JPS61254720A - Construction work of embankment - Google Patents

Abstract

PURPOSE:To make the adjustment of strength of embankment easier as well as make excavation work easier by constructing the embankment of homogeneous soil quality by a method in which while discharging water in the cofferdam, a self-hardening stabilizer liquid is injected subsitutionally and hardened. CONSTITUTION:Steel tubular sheet piles 2 are closely driven into the seabed 3 by surrounding an area where a foundation 1 is to be formed to obtain a cofferdam work. While discharging water in the area surrounded by the sheet piles 2, a self-hardening stabilizer liquid 10 is injected subsitutionally and hardened, and a strengthening layer 12 is provided on the stabilizer liquid 10 to construct an embankment 11. Pits are excavated from the upper end of the embankment 11 and concrete is driven to form the foundation 1 of underground continuous wall. Since the stabilizer liquid 10 is hardened to form the embankment 11 of homogeneous soil quality to the upper end from the seabed face 3, excavation in forming the foundation 1 can be made easier and the adjustment of the strength of hardened embankment can be made possible by varying the mixing ratio of the stabilizer liquid 10.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for constructing a rocky island when forming foundations for bridge piers, abutments, etc. in water.

(Prior art) As is well known, when constructing foundations such as bridge piers and abutments that are formed underwater, it is not possible to directly grasp the seabed, so it is necessary to prepare a site that protrudes above the surface of the water at the site where the foundation is to be formed. A built-up island is constructed, and then the foundation is formed using, for example, the caisson construction method or the continuous underground wall construction method.

The area of the island was determined by considering external forces (waves, current speed, etc.), and conventionally the island was constructed using the method shown in Figure 2.

The method shown in the figure is to first place earthen sheet piles with connecting fittings, such as steel pipe sheet piles 2, in close contact with the site where the foundation 1 is planned to be constructed, and
A cofferdam will be constructed to surround the planned site by pouring the cofferdam underneath.

Next, the area surrounded by the W4 pipe sheet piles 2 is filled with earth and sand 4 to be backfilled, and a built-up island 5 is constructed.

Thereafter, for example, excavation is performed from the top surface of the rocky island 5, and a foundation 1 that reaches the supporting ground layer is formed using a continuous underground wall construction method or the like.

Here, since the Tsukijima 5 which has only been filled with earth and sand 4 before the foundation 1 is constructed is water permeable, deep wells 6 are installed at appropriate locations to drain the Tsukishima 5, or before the foundation 1 is formed. Ground improvement office! Supplementary construction methods such as 7th grade were also used.

(Problems to be Solved by the Invention) In the Tsukishima construction method shown in Figure 2, it is difficult to obtain homogeneous soil quality because the Tsukishima 5 is backfilled with earth and sand 4, and the strength of the Tsukishima 5 is also adjusted. It was difficult to do so.

Moreover, since the Tsukijima 5 is permeable, especially when forming the foundation 1 using the continuous underground wall construction method, it is necessary to use auxiliary construction methods in order to ensure the stability of the excavation hole, which lengthens the construction period.
The disadvantage was that the construction costs were high.

This invention was made in view of these problems, and its purpose is to obtain homogeneous soil quality, enable arbitrary strength adjustment, and shorten the construction period by eliminating the need for auxiliary construction methods. The purpose of the present invention is to provide a method of constructing a rocky island that can reduce construction costs.

(Means for solving problems) In order to achieve the above object, the present invention provides a bridge pier.

In the construction method of Tsukishima, which is used when forming foundations such as bridge abutments in the water, after constructing a cofferdam at the site where the foundation is planned to be formed, water within the cofferdam is drained and the interior of the cofferdam is self-hardened and stabilized. It is characterized by displacing and injecting a liquid to harden the self-hardening stabilizing liquid in the cofferdam to form a built island.

(Function) The self-hardening stabilizing liquid injected into the cofferdam hardens over time, and forms a built-up island together with the cofferdam.

By appropriately adjusting the components in the self-hardening stabilizer, it is possible to arbitrarily set the curing time and curing strength.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows an embodiment of the Tsukishima construction method according to the present invention.

The construction method shown in the figure is the same as the conventional method described above.
Steel pipe sheet piles 2 of connecting metal frames are closely placed under the seabed 3 so as to surround the site where the foundation 1 is planned to be formed, and cofferdam work is performed.

Next, while the seawater inside the steel pipe sheet pile 2 is drained from the upper part thereof using a pump, the self-hardening stabilizing liquid 10 is replaced and injected close to the seabed surface 3 through a tremie pipe or the like.

The self-hardening stabilizer 10 is a hardening agent, such as cement.

It is a mixture of blast furnace cement and bentonite 2 additive in water in an appropriate ratio, and clay or local earth and sand may be mixed in depending on the case.

Here, prior to the replacement injection of the self-hardening stabilizing liquid 10, the mud on the seabed surface 3 in the area surrounded by the steel pipe sheet piles 2 is dredged so as to obtain good bonding strength between the hardened stabilizing liquid 1o and the seabed surface 3. It is preferable to

In addition, the injection amount of the self-hardening stabilizing liquid 10 is not injected up to the upper end of the steel pipe sheet pile 2 in this embodiment, but is determined based on the tidal level displacement of the sea surface (HL-L).
Although the injection is kept at approximately the middle position of L), it is of course possible to inject to the vicinity of the upper end.

The injected self-hardening stabilizer 10 will harden over time, and after hardening it will have a strength of 5-20 kg/ci and 10
The hydraulic conductivity is approximately -6 to 10-'am/sea, and the built-up island 11 is constructed integrally with the steel pipe sheet pile 2.

In this embodiment, a reinforced W 112 made of cement and gypsum is provided on the upper surface of the hardened self-hardening stabilizer 10, but this is because the excavating machine placed on the Tsukishima 11 when forming the foundation 1 This design was designed to ensure greater safety in consideration of the weight of the vehicle, and may not necessarily be necessary depending on the weight.

When the construction of the island 11 is completed, a trench is excavated from its upper end, concrete is poured, and the foundation 1 is formed using an underground continuous wall.

The means for forming the foundation 1 may be not only an underground continuous wall but also a caisson foundation.

Moreover, the cofferdam is not limited to the steel pipe sheet pile 2, but may be other means.

(Effects of the Invention) As explained above in the examples, according to the method for constructing an island according to the present invention, by hardening the self-hardening stabilizing liquid, an island with uniform soil quality from the seabed surface to the top can be obtained, and the foundation Not only is excavation easy to perform when forming, but the curing strength can be adjusted arbitrarily and over a wide range by changing the blending ratio of the stabilizing liquid. It can easily and easily respond to changes in the stacking of foundation excavation machines and caisson boxes.

Furthermore, since the soil of the island is homogeneous and has stable strength, the area of the entire island can be made smaller than before.

Furthermore, since the hardened self-hardening stabilizer is water-impermeable and not water-permeable like conventional sand backfill, foundation construction can be performed directly without using auxiliary construction methods such as deep wells or deep mixing. A significant reduction in construction time and cost will be achieved.

[Brief explanation of the drawing]

FIG. 1 is a plan view (A) and a sectional view (B) showing an example of the construction method of the present invention, and FIG. 2 is a plan view (A) and a sectional view (B) showing an example of the conventional construction method. １・・・・・・・・・Fundamentals ２．・・・・・・
・・Steel pipe sheet pile 3・・・・・・・・・・・
・・・・・・・・・Earth Sand 5・・・・・・Tsukishima
6・・・・・・・・・Davewell 7・・・・・・
...Soil improvement treatment 10...Self-hardening stabilizer 11...Tsukishima (present invention) 12...Reinforcement layer 11 Figure 2 (B) L ] ″Lf

Claims (1)

[Claims] In the construction method of Tsukishima, which is used when forming the foundations of bridge piers, abutments, etc. in the water, after constructing a cofferdam at the site where the foundation is planned to be formed, water inside the cofferdam is removed and self-contained water is added to the interior of the cofferdam. A construction method for constructing an island, which comprises displacing and injecting a hard stabilizing liquid to harden the self-hardening stabilizing liquid within the cofferdam to form a built island.