A device and method for testing apparent resistivity and true resistivity of soil during infiltration

Abstract

The present invention discloses a device and method for testing the apparent resistivity and true resistivity of soil during infiltration. The device belongs to the field of geotechnical engineering, and includes an automatic pressurized infiltration device and a resistivity testing device, wherein the automatic pressurized infiltration device is composed of a hydraulic cylinder, a hydraulic rod, a pressure sensor, a sealing compression cover plate, a permeable stone plate and other equipment; the resistivity testing device includes an apparent resistivity testing system and a true resistivity testing system, and the apparent resistivity testing system and the true resistivity testing system are respectively connected to a circuit switcher; the present invention obtains soil samples with different water contents by infiltrating water of different masses into the soil under high pressure, and measures the variation law of the apparent resistivity and the true resistivity under different soil moisture contents and different electrode spacings through the true resistivity testing system and the apparent resistivity testing system with multiple groups of coil electrodes installed from top to bottom, wherein the sandy soil sample with a larger permeability coefficient can be directly infiltrated, and the clay soil sample with a smaller permeability coefficient needs to be pressurized for infiltration.

Description

Technical Field

[0001] The invention belongs to the field of geotechnical engineering, and in particular relates to a device and method for testing apparent resistivity and true resistivity of soil during a penetration process. Background Art

[0002] Geoelectric properties are an important characteristic that characterizes the structural changes of soil. In view of the advantages of soil resistivity characterization methods such as non-destructive, high efficiency and low cost, they are widely used in geological exploration, groundwater and pollutant migration research fields. Soil resistivity is measured when the conductivity is uniform and isotropic within the range of electric field control. It is divided into two categories according to the test method: apparent resistivity and true resistivity. These two types of test methods are often used in actual field exploration due to the penetration of groundwater and the infiltration and sedimentation effect of the soil. The distribution of water after infiltration into the soil is complicated. Sandy soil with a larger permeability coefficient has a larger porosity than clay soil, and it is easier to infiltrate more water. Water has better ion exchange properties. Penetration into the soil will significantly improve the conductivity of the soil and reduce the resistivity of the soil.

[0003] In the existing research on the resistivity change characteristics of soil during the infiltration process, the apparent resistivity is taken as the measured final resistivity by default. There are few studies on the true resistivity obtained by another test method. However, the measured true resistivity and apparent resistivity are essentially different, and the characterization relationship between the two needs to be studied. Therefore, in this type of research, it is necessary to design a device and method that can accurately measure the apparent resistivity and true resistivity change data of soil during the infiltration process. Summary of the invention

[0004] Purpose of the invention: The purpose of the present invention is to solve the defects existing in the prior art, and propose a device and method for testing the apparent resistivity and true resistivity of soil during infiltration. The present invention measures the change law of the apparent resistivity and true resistivity under different soil moisture contents and different electrode spacings to explore the relationship between the apparent resistivity and the true resistivity.

[0005] Technical solution: In order to achieve the above purpose, the present invention adopts the following technical solution:

[0006] The present invention discloses a device for testing apparent resistivity and true resistivity of soil during infiltration.

[0007] Includes automatic pressurized penetration device and resistivity testing device;

[0008] The automatic pressurized infiltration device comprises a pressurized infiltration system, a water inlet system and a water outlet system;

[0009] The pressure infiltration system includes an E-shaped crossbeam (1), a hydraulic rod (2), a hydraulic cylinder (3), a sealing compression cover plate (6), a water storage cavity (8), a permeable stone slab (9), a drainage plate (18), and an acrylic glass column (26);

[0010] The water inlet system includes a water level sensor (14), a water storage tank (21), a self-priming pump (22), a water inlet flow sensor (23), a water inlet pipe (24), and a water stop valve (25);

[0011] The water outlet system includes a water collection cavity (11), a water outlet pipe (12), a water collector (15), and a water stop valve (25);

[0012] The resistivity testing device includes a wire (10), a circuit switcher (13), a resistivity tester (16), a graphite electrode plate (19), and a coil electrode (20);

[0013] Further, the hydraulic cylinder (3) is installed at the middle position at the top of the E-shaped crossbeam (1). A hydraulic rod (2) is installed at the lower end of the hydraulic cylinder (3).

[0014] The hydraulic rod (2) is connected to the hydraulic cylinder (3), and a pressure sensor (4) is installed between them. At the other end of the hydraulic rod (2), a sealing compression cover plate (6) is installed. The sealing compression cover plate (6) is installed below the hydraulic rod (2). A water storage cavity (8) is installed outside the hydraulic rod (2) and the sealing compression cover plate (6);

[0015] On the top surface of the E-shaped crossbeam (1), on one side of the hydraulic cylinder (3), a hydraulic cylinder controller (5) is also installed.

[0016] Further, the water storage tank (21) is installed in the middle and lower part inside the E-shaped crossbeam (1). An inlet water pipe (24) is connected to the upper end of the water storage tank (21).

[0017] The water storage tank (21) is connected to the water storage cavity (8) through the installed inlet water pipe (24);

[0018] A self-priming pump (22) is installed at the connection between the inlet water pipe (24) and the water storage tank (21).

[0019] A water stop valve (25) is installed on one side of the inlet water pipe (24) close to the water storage cavity (8).

[0020] A water inlet flow sensor (23) is installed on one side of the inlet water pipe (24) close to the self-priming pump (22).

[0021] Furthermore, a water inlet pipe thread (2401) is provided on the surface of the water inlet pipe (24) on one side close to the water storage chamber (8), and the water inlet pipe (24) is connected to the water storage chamber (8) through a hollow tightening bolt tube (2402) provided at the connection point of the outer wall of the water storage chamber (8), and a tightening thread (2403) is also provided on the right end surface of the hollow tightening bolt tube (2402).

[0022] Furthermore, a permeable stone plate (9) is installed inside the water storage chamber (8), and the permeable stone plate (9) is fixedly installed at the base inside the water storage chamber (8).

[0023] A rubber sealing ring layer (7) is installed on the upper inner wall of the base of the water storage chamber (8).

[0024] A water level sensor (14) is also attached to the lower end of the sealing compression cover plate (6), and the water level sensor (14) is built into the water storage chamber (8).

[0025] Furthermore, the permeable stone slab (9) is provided with at least 8 permeable stone slab fixing holes (901) evenly distributed along the middle layer of the outer wall and at the corresponding positions of the side wall of the water storage chamber (8), and the permeable stone slab fixing holes (901) are provided with fixing threaded bolts (902) matching therewith;

[0026] One-way locking threads (903) are provided on the inner wall of the permeable stone slab fixing hole (901) and on the surface of the fixing threaded bolt (902).

[0027] Furthermore, an acrylic glass column (26) is installed at the lower end of the water storage chamber (8).

[0028] A fixing tooth (2601) is welded to the bottom of the side wall of the water storage chamber (8).

[0029] A tooth groove (2602) adapted to the fixed tooth (2601) is installed on the top of the side wall of the acrylic glass column (26).

[0030] Removable graphite electrode plates (19) are installed on the top and bottom layers of the acrylic glass column (26), and an electrode wiring hole (1901) is opened at the center of the right side wall of the graphite electrode plate (19) and at a corresponding position of the side wall of the acrylic glass column (26). The electrode wiring hole (1901) is connected to the wire (10) through a graphite electrode wiring rod (1902) installed.

[0031] Furthermore, coil electrode fixing grooves (2603) are evenly distributed on the inner wall of the acrylic glass column (26).

[0032] A plurality of coil electrodes (20) are evenly arranged from top to bottom on the inner wall of the acrylic glass column (26), and the coil electrodes (20) are embedded in the coil electrode fixing grooves (2603);

[0033] A wiring port is provided on the right side wall of the acrylic glass column (26), and a coil electrode connector (2604) is arranged in the wiring port.

[0034] The coil electrodes (20) are connected to the wire (10) through the arranged coil electrode connector (2604);

[0035] A circuit switch (13) is also arranged inside the H-shaped crossbeam (1), and the wire (10) is connected to the circuit switch (13);

[0036] The other end of the circuit switch (13) is connected to a resistivity tester (16) arranged, and a computer interface (17) is attached to the resistivity tester (16).

[0037] Furthermore, a drainage plate (18) is fixedly arranged at the bottom of the acrylic glass column (26).

[0038] A plurality of drainage holes (1801) are provided on the drainage plate (18);

[0039] A water collection cavity (11) is provided at the bottom of the acrylic glass column (26) and at the lower end of the drainage plate (18). An outlet pipe (12) is provided at one end of the water collection cavity (11), and the water collection cavity (11) is fixedly connected to the outlet pipe (12);

[0040] A water collector (15) is also arranged at the tail end of the outlet pipe (12), and the tail end of the outlet pipe (12) is connected to the water collector (15);

[0041] A water stop valve (25) is also arranged on the side of the outlet pipe (12) close to the water collection cavity (11).

[0042] Furthermore, a test method for a test device for apparent resistivity and true resistivity of soil during the infiltration process is as follows. The specific test steps are as follows:

[0043] (1) Prepare soil samples with different permeability coefficients and measure the initial moisture content;

[0044] (2) Inject water into the water storage tank (21) for infiltration. Load the prepared soil sample into the acrylic glass column (26), and then cover the water storage cavity (8) to ensure that the fixed teeth (2601) welded to the bottom of the side wall of the water storage cavity (8) and the tooth grooves (2602) engraved on the top of the side wall of the acrylic glass column (26) are firmly fixed;

[0045] (3) After ensuring that all lines are connected, connect the computer interface (17) on the resistivity tester (16) to the computer, open the water stop valve (25) and the self-priming pump (22), and inject water into the water storage chamber (8) according to the moisture content of the soil sample planned in the experimental plan, wait for the water injection to be completed, and record the water volume in the water storage chamber (8) through the water inlet flow sensor (23);

[0046] (4) After the water injection is completed, the hydraulic cylinder controller (5) is turned on to pressurize the hydraulic rod (2) on the hydraulic cylinder (3) to the sealing compression cover plate (6) and pressurize the hydraulic cylinder, and the water in the water storage chamber (8) penetrates into the soil and the water level sensor (14) records the drop in the water level in the water storage chamber (8);

[0047] (5) First, the true resistivity test system is connected through the circuit switch (13), and then a group of coil electrodes (20) are connected according to the previously planned apparent resistivity electrode spacing;

[0048] (6) Calculate the amount of water infiltrating the soil using the water inlet flow sensor (23) and the water level sensor (14), read the data on the external computer, and make corresponding records of the water content and resistivity during the infiltration process based on the pre-measured water content;

[0049] (7) Repeat the above steps (1) to (5), connect the coil electrodes (20) with different spacings in sequence, and finally measure the true resistivity and apparent resistivity data.

[0050] Beneficial effect: Compared with the prior art, the present invention is characterized in that: 1. The present invention can measure the changing law of apparent resistivity and true resistivity at different soil moisture contents during the infiltration process to explore the relationship between apparent resistivity and true resistivity; 2. The water storage chamber and the acrylic glass column are used in combination for pressurized infiltration, and under the joint action of the true resistivity test system equipped with upper and lower plate electrodes and the apparent resistivity test system equipped with multiple groups of coil electrodes from top to bottom, dynamic collection of resistivity test data under various electrode spacings is performed; 3. The acrylic glass column is made of high-strength insulating non-conductive acrylic material, which not only avoids the influence of conductive materials on the resistivity test results but also ensures the strength of the overall experimental device during pressurized infiltration. The graphite electrode plate in the true resistivity test system is made of graphite material with good conductivity and good corrosion resistance, which effectively avoids It prevents the electrode from being corroded during the penetration process and affecting the test results; 4. The inner walls of the 8 permeable stone plate fixing holes and the surfaces of the fixed threaded bolts along the middle layer of the outer wall of the permeable stone plate and the corresponding parts of the side wall of the water storage chamber are respectively engraved with one-way locking threads, which is convenient for the fixed threaded bolts to be inserted into the permeable stone plate fixing holes and more firmly prevent them from falling during the penetration process; 5. The fixing teeth welded on the bottom of the side wall of the water storage chamber and the tooth grooves engraved on the top of the side wall of the acrylic glass column are convenient for the two-part device to be flexibly disassembled and loaded with samples, and at the same time, it also ensures that the sealing compression cover plate is built into the water storage chamber with a rubber sealing ring layer to form a better airtight whole; 6. The inner wall of the acrylic glass column loading layer is equipped with multiple sets of coil electrodes from top to bottom, which is convenient for arbitrarily adjusting the required various electrode spacings. At the same time, the coil electrodes are embedded in the coil electrode fixing grooves for flexible disassembly and replacement of coil electrodes of different diameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0052] Figure 2 It is a schematic diagram of the decomposed structure of the sample loading process of the hydraulic cylinder, the water storage chamber, and the acrylic glass column in the present invention;

[0053] Figure 3 It is a schematic diagram of the cross-sectional structure of the permeable stone slab in the present invention;

[0054] Figure 4 It is a structural schematic diagram of a fixed threaded bolt provided with a one-way locking thread in the present invention;

[0055] Figure 5 It is a schematic diagram of a permeable stone slab provided with permeable stone slab fixing holes in the present invention;

[0056] Figure 6 It is a schematic diagram of the installation cross-sectional structure of a graphite electrode plate with electrode wiring holes in the present invention;

[0057] Figure 7It is a schematic diagram of the structure of the graphite electrode connecting rod in the present invention;

[0058] Figure 8 It is a schematic diagram of the fixing teeth structure at the bottom of the water storage chamber side wall and the top of the acrylic glass column side wall in the present invention;

[0059] Fig. 9 It is a schematic diagram of the structure of the connection device between the water inlet pipe and the water storage chamber in the present invention;

[0060] Fig.10 It is a schematic diagram of the coil electrode installation structure in the present invention;

[0061] Fig.11 It is a structural schematic diagram of a drainage board with drainage holes in the present invention;

[0062] In the figure, 1 is a Japanese-shaped crossbeam; 2 is a hydraulic rod; 3 is a hydraulic cylinder; 4 is a pressure sensor; 5 is a hydraulic cylinder controller; 6 is a sealing compression cover plate; 7 is a rubber sealing ring layer; 8 is a water storage cavity; 9 is a permeable stone plate; 901 is a fixing hole of the permeable stone plate; 902 is a fixing thread bolt; 903 is a one-way locking thread; 10 is a wire; 11 is a water collection cavity; 12 is a water outlet pipe; 13 is a circuit switcher; 14 is a water level sensor; 15 is a water collector; 16 is a resistivity tester; 17 is a computer interface; 18 is a drainage board; 1 801 is a drain hole; 19 is a graphite electrode plate; 1901 is an electrode wiring hole; 1902 is a graphite electrode wiring rod; 20 is a coil electrode; 21 is a water storage tank; 22 is a self-priming pump; 23 is a water inlet flow sensor; 24 is a water inlet pipe; 2401 is a water inlet pipe thread; 2402 is a hollow tightening bolt tube; 2403 is a tightening thread; 25 is a water stop valve; 26 is an acrylic glass column; 2601 is a fixing tooth; 2602 is a tooth groove; 2603 is a coil electrode fixing groove; 2604 is a coil electrode connector. DETAILED DESCRIPTION

[0063] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0064] The invention has a wide application range, and mainly divides applicable soil samples into two categories. Sandy soil samples with a larger permeability coefficient can be directly infiltrated, while clay soil samples with a smaller permeability coefficient need to be pressurized for infiltration.

[0065] like Figure 1 As shown, the test device for testing the apparent resistivity and true resistivity of soil during the penetration process of the present invention comprises two parts: an automatic pressurized penetration device and a resistivity test device;

[0066] The automatic pressurized infiltration device comprises a pressurized infiltration system, a water inlet system and a water outlet system;

[0067] The pressurized infiltration system includes a Japanese-shaped crossbeam 1, a hydraulic rod 2, a hydraulic cylinder 3, a sealing compression cover plate 6, a water storage chamber 8, a permeable stone plate 9, a drainage plate 18 and an acrylic glass column 26.

[0068] The water inlet system includes a water level sensor 14, a water storage tank 21, a self-priming pump 22, a water inlet flow sensor 23, a water inlet pipe 24 and a water stop valve 25;

[0069] The water outlet system includes a water collection cavity 11, a water outlet pipe 12, a water collector 15 and a water stop valve 25;

[0070] The resistivity testing device includes a conductor 10 , a circuit switch 13 , a resistivity tester 16 , a graphite electrode plate 19 and a coil electrode 20 .

[0071] Furthermore, the hydraulic cylinder 3 is installed in the middle of the top of the S-shaped beam 1, and a hydraulic cylinder controller 5 is installed on the top surface of the S-shaped beam 1 to control the operation of the hydraulic cylinder 3;

[0072] The hydraulic rod 2 is connected to the hydraulic cylinder 3 and a pressure sensor 4 for recording the pressurized load value is installed between them. The sealed compression cover plate 6 is located below the hydraulic rod 2, and the hydraulic rod 2 is located above the sealed compression cover plate 6 and can be freely extended and retracted for pressurization as needed.

[0073] Furthermore, the water storage tank 21 is installed in the Japanese-shaped cross beam 1, and the water storage chamber 8 is connected to the water storage tank 21 through a water inlet pipe 24. A self-priming pump 22 is installed between the water inlet pipe 24 and the water storage tank 21 for pressurizing water into the water storage chamber 8;

[0074] The water inlet pipe 24 is provided with a water stop valve 25 on the side close to the water storage chamber 8 , and a water inlet flow sensor 23 on the side close to the self-priming pump 22 .

[0075] Furthermore, the water inlet pipe 24 is engraved with a water inlet pipe thread 2401 on the surface of the side close to the water storage chamber 8, and the outer wall connection of the water storage chamber 8 is connected to the water inlet pipe 24 through a hollow tightening bolt tube 2402. The right end surface of the hollow tightening bolt tube 2402 is engraved with a tightening thread 2403, which is used to screw into the threaded hole at the corresponding position of the left side wall of the water storage chamber 8.

[0076] Furthermore, the permeable stone slab 9 is fixed at the base of the water storage chamber 8, and a rubber sealing ring layer 7 is laid on the inner wall of the upper part of the base of the water storage chamber 8 to ensure the loss of water during the pressurization process;

[0077] A water level sensor 14 is attached below the sealing compression cover plate 6 and built into the water storage chamber 8, so as to measure the amount of water infiltration in the water storage chamber 8 in real time.

[0078] Furthermore, the permeable stone slab 9 is provided with 8 permeable stone slab fixing holes 901 along the middle layer of the outer wall and at the corresponding positions of the side wall of the water storage chamber 8, and the inner wall of the permeable stone slab fixing hole 901 and the surface of the fixing threaded bolt 902 are respectively engraved with a one-way locking thread 903, so that the fixing threaded bolt 902 can be stuck and inserted into the permeable stone slab fixing hole 901 without falling off.

[0079] Furthermore, a fixing tooth 2601 is welded on the bottom of the side wall of the water storage chamber 8, and a tooth groove 2602 is engraved on the top of the side wall of the acrylic glass column 26, so that the water storage chamber 8 and the acrylic glass column 26 can be flexibly disassembled for easy sample loading;

[0080] The uppermost and lowermost layers of the acrylic glass column 26 (sample loading layer) are respectively provided with detachable graphite electrode plates 19. Electrode connection holes 1901 are punched at the center of the right side wall of the graphite electrode plate 19 and at corresponding positions of the side wall of the acrylic glass column 26. The graphite electrode connection rod 1902 is connected to the wire 10.

[0081] Furthermore, the inner wall of the acrylic glass column 26 is provided with multiple groups of coil electrodes 20 from top to bottom, so as to facilitate the adjustment of various electrode spacings as required;

[0082] The coil electrode 20 is embedded in the coil electrode fixing groove 2603 and connected to the wire 10 through a coil electrode connector 2604 punched and placed on the right side wall of the acrylic glass column 26. The coil electrode fixing groove 2603 can facilitate flexible disassembly and replacement of coil electrodes 20 with different diameters.

[0083] The wire 10 is connected to a circuit switch 13 , and the circuit switch 13 is connected to a resistivity tester 16 . A computer interface 17 is attached to the resistivity tester 16 .

[0084] Furthermore, a drainage board 18 is fixed to the bottom of the acrylic glass column 26, and a drainage hole 1801 is punched on the drainage board 18. A water collecting cavity 11 is left at the bottom of the acrylic glass column 26. The water collecting cavity 11 is fixedly connected to the water outlet pipe 12, and the tail end of the water outlet pipe 12 is connected to the water collector 15. A water stop valve 25 is provided on the side of the water outlet pipe 12 close to the water collecting cavity 11.

[0085] Furthermore, a test method for a soil apparent resistivity and true resistivity test device during the infiltration process is provided. Taking unsaturated clay soil with a small permeability coefficient as an example, the specific test steps are as follows:

[0086] (1) Preparation of soil samples with different permeability coefficients and determination of their water content in advance;

[0087] (2) Pour sufficient water into the water storage tank 21 for infiltration, load the prepared soil sample into the sample loading layer of the acrylic glass column 26, and then cover the water storage chamber 8, ensuring that the fixing teeth 2601 welded on the bottom of the side wall of the water storage chamber 8 and the tooth grooves 2602 engraved on the top of the side wall of the acrylic glass column 26 are well fixed;

[0088] (3) After ensuring that all lines are connected, connect the computer interface 17 on the resistivity tester 16 to the computer, open the water stop valve 25 and the self-priming pump 22, and inject a certain amount of water into the water storage chamber 8 according to the moisture content of the soil sample planned in the experimental plan. Wait until the water injection is completed, and record the water volume in the water storage chamber 8 through the water inlet flow sensor 23;

[0089] (4) After the water injection is completed, the hydraulic cylinder controller 5 is turned on to pressurize the hydraulic rod 2 on the hydraulic cylinder 3 to the sealing compression cover plate 6 and further pressurize the hydraulic cylinder 3, and the water in the water storage chamber 8 slowly penetrates into the soil and the water level sensor 14 records the drop in the water level in the water storage chamber 8;

[0090] (5) First, the true resistivity test system is turned on through the circuit switch 13, and then a group of coil electrodes 20 are first connected according to the previously planned apparent resistivity electrode spacing;

[0091] (6) Calculate the amount of water infiltrating the soil using the water inlet flow sensor 23 and the water level sensor 14, read the data on the external computer, and make corresponding records of the water content and resistivity during the infiltration process based on the pre-measured water content;

[0092] (7) Repeat the above steps (1) to (5) to sequentially connect the coil electrodes 20 with different spacings to measure the true resistivity and apparent resistivity data.

[0093] Example

[0094] In this example, unsaturated clay with a small permeability coefficient is used as the experimental object. A soil apparent resistivity and true resistivity test device involved in the infiltration process requires the preparation of clay samples with different permeability coefficients in advance and the measurement of the pre-water content. Before placing the clay sample, check in advance whether the water sample to be infiltrated in the water storage tank 21 is sufficient and whether the air tightness of the water storage chamber 8 is intact. Then, unscrew the hollow tightening bolt tube 2402 on the water inlet pipe 24 from the left side wall of the water storage chamber 8 and control the hydraulic cylinder 3 to move the hydraulic rod 2 upward until it is separated from the water storage chamber 8. Figure 2 , Figure 8 As shown,

[0095] With the cooperation of the fixing teeth 2601 and the tooth grooves 2602, the water storage chamber 8 is removed from the acrylic glass column 26, and the graphite electrode plate 19 is removed. After checking that the coil electrode 20 placed on the inner wall of the acrylic glass column 26 is intactly embedded in the coil electrode fixing groove 2603, the pre-prepared soil sample is loaded into the sample loading layer of the acrylic glass column 26, and then the graphite electrode plate 19 is laid out and the graphite electrode wiring rod 1902 is inserted from the outer wall of the device into the electrode wiring hole 1901 on the graphite electrode plate 19. The graphite electrode plate 19 is subjected to the combined action of the upper and lower pressures and the graphite electrode wiring rod 1902 to achieve the purpose of both fixing and wiring. Then, the water storage chamber 8 is placed on the acrylic glass column 26 and the water inlet pipe 24 is tightened to the left wall of the water storage chamber 8. After checking that all lines are connected, the water stop valve 25 is opened, and the self-priming pump 22 is started to pressurize the water into the water storage chamber 8 and record the storage flow through the water inlet flow sensor 23. The amount of water in the water chamber 8 is determined by starting the hydraulic cylinder 3 to press the hydraulic rod down to the sealing compression cover plate 6 and further pressurizing it. The amount of water infiltrating into the soil is recorded according to the water level drop in the water storage chamber 8 measured by the water level sensor 14. The first group of coil electrodes 20 is first connected through the circuit switch 13 according to the pre-planned electrode spacing scheme, and the graphite electrode plate 19 of the true resistivity test system is connected at the same time. The apparent resistivity and true resistivity under the first group of electrode spacing are tested by the resistivity tester 16, and the data are recorded by an external computer. According to the measured pre-measured water content, the corresponding records of water content and resistivity during the infiltration process are made. Subsequently, different groups of coil electrodes 20 are connected in turn according to the pre-planned electrode spacing scheme. The first group of steps is repeated to sort out the variation rules of apparent resistivity and true resistivity under different water contents and different electrode spacings. The relationship between apparent resistivity and true resistivity is explored through resistivity inversion technology. Regarding the true resistivity ρ z The calculation formula is as follows:

[0096]

[0097] Among them, R z is the resistivity value tested by the true resistivity test system, S z is the cross-sectional area of ​​the graphite electrode plate 19, L z is the center distance between the upper and lower graphite electrode plates 19;

[0098] About Apparent Resistivity ρ s The calculation formula is as follows:

[0099]

[0100] Among them, R s is the resistivity value tested by the apparent resistivity test system, S s is the cross-sectional area of ​​the coil electrode 20, L sThe distance between the two groups of coil electrodes 20 connected was determined for the experimental plan.

[0101] In the specific implementation of the present invention, for sandy soil samples with a large permeability coefficient, there is no need to perform pressurized infiltration, and the resistivity test steps of the direct infiltration process without pressurization in the above example can be directly performed.

[0102] The above description is only a preferred specific implementation manner of the present invention, but its protection scope is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A device for testing apparent resistivity and true resistivity of soil during infiltration, characterized in that: It includes an automatic pressure - penetration device and a resistivity testing device; The described automatic pressure - penetration device includes a pressure - penetration system, a water inlet system and a water outlet system; The pressure - penetration system includes a day - shaped cross - beam (1), a hydraulic rod (2), a hydraulic cylinder (3), a sealing and compression cover plate (6), a water storage cavity (8), a permeable stone slab (9), a drainage plate (18) and an acrylic glass column (26); The water inlet system includes a water level sensor (14), a water storage tank (21), a self - priming pump (22), a water inlet flow sensor (23), a water inlet pipe (24) and a stop valve (25); The water outlet system includes a water collection cavity (11), a water outlet pipe (12), a water collector (15) and a stop valve (25); The resistivity testing device includes a wire (10), a circuit switcher (13), a resistivity tester (16), a graphite electrode plate (19) and a coil electrode (20); An acrylic glass column (26) is installed at the lower end of the water storage cavity (8), Fixed teeth (2601) are welded at the bottom of the side wall of the water storage cavity (8), A tooth groove (2602) adapted to the fixed teeth (2601) is installed at the top of the side wall of the acrylic glass column (26), Removable graphite electrode plates (19) are installed at both the top layer and the bottom layer of the acrylic glass column (26). At the center of the right - hand side wall of the graphite electrode plate (19) and at the corresponding position on the side wall of the acrylic glass column (26), electrode connection holes (1901) are provided. The electrode connection holes (1901) are connected to the wire (10) through installed graphite electrode connection rods (1902); Coil electrode fixing grooves (2603) are evenly distributed on the inner wall of the acrylic glass column (26), Multiple groups of coil electrodes (20) are evenly installed from top to bottom on the inner wall of the acrylic glass column (26). The coil electrodes (20) are embedded in the coil electrode fixing grooves (2603); A wiring port is provided on the right - hand side wall of the acrylic glass column (26), and a coil electrode connector (2604) is installed in the wiring port, The coil electrodes (20) are connected to the wire (10) through installed coil electrode connectors (2604); A circuit switcher (13) is also installed inside the day - shaped cross - beam (1), and the wire (10) is connected to the circuit switcher (13); The other end of the circuit switcher (13) is connected to an installed resistivity tester (16), and a computer interface (17) is attached to the resistivity tester (16).

2. A device for testing apparent resistivity and true resistivity of soil during infiltration according to claim 1, characterized in that: The hydraulic cylinder (3) is installed at the middle position at the top of the day - shaped cross - beam (1). A hydraulic rod (2) is installed at the lower end of the hydraulic cylinder (3), The hydraulic rod (2) is connected to the hydraulic cylinder (3), and a pressure sensor (4) is installed between them. The other end of the hydraulic rod (2) is provided with a sealing and compression cover plate (6). The sealing and compression cover plate (6) is installed below the hydraulic rod (2). A water storage cavity (8) is installed outside the hydraulic rod (2) and the sealing and compression cover plate (6); On the top surface of the "day"-shaped crossbeam (1), a hydraulic cylinder controller (5) is also installed on one side of the hydraulic cylinder (3).

3. The device for testing apparent resistivity and true resistivity of soil during infiltration according to claim 1, characterized in that: The water storage tank (21) is installed in the middle and lower part inside the "day"-shaped crossbeam (1). An inlet pipe (24) is connected to the upper end of the water storage tank (21). The water storage tank (21) is interconnected with the water storage cavity (8) through the installed inlet pipe (24). A self-priming pump (22) is installed at the connection between the inlet pipe (24) and the water storage tank (21). A water stop valve (25) is installed on one side of the inlet pipe (24) close to the water storage cavity (8). An inlet flow sensor (23) is installed on one side of the inlet pipe (24) close to the self-priming pump (22).

4. A device for testing apparent resistivity and true resistivity of soil during infiltration according to claim 3, characterized in that: On the surface of one side of the inlet pipe (24) close to the water storage cavity (8), an inlet pipe thread (2401) is provided. The outer wall connection of the water storage cavity (8) is connected to the inlet pipe (24) through a hollow tightening bolt pipe (2402). A tightening thread (2403) is also provided on the right end surface of the hollow tightening bolt pipe (2402).

5. The device for testing apparent resistivity and true resistivity of soil during infiltration according to claim 1, characterized in that: A permeable stone slab (9) is installed inside the water storage cavity (8). The permeable stone slab (9) is fixedly installed at the base inside the water storage cavity (8). A rubber sealing ring layer (7) is installed on the upper inner wall of the base of the water storage cavity (8). A water level sensor (14) is also attached to the lower end of the sealing compression cover plate (6). The water level sensor (14) is placed inside the water storage cavity (8).

6. A device for testing apparent resistivity and true resistivity of soil during infiltration according to claim 5, characterized in that: At least 8 permeable stone slab fixing holes (901) are evenly distributed along the middle layer of the outer wall of the permeable stone slab (9) and the corresponding part of the side wall of the water storage cavity (8) in a circle. A fixing threaded bolt (902) adapted to it is installed on the permeable stone slab fixing holes (901). Unidirectional locking threads (903) are provided on the inner wall of the permeable stone slab fixing holes (901) and the surface of the fixing threaded bolt (902).

7. The device for testing apparent resistivity and true resistivity of soil during infiltration according to claim 1, characterized in that: A drainage plate (18) is fixedly installed at the bottom of the acrylic glass column (26). A number of drainage holes (1801) are provided on the drainage plate (18). At the bottom of the acrylic glass column (26), a water collection cavity (11) is provided at the lower end of the drainage plate (18). An outlet pipe (12) is provided at one end of the water collection cavity (11). The water collection cavity (11) is fixedly connected to the outlet pipe (12). A water collector (15) is also installed at the tail end of the outlet pipe (12). The tail end of the outlet pipe (12) is connected to the water collector (15). A water stop valve (25) is also installed on one side of the outlet pipe (12) close to the water collection cavity (11).

8. The method for testing the apparent resistivity and true resistivity of soil during infiltration according to any one of claims 1 to 7, characterized in that: The specific test steps are as follows: (1) Prepare soil samples with different permeability coefficients and measure the initial moisture content. (2) Inject water into the water storage tank (21) for infiltration. Load the prepared soil sample into the acrylic glass column (26). Then cover the water storage cavity (8) to ensure that the fixed teeth (2601) welded at the bottom of the side wall of the water storage cavity (8) and the tooth grooves (2602) engraved on the top of the side wall of the acrylic glass column (26) are firmly fixed. (3) After ensuring that all lines are connected, connect the computer interface (17) on the resistivity tester (16) to the computer, open the water stop valve (25) and the self-priming pump (22), and inject water into the water storage chamber (8) according to the soil sample moisture content planned in the experimental plan. Wait until the water injection is completed, and record the water volume in the water storage chamber (8) through the water inlet flow sensor (23); (4) After the water injection is completed, the hydraulic cylinder controller (5) is turned on to pressurize the hydraulic rod (2) on the hydraulic cylinder (3) to the sealing compression cover plate (6) and pressurize the hydraulic cylinder, and the water in the water storage chamber (8) penetrates into the soil and the water level sensor (14) records the drop in the water level in the water storage chamber (8); (5) First, the true resistivity test system is connected through the circuit switch (13), and then a group of coil electrodes (20) are connected according to the previously planned apparent resistivity electrode spacing; (6) Calculate the amount of water infiltrating the soil using the water inlet flow sensor (23) and the water level sensor (14), read the data on the external computer, and make corresponding records of the water content and resistivity during the infiltration process based on the pre-measured water content; (7) Repeat the above steps (1) to (5), connect the coil electrodes (20) with different spacings in sequence, and finally measure the true resistivity and apparent resistivity data.

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