JPH01182412A - Method of placing underwater concrete - Google Patents

Abstract

PURPOSE:To prevent a stabilizing liquid from being contaminated, by placing a predetermined amount of special concrete having an underwater separation resistance, into the bottom part of a piling hole filled therein with the stabilizing liquid, and by pumping normal concrete into a part below the bottom part of the hole so as to place the same. CONSTITUTION:A cavity 3 is formed in an natural mountain 1 while charging a stabilizing liquid 2. Then, a tremie pipe 3 is planted in the cavity 3, being extended to the bottom of the latter, and a suitable amount of special concrete 14 is placed. The special concrete is the one added with water-soluble high polymer as a builder, having an underwater separation resistance. Then, normal concrete 4 is pumped and placed in the cavity 3 below the special concrete 14 so as to raise the special concrete 14. With this arrangement, it is possible to reuse the stabilizer, and to make the upper surface of the concrete smooth.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention provides underwater concrete casting that prevents deterioration of stabilizing solution and water pollution by using special concrete that has resistance to separation in water for initial casting. Regarding the method.

[Conventional technology]

Generally, when pouring concrete into the soil, when excavating the place where concrete is to be poured, a cavity of a predetermined size is excavated while filling the excavated area with stabilizing liquid to prevent the soil wall from collapsing. However, a so-called underwater concrete casting method is often used in which concrete is then poured into a cavity filled with the stabilizing liquid. As shown in FIGS. 5 to 7, for example, a conventional pouring method involves excavating a cavity 3 of a predetermined size while supplying a stabilizing liquid 2 into the ground 1, and then pouring ordinary concrete into the ground. 4 is charged from the bottom of the cavity 3 using the tremie tube 5 or the like so as not to cause any disturbance with the stabilizing liquid 2. The concrete 4 to be charged fills the cavity 3 and rises while its upper end surface comes into contact with the stabilizing liquid 2, so that the pushed up stabilizing liquid 2 is pumped out by the pump 6 and remains in a reusable state. It will be used for the next excavation.

[Problem to be solved by the invention]

However, in such conventional underwater concrete placement, ordinary concrete is used, and therefore the stabilizing liquid that comes into contact with the poured concrete 4 deteriorates due to the cement content in the concrete, and the deteriorated stabilizing liquid 2a is discarded. Since it had to be disposed of, the amount of stabilizer used increased and the amount of stabilizer discarded also increased, making it uneconomical.

Alternatively, the water above the concrete is contaminated by cement, etc., causing water pollution in the surrounding area.

In addition, as shown in FIG. 6, a deteriorated part 4a of the concrete occurs on the top surface of the concrete 4 that was in contact with the stabilizing liquid 2, so the deteriorated concrete 4
It was necessary to remove the part a using a vacuum truck 6, etc., and the height of the concrete was increased in anticipation of the part to be removed, resulting in poor workability and economy. Furthermore, as shown in FIG.
(see figure) is high and the outer periphery of the ground 1 in contact with the excavated wall 1a is low. Problems arise, such as the need for extra work such as cutting and filling in low peripheral areas.

□In order to eliminate the various drawbacks mentioned above, it would be possible to use special concrete that has properties such as underwater separation resistance and self-levelling properties, but this would result in high material costs. The problem arises that the amount increases significantly.

The present invention has been made in view of these conventional problems, and aims to solve the above problems by using special concrete at the initial stage of concrete pouring.

[Means to solve the problem]

In order to achieve the above object, the present invention, when placing underwater concrete, first places a small amount of special concrete that has underwater separation resistance and self-leveling properties compared to the total amount of concrete required for placing, and then A concrete structure is formed by force-feeding the concrete to the underside of the poured special concrete without contacting with stabilizing liquid, seawater, etc., pushing up the special concrete with the ordinary concrete, and pouring the ordinary concrete to form a concrete structure. This is a method of placing underwater concrete.

[Effect]

With this invention having the above configuration, it is the special concrete part that has underwater separation resistance and self-leveling properties that comes into contact with the stabilizing liquid from the beginning of concrete pouring to the end of concrete pouring. Since the concrete components do not dissolve into the stabilizing solution and the stabilizing solution does not deteriorate, all the stabilizing solution recovered during concrete pouring can be reused, and special concrete has self-leveling properties, making it easy to pour. Since the top end surface of the raised concrete is finished flat, steps such as leveling the top end surface can be omitted, improving work efficiency.

This is an underwater concrete placement method that has significantly improved economic efficiency.

〔Example〕

The present invention will be explained below based on the drawings. FIGS. 1 to 3 are diagrams showing one embodiment of the present invention. however,
The same parts as in the conventional example are given the same reference numerals, and redundant explanation will be omitted.

First, as shown in FIG. 1, a cavity 3 of a predetermined size is excavated while supplying a stabilizing liquid 2 to a ground l.

When the excavation is completed, the tremie pipe 5 is erected so that its lower end reaches the bottom of the cavity 3, and an appropriate amount of special concrete 14 is poured first. The special concrete 14 used here is made by adding a water-soluble polymer admixture to give the concrete consistency and resistance to separation in water, so that the concrete does not dissolve into the stabilizing liquid. It also has a self-leveling property in which the top surface of the poured concrete is in a horizontal state. In addition, the above-mentioned appropriate amount means that the concrete should be poured so that the top surface of the concrete is sufficiently thick to completely block contact between the ordinary concrete 4 and the stabilizing liquid 2 at the end of concrete pouring, and the top surface is horizontal. It means the amount prepared by the rising height.

In this way, after the initial casting of the special concrete 14 is completed, the ordinary concrete 4 is forced to the underside of the special concrete 14 by the tremie pipe 5 which is initially set up.

As the amount of normal concrete 4 being pumped increases, the pressure pushes the special concrete 14 up as shown in Figure 2. (Also, the specific gravity of special concrete can be reduced by using lightweight aggregate etc. possible).

Although a slight slope is formed at the boundary S with the ordinary concrete 4 in the process of being pushed up, the surface 14a in contact with the stabilizing liquid 2 always maintains a horizontal level state, and the concrete components into the stabilizing liquid 2 are Concrete is poured while maintaining a state of no welding. Therefore, the stabilizing liquid 2 pumped out as concrete is poured out does not deteriorate as in the conventional case, and can be reused at other places.

As shown in FIG. 3, the upper end of the concrete structure cast as described above is formed of special concrete 14, and the upper surface 14 of this special concrete 14 is
a forms a flat level surface.

Fig. 4 shows an example of a bridge pier constructed underwater.The part corresponding to the cavity 3 formed by the formwork 11, 12, etc. is filled with special concrete via a tremie pipe etc. during initial pouring. By applying the method of pouring ordinary concrete through a tremie pipe or the like after completing the initial pouring, construction can be carried out in the same manner as in the embodiments shown in FIGS. 1 to 3.

〔Effect of the invention〕

Since the present invention is configured as described above, it produces the effects described below.

First, special concrete that comes into contact with stabilizing liquid, seawater, etc. does not dissolve the concrete components, so it can prevent water pollution (water pollution). Similarly, since degraded components do not dissolve into the stabilizing solution, all of the stabilizer recovered during concrete pouring can be reused, and no degraded stabilizing solution is generated, which improves economic efficiency and workability. improves. The top surface of poured concrete does not deteriorate, and at the same time, the top surface is always flat, so
This eliminates the need for the conventional work of removing deteriorated concrete and leveling the top surface, improving work efficiency and economy. Since special concrete only needs to be used for the initial pouring, there is no significant increase in material costs, and unlike conventional concrete, there is no need to remove parts after pouring, which actually improves economic efficiency.

[Brief explanation of the drawings] Figure 1 is a cross-sectional view showing the initial pouring process in the example, Figure 2 is a cross-sectional view showing the ordinary concrete pouring process in the example, and Figure 3 is the pouring process in the example. A cross-sectional view showing completion;
Fig. 4 is a sectional view showing another embodiment, and Figs.
The figure shows the deterioration state of the stabilizing liquid, FIG. 6 shows the discharge state of the deteriorated stabilizing liquid, and FIG. 7 shows the state of the deteriorated upper end of the poured concrete. 2...Stabilizing liquid, 4...Normal concrete, 14...Special concrete.

Claims (1)

[Claims] When placing underwater concrete, a small amount of special concrete with underwater separation resistance and self-leveling properties is placed first compared to the total amount of concrete required for placement, and then ordinary concrete is brought into contact with stabilizing liquid, seawater, etc. An underwater concrete placing method characterized in that a concrete structure is formed by force-feeding the special concrete to the underside of the placed special concrete and placing the special concrete while pushing it up with ordinary concrete.