JPH0313617A - Horizontal drain construction method in submarine - Google Patents

Abstract

PURPOSE:To improve the quality of material, the reliability and profitability, and to facilitate execution of laying by vertically placing drain materials, in such a manner as to piece a net where a horizontal drain material to which a weight such as a reinforcement or the like is previously fitted on the submarine ground surface. CONSTITUTION:A plastic net 2 is laid on the submarine ground 1, and drain materials 3 are vertically placed in the ground 1 in such a manner as to pierce the net 2. Then, a horizontal drain material 4 is laid thereon, and the head portions 3A of the drain materials 3 are bent to be sandwiched between the plastic net 2 and the horizontal drain material 4. By this arrangement, excessive interstitial water in the ground 1 is collected in the drain materials 3, discharged outside the zone by the horizontal drain material 4, and sliding breakage of foundation due to earth filling can be prevented.

Description

[Detailed Description of the Invention] 13-1) Industrial Application Field The present invention is a horizontal method for improving soft ground on the seabed when constructing underwater structures in the ocean or performing reclamation work. Regarding drain construction method.

(3-21 Conventional technology When constructing a structure underwater in the ocean or carrying out reclamation work, if the seabed ground is soft, it is necessary to improve the ground in advance. This ground improvement Conventionally, a method such as Hiro's was used.That is, drain material is driven vertically into the seabed ground surface to collect excess pore water in the ground.
The ground was improved by promoting consolidation and subsidence of the ground by draining water out of the area through sandy soil (sand mat) that was laid on the ground to a thickness of about 1 meter.

This conventional method while heating had the following drawbacks.

■ In recent years, it has become difficult to obtain high-quality sand suitable for this sand mat, and since it is a natural product, the quality varies widely.

■ The construction of this sand mat involves laying a thin layer of high-quality sand on the seabed ground surface, but in order to ensure the required thickness from the viewpoint of workability, a considerable premium is paid to the required quantity. must be taken into account.

■ During reclamation work, a large uneven load is applied to the sand mat and the ground. At that time, if the ground slips and breaks, the continuity of the sand mat and drain material is lost, and ground improvement cannot be carried out.

■ In the case of a waste disposal site, the amount of waste that can be disposed of is reduced by the thickness of the sand mat.

(3-31 Problems to be Solved by the Invention The present invention solves the drawbacks of the conventional seabed soil improvement method described above, and improves the quality and reliability of the material by using factory-produced horizontal drain material. Excellent economy.

It is easy to construct the ground, and in the case of a landfill, it can withstand uneven loads without causing the ground to slide, and in the case of a waste disposal site, it is a ground improvement method that does not reduce the amount of disposal. The purpose of this project is to provide a horizontal drainage construction method on the seabed.

(3-41 Means for Solving the Problems) The present invention uses the horizontal drain construction method on the seabed for ground improvement as follows (a)
The above-mentioned problems are solved by following the process steps of (cl). (a) Lay a plastic net on the seabed ground surface to be improved (bl) Drain through the net. (C) A horizontal drain material with weights such as reinforcing bars attached in advance is laid on top of the net.This horizontal drain material, like the drain material cast vertically, maintains water permeability for the required period of time. After the net and horizontal drain material are laid, weights such as reinforcing bars are attached to prevent them from floating up.

(3-5) Example Embodiments of the present invention will be described below based on the drawings.

First, as shown in Figure 1, a plastic net 2 is laid on the seabed ground l to be modified (step (a) above).
, the illustrated WL is the sea level.

Furthermore, as shown in FIG.
l) At this time, the casting mandrel penetrates the net (
However, use a net with appropriate strength so that the tip of the mandrel does not pull the net into the ground.

In addition, the head 3A of the drain material is left on the ground surface for a length of approximately l- (.

Next, as shown in FIG. 3, a horizontal drain material 4 is laid on top of this (step (c) above). and the horizontal drain material 4.

FIG. 4 is a diagram illustrating the horizontal drain material 4 used in the present invention. As shown in the figure, reinforcing bars 5 are attached to the horizontal drain material 4 in a grid pattern to prevent the horizontal drain material from lifting up during installation. is prevented. In addition to the method of using reinforcing bars, there are other methods of preventing uplifting, such as using wire, sandbags, etc. Furthermore, when laying the reinforcing bars 5, the reinforcing bars 5 are arranged so as not to hit the driving portion of the mandrel 3.

This horizontal drain material uses a prefabricated drain material that is made of a core material made of resin molded into a porous band shape and covered with a filter material made of a fibrous material such as non-woven fabric.
When laying it, there are methods such as making it into a single piece of about 1h x 20m, or continuous construction by making it into a roll about 10 to 15m wide.

FIG. 5 is a perspective view showing a method of laying the horizontal drain material described above on a wide seabed ground. That is, as shown in the figure, the end portions 6 of adjacent horizontal drain materials 4 are laid overlapping each other to provide strength at the connecting portion and at the same time to ensure that there are no discontinuities in the drainage.

If the above method is used, as shown in Fig. 3, excess pore water in the ground 1 will be collected by the drain material 3 as shown by the arrow, and will be carried horizontally by the horizontal drain material 4 as shown by the arrow. , taken out of the area and drained. There is also no need for sand, and the total thickness of the net and horizontal drain material is only 17 cm, so there is no loss in landfill height.

(3-61 Effects of the Invention The present invention replaces the conventionally used sand mat by driving a drain material vertically when improving seabed ground and transporting water collected by the drain material horizontally. By using a horizontal drain material, etc., the following excellent effects can be achieved.

■ Since the drain material used is a factory product, it is economical and there is little regional difference in price.

■ Construction management with uniform quality and high reliability of materials;
Quality control is easy.

■ By laying the net, it is possible to prevent the ground from slipping and breaking due to land reclamation.

■ In the case of a waste disposal site, there is no loss of disposable amount.

[Brief explanation of drawings]

Figures 1 to 3 are diagrams illustrating the horizontal drain construction method according to the present invention according to its construction procedure, Figure 4 is a diagram illustrating the horizontal drain material used in the present invention, and Figure 5 is a diagram illustrating the horizontal drain material used in the present invention. FIG. 2 is a perspective view showing a method of laying the ground on a wide seabed. 1...Ground (seafloor ground) 2...Plastic net 3...Drain material 3A...Head 4...Horizontal drain material 5...Reinforcement bar 6...End WL...-Sea water level

Claims (3)

[Claims] (1) Horizontal drain construction method on the seabed for ground improvement performed according to the following process steps (a) to (c). (a) Laying a net (made of plastic) on the seabed ground surface to be improved (b) Driving drain material vertically through the net (c) Horizontal drain material with weights such as reinforcing bars attached in advance to be placed on the said net. (2) The drain material and the horizontal drain material are prefabricated drain materials in which the outside of a core material made of resin molded into a porous band shape is covered with a filter material made of a fibrous material such as non-woven fabric. A horizontal drain construction method on the seabed according to claim 1. (3) The horizontal drain material has a width of about 10 to 15 m and is laid continuously or piece by piece, with adjacent ends slightly overlapping in size, as claimed in claim 2. Horizontal drain construction method on the seabed as described in .