JPS5812412B2 - Underwater soil improvement method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a construction method for driving sand piles using hollow pipes in order to improve soft ground at the bottom of water.

In such construction methods, especially when driving long sand piles or sand piles with a large diameter, it is necessary to increase the size of the hollow pipe.

In this case, if a single hollow tube is used as in the past, the volume inside the hollow tube will increase, and the time required to suck and exhaust air into the hollow tube will increase, which will be a major obstacle in terms of construction efficiency, and the air supply equipment will also need to be large. Must.

In addition, in the case of improvement of the underwater ground, buoyancy acts on the hollow tube due to the presence of water at the depth of the water, but if the hollow tube is large, the buoyancy will also be large, so when driving the hollow tube into the original ground, There are cases where the hollow tube cannot be driven into the original ground due to insufficient penetration force.

This is to prevent water from entering the hollow tube by introducing compressed air into the tube or closing the lower end of the tube for construction reasons as well as the buoyancy of the hollow tube itself.

Furthermore, if the hollow tube becomes long, its strength may be insufficient and buckling may occur.

In view of these problems, the present invention uses a double hollow tube, and the details thereof will be explained as follows.

In the figure, A is a hollow pipe for constructing sand piles in which an inner pipe 1 and an outer pipe 2 are concentric and a compartment 3 is provided between the two pipes.The compartment 3 is closed at the top and bottom, and there are many A water passage hole 4 is formed in the outer tube 2.

Further, a penetrating machine 5 such as an exciter is installed on the hollow tube A, and a hopper 6 is installed on one side of the upper end of the outer tube 2.
An air valve 7 and an air supply port 8 are provided to communicate or cut off communication between the air valve 6 and the inside of the inner pipe 1.

Further, the lower end of the outer tube 2 is made to protrude further than the lower end of the inner tube 1, a protrusion 9 is provided inside the outer tube 2, and a lid 11 is attached to the lower part.

Next, to explain the construction method, first, as shown in Fig. 2 I, the hollow tube A is submerged in water.
Water flows into the compartment 3 from there.

When the hollow tube A reaches the ground 10, the valve 7 is opened and the hopper 6
The sand is started to be introduced into the ground by the penetrating device 5, and when it reaches a predetermined depth, the valve 7 is closed as shown in Fig. Hollow tube A
While discharging the sand from the lower end, pull up the hollow tube A slightly leaving the lid 11 intact, then remove the air from the air supply port 8 as shown in Figure 2 (■), open the valve 7, and introduce sand from the hopper 6. By penetrating the hollow tube A again, the sand pile B is compacted.

By repeating these operations, sand piles are formed.

It should be noted that this example is just an example of implementation, and it goes without saying that it can also be applied to the construction of general sand piles such as the sand drain method.

In the above embodiment, when the hollow tube A is inserted into water, water flows into the compartment 3 through each water passage hole 4 of the outer tube 2 to reduce buoyancy, and when the hollow tube A is pulled up, water flows into the compartment 3. Water is discharged from the water hole 4.

This suction and drainage may be carried out using the water's own weight, or the compartment may be vacuum-suctioned during water suction, and the compartment may be pressurized during water discharge to improve the suction and drainage speed.

As described above, the present invention reduces the buoyancy even in the case of the large-diameter hollow tube A due to the inflow of water into the compartment 3, making it easy to penetrate, and also uses a double hollow tube. The weight increases and the penetration force increases.

Further, the amount of air used is only a small amount in the inner tube 1, and the air intake and exhaust time is greatly shortened.

Furthermore, since the pipe is a double pipe, buckling is less likely to occur even when the pipe is long, making it possible to construct ultra-long, large-diameter sand piles.

[Brief explanation of drawings]

FIG. 1 is a partially cutaway vertical sectional view of a hollow tube used in the construction method of the present invention, and FIG. 2 is a longitudinal sectional view of each step of the construction method of the present invention. A...Hollow tube, 1...Inner tube, 2...Outer tube, 3...Compartment.

Claims (1)

[Claims] 1. A sand pile construction method characterized by providing a compartment between an inner pipe and an outer pipe having water holes, and adjusting the weight of the construction equipment underwater by supplying and draining water from the water holes in the outer pipe. .