson 3 on a rubble foundation 4, and in the present embodiment, the ground immediately below the rubble foundation 4 is the ground 2 to be improved.

In the present embodiment, a drilling machine 5 that can perform underground drilling on an arbitrary track from the ground surface is used. The drilling machine 5 has a configuration in which a long drill pipe 7 (see FIG. 3) is fed out and pulled back by a main body 6 (see FIGS. 1 and 2) installed on the ground surface. By drilling the drill pipe 7 while supplying a drilling fluid such as water or muddy water to the bit 8 provided at a high pressure, the ground is pierced by a jet jet, or the bit 8 is rotated to perform excavation, or both. Are appropriately used together, whereby a small diameter (for example, 200 to 300 m
(approximately mφ) can be formed over a long distance of several hundred meters. During drilling, the borehole is protected by the drilling fluid being filled with mud as a stable liquid in the borehole to protect the borehole wall, and the mud overflows to the ground surface, so that the drilling soil is discharged to the ground surface. ing.

The drilling machine 5 is capable of arbitrarily and strictly controlling the direction of excavation by remote control by a control mechanism (not shown) when excavating as described above. After the bit 8 has penetrated the ground at an angle of about a degree, it is possible to freely form a hole of a desired route by performing digging while correcting the trajectory so as to match a previously set trajectory.

As shown in FIG. 3, a reamer 10 is provided at the rear of the bit 8 for accommodating the stirring blades 9 and can be spread radially. As shown in FIG. After the excavation is completed, the agitating blade 9 is deployed by remote control and the reamer 10 rotates, and the drill pipe 7 is pulled back in this state after the excavation is completed, as shown in FIG. By retreating in the borehole, the small diameter borehole formed during excavation is expanded to a larger diameter (for example, about 600 mmφ) by the stirring blade 9,
At this time, the drilling earth and the drilling fluid are sufficiently stirred and mixed by the stirring blade 9. As the drilling fluid supplied at that time, a liquid solidifying material (for example, cement milk) that can be solidified by stirring and mixing with earth and sand can be used. By using such a liquid solidified material, the earth and sand generated by the diameter drilling and the liquid solidified material are naturally stirred and mixed, and a columnar ground improvement body 13 is naturally formed in the enlarged hole. It has become. In addition, so that the earth and sand and the liquid solidified material are efficiently stirred at the time of diameter expansion drilling,
The discharge port of the liquid solidifying material at the time of the diameter enlargement drilling is preferably provided on the main body 6 side (the front side in the direction in which the diameter enlargement drilling is performed) with respect to the stirring blade 9.

In order to improve the ground on the support ground of the revetment structure 1 which is an existing structure using the above-mentioned drill machine 5, as shown in FIGS. 1 and 2, a drill machine 5 is provided near the revetment structure 1. The drilling fluid is supplied at a high pressure to the bit 8 through the drill pipe 7, and the drill pipe 7 is supplied from the entrance 11 previously provided on the ground surface as shown in FIG.
掘 Dig into the ground at an angle of about 200-300
A pilot hole 12 of about mmφ is drilled. As the drilling fluid, water or muddy water that functions as a stabilizing liquid for the hole wall may be used. The water is filled in the pilot hole 12 as muddy water, the hole wall is protected, and the water overflows from the entrance 11 to the ground surface. The sediment is discharged by putting it out.

When the pilot hole 12 reaches the ground 2 to be improved, the trajectory is corrected by remote control, and the pilot hole 12 is excavated in the horizontal direction along the length direction of the revetment structure 1 so that the pilot hole 12 is Drill the hole almost horizontally. When the pilot hole 12 has been drilled to a predetermined position, the excavation is stopped, the stirring blade 9 stored in the reamer 10 is deployed by remote control, and this time drilling is performed while pulling back the drill pipe 7. In this case, a liquid solidifying material such as cement milk is used as a drilling fluid. As a result, the earth and sand produced by the diameter enlargement drilling and the cement milk as the drilling fluid are naturally stirred and mixed, and if the cement milk hardens after a predetermined time has elapsed, the columnar ground improvement body 13 is naturally formed. Note that the reamer 10 is
After retreating to the position where it comes off, the stirring blade 10 may be housed and the drill pipe 7 may be pulled out, but the diameter drilling is continued to the surface as it is, and the entire length of the pilot hole 12 is backfilled as the ground improvement body 13. That is fine.

By repeatedly performing the above operation,
Alternatively, a plurality of the above-described ground improvement bodies 13 are formed at predetermined intervals so as to cover the entire ground 2 to be improved by performing a parallel operation by a plurality of drill machines 5. In the example shown in the figure, the ground improvement body 13 is formed in three rows and nine rows of caisson 3 over a length of approximately two caisson 3, but the number and mutual interval thereof are determined according to the current ground condition and the required degree of improvement. Usually, the sum of the volumes of the ground improvement bodies 13 in each region is 50 to 60% of the volume of the ground 2 to be improved.
It is good to set so that it is about.

In the above case, as a formation pattern of the ground improvement body 13 with respect to the ground 2 to be improved, in addition to the pattern shown in FIG. 2, for example, the main body of the drill machine 5 installed at an arbitrary position as shown in FIG. The ground improvement body 13 is formed so as to be distributed to both sides from the part 6, and the ground improvement body 13 is provided not only in the horizontal direction parallel to the seawall structure 1 but also in such a manner as to extend radially from the main body part 6. The body 13 may be provided. Further, instead of performing the work on the ground 2 to be improved from the land side as described above,
Alternatively, in parallel with this, a work stage 14 is provided on the sea surface as shown in FIG. 5, a main body 6 of the drilling machine 5 is installed there, and a pilot hole 12 is drilled from the sea floor, and a ground improvement body 13 is similarly formed. Can also be formed. In this case, a guide pipe 15 may be provided under the sea to guide the drill pipe 7 and prevent muddy water and excavated earth and sand from diffusing into the sea.

According to the above-mentioned method, by adopting the drilling machine 5 capable of drilling underground in an arbitrary track, the ground improvement can be performed horizontally below the existing revetment structure 1 by excavating from the surface of the ground. The body 13 can be formed, so that there is no need to provide a large-scale shaft, which has been conventionally required, and it is possible to contribute to shortening of the construction period and reduction of the construction cost, and also, to a small extent capable of installing the main body 6 of the drilling machine 5 Since it is sufficient to secure only a small space, there is almost no restriction on the location conditions, and therefore it is possible to efficiently carry out ground improvement as a measure for preventing liquefaction of the ground supporting the existing structure. In addition, by using cement milk as a liquid solidifying material as a drilling fluid at the time of diameter drilling, the diameter drilling and injection of the liquid solidifying material and the mixing and stirring of the earth and sand are performed at the same time. It is reasonable.

As described above, the method of the present invention is particularly suitable to be applied to the supporting ground of an existing structure, but is not limited thereto. Of course, the conventional general ground improvement method cannot be applied as it is due to special location conditions where the exclusive site is limited or the like, or it can be applied to the mere vacant land. And
The formation pattern of the ground improvement body 13 may be set arbitrarily and optimally according to the scale, form, and conditions of the target ground. For example, the ground improvement body 13 may be arranged in a lattice shape so as to intersect vertically and horizontally. It does not preclude formation, or formation in a state inclined in the vertical direction, and formation in the vertical direction if necessary.

The drill 5 used in the present invention
Any material can be used as long as it can drill the pilot hole 12 from the surface of the ground at an arbitrary orbit and can form the ground improvement body 13 while expanding the diameter of the pilot hole. Yes, and the work process can be appropriately changed. For example, in the above-described embodiment, the drilling machine 5 of the type for drilling using a drilling fluid is employed. However, the drilling machine 5 for drilling with a normal rotating bit without using the drilling fluid, or the jetting of the drilling fluid by jetting Any type such as a type in which a bit is rotated and a type in which a jet injection of drilling fluid and a rotary bit are used in combination can be adopted. Further, in the above, cement milk as a liquid solidifying material was used as a drilling fluid at the time of diameter drilling, but the invention is not limited thereto, and depending on the type of drilling machine, only liquid solidifying material may be supplied or liquid solidifying material may be supplied. And both drilling fluids. Of course, the liquid solidifying material is not limited to cement milk, and other chemicals can be used.

[0020]

As described above, the ground improvement method according to the present invention uses a drilling machine capable of making an underground drilling in an arbitrary track from the surface of the ground, and drills a pilot hole in the ground to be improved by the drilling machine. After that, a liquid-solidifying material was injected while expanding the pilot hole to form a columnar ground improvement body, and a large number of such ground improvement bodies were formed at predetermined intervals over the entire area of the target ground. When applied to the ground supporting existing structures, it is not necessary to provide large-scale shafts, which contributes to shortening the construction period and cost.In addition, it is not necessary to secure the space for installing shafts. It is hardly restricted, and is therefore particularly suitable for performing a ground improvement on a supporting ground of an existing structure to which a conventional general ground improvement method cannot be applied.

In particular, if the pilot hole is drilled in a substantially horizontal state in the ground to be improved by digging from the vicinity of the existing structure toward the ground therebelow, the support structure for the existing structure may be drilled. Ground improvement as an anti-seismic reinforcement measure can be implemented efficiently and reliably.

In the case where a drilling machine of the type of drilling using a drilling fluid is employed, if a liquid solidifying material is used as a drilling fluid when drilling a pilot hole with a large diameter, the drilling and the liquid solidification can be performed. It is reasonable that the injection of the material and the mixing and stirring with the earth and sand are performed simultaneously.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an embodiment in which the present invention is applied to a support ground of an existing seawall structure.

FIG. 2 is a plan view showing a formation pattern of the ground improvement body.

FIG. 3 is an enlarged view showing a step of forming a ground improvement body.

FIG. 4 is a plan view showing another formation pattern of the ground improvement body.

FIG. 5 is a sectional view showing another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Revetment structure (existing structure) 2 Ground to be improved 5 Drilling machine 6 Main body 7 Drill pipe 8 Bit 9 Stirrer blade 10 Reamer 12 Pilot hole 13 Ground improvement body

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshiyuki Ohara 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Corporation (72) Inventor Hiromi Tan 1-3-2 Shibaura, Minato-ku, Tokyo Shimizu Corporation Co., Ltd. (72) Inventor Shohei Kato 3-20-16 Nishiazabu, Minato-ku, Tokyo Inside Japan Ocean Drilling Co., Ltd. (72) Inventor Junro Nitta 3-20-16 Nishiazabu, Minato-ku, Tokyo Hiroshi Nihonkai Drilling Co., Ltd. (72) Inventor Ryoichi Tatebayashi 3-20-16 Nishiazabu, Minato-ku, Tokyo Japan Sea Hiroshi Drilling Co., Ltd. Drilling Co., Ltd.

Claims (3)

[Claims] 1. A drill machine capable of forming a hole in the ground on an arbitrary track from the surface of the ground, and after drilling a pilot hole in the ground to be improved by drilling by the drill machine, the pilot machine is used by the drill machine. At the same time as drilling the hole, the liquid solidification material is injected into the pilot hole, and the soil and liquid solidified material produced by the hole drilling are stirred and mixed to form a columnar ground improvement body. And improving the ground by forming a large number of ground improvement bodies at predetermined intervals over the entire area of the ground to be improved. 2. When the ground improvement method according to claim 1 is applied to a ground supporting an existing structure, the ground is improved by digging from a vicinity of the existing structure to a ground below the existing structure by the drilling machine. A ground improvement method, wherein the pilot hole is drilled in the ground in a substantially horizontal state. 3. The ground improvement method according to claim 1, wherein the drilling machine employs a drilling machine using a drilling fluid, and when drilling the pilot hole, the drilling fluid is used. Ground improvement method using the liquid solidified material as the above.