JPH04111808A - Construction work of sheathing wall for undeground tank - Google Patents

Abstract

PURPOSE:To construct a sheathing wall before the excavation of the ground by a method in which concrete is placed into a trench excavated by a chain cutter. CONSTITUTION:A preceding trench 3a by one excavating operation is formed by a chain cutter l. At the time when the trench 3a is formed, concrete C mixed with a reinforcing material such as fibre or metal net is placed into the trench 3a and hardened to form a preceding thin wall 4a. The ground G is then excavated to expose the inner surface of the wall 4a as the excavation proceeds. A follow thin wall 4b is formed on the inside of the lower end of the wall 4a in such a way as to lap the upper part on the lower end inside. Many Chin walls 4a, 4b, 4b...4n are integrated vertically at fixed intervals in a clinker- shaped form to form a sheathing wall 4. After the wall 4 is constructed, bottom slab and side walls for constructing an underground tank are constructed inside and the area between the wall 4 and the side walls is embedded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a construction method for efficiently constructing an earth retaining wall when constructing an underground tank on the ground such as soft rock.

(Prior Art) As is well known, when constructing an underground structure such as an underground tank, the site where the underground structure is to be constructed is first surrounded by a retaining wall.

In this case, for example, in soft rock or other ground, as a type of construction method for retaining walls when constructing an underground tank, the ground is excavated along the shape of the underground tank, and then concrete is sprayed onto the exposed ground. In addition to constructing concrete, there is a method of spraying that allows the concrete to adhere to the ground using rock bolts.

However, such an earth retaining wall construction method has the following technical problems.

(Problems to be Solved by the Invention) In other words, in the method of constructing earth retaining walls by spraying concrete, the ground exposed by excavation is not necessarily smooth, and when spraying, concrete scatters around the surroundings and uneven spraying occurs. The thickness was uneven, leading to material waste, impact on the work environment, and quality control problems.

This invention solves the above-mentioned problem, and by using a trench excavated by a chain cutter and placing concrete in the trench, an earth retaining wall for an underground tank can be constructed before cutting the roots of the ground. It provides a construction method for walls.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the present invention, when constructing an underground tank on the ground such as soft rock, cuts a trench of a predetermined depth along the periphery of the planned construction site of the underground tank using a chain cutter. After excavating and pouring concrete into this trench to form a leading thin wall, excavating the ground inside the trench, and then excavating the ground inside the lower end of the leading thin wall so that its upper side overlaps with the lower end of the leading thin wall. The method is characterized in that a trailing thin wall is formed using the same procedure as described above, and the retaining wall is constructed by partially overlapping the leading and trailing thin walls.

A lock bolt may be driven into the overlapping portion so as to pass through the leading and trailing thin walls.

(Function) The narrow groove excavated with a chain cutter will be used as part of the retaining wall after the concrete poured inside it hardens.

The constructed earth retaining wall becomes a continuous wall having overlapping parts where parts of the leading and trailing thin walls overlap each other at predetermined depths.

By driving rock bolts into the overlapping parts, the joint strength between the thin walls can be increased.

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described in detail using the drawings.

1 to 8 show a construction method for an earth retaining wall for an underground tank according to the present invention.

In the construction method shown in the figure, first, as shown in Figure 1,
A pre-excavation groove 3a having a depth of one chain cutter 1 is excavated in a circular manner along the periphery of the planned construction site, which is the outer diameter of the underground tank.

This chain cutter 1 is arranged at the tip of an arm 2a provided on a base machine 2.

The structure of this chain cutter 1 is such that a chain is suspended between sprockets, and a large number of drilling bits are arranged on the outside of this chain.The sprocket is rotated by a hydraulic motor and penetrates into the ground. An excavated groove with a constant narrow width and a depth corresponding to the bit width is formed.

After lowering the chain cutter 1 in a substantially vertical position, the base machine 2 is moved along the circumference to form an annular pre-excavation groove 3a of one excavation depth.

In this case, the inclination of the excavated groove 3a is close to vertical, but in consideration of the overlapping margin between the thin walls, which will be described later, the inclination is set so that it slightly expands toward the lower outer circumferential side, and the excavation angle of the arm 2a is adjusted. The angle of inclination is set by

When the pre-excavation groove 3a is formed, as shown in FIG. 2, concrete C mixed with reinforcing materials such as fibers and wire mesh is placed inside the excavation groove 3a, and as it hardens, the pre-excavation thin u4a is formed.

Here, while the concrete C has hardened to some extent, excavation and root cutting of the ground G inside the planned construction site is performed as shown in Fig. 3, and along with this excavation, the inner surface of the preceding thin wall 4a is sequentially cut. be exposed.

Note that a breaker, a ripper, etc. are used for root cutting and excavation of the ground.

Moreover, the root cutting excavation depth at this time is set to a depth that extends to a state where the end side of the leading thin wall 4a is slightly buried inside the ground G.

Next, a trailing thin wall 4b is formed inside the lower end of the leading thin wall 4a so that its upper side overlaps this portion.

At this time, the trailing thin wall 4a is formed by the same process as the leading thin wall 4a (see FIG. 4).

As shown in FIG. 5, the thin wall 4b is joined with the upper end of the thin wall 4b superimposed on the lower end of the thin wall 4a.

Next, as shown in FIG. 6, the leading and trailing thin walls 4a, 4
At the joining part 5 of b, a rock bolt 6 is driven almost horizontally toward the ground side through the thin walls 4a and 4b,
With the thin walls 4a and 4b completely joined together, their tips are fixed to the ground G side, and their rear ends are fixed to the surface of the splicing part 5.

By repeating the above work cycle consisting of excavation with the chain cutter 1 - concrete placement - root cutting excavation of the ground - driving of lock bolts, a large number of thin walls 4a, 4b...4n are formed vertically as shown in Fig. 7. An integrated earth retaining wall 4 is formed by overlapping in a clinker-like manner at regular intervals.

When the construction of the earth retaining wall 4 is completed, the bottom plate 7 which constitutes the underground tank T inside thereof is shown in FIG. side wall 8
is constructed, and when the construction of the side wall 8 is completed, the space between the retaining wall 4 and the side wall 8 is backfilled, and the construction is completed.

(Effects of the Invention) As explained in detail in the examples above, in the construction method of an earth retaining wall for an underground tank according to the present invention, a narrow groove excavated with a chain cutter can be used as it is for an earth retaining wall. Compared to the conventional concrete spraying method, there is no waste of materials and no impact on the working environment.

In addition, since the width of the excavated groove is uniform, the thickness is uniform, and quality control problems can be solved.

Furthermore, the earth retaining wall constructed in this way is a continuous clinker-like wall with overlapping parts for each excavation depth, and the overlapping parts are concrete joints.
A certain degree of self-sustaining strength can also be expected.

Furthermore, in this invention, by driving rock bolts into the overlapping portions, it is possible to increase the joint strength between the thin walls that constitute the earth retaining wall.

[Brief explanation of the drawing]

FIGS. 1 to 8 are cross-sectional explanatory diagrams showing the sequence of steps in the construction method of this invention. 1... Chain cutter 3a... Leading excavation groove 3b... Trailing excavation groove 4... Earth retaining walls 4a to 4n... Thin wall 5... Overlapping portion 6・・・・・・Rock bolt

Claims (2)

[Claims] (1) When constructing an underground tank on soft rock or other ground, a trench of a specified depth is excavated with a chain cutter along the area where the underground tank is planned to be constructed, and concrete is poured into this trench to form a thin wall. After forming a thin wall, excavate the inner ground, and then form a trailing thin wall inside the lower end of the leading thin wall in the same manner as above so that its upper side overlaps with the leading thin wall. A construction method for an earth retaining wall for an underground tank, characterized by constructing the earth retaining wall so that rows of thin walls are partially overlapped. (2) The method for constructing an earth retaining wall for an underground tank according to claim 1, wherein rock bolts are driven into the overlapping portion so as to penetrate the leading and trailing thin walls.