CN114965205B - A method for calculating the permeability coefficient of porous aquifer based on flow velocity and flow direction measurement - Google Patents

Abstract

The present invention provides a method for obtaining the permeability coefficient of a porous aquifer based on flow velocity and flow direction measurement, and uses an experimental device for obtaining the permeability coefficient of a porous aquifer based on flow velocity and flow direction measurement, the device comprising a trough, multiple river channels, at least one well pipe, a flow velocity and flow direction monitor, a pressure plate and a flow metering unit; the permeability velocity of seepage particles in the trough and the velocity component of a measuring point in the well pipe are calculated through indoor experiments, thereby calculating the ratio λ of the permeability velocity of seepage particles in the trough to the velocity component of the measuring point; in the field work area, the groundwater velocity in the borehole is measured by a groundwater velocity and flow direction meter, and the velocity component of the groundwater velocity in the borehole in the horizontal flow direction of the groundwater flow in the work area is calculated, thereby calculating the permeability coefficient of the aquifer in the work area. The groundwater velocity and flow direction meter is used to quickly obtain the permeability coefficient of the aquifer, which solves the disadvantages of the traditional pumping test and water pressure test that are difficult to operate and relatively time-consuming, and can be applied to any working conditions.

Description

A method for calculating the permeability coefficient of porous aquifer based on flow velocity and flow direction measurement

Technical Field

The invention relates to the technical field of physical simulation experiments, and in particular to a method for obtaining a porous aquifer permeability coefficient based on flow velocity and flow direction measurement.

Background technique

At present, in the measurement of groundwater dynamic parameters, the permeability coefficient of aquifer is an important hydrogeological parameter, which is of great significance in calculating well water output, reservoir leakage, groundwater resource evaluation and groundwater pollution prevention and control. Hydrogeological parameters can be obtained by both indoor test methods and field test methods. Among them, the indoor test method is to apply Darcy's theorem indoors to obtain the permeability coefficient of the original soil in the field, while the field test method mainly uses pumping method and water pressure method to obtain the permeability coefficient of the aquifer. The pumping/water pressure method mainly includes constant flow pumping/water pressure method, constant drawdown pumping/water pressure method, etc. Among them, the constant flow pumping/water pressure method extracts water from the logging well at a fixed flow rate (that is, injects water into the logging well at a fixed flow rate) to make the water flow movement between the aquifer and the logging well reach a steady state, and obtains the permeability coefficient of the aquifer according to the relationship between flow and drawdown in the steady state; and the fixed drawdown pumping/water pressure method is to keep the water level drawdown in the logging well unchanged by pumping/water pressure, and obtain the permeability coefficient of the aquifer according to the relationship between flow and drawdown. Pumping test and water pressure test are not easy to operate and are relatively time-consuming.

Summary of the invention

In view of this, in order to solve the above problems, an embodiment of the present invention provides a method for calculating the permeability coefficient of a porous aquifer based on flow velocity and flow direction measurement.

The embodiment of the present invention provides a method for obtaining the permeability coefficient of a porous aquifer based on flow velocity and flow direction measurement, using an experimental device for obtaining the permeability coefficient of a porous aquifer based on flow velocity and flow direction measurement, the experimental device for obtaining the permeability coefficient of a porous aquifer based on flow velocity and flow direction measurement comprising a trough body, a plurality of river channels, at least one well pipe, a flow velocity and flow direction monitor, a pressure plate, and a flow metering unit;

The trough body is open upwards for storing seepage particles, and a plurality of pressure measuring holes are provided through the side wall and/or bottom wall of the trough body; a plurality of the river channels are located at the periphery of the trough body and are connected to the trough body, and a water outlet is provided at the bottom of at least one of the river channels; the lower end of the well pipe is blocked and installed in the trough body to simulate a monitoring well, and a plurality of water inlet holes are provided through the well pipe; the probe of the flow velocity and direction monitor extends into the well pipe to measure the flow direction and velocity of the water flow in the well pipe; the pressure measuring tube of the pressure measuring plate is connected to the pressure measuring hole through a connecting pipe, and the flow metering unit is used to measure the flow rate of the stable flow in the trough body;

The method for obtaining the permeability coefficient of porous aquifer based on flow velocity and flow direction measurement includes the following steps:

S1. Calculate the infiltration velocity Vi of the seepage particles in the tank;

S1.1. Use the flow metering unit to measure the flow rate Q of the steady flow in the tank. According to the two-dimensional flow formula of the diving profile without infiltration recharge: Q = (K (h ₁ ² -h ₂ ² )/2L) * B, the permeability coefficient K of the seepage particles in the tank is obtained as follows:

In the formula, Q is the flow rate of the steady flow of the trough, L is the length of the trough, B is the width of the trough, _h1 is the water level height of the river channel at the water inlet end, and _h2 is the water level height of the river channel at the water outlet end;

S1.2. Based on V=KI, the hydraulic gradient I _i at the i-th measuring point in the well pipe is calculated according to the measurement data of the pressure plate, and the expression of the seepage velocity V _i of the seepage particles in the tank is calculated as follows:

S2. Use the flow velocity and flow direction monitor to measure the flow velocity and flow direction of each measuring point in the well pipe. According to the actual horizontal flow direction of the groundwater in the tank, the flow velocity and flow direction of the groundwater at each measuring point, the expression of the velocity component _vi of the groundwater flow velocity at the ith measuring point in the horizontal flow direction of the groundwater in the tank is:

Where: S _i is the groundwater velocity at the i-th measuring point in the well pipe measured by the velocity and direction monitor, α _i is the groundwater flow direction at the i-th measuring point, β is the true horizontal flow direction of the groundwater in the tank, and γ _i is the angle between the actual flow direction of the groundwater at the i-th measuring point and the horizontal direction;

Then the formula for the ratio λ of the seepage velocity of the seepage particles in the tank to the velocity component at the measuring point is:

Where: n is the total number of measuring points;

S3. Arrange at least one borehole along the groundwater flow direction in the work area, and use a groundwater flow velocity and direction meter to measure the groundwater flow velocity S in each _borehole . V_工j ＝λv_工j , we get

Where, _Vgongj is the velocity component of the groundwater velocity in the jth borehole in the horizontal flow direction of the groundwater flow in the work area, _αgongj is the groundwater flow direction measured by the velocity and direction instrument in the jth borehole, _βgong is the true horizontal flow direction of the groundwater in the work area, and _γgongj is the angle between the actual flow direction of the groundwater in the jth borehole and the horizontal direction;

According to K = V/I, the formula for calculating the seepage coefficient of the aquifer based on the groundwater flow velocity in the jth borehole is:

Then the permeability coefficient _Ktrue in the work area is the average value of the permeability coefficients _Kworkj calculated by multiple boreholes in the work area, and the expression is:

Where: I is the average hydraulic gradient of groundwater in the work area.

Furthermore, when the work area is smaller than the preset range, the water level _H1 of the upstream borehole, the water level _H2 of the downstream borehole, the distance L between the upstream borehole and the downstream borehole, and the average hydraulic gradient of the groundwater in the work area are measured.

but

Furthermore, the hydraulic gradient and flow direction of groundwater are stable, j = 1;

but

Furthermore, the experimental device for obtaining the permeability coefficient of a porous aquifer based on flow velocity and flow direction measurement also includes a plurality of overflow structures, each of the river channels is provided with an overflow structure, and the overflow structure includes:

A water tank, the bottom of which is connected to the bottom of the riverbed via a connecting pipe; and

The driving mechanism drives the water tank to move up and down.

Furthermore, the driving mechanism includes a driving motor and a linear screw slide, the water tank is installed on the linear screw slide, and the driving motor drives the screw of the linear screw slide to rotate.

Furthermore, it also includes a base, the tank body, the river channel and the overflow structure are fixed on the base, and the bottom of the base is provided with universal wheels; and/or,

The flow metering unit includes a measuring cylinder and a timer. A water baffle is provided in the water tank to form a water storage chamber and a drainage chamber in the water tank. The connecting pipe is connected to the water storage chamber. The bottom of the drainage chamber is connected to the drainage pipe. The water outlet end of the drainage pipe is opposite to the measuring cylinder to discharge water into the measuring cylinder. The timer is used to record the drainage time.

Furthermore, the river channel is provided with two, respectively located on opposite sides of the trough body, a first partition plate is fixed in the trough body to divide the trough body into two chambers both connected to the two river channels, and the well pipe is installed in one of the chambers;

One of the river channels is provided with a second partition plate opposite to the first partition plate, forming two partitioned sub-river channels respectively connected to two chambers. Two water tanks connected to the river channel are provided, and the two water tanks are connected to the two sub-river channels one by one.

Furthermore, the well pipes are provided in plurality and are installed at intervals in one of the chambers.

Furthermore, a clamping groove is fixed on the bottom wall of the groove body, and the well pipe is inserted in the clamping groove.

Furthermore, the slots are provided in plurality and have different diameters, and the plurality of slots are radially arranged in sequence to form a slot assembly, and the well pipes are provided in plurality and have different diameters to match the slots of different diameters.

The technical solution provided by the embodiment of the present invention has the following beneficial effects: the present invention includes two parts: indoor experiment and field work area application. The infiltration velocity of the seepage particles in the tank and the velocity component of the measuring point in the well pipe are calculated through indoor experiments. The infiltration velocity of the seepage particles flowing in the tank is used to simulate the infiltration velocity of the groundwater in the aquifer in the field work area, and the velocity component of the measuring point in the well pipe is used to simulate the groundwater velocity in the borehole in the field work area, thereby calculating the ratio λ of the infiltration velocity of the seepage particles in the tank and the velocity component of the measuring point, that is, the conversion coefficient between the infiltration velocity of the groundwater in the aquifer in the field work area and the groundwater velocity in the borehole in the field work area. In the field work area part, the groundwater velocity in the borehole is measured by a groundwater velocity and direction meter, and the velocity component of the groundwater velocity in the borehole in the horizontal flow direction of the groundwater flow in the work area is calculated, thereby calculating the permeability coefficient of the aquifer in the work area. The groundwater velocity and direction meter is used to quickly obtain the permeability coefficient of the aquifer, which solves the shortcomings of traditional pumping test and water pressure test that are difficult to operate and time-consuming, and can be applied to any working conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic structural diagram of an embodiment of an experimental device for obtaining the permeability coefficient of a porous aquifer based on flow velocity and flow direction measurement provided by the present invention;

FIG2 is a side view of the experimental device for obtaining the permeability coefficient of a porous aquifer based on flow velocity and flow direction measurement in FIG1;

FIG. 3 is a top view of the experimental device for obtaining the permeability coefficient of a porous aquifer based on flow velocity and flow direction measurements in FIG. 1 .

In the figure: trough body 1, pressure measuring hole 1a, first dividing plate 1b, river channel 2, sub-river channel 2a, well pipe 3, flow velocity and direction monitor 4, overflow structure 5, water tank 51, water storage chamber 51a, drainage chamber 51b, screw rod 52, connecting pipe 6, base 7, universal wheel 8, measuring cylinder 9, drainage pipe 10, baffle plate 11, second dividing plate 12, slot 13, water supply pipe 14.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described below in conjunction with the accompanying drawings.

An embodiment of the present invention provides a method for calculating the permeability coefficient of a porous aquifer based on flow velocity and direction measurement, using an experimental device for calculating the permeability coefficient of a porous aquifer based on flow velocity and direction measurement, please refer to Figures 1 to 3, the experimental device for calculating the permeability coefficient of a porous aquifer based on flow velocity and direction measurement includes a trough body 1, multiple river channels 2, at least one well pipe 3, a flow velocity and direction monitor 4, a pressure plate and a flow metering unit.

The trough body 1 is open upwards and is used to store seepage particles. The seepage particles can be seepage particles, specifically quartz sand. The length direction of the trough body 1 is the due north-south direction. The side walls and/or bottom walls of the trough body 1 are penetrated by a plurality of pressure measuring holes 1a. Specifically, the opposite side walls of the trough body 1 are provided with a plurality of groups of pressure measuring holes 1a in parallel, and each group of pressure measuring holes 1a is vertically arranged as nine along the vertical section. A plurality of river channels 2 are located at the periphery of the trough body 1 and are connected to the trough body 1. Water is injected into the trough body 1 through the river channels 2, and a water outlet is provided at the bottom of at least one of the river channels 2. Water flows in the pores of the seepage particles, and a water outlet is provided at the bottom of each river channel 2. By injecting water into different river channels 2, the flow direction of the water flow in the seepage particles can be changed, and a scale is provided on the side wall of the river channel 2.

The lower end of the well pipe 3 is blocked and installed in the tank body 1 to simulate a monitoring well. The well pipe 3 is penetrated by a plurality of water inlet holes and is made of PVC. The probe of the flow velocity and direction monitor 4 extends into the well pipe 3 to measure the flow direction and velocity of the water flow in the well pipe 3. Specifically, a domestically produced G.O.Sensor new intelligent groundwater flow velocity and direction monitor is used. The instrument is composed of a high-resolution monitoring screen, a cable, and a data acquisition probe. The probe is used to observe the movement of colloidal particles in the water in the well pipe 3 to calculate the flow velocity and direction of the water in the well pipe 3. The pressure measuring tube of the pressure measuring plate is connected to the pressure measuring hole 1a through a connecting hose. The pressure measuring tube of the pressure measuring plate is a transparent quartz tube, and the connecting hose is a transparent silicone hose. The pressure measuring plate adopts an upright movable blackboard. Each pressure measuring hole 1a is equipped with a sand cap to prevent uniform sand from clogging. The flow metering unit is used to measure the flow of the stable flow in the tank body 1.

Furthermore, the experimental device for obtaining the permeability coefficient of the porous aquifer based on the flow velocity and flow direction measurement also includes a plurality of overflow structures 5, each of the river channels 2 is provided with an overflow structure 5, and the overflow structure 5 includes a water tank 51 and a driving mechanism. The bottom of the water tank 51 is connected to the bottom of the river channel 2 through a connecting pipe 6; the driving mechanism drives the water tank 51 to move up and down. Since the water tank 51 is connected to the river channel 2, the height of the water tank 51 is controlled by driving the water tank 51 up and down by the driving mechanism, so that the water level of the river channel 2 can be accurately controlled and the required hydraulic gradient can be set.

Specifically, the driving mechanism includes a driving motor and a linear screw slide, the water tank 51 is installed on the linear screw slide, the driving motor drives the screw 52 of the linear screw slide to rotate, and the linear screw slide can provide a guide for the up and down movement of the water tank 51. In other embodiments, the driving mechanism can be a cylinder, a hydraulic cylinder, etc., and the water tank 51 is fixed on the piston rod of the cylinder or the hydraulic cylinder. A scale is provided on the screw 52 of the linear screw slide to facilitate reading the height of the water tank 51.

In order to improve the integration of the entire device, the trough body 1, the river channel 2 and the overflow structure 5 are fixed on the base 7, and the base 7 is welded by stainless steel bars. The bottom of the base 7 is provided with universal wheels 8 to facilitate the movement of the device.

The flow metering unit includes a measuring cylinder 9 and a timer. A drain pipe 10 is connected to the bottom of the water tank 51. A water baffle 11 is provided in the water tank 51 to form a water storage chamber 51a and a drainage chamber 51b in the water tank 51. The connecting pipe 6 is connected to the water storage chamber 51a, and water can be directly added to the water storage chamber 51a. The water storage chamber 51a can also be connected to an external water supply device through a water supply pipe 14. The drain pipe 10 is connected to the drainage chamber 51b. The outlet end of the drain pipe 10 is opposite to the measuring cylinder 9, and the water is discharged into the measuring cylinder 9. The timer is used to record the drainage time. The volume V of the water flowing out of the tank body 1 within the preset time Δt is measured by the measuring cylinder 9, and the flow rate Q of the stable flow of the tank body 1 is calculated by the volume method, Q=V/Δt, V is the volume of the water flowing out within the Δt time, and the operation is convenient. In other embodiments, a flow meter can also be used for measurement.

Furthermore, there are two river channels 2, which are respectively located on opposite sides of the trough body 1, one of which is the water inlet end river channel and the other is the water outlet end river channel. The water of the water inlet end river channel flows out from the water outlet end river channel through the trough body 1. A first partition plate 1b is fixed in the trough body 1 to divide the trough body 1 into two chambers both connected to the two river channels 2, and the well pipe 3 is installed in one of the chambers. One of the river channels 2 is provided with a second partition plate 12 opposite to the first partition plate 1b, forming two partitions and sub-river channels 2a connected to the two chambers respectively. There are two water tanks 51 connected to the river channel 2, and the two water tanks 51 are connected to the two sub-river channels 2a one by one. Specifically, the first partition plate 1b can be detachably installed in the trough body 1, dividing the trough body 1 into two, one of which is installed with a well pipe 3 to simulate a monitoring well, and the other chamber is not installed with a well pipe 3, which can simultaneously simulate the submerged flow of the aquifer under two different conditions of natural flow field and drilling interference flow field. For easy observation, the trough body 1, the river channel 2, the first partition plate 1b, the water tank 51, and the second partition plate 12 are made of transparent materials, such as organic glass or acrylic plate. The side wall of the trough body 1 and the first partition plate 1b are reinforced with organic glass reinforcing ribs to increase the contact area between adjacent glass bodies, thereby making the trough body 1 stronger.

The trough body 1 is 150 cm long, 100 cm wide and 100 cm high. The trough body 1 is bonded with a 20 mm thick transparent organic glass plate. The river channel 2 is 10 cm long, 100 cm wide and 100 cm high. There are multiple well pipes 3, which are installed at intervals in one of the chambers to simulate the situation of multiple monitoring wells. Specifically, the well pipe 3 can be detachably installed in the trough body 1. In this embodiment, a card slot 13 is fixed on the bottom wall of the trough body 1. The well pipe 3 is inserted in the card slot 13 for easy installation. In other embodiments, the well pipe 3 can be connected by threading or snap-on connection.

The described card slot 13 is provided with multiple and different diameters, and multiple described card slots 13 are sequentially sleeved in the radial direction to form a card slot assembly. The described well pipe 3 has multiple and different diameters, which are adapted to the described card slots 13 of different diameters. By changing the diameter of the well pipe 3, the experiment is carried out to explore the relationship between the measured flow velocity under different aperture conditions and the infiltration velocity of the porous aquifer in the trough body 1. The well pipe 3 includes a round hole flower pipe, a vertical groove flower pipe, a flat groove flower pipe, etc. The described card slot assembly has multiple groups, which are installed at intervals on the bottom wall of the trough body 1, so as to facilitate the installation of the well pipe 3 at different positions in the trough body 1. In this embodiment, the well pipe 3 is a round hole flower pipe, and the card slot 13 can hold well pipes 3 with outer diameters of 63mm, 75mm, and 110mm, with a height of 1m. The outer side of the pipe wall is wrapped with a finer mesh to prevent a large amount of sand from entering the well pipe 3.

Specifically, the experimental method for obtaining the permeability coefficient of a porous aquifer based on flow velocity and flow direction measurement includes the following steps:

S1, calculating the infiltration velocity Vi of the seepage particles in the tank body 1;

S1.1. Use the flow metering unit to measure the flow rate Q of the steady flow of the tank body 1. Specifically, use the measuring cylinder 9 to measure _the volume Vvolume of water flowing out of the tank body 1 within the preset time Δt, and use the volume method to calculate the flow rate Q of the steady flow of the tank body 1, Q= _Vvolume /Δt, _Vvolume is the volume of water flowing out within the Δt time, and can also be directly measured by a flow meter.

According to the two-dimensional flow formula of the non-infiltration recharge phreatic profile: Q = (K (h ₁ ² -h ₂ ² )/2L) * B, the expression of the permeability coefficient K of the seepage particles in the trough 1 is obtained as follows:

Where Q is the flow rate of the steady flow of the trough 1, L is the length of the trough 1, B is the width of the trough 1, _h1 is the water level height of the river channel 2 at the water inlet end, and _h2 is the water level height of the river channel 2 at the water outlet end.

S1.2. According to Darcy's formula Q=KIA and Q=VA, V=KI can be obtained. Based on V=KI, the hydraulic gradient I _i at the i-th measuring point in the well pipe 3 is calculated according to the pressure plate measurement data. The infiltration velocity V _i of the seepage particles in the tank body 1 is calculated as follows:

Specifically, the pressure measuring holes 1a located on both sides of the true horizontal flow direction of the groundwater in the trough body 1 are selected (the pressure measuring holes 1a can be the pressure measuring holes 1a on the bottom wall of the trough body 1 or the pressure measuring holes 1a on the side wall of the trough body 1), the water level in the pressure measuring tube connected to the pressure measuring holes 1a is read, and the distance between the pressure measuring holes 1a is measured, so that the hydraulic gradient I _i in the well pipe 3 can be calculated.

S2. Use the flow velocity and flow direction monitor 4 to measure the flow velocity and flow direction of each measuring point in the well pipe 3. According to the actual horizontal flow direction of the groundwater in the tank body 1, the flow velocity and flow direction of the groundwater in each measuring point, the expression of the flow velocity component _vi of the groundwater flow velocity at the ith measuring point in the horizontal flow direction of the groundwater in the tank body 1 is:

Wherein: S _i is the groundwater velocity at the i-th measuring point in the well pipe 3 measured by the velocity and direction monitor 4, α _i is the groundwater flow direction at the i-th measuring point, β is the actual horizontal flow direction of the groundwater in the tank 1, and γ _i is the angle between the actual flow direction of the groundwater at the i-th measuring point and the horizontal direction;

Then the formula for the ratio λ of the seepage velocity of the seepage particles in the tank 1 to the velocity component at the measuring point is:

Where: n is the total number of measuring points, _Ii is the hydraulic gradient of the ith measuring point in the well pipe 3, _vi is the velocity component of the groundwater velocity at the ith measuring point in the horizontal flow direction of the groundwater in the trough 1, Q is the flow rate of the steady flow of the trough 1, L is the length of the trough 1, B is the width of the trough 1, _h1 is the water level height of the water tank 51 at the water inlet end, and _h2 is the water level height of the water tank 51 at the water outlet end;

S3. Arrange at least one borehole along the groundwater flow direction in the work area, and use a groundwater flow velocity and direction meter to measure the groundwater flow velocity S in each _borehole . V_工j ＝λv_工j , we get

Wherein, _Vgongj is the velocity component of the groundwater velocity in the jth borehole in the horizontal flow direction of the groundwater flow in the work area, λ is the ratio of the seepage velocity of the seepage particles in the tank 1 to the velocity component of the measuring point, _αgongj is the groundwater flow direction measured by the velocity and direction instrument in the jth borehole, _βgong is the true horizontal flow direction of the groundwater in the work area, and _γgongj is the angle between the actual flow direction of the groundwater in the jth borehole and the horizontal direction;

According to K = V/I, the formula for calculating the seepage coefficient of the aquifer based on the groundwater flow velocity in the jth borehole is:

Then the permeability coefficient _Ktrue in the work area is the average value of the permeability coefficients _Kworkj calculated by multiple boreholes in the work area, and the expression is:

Where: I is the average hydraulic gradient of groundwater in the work area, λ is the ratio of the infiltration velocity of the seepage particles in the trough 1 to the velocity component of the measuring point, _αgongj is the groundwater flow direction measured by the velocity and direction meter in the j-th borehole, _βgong is the true horizontal flow direction of groundwater in the work area, _γgongj is the angle between the actual flow direction of groundwater in the j-th borehole and the horizontal direction, _Kgongj is the permeability coefficient obtained by using the measured groundwater flow velocity and direction in the j-th borehole in the work area, and _Ktrue is the permeability coefficient of the aquifer in the work area.

The trough 1 is filled with uniform seepage particles, and water is supplied to the river channel 2. The water in the river channel 2 flows into the trough 1, and flows into the pressure measuring tube through the pressure measuring hole 1a and the connecting pipe 6. The air in the trough 1 and the pressure measuring tube is discharged by repeated saturation. The well pipe 3 is installed in the trough 1 to simulate the layout of the groundwater monitoring well in the actual porous aquifer. The probe of the flow velocity and direction monitor 4 is placed in the well pipe 3 to monitor the flow velocity and direction of the groundwater in the well pipe 3. The flow velocity and direction data of the groundwater in the well pipe 3 can be read through the monitoring screen of the flow velocity and direction monitor 4. A plurality of pressure measuring holes 1a are arranged on the side wall and the bottom wall of the trough 1. The density of the pressure measuring holes 1a can be set as needed, and the flow field of the two-dimensional flow of the phreatic profile of the aquifer in the trough 1 can be accurately depicted. The hydraulic gradient at the position of the probe in the well pipe 3 can be calculated through the data monitored by the pressure measuring plate. By changing the hydraulic gradient, uniform sand particle size, characteristics of well pipe 3 and other conditions, the relationship between the measured flow velocity and the seepage velocity of the porous aquifer in the trough 1 can be explored, and the method for calculating the permeability coefficient of the porous aquifer under multi-factor conditions can be obtained using Darcy's formula.

Specifically, when the scope of the work area is smaller than the preset scope, the preset scope is 1 square kilometer. The specific scope value is set according to the actual situation of the work area. When the scale of the work area is small, the hydraulic gradient and flow direction of the groundwater are stable. The water level _H1 of the upstream borehole, the water level _H2 of the downstream borehole, and the distance L between the upstream borehole and the downstream borehole are measured. The upstream borehole and the downstream borehole are located upstream and downstream of the above n boreholes, respectively. The average hydraulic gradient of the groundwater in the work area is The hydraulic gradient applicable to each borehole is then/>

When the scale of the work area is small, the hydraulic gradient and flow direction of the groundwater are stable, and only one borehole can be set. The groundwater flow line is basically horizontal, that is, γ is close to 0, j = 1;

but

The present invention includes two parts: indoor experiment and field work area application. The infiltration velocity of the seepage particles in the tank body 1 and the velocity component of the measuring point in the well pipe 3 are calculated through the indoor experiment. The infiltration velocity of the seepage particles flowing in the tank body 1 is used to simulate the infiltration velocity of the groundwater in the aquifer in the field work area, and the velocity component of the measuring point in the well pipe 3 is used to simulate the groundwater velocity in the borehole in the field work area, thereby calculating the ratio λ of the infiltration velocity of the seepage particles in the tank body 1 and the velocity component of the measuring point, that is, the conversion coefficient of the infiltration velocity of the groundwater in the aquifer in the field work area and the groundwater velocity in the borehole in the field work area. In the field work area part, the groundwater velocity in the borehole is measured by a groundwater velocity and flow direction meter, and the velocity component of the groundwater velocity in the borehole in the horizontal flow direction of the groundwater flow in the work area is calculated, so that the permeability coefficient of the aquifer in the work area can be calculated. The groundwater velocity and flow direction meter is used to quickly obtain the permeability coefficient of the aquifer, which solves the shortcomings of traditional pumping test and water pressure test that are difficult to operate and relatively time-consuming, and can be applied to any working conditions.

In this document, the directional words such as front, back, top, and bottom are defined by the positions of the components in the drawings and the positions of the components relative to each other, and are only for the sake of clarity and convenience in expressing the technical solution. It should be understood that the use of the directional words should not limit the scope of protection claimed in this application.

In the absence of conflict, the above embodiments and features in the embodiments may be combined with each other.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (10)

1. A method for obtaining the permeability coefficient of a porous aquifer based on flow velocity and flow direction measurement, characterized in that an experimental device for obtaining the permeability coefficient of a porous aquifer based on flow velocity and flow direction measurement is used, and the experimental device for obtaining the permeability coefficient of a porous aquifer based on flow velocity and flow direction measurement comprises a tank body, a plurality of river channels, at least one well pipe, a flow velocity and flow direction monitor, a pressure plate, and a flow metering unit; The trough body is open upwards for storing seepage particles, and a plurality of pressure measuring holes are provided through the side wall and/or bottom wall of the trough body; a plurality of the river channels are located at the periphery of the trough body and are connected to the trough body, and a water outlet is provided at the bottom of at least one of the river channels; the lower end of the well pipe is blocked and installed in the trough body to simulate a monitoring well, and a plurality of water inlet holes are provided through the well pipe; the probe of the flow velocity and direction monitor extends into the well pipe to measure the flow direction and velocity of the water flow in the well pipe; the pressure measuring tube of the pressure measuring plate is connected to the pressure measuring hole through a connecting pipe, and the flow metering unit is used to measure the flow rate of the stable flow in the trough body; The method for obtaining the permeability coefficient of porous aquifer based on flow velocity and flow direction measurement includes the following steps: S1. Calculate the infiltration velocity Vi of the seepage particles in the tank; S1.1. Use the flow metering unit to measure the flow rate Q of the steady flow in the tank, according to the two-dimensional flow formula of the diving profile without infiltration recharge: , the expression of the permeability coefficient K of the seepage particles in the tank is obtained as: ; In the formula, Q is the flow rate of the steady flow of the trough, L is the length of the trough, B is the width of the trough, _h1 is the water level height of the river channel at the water inlet end, and _h2 is the water level height of the river channel at the water outlet end; S1.2. Based on V=KI, the hydraulic gradient I _i at the i-th measuring point in the well pipe is calculated according to the measurement data of the pressure plate, and the expression of the seepage velocity V _i of the seepage particles in the tank is calculated as follows: ; S2. Use the flow velocity and flow direction monitor to measure the flow velocity and flow direction of each measuring point in the well pipe. According to the actual horizontal flow direction of the groundwater in the tank, the flow velocity and flow direction of the groundwater at each measuring point, the expression of the velocity component _vi of the groundwater flow velocity at the ith measuring point in the horizontal flow direction of the groundwater in the tank is: ; Where: S _i is the groundwater velocity at the i-th measuring point in the well pipe measured by the velocity and direction monitor, α _i is the groundwater flow direction at the i-th measuring point, β is the true horizontal flow direction of the groundwater in the tank, and γ _i is the angle between the actual flow direction of the groundwater at the i-th measuring point and the horizontal direction; Then the formula for the ratio λ of the seepage velocity of the seepage particles in the tank to the velocity component at the measuring point is: ; Where: n is the total number of measuring points; S3. Arrange at least one borehole along the groundwater flow direction in the work area, and use a groundwater flow velocity and direction meter to measure the groundwater flow velocity S in each _borehole . ,/> ,get ; Where, _Vgongj is the velocity component of the groundwater velocity in the jth borehole in the horizontal flow direction of the groundwater flow in the work area, _αgongj is the groundwater flow direction measured by the velocity and direction instrument in the jth borehole, _βgong is the true horizontal flow direction of the groundwater in the work area, and _γgongj is the angle between the actual flow direction of the groundwater in the jth borehole and the horizontal direction; According to K=V/I, the formula for calculating the seepage coefficient of the aquifer based on the groundwater velocity in the jth borehole is: ; Then the permeability coefficient _Ktrue in the work area is the average value of the permeability coefficients _Kworkj calculated by multiple boreholes in the work area, and the expression is: ; Where: I is the average hydraulic gradient of groundwater in the work area. 2. The method for obtaining the permeability coefficient of a porous aquifer based on flow velocity and flow direction measurement according to claim 1, characterized in that when the scope of the work area is smaller than the preset scope, the water level _H1 of the upstream borehole of the work area, the water level _H2 of the downstream borehole, the distance L between the upstream borehole and the downstream borehole, and the average hydraulic gradient of the groundwater in the work area are measured. ; but . 3. The method for obtaining the permeability coefficient of a porous aquifer based on flow velocity and flow direction measurement according to claim 2, characterized in that the hydraulic gradient and flow direction of groundwater are stable, j=1; but . 4. The method for obtaining the permeability coefficient of a porous aquifer based on flow velocity and flow direction measurement according to claim 1 is characterized in that the experimental device for obtaining the permeability coefficient of a porous aquifer based on flow velocity and flow direction measurement further comprises a plurality of overflow structures, each of the river channels is provided with one overflow structure, and the overflow structure comprises: A water tank, the bottom of which is connected to the bottom of the riverbed via a connecting pipe; and The driving mechanism drives the water tank to move up and down. 5. The method for obtaining the permeability coefficient of porous aquifers based on flow velocity and direction measurement as described in claim 4 is characterized in that the driving mechanism includes a driving motor and a linear screw slide, the water tank is installed on the linear screw slide, and the driving motor drives the screw of the linear screw slide to rotate. 6. The method for obtaining the permeability coefficient of a porous aquifer based on flow velocity and flow direction measurement according to claim 4, characterized in that it also includes a base, the tank body, the river channel and the overflow structure are fixed on the base, and the bottom of the base is provided with universal wheels; and/or, The flow metering unit includes a measuring cylinder and a timer. A water baffle is provided in the water tank to form a water storage chamber and a drainage chamber in the water tank. The connecting pipe is connected to the water storage chamber. The bottom of the drainage chamber is connected to the drainage pipe. The water outlet end of the drainage pipe is opposite to the measuring cylinder to discharge water into the measuring cylinder. The timer is used to record the drainage time. 7. The method for obtaining the permeability coefficient of a porous aquifer based on flow velocity and flow direction measurement according to claim 1, characterized in that the river channel is provided with two, respectively located on opposite sides of the trough body, a first partition plate is fixed in the trough body to divide the trough body into two chambers both connected to the two river channels, and the well pipe is installed in one of the chambers; One of the river channels is provided with a second partition plate opposite to the first partition plate, forming two partitioned sub-river channels respectively connected to two chambers. Two water tanks connected to the river channel are provided, and the two water tanks are connected to the two sub-river channels one by one. 8. The method for obtaining the permeability coefficient of a porous aquifer based on flow velocity and flow direction measurement as described in claim 7 is characterized in that a plurality of the well pipes are provided and installed at intervals in one of the chambers. 9. The method for obtaining the permeability coefficient of a porous aquifer based on flow velocity and flow direction measurement as described in claim 8, characterized in that a slot is fixed on the bottom wall of the trough body, and the well pipe is inserted into the slot. 10. The method for obtaining the permeability coefficient of porous aquifers based on flow velocity and direction measurement as described in claim 9 is characterized in that there are multiple slots with different diameters, and the multiple slots are sequentially arranged in radial direction to form a slot assembly, and the well pipe is provided with multiple slots with different diameters to match the slots of different diameters.