JP2886355B2 - Vibration compaction method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for compacting a ground which is liable to be liquefied by vibrations, such as a saturated loose sand ground or a sandy ground having a high fine particle content. It is related to the method of construction.

[0002]

2. Description of the Related Art Conventionally, vibration compaction methods such as rod compaction method, vibro flotation method, direct power compaction method, vibro flotting method, etc. have been used to compact the ground by vibrating a vibrating rod while vibrating a saturated sand ground. The method of hardening is known.

[0003] However, in any of the above-mentioned construction methods, since the loose sand ground is directly vibrated, excessive pore water pressure is generated by the same mechanism as at the time of the earthquake, and it is inevitable that the rod periphery becomes muddy (liquefied). .

[0004] As a result, there is a problem that the vibration energy is rapidly attenuated in the vicinity of the vibration rod, and the compaction effect is greatly reduced.

Further, when the target sand ground contains fine grains, the vibration energy is more greatly attenuated, and there is a problem that the compaction effect by the vibration rod method is extremely low.

Conventionally, a large number of drain pipes are driven into the deep part of the soft ground, and then a plurality of sand compaction piles are driven into the shallow part of the surrounding ground by a vibro composer method, and the ground is integrated by the volume of the sand compaction pile. Along with the compression, the deep part of the ground is compressed by the land subsidence due to the impact or vibration at the time of pile driving, and the water contained in the soft ground flows out to the drain pipe along the pressure gradient and is discharged by the compression force. ,
There is also known a compaction method in which groundwater is reduced by the water compaction effect.

However, in this method, since the ground is compressed by discharging water by compressing the ground to lower the groundwater and compacting by the water-tightening effect, almost no excessive pore water pressure is generated, and sufficient tightening is not performed. No hardening effect is obtained.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a vibration compaction method using a vibrating rod, in which a vibrating rod is liquefied due to the generation of excessive pore water pressure, and vibration energy is rapidly attenuated near the vibrating rod. An object of the present invention is to solve the problem that the compacting effect is significantly reduced.

[0009]

According to the present invention, in order to solve the above-mentioned conventional problems, a plurality of drain pipes 2 are arranged around a vibrating rod 1 and these drain pipes 2 are connected to a vibrating body 4 for drain pipes. When the vibrating rod 1 is lifted upward, the vibrating rod 1 is press-fitted by the vibrating rod vibrating body 3 mounted on the upper part of the vibrating rod 3 while applying vertical or shear vibration to compact the ground. At the same time, a vibration compaction method is proposed in which the excess pore water pressure generated in the ground due to the vibration is eliminated by the drain pipe 2.

[0010]

In a soft ground to be improved, excessive pore water generated by vibration of the vibrating rod 1 during compaction by vibration is discharged to the ground surface via the drain pipe 2 and the vibrating rod 1
Is prevented from being liquefied, the vibration energy of the vibration rod 1 is effectively transmitted, and the vibration compaction is reliably performed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A plurality of drain pipes 2 are arranged around a vibrating rod 1 made of H-shaped steel or the like, a vibrating rod vibrator 3 is mounted on the head of the vibrating rod 1, and a head of each drain pipe 2 is provided. An annular drain pipe vibrator 4 having a cavity at the center where the vibrating rod 1 can be inserted is mounted on the part.

First, as shown in FIGS. 1 and 2, each drain pipe 2 is pressed into the ground to a required depth by the vibration of the drain pipe vibrator 4 while the vibrating rod 1 is left on the ground. Then, as shown in FIG. 3, the vibrating rod 1 is pressed into the vibrating rod vibrating body 3 while applying vertical or shear vibration to compact the ground, and at the same time, excessive vibration generated in the ground due to the vibration is obtained. The pore water pressure is eliminated by the surrounding drain pipes 2.

As described above, when the vibration is compacted by the vibrating rod 1, the vibration generates excessive pore water. The excessive pore water pressure is discharged to the ground surface through the drain pipe 2. Liquefaction is prevented, vibration energy of the vibration rod 1 is effectively transmitted, and vibration compaction is reliably performed.

The drain pipe 2 includes a steel pipe, a perforated pipe,
Various pipes such as a drain pipe made of an artificial material can be used.

Comparative experimental example

A plurality of drainage pipes 2 are installed on the ground around the vibrating rod (H-shaped steel) 1 at the reclaimed land at Takakake-numa, Rokkasho-mura, Kamikita-gun, Aomori Prefecture, as shown in FIG. The Nd value obtained by performing vibration compaction while draining with the drain pipe 2 and the Nd value obtained by performing vibration compaction without installing the drain pipe 2 were measured at a point 1 m from the vibration rod.

The results are shown in FIG. 5 (in the figure, ○ is the result of conventional non-drain compaction, ● is the result of compaction by draining through drain pipe 2, and ▲ is the result of using drain pipe 2 and well point together. The results of compaction after draining are shown, and the dotted line and chain line show the initial state before compaction).

From these results, it can be seen that the Nd value is much higher when vibration compaction is performed simultaneously with drainage than when vibration compaction is performed without drainage.

In the case where the drainage pipe 2 was installed, a fountain was observed from the upper part of the drainage pipe 2 at the same time as the start of vibration compaction, and it was found that the excess pore water pressure had been dissipated.

[0020]

As described above, according to the present invention, the vibration energy is effectively transmitted by removing excess pore water pressure during compaction, and the N value after compaction and the strength (resistance) against liquefaction.
Increase.

In addition, since the effective range of compaction is expanded, it is possible to reduce the construction period and construction cost by increasing the compaction work pitch, and if the work is performed at the same pitch as before, the N value will increase. In addition, improvement in earthquake resistance is expected, and it is possible to cope with prevention of liquefaction even in the case of a stronger earthquake.

Further, the effect of vibration compaction is exerted even on a sand ground containing fine particles, and the compaction of the ground, which is difficult with the conventional vibration compaction, becomes possible.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional side view showing a construction state of the present invention.

FIG. 2 is a longitudinal side view showing a construction state of the present invention.

FIG. 3 is a vertical sectional side view showing a construction state of the present invention.

FIG. 4 is a diagram showing an outline of experimental conditions and compaction state of the present invention.

FIG. 5 is a diagram showing experimental results of the present invention.

[Description of Signs] 1 Vibrating rod 2 Drain pipe 3 Vibrating body for vibrating rod 4 Vibrating body for drain pipe

Claims (1)

(57) [Claims] 1. A plurality of drain pipes are arranged around a vibrating rod, these drain pipes are pressed into the ground by a drain pipe vibrating body, and after the drain pipe vibrating body is pulled upward, the vibrating rod is removed. Pressing in while applying vertical or shearing vibration by the vibrating body for the vibrating rod attached to the upper part, compacting the ground, and removing excess pore water pressure generated in the ground by the vibration by the drain pipe. Vibration compaction method.