JPH0465932B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Technical Field] The present invention is aimed at reducing ground subsidence caused by lowering of the groundwater level in the surrounding ground due to ground excavation when installing structures such as sewer pipes using the cut-and-cut method in urban areas. This relates to an excavation method that does not cause subsidence of the surrounding ground, which can be prevented.

[Prior art]

In urban areas such as residential areas, when excavating the ground using the cut-and-cover method and installing sewer pipes, etc., or laying foundations and installing structures, conventionally, retaining walls were built and the ground was dug under dry conditions. They were conducting excavation, but
Groundwater leaks from the lower end of the retaining wall, lowering the surrounding groundwater level and causing ground subsidence.

In addition, in conventional open-cut construction methods, the well point method and chemical injection method are used to prevent the groundwater level in the surrounding ground from dropping and prevent ground subsidence, but depending on the ground conditions, the groundwater level may drop. This problem could not be completely prevented, causing the ground to subside and causing insurance issues with surrounding areas.

In conventional underwater structure construction, steel sheet piles with sections are driven in double layers, and earth and sand is put between the steel sheet piles to close off the open ocean and the inside of the construction, and to drain the water inside. A structure was being constructed, but due to the high construction costs, H was used as a countermeasure.
Steel piles are jointed and driven, a rubber cone filled with water is inserted into the hollow part of the joint between the H steel pile and the H steel pile, compressed air is filled on top of it, and the rubber cone is inserted into the H steel pile.
The hollow parts of the steel pile joints were filled with water to ensure close contact between the hollow parts of the H steel pile joints and the rubber cone, and the enclosure created using the H steel piles was completed into an H steel pile enclosure wall using the method described above to block running water from the open ocean. Later, an invention was made in 1971-47120 regarding a method for constructing a water-stop foundation structure by completing the excavation of the foundation from the seabed ground within the enclosure wall, but in this case, it was invented to cut off the flow of water from the open ocean. It is not applicable to ground excavation in urban areas on land.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned conventional problems, and is an excavation that does not cause subsidence of the surrounding ground, which can completely prevent a drop in water level during excavation of the ground in urban areas, etc., and prevent ground subsidence. The purpose is to provide a construction method.

[Structure of the invention]

To achieve the above object, the excavation method of the present invention that does not cause subsidence of the surrounding ground is to dig a continuous trench in the ground along the excavated part, and to pour concrete with reinforced concrete into the trench. After driving steel sheet piles to form a continuous underground soil retaining wall, the ground is excavated to a predetermined depth while pouring water into the excavated area so that the water level is at least equal to the surrounding groundwater level. After pouring concrete to make it watertight with the continuous underground retaining wall, drain the poured water, install sewer pipes, etc.
It is characterized by constructing the foundation of a structure, and since the water level in the excavated part is always equal to or higher than the surrounding groundwater level, the groundwater level in the surrounding ground may drop and ground subsidence may occur. It can be prevented.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings, which are front sectional views showing the ground in one embodiment during excavation work by the excavation method of the present invention.

This example shows a ground excavation work performed to install a structure such as a sewer pipe in the ground G of an urban area where there are residential buildings 1 etc. in the vicinity, and the work steps will be explained one by one.

First, along the excavated part shown by arrow A,
Two continuous trenches are dug in the trench, reinforcing bars 2 are installed in these trenches, and a continuous underground wall 3 is formed by pouring concrete, and anchors are installed to prevent this continuous underground retaining wall 3 from falling during excavation 4 is hanging.

Note that the continuous underground retaining wall may be made of materials other than the above-mentioned reinforced concrete, for example, it may be made of continuous steel sheet piles, and the groundwater in the surrounding ground G is drained from the excavated portion A by excavating the excavated portion A.
Any material may be used as long as it does not leak to the outside.

Next, while pouring water into the excavated part A, excavate that part with a closed clam shell or a suction pump with a cutter, etc. During the above excavation, if necessary, the excavated part shall be tilted. Excavation is continued while water supply is made so that the water level Wd of A is always above the groundwater level W of the surrounding ground G.

Once the ground has been excavated to a specified depth,
The foundation concrete 6 is poured so as to be watertight with the continuous underground retaining wall 3.

At this time, after the polluted soil is settled with a coagulant, the polluted soil is pumped up to the outside while water is injected into the interior and treated outside.On the other hand, after the internal water becomes clean, the foundation concrete is 6 is cast so as to be watertight with the continuous underground retaining wall 3. In this case, the foundation stones and concrete of the floor slab are constructed underwater by divers.

Next, after the construction of the foundation concrete 6 is completed, drainage is performed and structures such as sewer pipes are installed.

According to the excavation method of the present invention according to the above steps,
While injecting water into the excavated portion A, the water level Wd is always kept higher than the groundwater level W of the surrounding ground G, so that the surrounding groundwater level W is prevented from lowering.

〔Effect of the invention〕

As explained above, according to the excavation method of the present invention, it is possible to completely prevent a drop in the groundwater level in the surrounding ground even during excavation work, and there is an effect that ground subsidence can be prevented.

As a result, it is possible to eliminate the problems that occur during conventional excavation work, such as paying a huge amount of insurance money to the surrounding area due to subsidence of the surrounding ground.

[Brief explanation of the drawing]

The drawing is a front sectional view showing the ground in an embodiment during excavation work by the excavation method of the present invention. 3...Continuous underground wall, 6...Foundation concrete,
A... Excavation part, W... Groundwater level of surrounding ground,
Wd...Water level in the excavated area.

Claims (1)

[Claims] 1 After forming a continuous underground soil retaining wall along the excavated area, excavation is carried out to a specified depth while pouring water into the excavated area so that the water level is at least equal to the surrounding groundwater level, and the foundation concrete is placed in the same continuous manner as described above. A method of excavating the ground that drains water after pouring water to make it watertight with the underground retaining wall.