JPS6357566B2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a root cutting method using a caisson, in which water is stored inside the caisson, the entire caisson is made into a self-supporting earth retaining wall, and the part surrounded by the caisson is cut open. Yes, and used for relatively large-scale root cutting work.

Various root cutting methods have been developed in the past, but each method has its own advantages and disadvantages, and the most suitable method is selected depending on the scale of the root cutting, surrounding environment, topography, soil quality, etc. There is. for example,
The open-cut construction method requires less temporary construction materials, but the amount of excavated soil in the surrounding area increases, and there are problems such as how to increase the slope of the slope and how to deal with rain. In addition, in the construction method of constructing free-standing walls such as underground continuous walls around the root-cut ground, there are issues of how to increase the strength, rigidity, and water-stopping properties of the free-standing walls, and how to improve the accuracy of construction. be. Also, with the cutting beam method, there are various problems such as the strength, structure, and workability of cutting beams and other temporary construction materials when performing large-scale root cutting work.

The construction method of this invention was invented under the above-mentioned circumstances, and its main purpose is to carry out large-scale root cutting work efficiently and safely.

1 and 2 illustrate the principle of this invention. In the figures, 1 is a caisson. Water 4 is injected into the caisson 1, forming a kind of gravity wall.
That is, first, the caisson 1 is sequentially sunk to a predetermined depth so as to surround the root cut portion 5. After completing the sinking, a bottom cover 3 is provided on the caisson 1, and together with the side walls 2, a box is formed, and water 4 is stored inside to form a gravity-type earth retaining wall. Note that muddy water or the like may be used as the water 4 in order to increase the specific gravity. In addition, instead of pouring the water after the caisson 1 is sunk, as in the method described later, when the caisson 1 is sunk, water is used to excavate the bottom of the caisson 1, and the bottom cover 3 is installed by pouring underwater concrete. The water used for excavation can also be used as water 4 for the earth retaining wall.

In this way, after the caisson 1 and the earth retaining wall made of the water 4 inside the caisson 1 are made continuous around the outer periphery of the root cut portion 5, the inside is cut open. In this case,
Excavation can be carried out in the same way as conventional free-standing wall construction methods, so it is less affected by weather and is more efficient.

Further, if necessary, anchors 6 can be provided on the side wall 2 and bottom cover 3 of the caisson 1, as shown in FIG. Furthermore, as shown in FIG. 9, a stiffener 15 can be installed to reduce the thickness of the side wall 2.

In the figure, a indicates the original ground surface, and b indicates the excavation bottom. In addition, the scale of root cutting is several tens to hundreds of meters (for example, 100 meters) on a side when viewed from above, and the depth of excavation is several tens of meters.
(For example, 50m).

FIGS. 3 to 8 show the working procedure for a construction method in which water is used to excavate beneath the caisson 1 when the caisson 1 is sunk. The procedure will be explained below.

After leveling the ground, the ground at the cutting edge portion 7 of the caisson 1 is excavated, and the cutting edge portion 7, the underground beam 8, and the lower part of the side wall 2 are constructed.

Water is stored in the caisson 1, and an excavator excavates under the caisson 1, and the excavated earth and sand is discharged together with water through a drainage pipe 10, as shown in FIG.
Note that the earth and sand and water sent from the drainage pipe 10 pass through a separator installed on the gantry 9 or outside the caisson 1, and the water is circulated and used.

On the other hand, water is ejected from the cutting edge part 7 through a jet pipe 11 provided in the side wall 2, and the caisson 1 is lowered together with the gantry 9 by a jack by applying a reaction force to the earth anchor 12.

At this time, the water level in the caisson 1 is kept constant using the water supply pipe 13, etc., as shown in FIG.

When the caisson 1 is sunk to a certain depth, the gantry 9 is pulled up as shown in Figure 5, the side wall 2 of the caisson 1 is added, and the process of sinking and building the side wall 2 is repeated until the caisson 1 is sunk to a predetermined depth (see Figure 6). ).

As shown in FIG. 7, underwater concrete 14 is placed in the bottom cover 3 portion to provide the bottom cover 3.

Further, the cutting edge portion 7 is grouted using the jet pipe 11 (see FIG. 8).

Such a caisson 1 is connected to the outer periphery of the root cut portion 5 as shown in FIG. 1, and the water 4 in the caisson 1 is not drained, but its water level is maintained.

The part surrounded by the caisson 1 is cut open to perform root cutting to a predetermined depth.

When the root cutting depth is large and the side wall 2 is expected to become thick, the stiffener 15 is installed at an optimal position to suppress an increase in the thickness of the side wall 2.

The stiffener 15 is installed by being inserted from the ground after the caisson 1 is completely submerged.

This invention has the above structure, and since the caissons that store water inside function as earth retaining walls as gravity-type self-supporting walls, they can resist large earth pressures, especially in large-scale root cutting work. Efficient and highly safe construction is possible. In addition, the excavation itself for root cutting work is done using an open cut method, which provides excellent workability and allows construction to be completed in a short period of time. Also, unlike the open cut construction method, it does not require any special measures against rainwater, and is not affected by the weather much.

[Brief explanation of drawings]

Figure 1 is a plan view showing the principle of the construction method of this invention;
FIG. 2 is a longitudinal sectional view, FIGS. 3 to 8 are longitudinal sectional views showing the construction procedure when water is used to sink the caisson, and FIG. 9 is a cross sectional view of the stiffener portion. 1...Caisson, 2...Side wall, 3...Bottom cover, 4
...Water, 5... Root cutting part, 6... Anchor, 7
...Blade tip, 8...Underground beam, 9...Gandle, 10...
... Drain pipe, 11 ... Jet pipe, 12
...Earth anchor, 13...Water supply pipe, 1
4...Underwater concrete, 15...Stiffener, a... Original ground surface, b... Excavation bottom.

Claims (1)

[Claims] 1. A caisson is sunk to a predetermined depth, and after the caisson is completely sunk, a bottom cover is installed and water is injected into the interior, thereby making the entire sunken caisson into an earth retaining wall with water stored inside, and this earth retaining wall is cut into roots. A root cutting method using a caisson, which is constructed continuously around a portion of the outer periphery, and is characterized by making an open cut in the ground in the portion surrounded by the earth retaining wall. 2. Excavation under the caisson is carried out with water stored inside the caisson, and the caisson built on the ground is sequentially sunk to a specified depth while pumping up the excavated soil and water, and after the sinking is completed, underwater concrete is placed at the bottom of the excavation. By providing a bottom cover to the caisson, the entire sunken caisson becomes an earth retaining wall with water stored inside, and this earth retaining wall is constructed continuously around the outer circumference of the root cut, and the ground in the area surrounded by the earth retaining wall is A root cutting method using a caisson that is characterized by an open cut.