JP2528686Y2 - Constant-level pumping tester - Google Patents

Description

[Detailed description of the invention] (Industrial application field) In this invention, groundwater is pumped out of the permeability test that is performed as part of the geological survey, and the water permeability coefficient K and the like are calculated based on the reduced water level S and the water yield Q. The present invention relates to a method for stabilizing a drop in water level when a pumping method is used to determine the water level.

(Prior art) The following is a description of the permeability test, particularly regarding the pumping method.

(A) Pumping groundwater using an electric submersible pump.

At this time, the water level stabilization method provides an electrical contact at a predetermined position, and when the contact is separated from the water surface, the pumping can be stopped.
When the water level rises again and comes into contact with the contact point, pumping starts. In the case of this method, when the electric submersible pump is operating, the water level is above the contact point, and it can be seen that the water level has dropped to the predetermined position only after the electric submersible pump stops. Further, the electric submersible pump has a disadvantage that the outer diameter is large and the boring diameter is about 150 mm, and the pump itself is long, so that a sufficiently deep boring must be excavated.

(B) Pumping method by air lift method The low water level stabilization method has no method. That is, since a certain amount of air is continuously fed into the pipe and water is pumped by using the buoyancy of the air, an air pipe, a pumping pipe, etc. Since there is no choice but to install an outer pipe outside the pumping pipe and measure the water level between the pumping pipe and the outer pipe, it is not possible to control the water level itself and the pumping amount itself. It is necessary to continuously pump water until Q becomes constant.

This is also unusual, since it is theoretically necessary to drill a borehole that is sufficiently deep below the groundwater table, which is very expensive.

(C) A method in which the suction hose tip of a mechanical pump placed on land is put in water to pump water.

When a suction hose is inserted deep underwater to pump water, there is no way to maintain the water level at a predetermined position, and continuous pumping is performed for a long time until the water level drop amount S and the pumping amount Q, which are determined by the mechanical capacity, become constant. There is a need.

Since these mechanical pumps are originally intended for discharge force and have a small negative pressure, the suction of air into the suction part weakens the negative pressure inside the suction and reduces the suction force.Therefore, it takes time before suction is started again. During that time, the water level recovers and the falling water level cannot be stabilized.
Furthermore, if air enters the machine part, watertightness is lost and the machine itself may not function. For this reason, it is not possible to use the present invention to stabilize the water level by taking in air.

(Problems to be solved by the invention) Unless water permeability in the soil is accurately grasped at the geological survey stage and reflected in the design, an unexpected disaster may occur during construction. In the case of highly permeable ground, it is particularly necessary to improve accuracy.

Test methods applicable to ground with high permeability and shallow groundwater include JFT method for recovery method, injection method for injection method, and pumping method for pumping water.

In the JFT method, the tip of a hollow pipe is kept watertight in advance and inserted to a predetermined depth, and then cut off from water outside the test section by a packer. Then, the tip is instantaneously opened and the groundwater recovery rate is measured.The measurement is performed by laying a wire with many electrical contacts at equal intervals in a hollow pipe, and every time groundwater passes through each contact. In this method, a pulse is generated to determine the relationship between distance and time.

In this case, it is doubtful whether the packer blocks the water outside the test section in the case of a gravel layer. Also, depending on the interval between the electrical contacts, measurement becomes impossible if the amount of water surface recovery is insufficient.

The injection method requires a large amount of water to be prepared in the case of high water permeability, and may not be able to cope with it depending on conditions. Also,
In many cases, clogging of soil gaps occurs and accurate values cannot be obtained.

Due to such a situation, at present, the only method that can obtain accurate data on highly permeable ground is a full-scale pumping test. In this pumping test, a well for pumping and about 6 wells for observation were excavated in the center, a pumping facility was set up in this well, and groundwater was pumped up. The steady flow analysis is performed from the water level state at the time of the above. Even if this pumping test is performed once, the scale is large, a long time is required, and the cost is large.

For these reasons, it is absolutely necessary to provide a simple, inexpensive, and accurate method for obtaining accurate values using the pumping method.

The basics of the test may be analyzed at the time when the lowered water surface and the pumped water amount Q become stable at the same time, but it is not easily stabilized unless one of them is fixed. For this reason, a method was devised to keep the water level constant.

(Means for solving the problem) The means for keeping the water level constant will be described with reference to the drawings. A) A pipe led from the jet (6) generating negative pressure to the side (4) generating negative pressure. A hard hollow pipe (2) that does not expand and contract is connected to (3). This hollow pipe (2)
Is the suction port (1).

B) The hollow pipe (2) is inserted into the boring hole so that it can be fixed at an arbitrary position and can be moved. That is, the hollow pipe is inserted into the borehole so as to be vertically movable.

C) The suction port (1) is cut obliquely, that is, formed so as to be inclined from the axial direction of the hollow pipe so that air can be easily taken in.

D) The suction port (1) may be formed by directly processing the hollow pipe (2), or may be formed by processing the hollow pipe (2). (Fig. 2,
(FIG. 3) (Operation) The operation when the hollow pipe (2) is set up in advance in the borehole and the suction port (1) is installed so as to be in the water is as follows.

When the power is operated to generate a negative pressure, water is sucked from the suction port (1) upon the negative pressure. When the water level drops and drops to near the highest position of the suction port (1), air starts to be sucked. At this time hollow pipe (2)
In the section (6) and (6), the negative pressure drops momentarily, but since the negative pressure is continuously generated and the water level rises at the same time, the suction port (1) is closed with water again and sucked. Become. The capacity of the jet (6) depends on the amount of pumped water.
Needless to say, use enough.

Since the repetition is performed naturally without interruption, the water level can be kept constant at the suction port (1).

Since the flow of water and air in the hollow pipe (2) during pumping is regular at certain intervals, the pumping amount Q can be obtained by measuring this amount, and when the pumping amount Q becomes constant, the steady flow occurs. State.

The pumping amount Q is measured by the difference between the driving water and the total discharge water among the devices that generate the negative pressure by injecting the high-pressure fluid, and the device that mechanically generates the negative pressure by the hollow pipe (2). A vacuum tank may be provided between the jets (6) to measure the increase in water or use a flow meter.

Embodiment An embodiment of the present invention will be described with reference to the drawings.

First Embodiment FIG. 1 shows a first embodiment of the present invention.

The first embodiment shows a case where water is pumped by utilizing a discharge negative pressure generated by injection of a high-pressure fluid.

A jet (6) for generating a negative discharge pressure is connected to a pump (5) for generating a high-pressure fluid, thereby constituting a negative pressure generating means. The discharge side is connected to a pipe (7) and a driving water tank (8) is connected. ). A flexible hollow pipe (3) that can withstand the negative pressure is connected to a side (4) of the jet (6) that generates a negative pressure, and a rigid hollow pipe (2) that does not expand and contract is connected to this end. The tip of the hollow pipe (2) is the suction port (1). The suction port (1)
Cut diagonally. The suction port (1) may be formed by directly processing the hollow pipe (2), or may be formed by processing the hollow pipe (2). . An overflow groove (9) is provided in the driving water tank (8), and the overflowed water is guided to the notch tank (10) and measured. This overflowed water corresponds to the amount of groundwater being sucked. In addition, the measurement of the sucked ground water is not limited to the notch tank (10), but may be performed by a measuring basin or a flow meter.

Second Embodiment FIG. 4 shows a second embodiment of the present invention.

In the second embodiment, a negative pressure is generated by a mechanical vacuum device. A vacuum tank (11) is provided between a hollow pipe (2) and a negative pressure generator (6), and suction is performed here. The method for measuring the amount of groundwater drained is shown. The specific method of measuring the amount of pumped water is determined by the rising speed of the water surface in the vacuum tank (11). When the vacuum tank (11) is full, the water level is lowered again by the drain pump (12).

(Effect of the invention) The permeability coefficient of highly permeable ground such as gravel layer is 1-1.
It is about × 10 ^-2 cm / sec. When this is expressed in terms of the specific amount of water, it is as follows.

For example, a drilling hole of φ86mm was drilled in the ground with a permeability of 5 × 10 ^-1 cm / sec in an unpressurized imperfect well, and the pumping rate Q when the groundwater was lowered 1.0m from the equilibrium water level to a steady flow was approximated. Q = K x 4 x r x S (CGS unit) = 5.0 x 10 ^-1 x 4 x 4.3 x 100 = 860 cc / sec = 51.6 l / min where K: permeability coefficient (cm / sec) r: radius of the hole (cm) S: falling water level (cm) That is, 52 l / min of water comes out.

In general, speaking of the on-site permeability test, the water level in the borehole is lowered by unsteady flow analysis, and the permeability coefficient K is calculated from the recovery speed of the water surface. It is not possible to lower. Therefore, injection method, JFT method, large-scale pumping method, etc. must be performed. However, these methods also have the problems described in (Problems to be solved by the invention), and in fact, they are not generalized.

Anyway, it is common to say that "permeability test with gravel cannot be relied upon" and "permeability coefficient with gravel is to be obtained but estimation is expensive because the test is expensive". This is because of the above-mentioned reason, and there is no appropriate test method.

By implementing the pumping test method that can keep the water level constant according to the present invention, it is possible to carry out boring with a small hole diameter of 86 mm, which is often used in ordinary geological surveys. Since the test is possible if there is 10 cm, the value can be obtained before using bentonite for protecting the pore wall, that is, before clogging occurs. In addition, the pumping method itself has a high cleaning effect even when bentonite is used for the scale, and is also advantageous in this respect.

Since accurate values can be obtained in a simple, inexpensive and accurate manner, many tests can be conducted at the stage of versatile geological survey, and the accuracy of design and construction can be improved, and the actual condition of highly permeable ground has been clarified. You.

[Brief description of the drawings]

FIG. 1 is a partially sectional perspective view showing a first embodiment of the invention, and FIG.
FIG. 3 is a sectional view of the suction port (1), FIG. 3 is a processing diagram of the suction port (1), and FIG. 4 is a partial sectional execution view showing a second embodiment of the invention. (1) Suction port (2) Hard hollow pipe (3) Bendable hollow pipe (4) Negative pressure generating pipe (5) High pressure injection pump (6) Negative pressure Generator (jet in Fig. 1) (7)… Discharge pipe (8)… Driving water tank (9)… Overflow groove (10)… Notch tank (11)… Vacuum tank (12) …… Sump pump

Claims (1)

(57) [Scope of request for utility model registration] 1. A negative pressure generating means, a boring hole capable of reaching at least below the groundwater level, and connected to a negative pressure side generated by the negative pressure generating means and inserted vertically into the boring hole. A hollow pipe, and a suction port provided at a tip of the hollow pipe, wherein the negative pressure generating means includes a pump for injecting a high-pressure fluid and a jet connected to the pump, and a discharge side of the jet is driven. Returning to the water tank, the hollow pipe is connected to the negative pressure side of the jet, the suction port is formed to be inclined from the axial direction of the hollow pipe, and a predetermined hole below the groundwater level in the borehole. A constant water level pumping tester characterized by being immersed in the height position.