Device and method for testing apparent resistivity and true resistivity of soil body in infiltration processTechnical Field
The invention belongs to the field of geotechnical engineering, and particularly relates to a device and a method for testing apparent resistivity and true resistivity of soil in a infiltration process.
Background
The ground electrical characteristic is an important characteristic for representing structural change of soil, and the soil resistivity characterization method has the advantages of no damage, high efficiency, low cost and the like, and is widely applied to the research fields of geological exploration, groundwater and pollutant migration and the like. The resistivity of the soil body is measured when the conductivity is uniform isotropy in the electric field control range, and the conductivity is divided into apparent resistivity and true resistivity according to test means, wherein the two test methods are often in the actual field exploration process due to the infiltration effect of underground water, and due to the infiltration deposition effect of the soil body, the distribution of the water after infiltration into the soil body is intricate, the sandy soil with larger infiltration coefficient has larger porosity than that of the cohesive soil, more water is easier to infiltrate, the water has better ion exchange property, the infiltration into the soil body can obviously improve the conductivity of the soil body, and the resistivity of the soil body is reduced.
In the existing research on the resistivity change characteristics of the soil body in the infiltration process, the apparent resistivity is defaulted to be the measured final resistivity, the research on the true resistivity obtained by another testing method is less, the measured true resistivity and the apparent resistivity are essentially independent, and the characterization relation between the true resistivity and the apparent resistivity is to be researched, so that a device and a method capable of accurately measuring the apparent resistivity and the true resistivity change data of the soil body in the infiltration process are needed to be designed in the research.
Disclosure of Invention
The invention aims to: the invention aims to solve the defects in the prior art, and provides a device and a method for testing apparent resistivity and true resistivity of soil in a infiltration process.
The technical scheme is that in order to achieve the purposes, the invention adopts the following technical scheme:
The invention relates to a soil apparent resistivity and true resistivity testing device in the infiltration process,
The device comprises an automatic pressurizing and penetrating device and a resistivity testing device;
the automatic pressurizing and penetrating device comprises a pressurizing and penetrating system, a water inlet system and a water outlet system;
the pressurizing and penetrating system comprises a Chinese character 'ri' shaped cross beam (1), a hydraulic rod (2), a hydraulic cylinder (3), a sealing compression cover plate (6), a water storage cavity (8), a permeable stone plate (9), a drainage plate (18) and an acrylic glass column (26);
The water inlet system comprises 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);
the water outlet system comprises a water collecting cavity (11), a water outlet pipe (12), a water collector (15) and a water stop valve (25);
the resistivity testing device comprises a lead (10), a circuit switcher (13), a resistivity tester (16), a graphite electrode plate (19) and a coil electrode (20);
Furthermore, the hydraulic cylinder (3) is arranged at the middle position of the top end of the Chinese character 'ri' -shaped cross beam (1), the lower end of the hydraulic cylinder (3) is provided with a hydraulic rod (2),
The hydraulic rod (2) is connected with the hydraulic cylinder (3) and a pressure sensor (4) is arranged between the hydraulic rod and the hydraulic cylinder, a sealing compression cover plate (6) is arranged at the other end of the hydraulic rod (2), the sealing compression cover plate (6) is arranged below the hydraulic rod (2), and a water storage cavity (8) is arranged outside the hydraulic rod (2) and the sealing compression cover plate (6);
A hydraulic cylinder controller (5) is further arranged on the top surface of the Chinese character 'ri' shaped cross beam (1) and on one side of the hydraulic cylinder (3).
Furthermore, the water storage tank (21) is arranged at the middle lower part of the inside of the cross beam (1) in the shape of Chinese character 'ri', the upper end of the water storage tank (21) is connected with a water inlet pipe (24),
The water storage tank (21) is connected with the water storage cavity (8) through a water inlet pipe (24) which is arranged;
A self-priming pump (22) is arranged at the joint of the water inlet pipe (24) and the water storage tank (21),
A water stop valve (25) is arranged at one side of the water inlet pipe (24) close to the water storage cavity (8),
A water inlet flow sensor (23) is arranged on one side of the water inlet pipe (24) close to the self-priming pump (22).
Further, a water inlet pipe thread (2401) is formed in the surface of one side, close to the water storage cavity (8), of the water inlet pipe (24), the water storage cavity (8) is connected with the water inlet pipe (24) through a hollow tightening bolt pipe (2402) formed in the outer wall connection position, and a tightening thread (2403) is further formed in the right end surface of the hollow tightening bolt pipe (2402).
Furthermore, a permeable stone plate (9) is arranged in the water storage cavity (8), the permeable stone plate (9) is fixedly arranged at the base in the water storage cavity (8),
A rubber sealing ring layer (7) is arranged on the inner wall of the upper part of the base of the water storage cavity (8),
The lower end of the sealing compression cover plate (6) is also provided with a water level sensor (14), and the water level sensor (14) is arranged in the water storage cavity (8).
Furthermore, at least 8 permeable stone plate fixing holes (901) are uniformly distributed along the middle layer of the outer wall and the corresponding part of the side wall of the water storage cavity (8), and fixing threaded bolts (902) matched with the permeable stone plate fixing holes (901) are arranged on the permeable stone plate fixing holes (901);
The inner wall of the permeable stone slab fixing hole (901) and the surface of the fixing threaded bolt (902) are provided with unidirectional locking threads (903).
Furthermore, an acrylic glass column (26) is arranged 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),
Tooth grooves (2602) matched with the fixed teeth (2601) are arranged at the top of the side wall of the acrylic glass column (26),
The top layer and the bottom layer of the acrylic glass column (26) are respectively provided with a detachable graphite electrode plate (19), an electrode wiring hole (1901) is formed in the center of the right side wall of the graphite electrode plate (19) and at the corresponding position of the side wall of the acrylic glass column (26), and the electrode wiring hole (1901) is connected with a lead (10) through an arranged graphite electrode wiring rod (1902).
Further, coil electrode fixing grooves (2603) are uniformly distributed on the inner wall of the acrylic glass column (26),
A plurality of groups of coil electrodes (20) are uniformly distributed on the inner wall of the acrylic glass column (26) from top to bottom, and the coil electrodes (20) are embedded in the coil electrode fixing grooves (2603);
A wiring port is arranged on the right side wall of the acrylic glass column (26), a coil electrode connector (2604) is arranged in the wiring port,
The coil electrode (20) is connected with the lead (10) through a coil electrode connector (2604) which is arranged;
A circuit switcher (13) is further arranged in the Chinese character 'ri' -shaped cross beam (1), and the lead (10) is connected with the circuit switcher (13);
The other end of the circuit switcher (13) is connected with an installed resistivity tester (16), and a computer interface (17) is additionally arranged on the resistivity tester (16).
Further, a drain board (18) is fixedly arranged at the bottom of the acrylic glass column (26),
A plurality of drain holes (1801) are formed in the drain plate (18);
A layer of water collecting cavity (11) is formed in the bottommost part of the acrylic glass column (26) and the lower end of the drain plate (18), a water outlet pipe (12) is formed in one end of the water collecting cavity (11), and the water collecting cavity (11) is fixedly connected with the water outlet pipe (12);
A water collector (15) is further arranged at the tail end of the water outlet pipe (12), and the tail end of the water outlet pipe (12) is connected with the water collector (15);
a water stop valve (25) is also arranged on one side of the water outlet pipe (12) close to the water collecting cavity (11).
Further, a test method of the soil apparent resistivity and true resistivity test device in the infiltration process comprises the following specific test steps:
(1) Preparing soil samples with different permeability coefficients and measuring the water content in advance;
(2) Injecting water into the water storage tank (21) for infiltration, filling the prepared soil sample into the acrylic glass column (26), and then covering 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) carved at the top of the side wall of the acrylic glass column (26) are completely fixed;
(3) After all lines are connected, a computer interface (17) on a resistivity tester (16) is connected to a computer, a water stop valve (25) and a self-priming pump (22) are opened, water is injected into a water storage cavity (8) according to the soil sample water content planned by an experimental scheme, and the water quantity in the water storage cavity (8) is recorded through a water inlet flow sensor (23) after the water injection is completed;
(4) After water injection is finished, a hydraulic cylinder controller (5) is opened to enable a hydraulic rod (2) on a hydraulic cylinder (3) to be pressurized to a sealing compression cover plate (6) and pressurized, and when water in a water storage cavity (8) permeates into soil and the water level descending amount in the water storage cavity (8) is recorded through a water level sensor (14);
(5) Firstly, switching on a true resistivity test system through a circuit switcher (13), and then firstly switching on a group of coil electrodes (20) according to the previously-planned apparent resistivity electrode spacing;
(6) Calculating the water quantity of the infiltrated soil body according to a water inlet flow sensor (23) and a water level sensor (14), reading data on an external computer, and recording the water content and the resistivity in the infiltration process according to the measured pre-water content;
(7) And (3) repeating the steps (1) - (5), and sequentially switching on coil electrodes (20) with different pitches to finally measure the true resistivity and apparent resistivity data.
Compared with the prior art, the invention has the advantages that 1, the invention can measure the change rule of apparent resistivity and true resistivity under different soil body water contents in the infiltration process so as to explore the relationship between the apparent resistivity and the true resistivity; 2, the water storage cavity and the acrylic glass column are matched for pressurizing and penetrating, and dynamic collection of resistivity test data under various electrode intervals is carried out under the combined action of a true resistivity test system provided with upper and lower plate-shaped electrodes and a visual resistivity test system provided with a plurality of groups of coil electrodes from top to bottom; the 3, the acrylic glass column is made of high-strength insulating non-conductive acrylic material, which not only avoids the influence of conductive material on the resistivity test result, but also ensures the strength of the whole experimental device in the pressurizing and penetrating process, the graphite electrode plate in the true resistivity test system is made of graphite material with good conductivity and corrosion resistance, which effectively avoids the electrode corrosion in the penetrating process, 4, the inner wall of 8 water-permeable stone plate fixing holes and the surface of a fixing threaded bolt, which are punched along the middle layer of the outer wall and the corresponding position of the side wall of the water storage cavity, are respectively carved with unidirectional locking threads, so that the fixing threaded bolt is conveniently blocked and inserted into the water-permeable stone plate fixing hole and is firmer and not dropped in the penetrating process, 5, the fixed teeth welded at the bottom of the side wall of the water storage cavity and the tooth grooves carved at the top of the side wall of the acrylic glass column are convenient for the two parts of the device to be flexibly detached, and the sealing and compressing cover plate is also ensured to be arranged in the water storage cavity with a rubber sealing ring layer to form a whole with good air tightness, 6, the inner wall of the acrylic glass column is provided with a plurality of groups of coil electrodes, which is convenient for randomly adjusting the needed electrode spacing, meanwhile, the coil electrodes are embedded in the coil electrode fixing grooves, so that the coil electrodes with different diameters can be conveniently and flexibly detached and replaced.
Drawings
FIG. 1 is a schematic view of the overall structure of the present invention;
FIG. 2 is a schematic diagram of an exploded structure of a hydraulic cylinder, a water storage cavity and an acrylic glass column in the sample loading process;
FIG. 3 is a schematic cross-sectional view of a water permeable stone panel according to the invention;
FIG. 4 is a schematic view of a fixing bolt with a unidirectional locking thread according to the present invention;
FIG. 5 is a schematic view of a water permeable stone panel according to the present invention with water permeable stone panel fixing holes;
FIG. 6 is a schematic view showing a mounting cross-sectional structure of a graphite electrode plate provided with an electrode wiring hole in the present invention;
FIG. 7 is a schematic view of a graphite electrode terminal bar according to the present invention;
FIG. 8 is a schematic view of the structure of the fixed teeth at the bottom of the side wall of the water storage cavity and the top of the side wall of the acrylic glass column in the invention;
FIG. 9 is a schematic diagram of the connection device of the water inlet pipe and the water storage cavity in the invention;
FIG. 10 is a schematic view of the coil electrode mounting structure of the present invention;
FIG. 11 is a schematic view of a drain board with drain holes according to the present invention;
In the figure, 1 is a cross beam in a Chinese character 'ri'; the hydraulic pressure sensor is characterized by comprising a hydraulic rod 2, a hydraulic cylinder 3, a pressure sensor 4, a hydraulic cylinder controller 5, a sealing compression cover plate 6, a rubber sealing ring layer 7, a water storage cavity 8, a water permeable stone plate 9, a water permeable stone plate fixing hole 901, a fixing bolt 902, a one-way locking screw 903, a wire 10, a water collecting cavity 11, a water outlet 12, a circuit switcher 13, a water level sensor 14, a water collector 15, a resistivity tester 16, a computer interface 17, a water draining plate 18, a water draining hole 1801, a graphite electrode plate 19, an electrode wiring hole 1901, a graphite electrode wiring rod 1902, a coil electrode 20, a water storage tank 21, a self-sucking pump 22, a water inlet flow sensor 23, a water inlet pipe 24, a water inlet pipe 2401, a hollow screwing bolt pipe 2403, a screwing screw thread 25, a water stopping valve 26, a acryl glass column 2601, a fixing tooth socket 2602, a coil electrode fixing groove 2603, and a coil electrode wire connector 2604.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments.
The invention has wide application range, mainly divides the applicable soil samples into two types, can directly permeate sand soil samples with larger permeability coefficient, and needs to permeate clay soil samples with smaller permeability coefficient under pressure.
As shown in figure 1, the testing device of the soil apparent resistivity and true resistivity testing device in the infiltration process comprises an automatic pressurizing infiltration device and a resistivity testing device;
the automatic pressurizing and penetrating device comprises a pressurizing and penetrating system, a water inlet system and a water outlet system;
the pressurizing and penetrating system comprises a Chinese character 'ri' shaped cross beam 1, a hydraulic rod 2, a hydraulic cylinder 3, a sealing compression cover plate 6, a water storage cavity 8, a permeable stone plate 9, a drainage plate 18 and an acrylic glass column 26,
The water inlet system comprises 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;
The water outlet system comprises a water collecting cavity 11, a water outlet pipe 12, a water collector 15 and a water stop valve 25;
the resistivity testing device comprises a lead 10, a circuit switcher 13, a resistivity tester 16, a graphite electrode plate 19 and a coil electrode 20.
Further, the hydraulic cylinder 3 is arranged in the middle of the top end of the Chinese character 'ri' shaped cross beam 1, and a hydraulic cylinder controller 5 is arranged on the surface of the top end of the Chinese character 'ri' shaped cross beam 1 and used for controlling the work of the hydraulic cylinder 3;
The hydraulic rod 2 is connected with the hydraulic cylinder 3, a pressure sensor 4 for recording the value of the pressurizing load is arranged between the hydraulic rod 2 and the hydraulic cylinder 3, the sealing compression cover plate 6 is positioned below the hydraulic rod 2, and the hydraulic rod 2 is positioned above the sealing compression cover plate 6 and can be freely stretched and pressurized according to the requirement.
Further, the water storage tank 21 is arranged in the cross beam 1 in the shape of Chinese character ri, the water storage cavity 8 is connected with the water storage tank 21 through a water inlet pipe 24, and a self-priming pump 22 is arranged between the water inlet pipe 24 and the water storage tank 21 and is used for pressurizing and injecting water into the water storage cavity 8;
a water stop valve 25 is arranged on the side, close to the water storage cavity 8, of the water inlet pipe 24, and a water inlet flow sensor 23 is arranged on the side, close to the self-priming pump 22.
Further, a water inlet pipe thread 2401 is engraved on the surface of one side of the water inlet pipe 24 near the water storage cavity 8, the junction of the outer wall of the water storage cavity 8 is connected with the water inlet pipe 24 through a hollow tightening bolt pipe 2402, and a tightening thread 2403 is engraved on the right end surface of the hollow tightening bolt pipe 2402 and is used for being screwed into a threaded hole engraved on the corresponding position of the left side wall of the water storage cavity 8.
Further, the permeable stone plate 9 is fixed at the base of the water storage cavity 8, and a rubber sealing ring layer 7 is paved on the inner wall of the upper part of the base of the water storage cavity 8 so as to ensure the water loss in the pressurizing process;
The water level sensor 14 is attached below the sealing compression cover plate 6 and is internally arranged in the water storage cavity 8, so that the infiltration amount of water in the water storage cavity 8 can be conveniently measured in real time.
Further, 8 permeable stone plate fixing holes 901 are formed in the corresponding positions of the middle layer of the outer wall and the side wall of the water storage cavity 8 in a circle, unidirectional locking threads 903 are respectively formed in the surfaces of the inner wall of the permeable stone plate fixing holes 901 and the surfaces of the fixing threaded bolts 902 in a carved mode, and the fixing threaded bolts 902 are conveniently locked and inserted into the permeable stone plate fixing holes 901 without falling.
Furthermore, fixed teeth 2601 are welded at the bottom of the side wall of the water storage cavity 8, tooth grooves 2602 are engraved at the top of the side wall of the acrylic glass column 26, so that the water storage cavity 8 and the acrylic glass column 26 can be flexibly disassembled and sample loading is facilitated;
The upper and lower layers of the acrylic glass column 26 (sample loading layer) are respectively provided with a detachable graphite electrode plate 19, an electrode wiring hole 1901 is punched in the center of the right side wall of the graphite electrode plate 19 and at a position corresponding to the side wall of the acrylic glass column 26, and the graphite electrode wiring rod 1902 is connected with the lead 10.
Further, a plurality of groups of coil electrodes 20 are arranged on the inner wall of the acrylic glass column 26 from top to bottom, so that the required electrode spacing can be adjusted at will;
The coil electrode 20 is embedded in the coil electrode fixing groove 2603 and is connected with the lead 10 through a coil electrode connector 2604 perforated and arranged on the right side wall of the acrylic glass column 26, and the coil electrode fixing groove 2603 can be convenient for flexibly disassembling and replacing the coil electrodes 20 with different diameters;
The wire 10 is connected to a circuit switch 13, the circuit switch 13 is connected to a resistivity tester 16, and a computer interface 17 is attached to the resistivity tester 16.
Further, a drain plate 18 is fixed at the bottom of the acrylic glass column 26, drain holes 1801 are drilled in the drain plate 18, a layer of water collection cavity 11 is reserved at the bottommost part of the acrylic glass column 26, the water collection cavity 11 is fixedly connected with a water outlet pipe 12, the tail end of the water outlet pipe 12 is connected with a water collector 15, and a water stop valve 25 is arranged on one side of the water outlet pipe 12 close to the water collection cavity 11.
Further, a test method of the soil apparent resistivity and true resistivity test device in the infiltration process takes unsaturated clay with smaller permeability coefficient as an example, and the specific test steps are as follows:
(1) Preparing soil samples with different permeability coefficients and measuring the water content in advance;
(2) Filling sufficient water into the water storage tank 21 for infiltration, filling the prepared soil sample into the sample filling layer of the acrylic glass column 26, and then covering 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 carved at the top of the side wall of the acrylic glass column 26 are completely fixed;
(3) After all lines are connected, a computer interface 17 on the resistivity tester 16 is connected to a computer, a water stop valve 25 and a self-priming pump 22 are opened, quantitative water is injected into the water storage cavity 8 according to the soil sample water content planned by an experimental scheme, and the water quantity in the water storage cavity 8 is recorded through a water inlet flow sensor 23 after the water injection is completed;
(4) After water injection is finished, opening a hydraulic cylinder controller 5 to enable a hydraulic rod 2 on a hydraulic cylinder 3 to be pressurized to a sealing compression cover plate 6 and further pressurized, slowly penetrating water in a water storage cavity 8 into soil, and recording the water level descending amount in the water storage cavity 8 through a water level sensor 14;
(5) The true resistivity test system is first turned on by the circuit switch 13, and then a set of coil electrodes 20 are first turned on according to the previously proposed apparent resistivity electrode spacing;
(6) Calculating the water quantity of the infiltrated soil body according to the water inlet flow sensor 23 and the water level sensor 14, reading data on an external computer, and recording the water content and the resistivity in the infiltration process according to the measured pre-water content;
(7) And repeating the steps (1) - (5), and sequentially switching on the coil electrodes 20 with different pitches to obtain the true resistivity and apparent resistivity data.
Examples
In the embodiment, unsaturated clay with smaller permeability coefficient is taken as an experimental object, the device for testing apparent resistivity and true resistivity of soil in the infiltration process needs to prepare clay samples with different permeability coefficients in advance and measure the water content in advance, before placing the clay samples, the water storage tank 21 is checked in advance whether the water sample to be infiltrated is sufficient or not and whether the air tightness of the water storage cavity 8 is good or not, then the hollow screwing bolt tube 2402 on the water inlet pipe 24 is unscrewed from the left side wall of the water storage cavity 8 and the hydraulic cylinder 3 is controlled to enable the hydraulic rod 2 to move upwards until the hydraulic rod is separated from the water storage cavity 8, as shown in figures 2 and 8,
Removing the water storage cavity 8 from the acrylic glass column 26 under the matched use of the fixing teeth 2601 and the tooth grooves 2602, taking down the graphite electrode plate 19, after the coil electrode 20 arranged on the inner wall of the acrylic glass column 26 is well checked and embedded into the coil electrode fixing groove 2603, starting to fill the prepared soil sample into the sample filling layer of the acrylic glass column 26, then arranging the graphite electrode plate 19, inserting the graphite electrode wiring rod 1902 into the electrode wiring hole 1901 on the graphite electrode plate 19 from the outer wall of the device, the graphite electrode plate 19 is subjected to the combined action of the up-down pressure and the graphite electrode wiring rod 1902 so as to achieve the purpose of fixing and wiring, then arranging the water storage cavity 8 on the acrylic glass column 26, screwing the water inlet pipe 24 on the left side wall of the water storage cavity 8, after all the circuit connection is checked, opening the water stop valve 25, starting the self-sucking pump 22 to pressurize and filling water into the water storage cavity 8, recording the water quantity in the water storage cavity 8 through the water inlet flow sensor 23, starting a hydraulic cylinder 3 to enable a hydraulic rod to be pressed down to a sealing compression cover plate 6 and further pressurized, recording the water quantity permeated into soil according to the water level drop quantity in a water storage cavity 8 obtained by actual measurement of a water level sensor 14, switching on a first group of coil electrodes 20 for the first time through a circuit switch 13 according to a preset electrode spacing scheme and simultaneously switching on a graphite electrode plate 19 of a true resistivity test system, testing apparent resistivity and true resistivity at the first group of electrode spacing through a resistivity tester 16 and recording data through an external computer, making corresponding records of the water content and the resistivity in the permeation process according to the measured preset water content, sequentially switching on different groups of coil electrodes 20 according to the preset electrode spacing scheme, repeating the first group of steps, finishing the apparent resistivity at different water contents and different electrode spacing, the true resistivity change rule is researched by resistivity inversion technology, and the relation between apparent resistivity and true resistivity is researched, and the calculation formula of the true resistivity rhoz is as follows:
wherein Rz is the resistivity value tested by the true resistivity test system, Sz is the cross-sectional area of the graphite electrode plates 19, and Lz is the center-to-center distance between the upper and lower graphite electrode plates 19;
The calculation formula for apparent resistivity ρs is as follows:
Wherein, Rs is the resistivity value tested by the apparent resistivity test system, Ss is the area cross-sectional area occupied by the coil electrodes 20, and Ls is the interval between two groups of coil electrodes 20 which are connected by the experimental scheme.
The invention can be used for directly carrying out the resistivity test step of the non-pressurized direct infiltration process according to the above example without carrying out pressurized infiltration on the sandy soil sample with larger permeability coefficient in the concrete implementation.
The foregoing description is only a preferred embodiment of the present invention, but the protection scope is not limited thereto, and any person skilled in the art, within the scope of the present invention, should make equivalent substitutions or modifications according to the technical solution and the inventive concept thereof, and should be covered by the protection scope of the present invention.