JPH0430490B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <<Industrial Application Field>> This invention relates to a method of constructing a continuous wall under water.

<<Conventional technology>> When constructing a large structure such as a bridge underwater in a river or the sea, an underground continuous wall is constructed as the foundation, and the foundation is constructed inside the continuous wall. There is.

The conventional method for constructing this continuous wall is to build an artificial island underwater, and excavate the inside of the artificial island to construct a continuous wall that reaches into the seabed.

However, this construction method had problems in terms of economy and construction period.

In response, the water area was closed off with a temporary cofferdam,
Another method being considered is to dry up the interior partitioned by cofferdams and excavate the ground surface to construct a continuous wall.

In this construction method, the construction of the continuous wall is completed by excavating near the inside of the cofferdam and pouring concrete into the excavated hole.

In this construction method, the continuous wall does not reach above the water, and the continuous wall part in the underwater ground works together with the cofferdam that protrudes above the water to improve the water-tightness and strength against water pressure inside the cofferdam in dry-up conditions. I try to keep it.

<Problems to be Solved by the Invention> However, in this construction method, when forming an excavation hole for a continuous wall, the lower side of the cofferdam is damaged due to the osmotic pressure effect due to water pressure outside the cofferdam. Water entered the inside of the hole and the walls of the borehole were prone to collapse.

In addition, as other construction methods, for example, JP-A-58-
As shown in No. 146618 and Japanese Unexamined Patent Publication No. 146619, box-shaped frames having a length that reaches the water bottom as guide holes are erected at predetermined intervals by slightly press-fitting into the water bottom ground, and the box-shaped There is also a method of constructing a continuous wall by excavating the underwater ground to a predetermined depth while filling the inside of the formwork with a stabilizing liquid, inserting a reinforcing bar cage into the excavation hole, and pouring concrete.

However, even with this construction method, it is difficult to increase the rigidity of the box-shaped formwork, and it is susceptible to shaking due to waves, etc., so the workability remains unstable.

This invention solves the problems of the various conventional techniques described above, and improves the low water-stopping property that is a drawback of the continuous wall construction method using temporary cofferdams. The purpose is to make it possible to construct continuous walls while fully taking advantage of the advantages of the above construction method.

≪Means for Solving the Problems≫ In order to achieve the above object, the present invention provides a step of closing underwater with a cofferdam; reaching the lower part of the cofferdam along the inside partitioned by the cofferdam; The process of injecting grout into the underwater ground to stop the water; A box-shaped formwork is installed near the inside of the cofferdam, and using the formwork as a guide, the underwater ground below it is excavated while filling it with muddy water. Process: The process of pouring concrete into the excavated hole and replacing muddy water with concrete; The process of dry-up the inside of the cofferdam after the concrete has hardened; This provides a method for constructing continuous walls underwater.

≪Operation≫ Water is stopped at the inner lower part of the cofferdam using grout in the preparation stage for construction of the continuous wall, so there is no collapse of the hole wall when the excavation hole is formed. In addition, since the box-shaped formwork is submerged in still water surrounded by the cofferdam, there is no shaking due to waves, which is a disadvantage of construction methods using the box-shaped formwork, and excavation and concrete pouring can be carried out in a stable state. able to perform work.

<<Example>> Hereinafter, an example of the present invention will be described in detail using the drawings.

FIGS. 1 to 6 are explanatory cross-sectional views showing the sequence of steps in the continuous wall construction method according to the present invention.

First, Figure 1 shows the deadline process.
In the sea area where the foundation is to be constructed, double cofferdams 1a and 1b made of steel pipes, steel pipe sheet piles, etc. are driven into the submarine ground E, and filler earth and sand 2 is cast and filled inside to construct double cofferdam 1. Sotome 3a by each double deadline 1
and the inside of the cofferdam 3b are partitioned watertightly. In this state, both the open sea 3a and the cofferdam interior 3b are at the same water surface WL, but the cofferdam interior 3b is a still water area, and the dynamic effects of waves and the like are removed.

Next, FIG. 2 shows the water stop process. In this process, a grouting pipe 4 is penetrated into the ground E along the inner side of the inner cofferdam 1a, grout is injected from the tip of the grouting pipe 4, and the grout is injected into the inner peripheral part of the inner cofferdam 1a as shown in the figure. A water stop layer 5 indicated by a chain line is formed.

The materials that make up this grout include:
The solidifying agent (trade name: Aqua Soil) previously developed by the present applicant is suitable as a material with higher water-stopping properties.

The consolidating material is a mixture of earth and sand with a caking agent, a caking agent, and fiber material added as necessary, and has good permeability and caking properties when put into water. It is the material. The more detailed composition and properties of the consolidation material are as follows.

The above-mentioned caking agent is made of a water-soluble natural, semi-synthetic or synthetic polymer, and is a type of paste-like substance that has the function of preventing the separation of soil particles and the incorporation of seawater.

To give specific examples of this caking agent, water-soluble natural polymers include various starches, konjac, funori, agar, sodium alginate, molasses, gum tragonto, gum albia, dextrin, levan,
Glue, gelatin, casein, collagen, etc. are used.

Examples of water-soluble semi-synthetic polymers include viscose, methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose,
Soluble starch, carboxymethyl starch, dialdehyde starch, etc. are used.

As the water-soluble synthetic polymer, polyvinyl alcohol, sodium polyacrylate, polyactylamide, polyethylene oxide, etc. are used.

In addition, the above-mentioned consolidation material is one that uses cement-based materials, lime-based materials, slag-based materials, asphalt-based materials, fly ash-based materials, etc., which have been conventionally used for soil stabilization treatment, singly or in combination, These consolidating materials bind and solidify the particles of earth and sand that have been put into the water, thereby stabilizing them and improving their strength.

As for the mixing ratio of these caking agents and caking agents, 1 to 5 parts by weight of caking agent and 50 to 200 parts by weight of caking agent to 1000 parts by weight of earth and sand are preferable in terms of economic efficiency and degree of achievement of effects. range.

Furthermore, the fiber material added as necessary is
The above-mentioned soil, caking agent, and caking agent have the function of imparting appropriate tensile strength by being dispersed inside the mixture in a solidified state and intertwined with each other.

More specifically, metal fibers such as carbon steel fibers and stainless steel fibers, glass fibers, asbestos fibers,
Inorganic fibers such as alumina fibers, organic fibers such as vinylon fibers and polypropylene fibers, and reinforcing material fibers such as carbon fibers and aramid fibers are used.

For this type of fiber material, the fiber diameter and fiber length are important in achieving the effect due to its function.The fiber diameter ranges from several microns to several millimeters, and the fiber length ranges from several millimeters to several centimeters. preferable.

The mixing amount thereof is preferably 5 to 50 parts by volume per 1000 parts (volume) of the mixture consisting of earth and sand, caking agent, and caking agent.

Therefore, in the solidified state, the water stop layer 5 having the above-mentioned composition effectively stops water that permeates into the ground E from the open sea 3a side and seeps out from the lower part of the cofferdam 1a.

Next, in Fig. 3, the box-shaped formwork 6 is
The case is shown in which the excavation preparation work is completed by this installation work, which is installed in a state where it is slightly sunk into the ground E along the inside part of point a.

Next, as shown in FIG. 4, excavation work is performed while filling the ground E with a stabilizing liquid 7 such as mud water using the formwork 6 as a guide.

In this process, water from the outside world normally springs out from the lower side of the cofferdam 1a due to its osmotic pressure, but due to the presence of the water stop layer 5, the excavation can be carried out well, and the spring water can cause damage to the hole wall. It can also prevent damage.

Next, as shown in FIG.
Then, concrete C is poured into the excavated hole 8 through a tremie pipe or the like to replace the stabilizer liquid 7 and concrete C.

In this embodiment, the amount of concrete C that is poured does not reach the sea, and the pouring is stopped when it is slightly protruding from the seabed E, and the box-shaped formwork 6 is pulled up.

In this state, the inside of the cofferdam 1 is dried up as shown in FIG. 6.

In a dry-up state, lateral pressure is applied to the double cofferdam 1, and lateral pressure is also applied to the protruding portion of the obtained underground wall panel 10 from the ground E, but the cooperation of both provides sufficient resistance to water pressure. In addition to exerting its power, the water stop layer 5 interposed between the underground wall panel 10 and the double cofferdam 1 effectively prevents water from flowing from the gap between the two.

As described above, after constructing the underground wall panel 10, that is, the continuous wall, a foundation such as a bridge can be constructed inside it.

<<Effects>> As explained in detail in the examples above, according to the method for constructing a continuous wall under water according to the present invention, the osmotic pressure from the outside when excavating an interior closed off by a cofferdam is reduced. There is no water leakage due to impact, and collapse of the hole wall during excavation can be prevented. Furthermore, when the borehole is being excavated, a box-shaped formwork is placed inside the cofferdam, which is a still water area, and this is used as a guide, so that the advantages of the excavation process using this formwork can be fully utilized.

[Brief explanation of drawings]

FIGS. 1 to 6 are explanatory cross-sectional views showing the sequence of steps in the continuous wall construction method according to the present invention. 1...Double cofferdam (cofferdam), 3a...Sotome, 3
b... Inside the cofferdam, 5... Water stop layer (grout),
6... Box-shaped formwork, 7... Mud water, 8... Excavation hole, C... Concrete, 10... Underground wall panel (continuous wall).

Claims (1)

[Scope of Claims] 1. A process of closing off water with a cofferdam; A process of injecting grout into the underwater ground that reaches the lower part of the cofferdam along the inner side partitioned by the cofferdam to stop water. ; A process in which a box-shaped formwork is installed near the inside of the cofferdam, and using the formwork as a guide, the submerged ground beneath the formwork is excavated while filling it with muddy water: Concrete is poured into the excavation hole and the muddy water is poured out. A method of constructing a continuous wall under water, which consists of the process of replacing concrete with concrete: the process of dry-up the inside of the cofferdam after the concrete has hardened;