JPH0454011B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for constructing underwater foundations such as breakwaters.

Conventionally, when constructing a breakwater as shown in Fig. 1, for example, rubble is placed on the underwater ground 1 to create a rubble mound 2, the surface of which is leveled by a diver, etc., and then the caisson 3 is piled with rubble. It was placed on the mound 2, and a concrete covering block 4 was constructed on the surface of the rubble mound to prevent the rubble mound from being scoured. However, the construction of underwater foundations such as the above-mentioned breakwaters had the following problems.

(1) The stability of the covered block depends on the leveling accuracy of the rubble mound surface, and this leveling becomes difficult as the water depth increases.

(2) Rubble may be sucked out from the voids between the covering blocks.

(3) As the covering block becomes larger, the construction machinery used for installation becomes larger, and the construction period and cost increase.

In addition, as another construction method for underwater foundations,
The method described in Publication No. 36217, that is, the method of solidifying the rubble mound with underwater concrete, is known, but even in this method, when the underwater concrete is placed, the underwater concrete penetrates into the inside of the rubble mound, causing the rubble to form. This results in solidification of the entire cross section of the mound, leading to problems such as excessive construction costs.

As a result of studies to solve the above problem, the inventor of the present invention found that it would be sufficient to lay a mesh material in a mound layer of rubble formed at the bottom of the water, and to solidify the rubble mound above the mesh material with concrete. However, the present invention was achieved.

That is, the present invention includes (1) a process of creating a mound smaller than the planned rubble mound on the bottom of the water using rubble; (2) a process of laying a mesh material on the entire surface of the small mound to an extent that underwater concrete cannot pass through; This is an underwater foundation construction method that consists of the following steps: (1) completing the planned mound by placing rubble again on top of the net material, and (4) placing underwater concrete on the rubble layer on the mesh material.

As the net-like material used in the present invention, it is preferable to use one under the conditions described below.

(1) The material is preferably synthetic fiber, such as nylon or polyester, from the viewpoint of strength and abrasion resistance, and polyester, which has excellent sedimentation properties in water, is more preferable. If the construction environment and construction conditions are severe and speedy construction is required, a high-density reticulated material mixed with lead fiber may be used.

(2) A polyester filament with a fineness of 150 to 500 deniers, for example 250 deniers, can be used.

(3) The number of doubling threads can be selected as appropriate depending on the purpose; for example, 20 threads may be used.

(4) It is desirable that the mesh size of the net is large enough to prevent rubble from leaking out and also to prevent underwater concrete from leaking out. For example, one side is 10mm, mesh length is 20mm
It may also be used as a mesh.

(5) The method of knitting the net can be selected from latsel knitting, frogmata knitting, knotless knitting, etc., making it easy to handle,
Considering the necessity of wide netting, Ratssel stitch is preferable.

(6) To prevent slippage at the knot points of the net, it is recommended that the net be treated with a hydrophobic resin such as polyester resin.

In the present invention, after forming a mound layer on the bottom of the water with rubble, or after placing a rubble layer on the net-like material, a step of leveling the surface may be added as necessary.

An embodiment of the present invention will be described below with reference to FIG. First, rubble is placed on the water bottom ground 1 to create a mound A that is smaller than the planned rubble mound 2.

Next, the net material 5 is laid on the surface of the small mound A. The mesh material 5 used has a mesh that does not allow the underwater concrete that will be applied later to pass through.

After laying the net material 5, rubble is poured on it until the planned rubble mound 2 is formed. However, it is preferable to carry out rubble so that the center part B where the caisson 3 will be installed in a later step is rather lacking in cross section as shown in the figure.

Thereafter, the surface is roughly leveled by a diver or the like so as to form the planned rubble mound 2. It is preferable that part B', where the caisson will be directly installed in a later process, is further subjected to main leveling.

Next, install the caisson in part B′,
The inside of the caisson 3 is filled with sand, etc., and underwater concrete 7 is cast under the caisson bottom slab through the injection hole 6 provided in the caisson bulkhead, etc., and the lacking portion B in the cross section is filled with ready-mixed concrete. At the same time, the ready-mixed concrete should also permeate into the gaps between the rubble stones in the surrounding area.

In addition, in parallel with the above, underwater concrete 7 is placed on the surface of the rubble mound other than directly under the caisson 3 so that ready-mixed concrete is thoroughly filled between the rubble stones in the surface layer of the rubble mound.

If you use the above-mentioned underwater concrete in which a thickening agent made of a known polymer substance is mixed with cement, aggregate, etc., there will be no separation of aggregate in water, and since the concrete is highly fluid, it can be When the concrete reaches the net material 5, the concrete stops penetrating. As a result of the above plan, a sturdy underwater foundation in which the surface layer of the rubble mound 2 is solidified with underwater concrete is completed.

It is also possible to use a canvas sheet made of synthetic fibers as a substitute for the net material 5, but there is a high risk of damage during rubble construction, and it is difficult for water to drain out during underwater concrete placement, making it difficult to use with filled concrete. Voids tend to form between the rubble, so canvas sheets are not suitable.

In contrast, the mesh material 5 in the present invention is of sufficient strength, so there is no risk of damage during rubble construction, and the mesh size is less than the maximum dimension of coarse aggregate in underwater concrete to be poured in a later process. If a net-like material is used, water will easily pass through, and the viscous concrete and the net-like material will come together to form a blocking film.

Furthermore, as mentioned above, the mesh material has good water permeability, so when it is laid down, it tends to sink in water, and if appropriate weights are provided, it can be easily installed underwater.

In FIG. 2, 11 is a work barge, 12 is a concrete pump, and 13 is a hose.

Figure 3 shows a side sectional view after pouring underwater concrete into the upper rubble layer and fixing only the upper rubble layer. A is a small rubble mound, 8 is an upper rubble, 5 is a mesh, and 9 is a Upper concrete consolidation layer,
1 indicates the bottom of the water, and 10 indicates the water surface.

By using the construction method of the present invention described in detail above, the present invention has the following effects.

(1) The construction period and cost will be improved because it will no longer be necessary to construct concrete covering blocks to protect the rubble mounds that were previously used.

(2) Most of the leveling work on the surface of the rubble mound is only a rough leveling, and in particular, as shown in Figure 2, the leveling work directly below the caissons can greatly save labor.

(3) By interposing the mesh material under the surface layer of the rubble mound, only the surface layer of the rubble mound can be consolidated, so the thickness of the concrete covering layer can be reduced, reducing construction time and construction costs. can be achieved.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view showing the conventional underwater foundation construction method, Figure 2 is a cross-sectional view explaining the underwater foundation construction method according to the present invention, and Figure 3 is an upper rubble layer placed on the surface of the net-like structure, which is fixed with underwater concrete. A side sectional view after the block has been formed is shown.

Claims (1)

[Scope of Claims] 1. A step of creating a mound smaller than the planned cross section of the rubble mound at the bottom of the water using rubble, a step of laying a mesh material with a mesh size that does not allow underwater concrete to pass through the entire surface of the small mound, and further steps of The process of completing the planned rubble mound by carrying out
An underwater foundation construction method comprising the step of placing underwater concrete in the planned rubble mound layer above the mesh material. 2 The process of creating a mound smaller than the planned rubble mound cross section on the water bottom using rubble, the process of laying a mesh material with a mesh size that does not allow underwater concrete to pass over the entire surface of the small mound, and the installation of the caisson after further rubble. A process of completing the planned rubble mound except for a part of the planned site, a process of installing the caisson on the planned rubble mound at the planned installation site, and installing underwater concrete directly under the planned rubble mound layer above the mesh material and the caisson. An underwater foundation construction method characterized by the following steps: