JPH09221738A - Ground improvement method and device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the ground at low cost without propagating noises or vibrations to the environment by continuously forcing a drain into the ground along a web of a sheet pile and discharging thereafter water which infiltrates into the drain in the region. SOLUTION: A sheet pile P is put into a chuck 1a of a pipe forcing and drawing machine 1 and drain D is placed along a web Pw of the pile P. Next an anchor plate 5 is attached to the lower end of the pile P and the lower end of the drain D is connected to the anchor plate 5. And a static load is applied to force the drain D and sheet pile P into the ground, following which if the chuck 1a has been lowered to a predetermined position, the chuck 1a is released and raised and the pipe P and drain D are lowered again. And the drain D is cut off to the same height as the sheet pile P, whereupon the upper end of the drain D is connected to a discharge pump and as soon as the water pressure rises and liquefaction is generated, water is discharged rapidly. As a result, a secondary disaster in an industrial complex can be surely prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for improving a ground such as a soft ground or a landfill where a liquefaction phenomenon easily occurs.

[0002]

2. Description of the Related Art For example, as a method for improving soft ground such as clayey soil, a sand drain method, a vertical drain method using a plastic board drain, and the like have already been used.

[0003]

[Problems to be solved by the invention] However,
Since the properties vary widely, it is difficult to select a construction method, and if the construction method is incorrect, the ground cannot be uniformly improved. In addition, the equipment used for these conventional methods is generally large, and the cost for construction is high. On the other hand, in recent years after the occurrence of a major earthquake, there has been a demand for the possibility of inexpensive ground improvement in preparation for liquefaction, although the ground is not soft. For example, in landfills on the Tokyo Bay shore where petroleum storage tanks stand, liquefaction of the ground may lead to catastrophic disasters, and we would be happy if the ground could be improved so that it could respond quickly if liquefaction occurred. is there.

[0004] The present invention has been proposed in view of the above circumstances, and by using a pile press-in and pull-out machine to press-fit a drain together with a sheet pile into the ground, the cost is lower than in the past, and noise and noise are reduced. It is an object of the present invention to provide a ground improvement method and a ground improvement method that can improve the ground without giving vibration to the surroundings.

[0005]

In order to achieve this object, in the ground improvement method according to the present invention, a drain is placed along a web portion of a sheet pile and is continuously press-fitted into a predetermined area by a pile press-in / pull-out machine together with the sheet pile. After that, the water that permeates the drain in the area is drained. Further, the ground improvement device according to the present invention, a sheet pile row formed in the ground of a predetermined area, a drain group embedded along each web portion inside the sheet pile row, and an upper end portion of the drain group. And a drainage device connected thereto. In the present invention, a drain having a core in a filter is used. This drain is grasped together with the sheet pile by a pile press-in / pull-out machine, and static load is applied to these to press-in the complex or the ground to be improved in the urban area. When the water gushes and the ground liquefies, the drainage device is operated to drain the water in the predetermined area surrounded by the sheet pile to the outside of the enclosure.

[0006]

FIG. 1 shows an embodiment of the present invention.
A description will be given based on FIGS. In this embodiment, the pile press-in / draw-out machine 1 that can travel on the upper end of the steel sheet pile Pn by itself is used. As shown in FIG. 1 and FIG. 2A, the pile press-in / pull-out machine 1 has a drain D wound in a roll shape on an upper part of a mast M. As the sheet pile, a U-shaped steel sheet pile P is used, and as the drain D, as shown in FIG. Then, while repeating the steps described below,
The steel sheet pile P and the drain D are press-fitted by the pile press-in / pull-out machine 1 so as to surround the outer periphery of the storage tank T.

A steel sheet pile P is put into a chuck portion 1a of a pile press-in / draw-out machine 1 shown in FIG.
The drain D along the ventral (or dorsal) side of. As shown in FIGS. 3A and 3B, an anchor plate 5 is attached to the lower end of the steel sheet pile P, and the lower end of the drain D is connected to the anchor plate 5. As shown in FIG. 4, the sheet pile P and the drain D are gripped by the chuck portion 1a, and a static load is applied to the drain P and the sheet pile P.
Into the ground. At this time, it is preferable to arrange a thin iron plate 6 for drain protection between the chuck portion 1a and the drain D. However, this iron plate 6 does not need to be pressed into the ground. When the chuck portion 1a is lowered to a predetermined position, the chuck portion 1a is opened and raised, and the steel sheet pile P and the drain
Is held down again. As shown in FIG. 5, when the steel sheet pile P is pressed into the ground, the drain D is cut by the cutter 7 so as to have substantially the same height as the steel sheet pile P.

In this way, as shown in FIG. 6A, a steel sheet pile row Pn is formed so as to surround the outer periphery of the storage tank T.
As shown in (b), each web part P of this steel sheet pile row Pn
The drain group Dn is buried along the inside of w. The upper end of each drain D and the drain pump 8 are connected by a pipe (not shown), and a drain pipe 9 is arranged outside the steel sheet pile Pn to obtain a ground improvement device 10. Then, when the water pressure of the ground rises due to the earthquake and liquefaction starts, the water permeating the drain group Dn inside the steel sheet pile row Pn is drained at once by the drain pump 8. This drainage action increases the ground density and prevents the base of the storage tank T from collapsing.

As described above, the ground improvement method of the present embodiment
Compared with the conventional device, since the pile press-in / pull-out machine 1 having a small length, width, and height is used, there is an effect that construction in a narrow city area is easy. Moreover, since the pile press-in / draw-out machine 1 is a self-propelled type, the steel sheet pile P and the drain D can be continuously and safely connected.
Moreover, it can be pressed in quietly.

The ground improvement apparatus 10 according to the present embodiment
Prevents the intrusion of water from the outside in the steel sheet pile row Pn, and drains the water inside the drain group Dn connected to the drain pump 8.
, The ground density can be quickly increased when liquefaction occurs. Since the drain D used at that time has the core C in the filter F, there is no concern that the filter F will be crushed by earth pressure. As a result, a remarkable effect is obtained in that a large amount of water is quickly discharged, liquefaction is reliably suppressed, and a secondary disaster due to damage to the storage tank T or the like can be prevented.

FIG. 7 shows another embodiment constructed on the outer periphery of a house H. In the present embodiment, the house H is located above the steel sheet pile P.
Is fixed, and the drain D embedded inside the steel sheet pile P is connected to a side groove 15 formed outside the steel sheet pile row P via a drainage pump 18. With such a configuration, drainage can be quickly performed even on soft ground, and wobbling of the foundation can be prevented.

In each of the embodiments described above, the construction cost per unit volume is lower than that of the conventional example, and it can be flexibly applied to various types of ground. Ideal for protecting large fire protection tanks. Furthermore, it can be applied to protection of gas pipelines and water pipelines as a measure against earthquakes.

The drain D does not necessarily need to be mounted on the mast M of the pile press-in / pull-out machine 1, but may be mounted on the upper front of the chuck 1a or the upper side of the slide frame 1b. For example, it may be placed on the ground.
Further, in the present embodiment, the U-shaped steel sheet pile is used, but the invention is not necessarily limited thereto, and a Z-shaped steel sheet pile may be used.
Drain group D on both sides as well as inside steel sheet pile Pn
n may be embedded. Further, the steel sheet pile row Pn does not necessarily need to be constructed so as to be closed, and may be formed in two parallel rows as shown in FIG. 8 depending on the properties of the ground.

[0014]

As described above, according to the soil improvement method and apparatus according to the present invention, a relatively small pile press-in / pull-out machine and a normal sheet pile are used without using a large-scale driving machine. Therefore, inexpensive and quiet construction is possible in an urban area. Moreover, when liquefaction occurs on the ground due to an earthquake or the like, water in the sheet pile can be quickly drained by the drain group buried along the sheet pile, so that secondary disasters in the complex etc. can be reliably prevented. It works. In general, it is extremely effective as a measure against future earthquakes in urban areas.

[0015]

[Brief description of drawings]

FIG. 1 is a side view of a pile press-in and pull-out machine used in an embodiment of the present invention.

FIG. 2 is an enlarged view of a drain, and FIG.
FIG. 2B is a sectional view taken along line II-II of FIG. 2A.

3A is a front view of a steel sheet pile and a drain put into a chuck portion, and FIG. 3B is a cross-sectional view taken along the line III-III of FIG. 3A.

FIG. 4 is a side view showing a state in which a drain and a steel sheet pile are being pressed into the ground by a pile press-in / draw-out machine.

FIG. 5 is an enlarged view showing a state in which a drain of a steel sheet pile pressed into the ground is being cut.

6A is a plan view of a ground improvement device, and FIG. 6B is an enlarged plan view of a steel sheet pile row and a drain group.

FIG. 7 is an enlarged sectional view of another embodiment constructed on the outer periphery of a house H.

FIG. 8 is a plan view of an embodiment in which a steel sheet pile row and a drain group are formed in two parallel rows.

[Explanation of symbols]

 1 Pile press-in / pull-out machine 8, 18 Drainage device (drainage pump) 10 Ground improvement device C Core D Drain Dn Drain group F Filter P Sheet pile (steel sheet pile) Pn Sheet pile row (steel sheet pile) Pw Web part

Claims (2)

[Claims] 1. A method for improving ground, in which a drain is placed along a web portion of a sheet pile and is continuously press-fitted into a predetermined area by a pile press-in / pull-out machine together with the sheet pile, and then water that permeates the drain in the area is drained. 2. A row of sheet piles formed in the ground in a predetermined area,
A ground improvement apparatus comprising: a drain group embedded along each web portion inside the sheet pile array; and a drainage device connected to an upper end portion of the drain group.