JPS59122627A - Construction of foundation under water - Google Patents

Abstract

PURPOSE:To greatly save the power of leveling work for the ground beneath a caisson by a method in which a net is laid on the surface of a small rubble- mound, a planned rubble-mound is further formed on the small rubble-mound, and underwater concrete is placed onto the upside of the net. CONSTITUTION:Rubble stones are put on the ground 1 under water to form a smaller rubble-mound A than a planned rubble-mound 2, and a net 5 is laid on the surface of the mound A. The net 5 has a mesh large enough to avoid the passage of underwater concrete. Rubble stones are then put up to a planned rubble-mound 2 in such a way as to form a recession at the center B of the mound 2 where a caisson 3 is to be installed. The mound 2 is roughly leveled off, the caisson 3 is set, and underwater concrete 7 is placed below the bottom plate of the caisson 3 through an injection port 6 and also to even the surface of the mound 2 other than the immediate under part of the caisson 3 through a hose 13.

Description

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

Conventionally, for example, when constructing a breakwater as shown in the figure, a rubble mound 2 was created by laying rubble on the underwater ground 1, the surface of which was leveled by a diver, and then a caisson 3 was 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 scouring of the rubble mound.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 for installation becomes larger, and the construction period and cost increase.

In addition, as another construction method for underwater foundations, Japanese Patent Application Laid-Open No. 57-362
The method described in Publication No. 17, 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 interior K of the rubble mound. This results in the entire cross section of the rubble mound being consolidated, leading to problems such as excessive construction costs.

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

In other words, the present invention includes (11) a step of creating a mound smaller than the planned ripple mound on the water bottom with riprap, (2) a step of laying a net-like material over the entire surface of the small mound, (3) a step of placing rubble again on the reticulate material. Plan Mau“
This is an underwater foundation construction method that consists of a combination of the following steps: (4) placing underwater concrete on a layer of rubble on a 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 having a fineness of 15 (1 to son denier, for example 250 f = -17) 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, it may be used as a mesh with a side of 10 mm and a mesh length of 20 mm.

(5) The method of knitting the net can be selected from Russell knitting, frogmata knitting, knotless knitting, etc. Russell knitting is preferable in consideration of ease of handling, necessity of wide netting, etc.

(6) - In order 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 placing a rubble layer on the net-like material, it is necessary to perform 4 steps. Depending on the situation, a step of leveling the surface may be added.

The present invention will be explained in detail below with reference to FIG. First, rubble is laid on the water bottom ground 1, and a hole mound A is created from 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 is one with a mesh size that is large enough to allow the underwater concrete to pass through.

After laying the net-like material 5, rubble is further carried out until the Knt mound 5 mound 2 is reached. 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 to form a planned rubble mound 2. It is preferable that the portion B', on which the caisson will be directly installed in a later step, is further subjected to main leveling.

Next, the caisson is installed in the part B', the caisson 3 is filled with sand, etc., and the underwater concrete 7 is poured under the caisson bottom plate through the injection hole 6 provided in the caisson bulkhead.
The BK fresh concrete is poured into the area lacking in the cross section, and the fresh concrete is mixed so that it also permeates into the gaps between the rubble stones in the vicinity.

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 the above-mentioned underwater concrete is made by mixing cement, aggregate, etc. with a thickening agent made of a known polymer substance, it goes without saying that aggregate separation will not occur underwater, and the concrete will become reef-free.
Because it is highly resistant, it penetrates sufficiently into the rubble layer, and when it reaches the mesh material 5, the penetration of concrete is stopped.

With the above plan, a sturdy underwater foundation in which the surface layer of the rubble mound 20 is solidified by 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 there is a risk of water leaking out during the installation of underwater concrete. Gaps easily form between concrete and rubble,
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. The concrete and the mesh material together form a blocking membrane.

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, 6 is an upper rubble, 5 is a separate body, and 9 is a The upper concrete consolidation layer, l is the bottom of the water, and 10 is the water surface.

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

(1) Concretion blocks used in the past to protect rubble mounds 1)-) #* Since the construction of overlay blocks is no longer necessary, the construction period and cost are improved.

(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 caisson can greatly save labor.

(3) By interposing a mesh material under the surface layer of the rubble mound, only the surface layer of the rubble mound is hardened! f: Since it is possible to reduce the thickness of concrete, the layer thickness of concrete covering power can be minimized.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing the conventional underwater foundation construction method. Fig. 2 is a cross-sectional view for explaining the underwater foundation construction method according to the present invention. A side cross-sectional view is shown after it has been fixed with concrete and made into blocks. Patent applicant: Goyo Construction Co., Ltd. 11!1

Claims (2)

[Claims] (1) A process of creating a mound smaller than the cross section of the planned rubble mound on the bottom of the water using rubble, a process of laying a mesh material on the entire surface of the small mound, and a process of further performing rubble to complete the gf rubble mound, An underwater foundation construction method comprising the step of placing underwater concrete in the planned rubble mound layer above the mesh material. (2) A process of creating a mound smaller than the planned rubble mound cross section on the water bottom using rubble, a process of laying netting material on the entire surface of the small mound, and a process of further carrying out rubble to remove part of the area where the caisson is to be installed. a step of completing the planned rubble mound at the planned installation location, a step of installing the caisson on the planned rubble mound at the planned installation location, and a step of pouring underwater concrete immediately below the planned rubble mound layer above the mesh material and the caisson. An underwater foundation construction method characterized by: