JPS58207420A - Ground water level-lowering work for pit excavation work - Google Patents

Abstract

PURPOSE:To greatly lower the level of ground water in the titled work by a method in which a casing pipe whose tip is connected to a water suction pipe is buried, a submergible pump is housed inside the pipe and connected to a water- pumping pipe, and ground water is sucked up with vacuum. CONSTITUTION:A casing pipe 1 whose tip is connected to a water suction pipe 3 is buried to a given depth in the surrounding area of a pit excavation section (a). Then, a submergible pump 4 is housed inside the pipe 1, and the tip of a water pumping pipe 5 connected to the pump 4 is introduced into the vacuum tank 7. When the pump 4 is operated while keeping the pressure on the water- pumping pipe 5 side negative, the ground water in the pit excavation section (a) is sucked up by the vacuum toward the water-pumping pipe 5 side and collected in the tank 7.

Description

[Detailed Description of the Invention] The present invention relates to a method for lowering the groundwater level during root cutting work, and is an improved method that can achieve a drastic reduction in the groundwater level compared to the conventionally known well point method. .

In order to facilitate root cutting work on soft ground, etc., it is necessary to lower the groundwater level within the root cutting area according to the root cutting depth. As a means of lowering the groundwater level, a well-point construction method is known that uses a device called a well-point, which has the function of polling by injecting pressurized water from a tip nozzle and the function of absorbing groundwater. This well point construction method is a method of evacuating groundwater into a vacuum tank through a pumping pipe connected to a well point, so it has the advantage of being applicable to a wide range of soil conditions. There is a limit to the depth to which the water level can be lowered, and considering the head loss of the pumping pipes, water collecting pipes, etc. connected to the well point, the possible water level reduction is about 5 to 7 meters below the ground surface. Therefore,
At excavation sites that require further lowering of the groundwater level,
Install well points on at least two levels, upper and lower.
Groundwater drainage work will be carried out in stages.

Therefore, it is inevitable that the amount of equipment used will increase, the work will become complicated, and this will be extremely disadvantageous in terms of economic efficiency.

Therefore, the present invention connects a water suction pipe to the tip of a casing pipe capable of accommodating a submersible pump, houses the submersible pump in the casing pipe when the burying (erecting) of the water suction pipe in the stratum is completed, and The inside of the lifting pipe connected to the submersible pump is maintained under negative pressure, and if necessary, the inside of the casing pipe is isolated from the atmospheric pressure side, and the submersible pump is operated to efficiently vacuum the groundwater in the cutting area. By making it possible to increase the lifting height as much as possible, the problems caused by the well point construction method described above are completely solved.

The construction method of the present invention will be explained below with reference to the illustrated embodiment.A water suction pipe 3 connected to the tip of a casing pipe 1 using a cutter regiser 2 is installed at intervals around the root cutting area a. Many have been built. A submersible pump 4 is housed within these casing pipes 1, and a pumping pipe 5 is connected to the discharge port side of the submersible pump 4. The tip of the water pump 5 is connected to a vacuum tank 7 via a collection pipe 6, etc., and a vacuum pump 8 and a submersible pump 9 are connected to this vacuum tank 7.
The vacuum pump 8 serves as a member to maintain the inside of the pumping pipe under negative pressure by placing the inside of the vacuum tank 7 under vacuum, and the submersible pump 9 serves as a member to remove groundwater accumulated in the vacuum tank 7 from the system. Each functions as a member for discharging water to the

The casing pipe 1 is large enough to accommodate the submersible pump 4, and the part that protrudes above the ground is sealed with a lid 11 to isolate it from the atmospheric pressure side, and underground water is drawn into the casing pipe 1 through the water suction pipe 3. Consideration is being given to encourage inflow.

The cutter reducer 2 is equipped with a plurality of cutting blades 2a protruding from the outer peripheral surface of the casing pipe 1, and eliminates the inconvenience that the casing pipe 1 hits the hole wall and cannot move forward when installing the water suction pipe 3. There is. A support cylinder 12 is provided inside the canter register 2 and is integrated with the inner wall of the canter register 2.
A rubber ring 13 is attached to the upper edge of the casing pipe 1 to absorb shock when the submersible pump 4 is housed in the casing pipe 1 and installed on the support tube 12, thereby preventing the submersible pump 4 from being damaged. In addition, a plurality of water holes 14 are provided in the peripheral wall of the support tube 12.
A water suction hole 3. is drilled in the water suction pipe 3. The groundwater flowing in from a passes through the water hole 14, rises through the gap formed between the submersible pump 4 and the casing pipe 1,
It is designed to flow into the suction port 4a of the submersible pump 4.

That is, according to the construction method of the present invention, when the submersible pump 4 is housed in the casing pipe 1 when the construction of the water suction pipe 3 is completed, and the submersible pump 4 is operated while maintaining the pumping pipe 5 side under negative pressure, The groundwater in the cutting area a is efficiently evacuated to the pumping pipe 5 side, and can be collected in the vacuum tank 7.

In this case, since negative pressure is acting on the discharge side of the submersible pump 4, the head of the submersible pump 4 increases, making it possible to significantly reduce the drop in sewage.

Incidentally, according to experiments with this construction method, it was possible to lower the groundwater level in practical terms with a diversion of about 30 m, confirming its superiority compared to the conventional well point construction method. In implementing this method, the casing pipe 1 is isolated from the atmospheric pressure side as necessary to promote the inflow of groundwater.

In the figure, 3b is a nozzle provided at the tip of the water suction pipe 3, 15 is a ball valve provided in the nozzle 3b, 16 is a check valve provided in the drain pipe 17 connected to the submersible pump 9 on the vacuum tank 7 side, 1
8 is an exhaust pipe.

The present invention is as described above, and includes a submersible pump housed in a casing pipe and a synergistic effect of the negative pressure acting on the discharge side of the submersible pump to discharge groundwater.
Since the actual lifting capacity can be increased, it is possible to build water suction pipes deeply, and it is effective when applied to root cutting work that requires a large reduction in the groundwater level. Also, the casing pipe used when installing the water intake pipe is that! ,
″!.

The operational advantages that can be achieved, combined with the fact that it can be carried out economically, make its practical value extremely great.

[Brief explanation of the drawing]

The drawings are only for explaining the construction method of the present invention; FIG. 1 is a schematic cross-sectional view of the cutting site, FIG. 2 is a front cross-sectional view of the drainage device, and FIG. 3 is an enlarged cross-sectional view of the second concave portion. In the figure, 1 is a casing pipe, 3 is a water suction pipe, 4 is a submersible pump, 5 is a pumping pipe, 7 is a vacuum tank, and a is a root cutting area. patent applicant

Claims (2)

[Claims] (1) Connect a water suction pipe to the tip of the shida casing pipe so that it can accommodate the submersible pump described later, and bury this water suction pipe around the root-cutting area to a predetermined depth. A submersible pump is housed in the casing pipe, and the tip of the lifting pipe connected to this submersible pump is introduced into a vacuum tank, and by operating the submersible pump while maintaining the inside of the pumping pipe under negative pressure, A method for lowering the groundwater level in root cutting work, characterized by vacuuming the groundwater through the water suction pipe to the pumping pipe side and discharging this groundwater out of the system. (2) A method for lowering the groundwater level in root cutting work as set forth in claim (1), characterized in that the inside of the casing pipe is isolated from the atmospheric pressure side to evacuate the groundwater.