JPH02108720A - Weak ground improving technique - Google Patents

Abstract

PURPOSE:To improve compaction effect by driving drain pipes in weak ground up to a deep layer portion and preparing in their vicinity compaction piles the compressive force of which performs drainage of water in the ground through the drain pipes. CONSTITUTION:Drain pipes 6 are driven into weak ground (G) up to the deep layer portion of the ground. Then, in the vicinity of the drain pipes 6, compaction piles are prepared. The preparation of the piles 5 compresses the ground to yield compressive force which causes water which is contained in the ground to be outflowed to the drain pipes 6 for drainage. It is thus possible to improve compaction effect in weak ground, enhance effect of improving the ground and prevent liquefaction in earth quake.

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention relates to a method for improving soft ground, such as on waterfronts, for the purpose of increasing its bearing capacity and preventing liquefaction during earthquakes.

``Conventional technology'' Conventionally, ground improvement methods aimed at increasing the bearing capacity of soft ground and preventing liquefaction during earthquakes include compacting sand, gravel, crushed stone, or slag, etc., into soft ground. A compaction pile construction method is known in which the ground is stabilized by constructing a large number of hardened compaction piles, and a typical example of this compaction pile construction method is the vibro-composer construction method.

When improving soft ground using this vibro-composer construction method, first, as shown in Figure 2 (,), a hollow vibrator 2 with a vibrator l fixed to its upper part is placed at the construction position on the soft ground G. Then, by driving the vibrator 1, the hollow vibrator 2 is driven into the soft ground G, as shown in FIG. 2(b). After driving the hollow vibrator 2 to a predetermined depth in this way, as shown in Fig. 2(c).
As shown in FIG. 2, sand 4 is introduced into the hollow vibrator 2 from the hopper 3 provided at the top of the hollow vibrator 2, and the sand 4 is poured into the hollow vibrator 2 as shown in FIGS. like,
By discharging the sand 4 from the lower end of the hollow vibrator 2 and pulling it out while vibrating the hollow pipe 2 up and down, a sand compaction pile 5 as shown in FIG. 2(g) is created.
We will continue to create.

"Problems to be Solved by the Invention" By the way, when the ground is improved by the compaction pile method described above, it is expected that in sandy soil, it will be effective in increasing the bearing capacity of the ground, reducing subsidence, and preventing fluidization during earthquakes. In clay soil, it can be expected to increase the bearing capacity of the ground and shear strength against sliding failure, reduce settlement, and promote consolidation. On the other hand, in clay soil saturated with water, vibration Or, little compaction effect due to impact can be expected, and a sufficient ground improvement effect cannot be achieved, and there is also a risk that the ground may liquefy, especially in the event of an earthquake.

This invention has been made in view of the above circumstances, and an object of the present invention is to provide a soft ground improvement method that is particularly suitable for improving water-saturated soft ground, in a soft ground improvement method that utilizes the compaction effect of vibration or impact. It is an object.

"Means for Solving the Problem" The soft ground improvement method of the present invention involves driving a drain pipe into the soft ground, positioning the lower end of the drain pipe in a deep part of the soft ground, and then The soft ground is compressed by creating a compaction pile, and the compressive force causes the water contained in the soft ground to flow out to the drain pipe and be discharged.

"Operation" In the soft ground improvement method of the present invention, a drain pipe is driven into the soft ground in advance, the lower end of the drain pipe is located deep in the soft ground, and then compaction is installed around the drain pipe. By constructing the soft ground, the shallow part of the soft ground is compressed by the volume of the compaction pile driven, and the deep part of the soft ground is compressed due to ground subsidence due to the impact and vibration when the compaction pile is driven, The compressive force causes the water contained in the soft ground to flow out along the pressure gradient to the drain pipe, and the water is further discharged through the drain pipe, thereby lowering the groundwater level in the soft ground, and The ground is compacted by water compaction effect. This drain pipe is left in the ground and also functions as a building stake.

"Embodiment" An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

In the soft ground improvement method of this embodiment, first, a large number of drain pipes each having an opening/closing mechanism at the lower end are driven into the soft ground G at predetermined intervals, and the lower end of each drain pipe is connected to the corresponding part. Its lower end is opened while it is located in the deep part of the soft ground G. Next, a plurality of sand compaction piles 5 are created in the ground around the drain pipe by, for example, a conventional construction method such as the vibrocombozae method.

When improving soft ground using the above-mentioned pipero convozer construction method, as described above, first, as shown in Fig. 2 (a), a hollow vibrator 2 with a vibrator l fixed to the upper part is used.
is installed at the construction position on soft ground G, and then the above-mentioned vibrator 1 is installed.
By driving, as shown in FIG. 2(b),
Drive hollow pipe 2 into soft ground G. After the hollow pipe 2 is driven to a predetermined depth in this manner, as shown in FIG. Figure 2 (c), (d), (e), (f)
As shown in Fig. 2(g), sand 4 is released from the lower end of the hollow pipe 2, and the hollow pipe 2 is pulled out while vibrating up and down, thereby creating a sand compaction pile 5 as shown in Fig. 2(g). To go.

When a large number of sand compaction piles 5 are created in the soft ground G in this way, as shown in FIG. At the same time, the deep part of the soft ground G is compressed due to ground subsidence due to shock and vibration when the compaction pile 5 is placed, and the compressive force causes water contained in the soft ground G to flow along the pressure gradient It flows out to a drain pipe and is further discharged onto the soft ground G through this drain pipe.

By lowering the groundwater level in the soft ground G in this way, the soft ground G is compacted by the water compaction effect.

In addition, in this soft ground improvement method, the water in the soft ground G is taken in only from the lower end of the drain pipe. Water may also be taken in from the side wall of the pipero. In this case, the drainage efficiency of the drain pipe can be increased, and the water compaction effect can be further improved.

Furthermore, in this embodiment, the sand compaction pile 5 was created using the vibro-composer method, but the sand compaction pile 5 may be created using other methods, and instead of the sand compaction pile 5, gravel, crushed stone, Alternatively, a compaction pile may be created by compressing and compacting slag, etc. When creating a compaction pile using gravel, for example, a machine such as an earth auger is used to drill a hole in the ground to a predetermined depth, then an appropriate amount of gravel is dropped into the hole, and a weight is used to add the gravel. All you have to do is compact the gravel by hitting the top surface.

"Effects of the Invention" The soft ground improvement method of this invention involves driving a drain pipe into the soft ground, positioning the lower end of the drain pipe in the deep layer of the soft ground, and then creating a compaction pile around it. By doing so, the soft ground is compressed, and the compressive force causes the water contained in the soft ground to flow out to the drain pipe and be discharged. It can be compacted by impact, and by lowering the groundwater level in the soft ground, the soft ground can be compacted by the water compaction effect, which further improves the compaction effect and improves the ground. can be increased. Furthermore, in this soft ground improvement method, the water in the soft ground is compacted after it has been drained, so liquefaction during earthquakes can be prevented.

[Brief explanation of the drawing]

Figures 1 and 2 are diagrams showing one embodiment of the present invention, with Figure 1 being an explanatory diagram for explaining the soft ground improvement method, and Figure 2 being
The figure is an explanatory diagram illustrating the Vibrocompoyer method. 1... Vibrator, 2... Hollow pipe, 3... Hopper 4... Sand, 5... Sand compaction pile, 6...・・・
...Drain pipe, G...Soft ground.

Claims (1)

[Claims] A drain pipe is driven into the soft ground, the lower end of the drain pipe is located deep in the soft ground, and then a compaction pile is constructed around the drain pipe to compress the soft ground, and the compressive force is used to compress the soft ground. A method for improving soft ground, characterized in that water contained in the soft ground is discharged by flowing out to the drain pipe.