JPH0668168B2 - Horizontal drain method on the seabed - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (3-1) Field of Industrial Application The present invention is for improving the soft ground on the seabed when constructing a structure in the water such as the ocean or performing land reclamation work. Regarding the horizontal drain method.

(3-2) Conventional Technology When constructing a structure in water such as the ocean or performing landfill work, when the seabed is soft, it is necessary to improve the ground in advance. The following method has been conventionally used for this ground improvement. That is, drain material is vertically driven into the seabed surface to collect excess pore water in the ground,
The ground was improved by promoting the consolidation settlement of the ground by draining it out of the area through the sandy soil (sand mat) laid on the ground with a thickness of about 1 m.

However, this conventional method has 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, there are many variations in quality.

The construction of this sand mat is to lay a thin layer of good quality sand on the surface of the seabed, but from the standpoint of workability, in order to secure the required thickness, a considerable surcharge is added to the required quantity. You have to consider it.

A large biased load is applied to the sand mat and ground during the landfill work. At that time, if the ground slips and breaks, the continuity of the sand mat and the drain material is lost, and the ground cannot be improved.

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.

(3-3) Problems to be Solved by the Invention The present invention solves the above-mentioned drawbacks of the conventional method for improving the seabed, and uses the horizontal drain material of the factory product to improve the quality and reliability of the material. It is excellent in efficiency and economy, is easy to lay, and does not cause ground slippage damage during landfill, withstands uneven load, and reduces the disposable amount in the case of a waste treatment plant. It is intended to provide a horizontal drain construction method on the seabed for ground improvement that does not exist.

(3-4) Means for Solving Problems The present invention solves the above problems by performing a horizontal drain construction method on the seabed for ground improvement according to the following process steps (a) to (c). -ing That is, (a) a plastic net is laid on the surface of the seabed to be improved, (b) a drain material is vertically laid through the net, and (c) a horizontal drain material to which a weight such as a reinforcing bar is attached beforehand. This horizontal drain material has the ability to retain water permeability for a required period, like a drain material that is vertically laid. After laying the net and horizontal drain material, attach weights such as reinforcing bars so that they will not float.

(3-5) Example An example of the present invention will be described below with reference to the drawings.
First, as shown in FIG. 1, a plastic net 2 is laid on the seabed 1 to be remodeled (step procedure (a) above).
The WL shown is the sea level. Further, as shown in FIG. 2, the drain material 3 is vertically driven into the ground 1 by penetrating the net 2 (step procedure (b) above). At this time, the mandrel for casting penetrates the net. Use a net with appropriate strength so that the tip of the mandrel will not be pulled into the net and the ground. The head 3A of the drain material is left on the ground surface for a length of about 1 m.

Then, as shown in FIG. 3, a horizontal drain member 4 is laid on the horizontal drain member 4 (the process procedure (c)). The head portion 3A of the drain material that has been previously cast is bent and sandwiched between the plastic net 2 and the horizontal drain material 4 as shown in the figure.

FIG. 4 is a diagram illustrating the horizontal drain member 4 used in the present invention. As shown in the figure, the reinforcing bars 5 are attached to the horizontal drain member 4 in a grid pattern to prevent the horizontal drain member from floating during installation. As a method of preventing the floating, there is a method of using a wire or sandbag in addition to the method of using a reinforcing bar. Further, at the time of laying, the rebar 5 is arranged so as not to hit the placed portion of the mandrel 3.

For this horizontal drain material, a prefabricated drain material is used in which the outer side of a core material formed by molding a resin into a band shape having porosity is covered with a filter material made of a fibrous material such as nonwoven fabric,
When laying, there is a method such that one piece of about 10 m x 20 m is used, or a roll having a width of about 10 to 15 m is continuously applied.

FIG. 5 is a perspective view showing a method of laying the horizontal drain material described above on a wide seabed. That is, as shown in the same drawing, the end portions 6 of the adjacent horizontal drain members 4 are laid while being overlapped with each other so as to have the strength of the connecting portion and at the same time eliminate the discontinuous portion in the drainage.

Using the above method, excess pore water in the ground 1 is collected by the drain material 3 as shown by the arrow as shown in FIG. 3, and is horizontally carried by the horizontal drain material 4 as shown by the arrow. , Taken out of the area and drained. In addition, no sand is required, and since the net and horizontal drain materials are only a few cm in total, there is no loss in landfill height.

(3-6) Effects of the Invention The present invention replaces the sand mat that has been conventionally used for vertically driving the drain material in the improvement of the seabed and carrying the water collected by the drain material in the horizontal direction. By using a horizontal drain material, the following excellent effects can be obtained.

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

Uniform quality and high material reliability. Construction management,
Easy quality control.

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

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

[Brief description of drawings]

1 to 3 are diagrams showing the horizontal drain construction method according to the present invention in accordance with its construction procedure, FIG. 4 is a diagram showing the horizontal drain material used in the present invention, and FIG. 5 is a diagram showing the horizontal drain material. It is a perspective view showing a method of laying on a wide seabed. 1 …… Ground (seabed ground) 2 …… Plastic net 3 …… Drain material, 3A …… Head 4 …… Horizontal drain material 5 …… Reinforcing bar, 6 …… End WL …… Seawater level

Claims (3)

[Claims] 1. A horizontal drain construction method on the seabed for ground improvement, which is carried out according to the following steps (a) to (c). (A) Laying a net (made of plastic) on the seabed surface to be improved. (B) A drain material is vertically placed through the net. (C) A horizontal drain material having a weight such as a reinforcing bar attached beforehand is laid on the net. 2. The drain material and the horizontal drain material are prefabricated drain materials in which a core material formed by molding a resin into a band shape having a porosity is covered with a filter material made of a fibrous material such as nonwoven fabric. The horizontal drain construction method on the seabed according to claim 1. 3. The horizontal drain member has a width of about 10 to 15 m and is continuously or individually set, and the adjacent end portions are laid one by one with a slight overlap of dimensions. The horizontal drain construction method on the seabed according to item 2.