JPH0447728B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a ground improvement method for preventing liquefaction of the ground during an earthquake, and an apparatus directly used to implement this method.

(Prior Art) Various methods such as the rod compaction method have been proposed as improvement methods for sandy ground.
To explain this rod compaction method as an example, the rod is placed in the construction position on a casting machine, and then the rod is vibrated by an exciter and penetrates into the ground, and when it reaches a predetermined depth. Pull up the rod, and from the ground surface into the gap created by this pulling up,
Replenishment materials such as sand, gravel, and crushed stone are supplied using a shovel dozer, etc., and the operations of penetrating, pulling up, and replenishing materials are repeated to compact the ground to the surface.

(This is the problem that the invention seeks to solve.) However, according to the construction method in the above example, the ground was completely disturbed by the penetration of the rod, and then compaction was carried out by repeating penetration and withdrawal while vibrating the rod, causing vibrations. This requires repeated compaction work, which tends to lengthen the construction period. In addition, the rod in the above-mentioned pouring machine completely disturbs the ground once and then compacts it by vibration, so there is little increase in strength on clay ground, and if the clay ground is in the middle, the clay layer will stick to the rod, and the clay layer Ground subsidence occurs after construction because it is not possible to replenish the gaps in the sand layer caused by vibrations below with sand or other replenishing materials.

The first purpose of the present invention is to shorten the construction period by completing the compaction work by vibration in one time, and the second purpose is to reduce disturbance of the ground even when the vibrating body is penetrated. In particular, the third purpose is to prevent ground subsidence after construction is completed in sandy ground with clay ground intervening.

(Means for Solving the Problems) The present invention includes the first means and second means shown below.

The first method is a ground improvement method, which involves the process of penetrating into the ground while vibrating a casing 1 made of a steel pipe that constitutes the vibrating body, and vibrating the casing that has reached a predetermined depth. A process of draining water from a drainage channel 6 disposed in the axial direction on the pipe wall of the casing and having a water passage part 6a formed in the channel wall, and excitation until the water level from this drainage channel no longer rises; After confirming that there is no rise in the water level, a process of introducing replenishment material 15 such as sand, gravel, crushed stone, etc. into the drainage channel from the upper part of the drainage channel, and after the addition, pulling out the casing;
This method includes the step of filling the voids in the ground caused by the pulling out with the replenishment material falling from the drainage channel. The casing is not limited to the tubular shape, but can also be H-shaped,
It may be groove-shaped, but in this case it is desirable to make it thin rather than thick.

The second means is a construction device of the above construction method, which includes a casing 1 constituting a vibrating body, a drainage channel 6 attached to the casing, and a replenishing material 15 for introducing sand or other replenishing material 15 into the drainage channel from above. Material input section 1
0. The casing 1 is made of a steel pipe that is vibrated by a vibrator 2, and is attached to a tower 4 so as to be movable up and down. The drainage channel 6 is arranged in the axial direction on the pipe wall of the casing 1, has a water passage portion 6a formed in the channel wall, and has an on-off valve 8 attached to its lower end, which normally closes the opening at the lower end. Above refill material 1
5 can open the on-off valve 8 from inside the drainage channel 6;
Therefore, the drainage channel 6 is also an input channel for replenishing material.

(Function) Function of the first solution: The vibrating casing 1 is penetrated into the ground, the ground is vibrated horizontally in a drainage state, the pore water pressure of the ground is increased once, and then the pore water pressure is applied until the pore water pressure no longer increases. By repeating shaking, the ground becomes compacted.

Effect of the second solution: The casing 1 is vibrated by the vibrator 2 and penetrates into the ground, but since the casing is a steel pipe, only the wall surface of the ground is not pushed apart, and there is little disturbance in the surrounding area. When the casing 1 reaches a predetermined depth, it is vibrated to increase the pore water pressure in the ground around the casing, and the drainage channel 6 is used to drain water and compact the ground to ensure that the pore water pressure does not increase. After checking with a convenient checking means, pull out the casing. At this time, the refill material introduced into the drain channel 6 from the refill material input section 10 fills the void created by the withdrawal.

(Example) Examples of the present invention will be described below with reference to the drawings. First, we will explain the equipment used for the ground improvement method, and then explain the method.

In FIGS. 2 to 4, a casing 1 constituting a vibrating body is mounted on a guide rail (not shown) of a tower 4 standing in front of a crawler crane 3, together with an exciter 2 that vibrates the casing. It can be moved up and down by operating the wire 5 along the line. The casing 1 is made of a large-diameter steel pipe, and drain pipes 6 are attached along the entire length of the casing at four equally spaced positions in the circumferential direction of the pipe wall of the casing. Each drainage pipe 6 is a half pipe attached to a wall surface by welding in a state where the pipe wall is sandwiched between the half pipes and facing each other. The split pipe has a second,
As shown in Figure 5, there are water passage slits 6 all over the pipe wall.
A is formed, and a spiral mesh 7 is stretched on the inner surface of the pipe so as to cover each slit. An on-off valve 8 for opening and closing the lower end opening is attached to the lower end of the drain pipe 6 by a hinge 9, and the valve is normally closed.

A sand receiver 10 is provided at the upper end of the casing 1, and sand thrown in from a burr 10a provided in the sand receiver can enter the upper end opening of each drainage pipe 6 from the bottom of the sand groove 10b.

A water level gauge 11 is disposed inside one of the drain pipes 6, and a measurement cord 12 of the water level gauge is connected to a recorder 13 outside the casing 1.

In FIG. 4, 14 is a sand basket. In the above example, the drainage channel 6 is constructed of a pair of divided pipes, but it may be formed only inside the pipe wall of the casing 1, and the cross-sectional shape is not limited to a semicircle, but may be a groove shape or a groove shape. It is not limited to pipes.

Next, the ground improvement method will be explained with reference to Figure 1. First, the casing 1 is installed at the construction position by the crawler crane 3 {Figure 1 B}, and then the exciter 2 is driven to vibrate the casing 1 while penetrating the casing into the ground {Figure 1 B}, Penetration is stopped when a predetermined depth is reached, and the casing is vibrated at this depth {Figure 1 C}. With this vibration, the pore water pressure in the ground around the casing increases, and the water in the ground rises from the water passage slit 6a of the drainage pipe 6 through the inside of the pipe 6.
Drained to 0a. Stop the excitation and allow the water level gauge 11 in the drain pipe 6 to fall {Fig. 1 D};
Vibrate the casing 1 again and confirm with the recorder 13 of the water level gauge 11 that the water level has not risen (see Figure 1). After that, the sand 15 is transferred to the sand receiving hopper 10a.
Insert {see Figure 1}. Then, the casing 1 is pulled out from the ground while being vibrated (see Figure 1). At this time,
The sand 15 in the sand tray 10 falls from the sand groove 10b into the drainage pipe 6, opens the on-off valve 8 at the lower end, falls downward, and fills the void created as the casing 1 is pulled out. As a result, the introduced sand 15 forms one sand column 16 as shown in FIG.

(Descension of the invention) According to the construction method of the present invention, compaction work can be performed by penetrating the vibrating body while exciting the vibrating body in the drainage state.
There is no need to repeat the penetration and extraction of the rod as in the past, which speeds up the work, and at the same time as the vibrating body is pulled out, the added replenishment material fills the void created by the pulling out and forms a pillar, creating a pile effect. It can increase the bearing capacity of sandy ground. Furthermore, ground improvement only involves compacting the ground, and the only replenishing material required is something that fills the voids created in the ground, providing an economical construction method. According to the device of the present invention, since a casing made of a steel pipe is used as the vibrating body, disturbance of the surrounding ground can be reduced compared to conventional rods, and the sandy ground under the clay layer has a compacting effect. Even if the construction subsides, no voids will be created, and no ground subsidence will occur after construction is completed. If a water level gauge is placed in the drainage channel, it is possible to measure the increase in water pressure during vibration, and the effect of ground improvement can be ascertained, thereby eliminating the need for boring inspections after completion of construction. By installing drainage channels on both the inside and outside sides of the pipe wall of the casing, the improved area extends to the outside of the casing.

[Brief explanation of the drawing]

Figures 1A to 3D are explanatory diagrams showing the construction process, Figure 1C is a sectional view after construction, Figure 2 is a partially cutaway front view of the casing, Figure 3 is a partially cutaway plan view of the casing, and Figure 4 is a partially cutaway plan view of the casing. The figure is a front view showing the state of use, and FIG. 5 is an enlarged perspective view of the main parts of the drain pipe. DESCRIPTION OF SYMBOLS 1... Casing, 2... Exciter, 4... Tower, 6... Drain channel, 6a... Water passage, 8... Opening/closing valve, 10... Replenishment material input part, 15... Replenishment material.

Claims (1)

[Scope of Claims] 1. Vibrating the casing, penetrating into the ground, and vibrating the casing that has reached a predetermined depth, and using a drainage channel provided in the axial direction on the wall of the casing during the vibration. After confirming that there is no rise in the water level, pour the replenisher into the drainage canal, and drop the replenishment material from the bottom of the drainage canal while pulling out the casing. A ground improvement method characterized by filling voids in the ground with wood. 2. A casing made of a steel pipe that is installed on the tower so that it can be raised and lowered and that can be vibrated by an exciter;
A drainage channel is formed with openings at both the upper and lower ends and a water passage is formed in the road wall, and a shut-off valve is installed at the lower end, and a replenishment material input part such as sand is connected to the opening at the upper end of this drainage channel. A ground improvement construction device, comprising: the refill material being able to fall through the drainage channel and below the lower end of the drainage channel. 3. A ground improvement construction device according to claim 2, characterized in that the drainage channels are installed facing both the inner and outer surfaces of the pipe wall of the casing.