JPS6125861B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an automatic control method for controlling groundwater level by pumping water in a pumping well.

Conventionally, when carrying out ground excavation work, a pumping well was built in the ground around the earth retaining wall, and water was pumped up here.
It lowers the groundwater level and reduces or prevents water pressure, earth pressure, or flooding, improving workability. Furthermore, when excavating a wide area of ground, it is necessary not only to lower the groundwater level, but also to control the surrounding groundwater level to balance the water level and prevent unbalanced forces from acting on the excavated area. Therefore, it is necessary to install a large number of pumping wells around the excavated ground and pump water in these pumping wells to maintain the surrounding ground water level at a target value. However, controlling and pumping water from a large number of pumping wells according to the ever-changing groundwater level is extremely complicated, and the efficiency of management and operation is not good.

This invention was made with attention to this problem, and its purpose is to provide an automatic control device for management operation when controlling the underground water level by pumping water from a large number of pumping wells.

In other words, this invention provides an observation well for water level observation at a location where the water level needs to be checked separately from the pumping well, and experimentally pumps water from each pumping well in advance to determine the influence of the amount of water pumped on the water level of the observation well. is determined, the difference between the current water level detected in the observation well and the target groundwater level is determined, and the pumping well is controlled and pumped based on this water level difference and the above-mentioned influence relationship to reach the target groundwater level. This is an automatic control device that maintains the amount of pumped water at the specified value.

Examples will be described below with reference to the drawings. 1st
2 are a plan view and a sectional view showing the arrangement of a pumping well and an observation well provided around the excavated ground. A steel pipe sheet pile 2 is built around a circular excavation part 1, and 13 pumping wells are built in a roughly circular shape outside of it.
There are W ₁ , W ₂ . . . W ₁₃ , and four observation wells A ₁ , A ₂ , A ₃ , and A ₄ are provided along the outer edge of the steel pipe sheet pile 2. Earth pressure and water pressure act on the steel pipe sheet pile 2 surface of the side wall of the excavation section 1 from the outside. The groundwater level 3 before pumping is high and a large water level acts on the steel pipe sheet pile 2, but the water level 4 after pumping becomes low and the acting water pressure can be reduced. In addition, this water pressure is balanced around the excavation portion 1 to prevent unbalanced force from acting on the steel pipe sheet pile 2.

Observation wells _A1 ... _A4 are provided at intervals on the outer edge of the steel pipe sheet piles 2 where it is necessary to detect and check the groundwater level, and a water level detector 5 for measuring the water level is installed at a predetermined position inside the wells. is set up. The water level in the observation well An slopes toward the pumping well Wm, and changes depending on the amount of water pumped in the pumping well Wm, but this relationship depends on the shape of the surrounding ground, geology,
This is complicated due to the influence of obstacles, etc., and is not required theoretically. Therefore, each pumping well Wm is used to pump water experimentally, and the influence coefficient K, which is the relationship between the amount of pumped water and the amount of water level change in each observation well An, is determined.

Kmn=Amount of water level change Ln of observation well An/Amount of pumped water Qwm of pumping well Wm In addition, the amount of water level change Ln of each observation well An is calculated by the following formula.

L ₁ =K ₁ . ₁ Q _W1 +K ₂ . ₁ Q _W2 +……+K ₁₃ . ₁ Q _W13 L ₂ = K ₁ . ₂ Q _W1 +K ₂ . ₂ Q _W2 +…… +K ₁₃ . ₂ Q _W13 L ₃ =K ₁ . ₃ Q _W1 +K ₂ . ₃ Q _W2 +…… ₊ K ₁₃ . 3 Q _W13 L ₄ =K ₁ . ₄ Q _W1 +K ₂ . ₄ Q _W2 +……+K ₁₃ . ₄ Q _W13 As above Related pumping well W ₁ ... W ₁₃
An embodiment of the device for controlling the groundwater level using the observation wells _A1 ... _A4 will be described below. Figure 3 is an overall schematic diagram of this control device, and shows each of the four observation wells.
The water level detected as water pressure by the water level detector 5 in An is input to the comparator 6, and compared with the target water level of each observation well An set here. For example, when the water level difference is 0, it is 0. When the voltage is +1m, it is converted to 1 volt, or when it is -1m, it is converted to -1 volt and output.

This water level difference signal is inputted to the influence degree calculator 7 provided for each observation well via the scanning device _SC1 . There are 13 influence coefficient setting devices mainly consisting of variable resistors, each of which is equipped with the influence coefficient of each pumping well, which can be taken out as an electrical output. Scanning device SC ₁
is equipped with 4 rotary switches and 13 contacts corresponding to the pumping wells for each rotary switch so that a voltage corresponding to the water level difference can be sequentially applied between each comparator 6 and the 13 influence coefficient setting devices. . Therefore, the influence degree calculator 7 calculates the pumped water amount of each pumping well for each observation well based on the influence coefficient and the water level difference from the comparator 6. The output voltages of the calculation results are summed by a series circuit formed on the output side of the scanning device SC ₂ (in this example, there are four observation wells, so the four voltages are summed). It is sent as an output voltage corresponding to the amount to three priority selectors 8a, 8b, and 8c (hereinafter referred to as selectors) arranged in parallel.

Here, the contact points for each rotary switch provided in the scanning devices SC ₁ and SC ₂ are set corresponding to the pumping wells W ₁ to _{W 13} from top to bottom in the figure, and each of these influence degree calculators 7 Each contact point on both the input and output sides is synchronously controlled on and off for each of the pumping wells W ₁ to _{W 13} .

In the device of this embodiment, water is pumped in priority order, so each pumping well Wm has three branch pipes 9.
a, 9b, and 9c are provided, and each one of them is combined to form three pumping trains, and each train is connected to one of the selectors 8 through a scanning device _SC3 for control. It's summery.

This scanning device SC ₃ is also controlled in synchronization with the scanning devices SC ₁ and SC ₂ , and the valves of the pumping wells W 1 to W 13 corresponding to the contacts that have become conductive in the scanning devices SC ₁ and SC ₂ are controlled in synchronization with the scanning devices SC ₁ and _{SC 2} . 10a,
The three switches 10b and 10c are interlocked and on/off controlled.

Therefore, as illustrated in FIG. 2, when the uppermost terminals of each of the scanning devices SC ₁ and SC ₂ are brought into conduction by a switch, the electrical connection is reached to the valves 10a, 10b, and 10c of the pumping well _W1 . Only three switches close synchronously, and other pumping wells W ₂ ~
Regarding W ₁₃ , scanning devices SC ₁ , SC ₂ ,
Synchronous control is performed between SC ₃ .

This selector 8 is in the form of a meter relay type voltmeter, and has a structure in which the circuit opens and closes depending on whether the total water pumping amount inputted by voltage is higher or lower than a set level. Assuming that 8c is 100% of the pump system's specified pumping amount, 8b is 70%, and 8a is
If you set 40%, for example, for a given pumping amount,
When the input is 100% or more, the three selector circuits close and valves 10c, 10b, and 10a are opened. When the input is 70% or more, 8b and 8a are closed and valves 10b and 10a are opened to increase the input to 40% or more. If so, only valve 8a is closed and valve 10a is opened. Conversely, if the signal is negative, all of the water pumps 11 are stopped. In this way, the three systems of branch pipes 9a, 9b, and 9c of the pumping well are selected with priority depending on the amount of water pumped, and the amount of water pumped is controlled.

Note that the valves 10a, 10 that control the amount of water pumped
Ideally, for b and 10c, the valve opening degree should be adjusted using an electromagnetic flowmeter and applying feedback so that the flow rate corresponds to the input voltage, but in this example, this was done by opening and closing the electromagnetic valve. . Further, the water pump 11 is turned on and off when the water level is below the set target water level or below the limit value, and is turned on when the water level is above the upper limit value.

The present invention is as described above, and in order to control and lower the groundwater level, an observation well is provided separately from the pumping well, the current water level is constantly detected by a water level detector installed in this observation well, and a comparator is used to detect the current water level. , compare the current water level and the target water level and find the difference.
The computing unit calculates the amount of water pumped for each pumping well based on the relationship between the effect of the pumping amount of the pumping well on the observed well water level change and the water level difference from the comparator. It pumps water in a controlled manner to maintain the groundwater level at a target value. Therefore, the groundwater level can always be accurately controlled based on the current water level. Additionally, the number of man-hours required for management operations can be significantly reduced.

If the selector is used to prioritize the pumping systems and selectively open and close them, if there are a large number of pumping wells, economical operation can be achieved without having to operate all the equipment when the amount of pumped water is low.

[Brief explanation of the drawing]

1 and 2 are a plan view and a vertical sectional view showing the arrangement of a pumping well and an observation well, and FIG. 3 is a schematic diagram showing the entire apparatus. 1... Excavation section, 2... Steel pipe sheet pile, 3... Groundwater level before pumping, 4... Groundwater level after pumping, 5... Water level detector, 6... Comparator, 7... Impact degree calculator,
8, 8a, 8b, 8c...priority selector, 9
a, 9b, 9c...branch pipe, 10a, 10
b, 10c... Valve, 11... Water pump,
A ₁ , A ₂ , A ₃ , A ₄ ... Observation well, W ₁ , W ₂ ... W ₁₃
... Pumping well, SC ₁ , SC ₂ , SC ₃ ... Scanning device.

Claims (1)

[Claims] 1. When pumping water in multiple pumping wells and controlling and lowering the groundwater level by detecting the groundwater level in an observation well, a water level detector that detects the groundwater level in the observation well, and the on-site sewage level and the target water level are used. a comparator that compares the water level difference between the two pumping wells, and a calculation unit that calculates the required water pumping amount of each pumping well based on the influence relationship between the pumping amount of each pumping well and the water level change of the observation well and the water level difference from the comparator. An automatic underground water level control device characterized by: