JPH0213683B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for lowering the groundwater level during root cutting work, which has been improved to achieve a wider 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 for lowering the groundwater level, a well point construction method is known that uses equipment called a well point, which has the function of injecting pressurized water from a tip nozzle to perform boring and the function of absorbing groundwater. This well point construction method is a method of vacuuming 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. For example, there is a limit to the depth to which the groundwater level can be lowered, and considering the head loss of the pumping pipes, water collection pipes, etc. connected to the well point, the possible lowering of the water level is about 5 to 7 meters below the ground surface. Therefore, at excavation sites where the groundwater level needs to be further lowered, well points should be installed in 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 pumping pipe connected to the submersible pump is maintained under negative pressure, and the inside of the casing pipe is isolated from the atmospheric pressure side as necessary, so that the underground water in the cutting area can be efficiently evacuated by operating the submersible pump. 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.

Below, the construction method of the present invention will be explained with reference to the illustrated embodiment. Around the cutting area a, water suction pipes 3 connected to the tip of the casing pipe 1 using a cutter reducer 2 are arranged at intervals. 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 water collection pipe 6, etc., and this vacuum tank 7 is equipped with a vacuum pump 8 and a submersible pump 9.
is attached, and the vacuum pump 8 is connected to the vacuum tank 7.
The submersible pump 9 functions as a member that maintains the inside of the water pump 5 under negative pressure by placing the inside under vacuum, and as a member that discharges groundwater accumulated in the vacuum tank 7 to the outside of the system.

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.
It is designed to promote the inflow of groundwater into the casing pipe 1 through the water suction pipe 3.

Cutter reducer 2 is casing pipe 1
This eliminates the inconvenience that the casing pipe 1 hits the hole wall and cannot move forward when the water suction pipe 3 is installed. A support cylinder 12 is provided inside the cutter reducer 2 and is integrated with the inner wall of the cutter reducer 2. A rubber ring 13 is attached to the upper edge of the support cylinder 12, and the submersible pump 4 is attached to the casing. The submersible pump 4 is housed in the pipe 1 and absorbs the impact when installed on the support tube 12, thereby preventing damage to the submersible pump 4. In addition, a plurality of water holes 14 are bored in the peripheral wall of the support tube 12, and the groundwater flowing in through the water intake holes 3a formed in the water intake pipe 3 flows through the water holes 14.
4, rises through the gap formed between the submersible pump 4 and the casing pipe 1, and flows 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 pump head of the submersible pump 4 increases and the water suction pipe 3 can be built deeper, which greatly reduces the drop in groundwater. It is possible to lower it. Incidentally, according to experiments with this construction method, it was possible to lower the groundwater level to approximately 30 meters in practical terms, confirming its superiority compared to the conventional well point construction method. In implementing this construction 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 installed at the tip of the water suction pipe 3,
15 is a ball valve provided in the nozzle 3b, and 16 is a drain pipe 1 connected to the submersible pump 9 on the vacuum tank 7 side.
7 is a check valve provided, and 18 is an exhaust pipe.

The present invention, as described above, discharges groundwater through the synergistic action of the submersible pump housed in the casing pipe and the negative pressure acting on the discharge side of this submersible pump, increasing the actual lifting capacity. This makes it possible to build water intake pipes deeply, making it effective for root cutting work that requires a large drop in the groundwater level. In addition, the casing pipe used when constructing the water intake pipe has the advantage of being able to be used as a housing member for the submersible pump in its original state, and combined with the fact that it can be done economically, its practical value is extremely high. It's a huge amount.

[Brief explanation of drawings]

The drawings are for explaining the construction method of the present invention. Figure 1 is a schematic cross-sectional view of the cutting site, Figure 2 is a front cross-sectional view of the drainage system, and Figure 3 is an enlarged cross-sectional view of the main part of Figure 2. . In the figure, 1 is a casing pipe, 3 is a water suction pipe, and 4
is a submersible pump, 5 is a lift pipe, 7 is a vacuum tank, a
is the root cutting area.

Claims (1)

[Claims] 1. A water suction pipe is connected to the tip of a casing pipe that can accommodate a submersible pump to be described later, and the water suction pipe is buried to a predetermined depth around the root-cutting area, and the burying is completed. At that point, a submersible pump is housed in the casing pipe, the tip of the lift pipe connected to the submersible pump is introduced into a vacuum tank, and the submersible pump is operated while maintaining the inside of the lift pipe under negative pressure. A method for lowering the groundwater level in root cutting work, characterized by vacuuming the groundwater within the root cutting area 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 according to claim 1, characterized in that the inside of the casing pipe is isolated from the atmospheric pressure side to vacuum the groundwater.