JPS6147277B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is applicable to underground works where the pressurized water level is high or involves deep excavation. In excavation work, it is used to lower the pressure water level in order to prevent slab bulges, where impermeable layers such as clay layers are pushed upwards due to the downward force caused by the weight of the soil at the top of the excavation. This article relates to a method for pumping pressurized water.

The conventional pumping method for this type of pressurized water consists of inserting a perforated steel pipe into the ground at the planned excavation location in a vertical position with the lower end reaching the planned excavation depth or higher. A drain pipe 03 with a submersible pump 04 simply connected to its lower end is inserted into the well 02, and when excavating a hypothetical soil layer cross section as shown in FIG. It was installed in a fixed position at or near the lowest part of well 02 to pump up and discharge pressurized water. Therefore, even if there are multiple impermeable layers, when excavating deep areas where slab bulges occur, the pressurized water below the lower impermeable layer, which does not cause disc blister, is also pumped up at the same time. Since it is necessary to lower the pressurized water level by transporting it out, it is necessary to pump up and discharge a large amount of pressurized water, and as a result, not only is the cost of pumping up and discharging a large amount of wastewater to the sewage system expensive, but also the pumping The operation and maintenance costs for the discharge equipment also increased, making it uneconomical in terms of overall construction costs.

In view of these circumstances, the present invention has been developed to minimize the pumping of pressurized water required to prevent the above-mentioned board bulges, and to proceed with the construction work in a very economically advantageous state as a whole. The purpose of this paper is to propose a method for pumping up pressurized water during excavation work.

The characteristic configuration of the method for pumping pressurized water in excavation work according to the present invention, which was developed to achieve the above object, is that in the pumping method detailed at the beginning, a submersible pump for pumping pressurized water is installed in the pumping well. , a pumping control device for controlling the rise of pressurized water from the lower part of the pumping well is inserted with the submersible pump positioned above, and the pumping control device is placed directly below the ground where excavation work has started. Excavation work within the unit excavation range that is located closest to the ground where excavation work has started and that is shallower than the final excavation depth in the impermeable layer below the aquifer layer. There is an impermeable layer inside that does not cause blistering.
Or, if there is no drop in pressurized water, it should be located in correspondence with an impermeable layer one level lower than the impermeable layer that may cause disc blister during excavation work within the planned unit excavation range. Then, only the water in the aqueous layer above the pumping control device is drained out of the pumping well, and after excavation up to the scheduled unit excavation, the pumping control device is operated within the range of the next scheduled unit excavation. In order to be located corresponding to the impermeable layer one level lower than the impermeable layer that may cause plate blister during excavation work, the upper impermeable layer is sequentially placed in correspondence with the impermeable layer below. The key point is that the excavation work is carried out while draining only the water in the layer.

In other words, by using a pumping control device that can arbitrarily suppress the rise of pressurized water from below, only the pressurized water that causes plate bulges can be pumped up and discharged as excavation progresses, thereby reducing the pressurized water level. This means that pumping and discharging of pressurized water can be carried out step by step, both in terms of location and time, and the amount and time required for drainage are kept to a minimum, and the cost of discharging wastewater is reduced to a minimum. The total construction cost was significantly reduced by combining the reductions in the amount of water and the operation and maintenance costs of the pumping and discharging equipment as much as possible.

Hereinafter, embodiments of the method of the present invention and the apparatus used in the method will be described in detail based on the drawings. As shown in FIG _. , a first impermeable layer b ₁ such as a clay layer, a second pressured water retention layer a ₂ , a second impermeable layer b ₂ , a third impermeable layer b 1
A water stop wall 8 such as a sheet pile is installed in the ground of the hypothetical soil layer cross section where the pressurized water retaining layer a ₃ and the third impermeable layer b ₃ exist.
The planned depth of excavation is set in the middle of the second pressurized water reservoir by using an earth drill (not shown) at an arbitrary underground position of the planned excavation area (usually in the center of the construction area) surrounded by A large number of holes 1a on the circumferential surface of the vertical hole drilled to or near the upper surface of the third impermeable layer _b3 exceeding
A steel pipe 1 having... is inserted and erected in a vertical position with its lower end reaching the upper surface of the third impermeable layer _b3 , and a ballast 9 is inserted into a vertical hole on the outer periphery of the steel pipe 1.
and fill the vertical hole portion of the outer periphery of the steel pipe 1 corresponding to each impermeable layer b ₁ , b ₂ , b ₃ with clay or mortar 1.
A pumping well 2 is configured by filling with 0,
A pressurized water pump 4 is connected to the lower end of the drain pipe 3 inserted into the pumping well 2 from above to constitute a pressurized water pumping device for excavation work.

Then, as clearly shown in FIGS. 3 to 5, a shaft-like member 11 of an appropriate length is fixedly extended downward from the lower end of the pump 4, and the shaft-like member 11 is attached to the lower end of the shaft-like member 11 vertically. Discs 12, 1 having a diameter slightly smaller than the inner diameter of the steel pipe 1 are placed opposite each other with an appropriate interval between them.
2, and this vertically opposed disc 12,
12, it can expand and contract in the radial direction as hydraulic pressure or pneumatic pressure is injected and extracted, and in its expanded state it is in close contact with the inner peripheral surface of the steel pipe 1 as shown in FIG. A water pumping control device 6 is constructed by attaching a rubber annular tube body 5 that can prevent the rise of water.

In the figure, 13 is a pipe for injecting and extracting hydraulic or pneumatic pressure into the annular tube body 5, and directly above the upper disk 12, a pipe 14 is used to supply water from the ground surface via a combustor. An opening 7 is provided for blowing out compressed air into the well 2,
In addition, the slime in the well 2 and groundwater are actively stirred and mixed to turn the slime into a sewage-like state for pumping treatment.

Then, as shown in Figure 6A, the first impermeable layer
The annular tube 5 is brought into close contact with the inner circumferential surface of the steel pipe 1 at the position b ₁ , and the water contained in the first pressurized water retention layer a ₁ above the first impermeable layer b ₁ is pumped and discharged by the pump 4. However, the first impermeable layer _b1 is pushed upward by the pressure of the pressurized water contained in the second pressurized water reservoir _a2 , and excavation is continued to the excavation depth _h1 where there is no risk of plate bulging. I do.

Next, as shown in Figure 6B, the second impermeable layer b ₂
The annular tube body 5 is brought into close contact with the inner circumferential surface of the steel pipe ₁ at the position of
The pressurized water contained in the pressured water layer a ₂ is the first pressured water layer.
The water contained in a ₁ is pumped up and discharged by the pump 4, and the first impermeable layer b ₁ is pushed upwards, preventing plate blister from occurring, while the second impermeable layer b ₂ is Excavation is carried out to an excavation depth _h2 at which there is no risk of disk bulging being pushed upward by the pressure of the pressurized water contained in the pressurized water layer _a3 .

Next _, as in the conventional method, as shown in FIG _. The pressurized water is pumped up and discharged by the pump 4 together with the water contained in the second pressurized water retention layer _a2 , thereby preventing the second impermeable layer _b2 from being pushed upwards and causing plate bulges. , excavate the remaining second artesian water reservoir _a2 to the planned final excavation depth _h3 .

[Brief explanation of the drawing]

The drawings show an embodiment of the method for pumping pressurized water in excavation work according to the present invention, FIG. 1 is a schematic vertical cross-sectional view showing a conventional pumping method, and FIG. 2 is a schematic vertical cross-sectional view showing a pumping method according to the present invention. Figure 3 is a vertical cross-sectional view of the main part, Figure 4 is an enlarged vertical cross-sectional view of the main part, Figure 5 is a cross-sectional view taken along the line V-V in Figure 4, and Figure 6 A to C are the method of the present invention. This is an explanatory diagram of staged water pumping using. 1...Perforated steel pipe, 2...Pumping well, 3...
Drain pipe, 4... submersible pump, 6... pumping control device.

Claims (1)

[Claims] 1. A pumping well is constructed by inserting a perforated steel pipe 1 into the ground at the planned excavation location in an upright position with its lower end penetrating multiple impermeable layers and reaching the planned final excavation depth or higher. 2, and in the pumping well 2, a submersible pump 4 for pumping pressurized water, and a pumping control device 6 for controlling the rise of pressurized water from the lower part in the pumping well 2, are installed in the pumping well 2. 4 is located at the upper level, and the pumping control device 6 is placed in the ground where the excavation work has started, among the impermeable layers that are lower than the aqueous layer directly below the ground where the excavation work has started. During excavation work within the unit excavation area that is located at the closest location and is scheduled to be shallower than the final excavation depth, an impermeable layer that is unlikely to cause plate blister or a drop in pressure water is required. Otherwise, the pumping control device 6 is located so as to correspond to an impermeable layer one lower than the impermeable layer that may cause plate bulges during excavation work within the planned unit excavation range. After draining only the water in the upper aqueous layer to the outside of the pumping well 2 and excavating to the planned unit excavation depth, the pumping control device 6 is operated to perform excavation work within the next scheduled unit excavation range. In order to be located corresponding to the impermeable layer one level lower than the impermeable layer that may cause disc blister, only the water in the upper aquifer layer is placed in order to correspond to the impermeable layer below. A method for pumping up pressurized water during excavation work, in which excavation work is carried out while draining water.