Device and method for measuring pore structure change of porous medium material in one-dimensional consolidation process based on spectrum induced polarization method

Abstract

The invention discloses a device and a method for measuring change of a pore structure of a porous medium material in a one-dimensional consolidation process based on a spectrum induced polarization method, the device comprises a sample cylinder, the sample cylinder is internally provided with a loading transition cover, the loading transition cover accommodates a top electrode ring, and the loading transition cover is provided with a bottom electrode ring; a top porous force transfer plate is arranged at the upper part of the sample soil body, and a bottom porous force transfer plate is arranged at the lower part of the sample soil body; at least two pairs of electrode probes are arranged on two sides of the sample soil body; and the bottom electrode ring is arranged below the bottom porous force transfer plate, and the bottom electrode ring and the top electrode ring are coaxial and have the same size. The device provided by the invention can detect and monitor electrical signals in the soil consolidation process, can realize quantitative research on pore characteristic evolution in the soil deformation development process under the action of an external load, and provides reliable technical support for deeply exploring the relation between physical and mechanical properties and electrical properties of the soil.

Description

Technical Field

[0001] The present invention belongs to the technical field of geotechnical testing, and in particular relates to a device and method for measuring pore structure changes of porous medium materials during a one-dimensional consolidation process based on a spectrum induced polarization method. Background Art

[0002] Deep soft soil layers are widely distributed in the southeastern coastal areas of my country. They have poor engineering properties such as high saturation, large porosity, high compressibility, and strong sensitivity. They are prone to significant deformation under the action of external forces, inducing geological disasters and threatening engineering construction and normal human activities. Therefore, studying the physical and mechanical properties of natural soft clay is of great engineering significance.

[0003] One-dimensional consolidation tests are an effective means of quantitatively studying the relationship between stress and deformation in soils. Under axial pressure, the intergranular solution of saturated soft clay is squeezed out, significantly reducing the soil's porosity and causing significant changes in the microscopic pore structure. This, coupled with the compaction and structural failure of the soft soil, results in a corresponding change in soil strength. However, consolidation tests only provide a macroscopic picture of the evolution of the soil's porosity with consolidation pressure and fail to capture the evolution of microscopic pore structure characteristics. Most existing methods, such as scanning electron microscopy, CT scanning, and image measurement, are limited by testing conditions and struggle to monitor pore structure changes during stress-deformation in porous media. Furthermore, methods commonly used in triaxial testing, such as direct current resistivity and bending element methods, only capture the macroscopic response of the soil and fail to capture the distribution of soil pore characteristics. Consequently, existing technologies and testing methods have significant limitations in exploring the microscopic deformation mechanisms of natural soft clays.

[0004] Spectral induced polarization (SIP) testing is widely used to study the particle size and microscopic pore characteristics of porous materials, demonstrating great potential for development. However, SIP is currently rarely applied to soils undergoing significant deformation, and the quantitative relationship between the measured electrical signals and the soil's physical and mechanical parameters remains unclear. Summary of the Invention

[0005] In view of the shortcomings of the existing technology, the present invention provides a device and method for measuring the changes in the pore structure of porous medium materials during one-dimensional consolidation process based on spectral induced polarization method.

[0006] In a first aspect, an embodiment of the present invention provides a device for measuring changes in the pore structure of a porous medium material during a one-dimensional consolidation process based on a spectral induced polarization method, the device comprising:

[0007] The sample cylinder is provided with:

[0008] a loading transition cover, wherein the loading transition cover accommodates a top electrode ring;

[0009] A soil sample body, wherein a top porous force transmission plate is provided on the upper portion of the soil sample body, and a bottom porous force transmission plate is provided on the lower portion of the soil sample body; and at least two pairs of electrode probes are provided on both sides of the soil sample body;

[0010] The bottom electrode ring is arranged below the bottom porous force transmission plate, and the bottom electrode ring is coaxial with the top electrode ring and has the same size.

[0011] In a second aspect, an embodiment of the present invention provides a method for measuring changes in the pore structure of a porous medium material during one-dimensional consolidation based on the spectral induced polarization method. The method is implemented based on the above-mentioned device for measuring changes in the pore structure of a porous medium material during one-dimensional consolidation based on the spectral induced polarization method. The method includes:

[0012] Install a device for measuring the changes in the pore structure of porous media materials during one-dimensional consolidation based on the spectral induced polarization method;

[0013] Liquid is introduced into the sample soil through the drainage hole at the bottom;

[0014] Align the center axis of the sample cylinder and the triaxial loading piston;

[0015] Set the loading conditions, set the signal acquisition frequency, load the sample soil in stages, and record the stress and deformation development of the sample soil;

[0016] When the deformation of the sample soil tends to be stable under each level of consolidation pressure, spectrum induced polarization test is carried out to collect electrical signals.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present application provides a device for measuring the changes in the pore structure of porous media materials during one-dimensional consolidation based on the spectrum induced polarization method. The device uses a loading transition cover to ensure that the spacing between the electrode rings remains unchanged during the consolidation test, and the electric field of the soil is uniformly and stably distributed. The device can effectively measure the electrical parameters of the soil within a certain height range, and then process the evolution of the macroscopic and microscopic pore characteristics of the soil under different stress levels, providing a basis for in-depth research on the coupling effect of particle compaction and structural damage in natural soft clay. The present application can be used to monitor the development of soil spectrum excitation method electrical signals during the hardening process of cement-reinforced soil, and provides a device for exploring the quantitative relationship between the mechanical characteristics and electrical properties of cement-reinforced soil. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of a device for measuring pore structure changes of porous media materials during one-dimensional consolidation based on spectral induced polarization method provided by an embodiment of the present invention;

[0020] Figure 2A schematic cross-sectional view of a loading transition cover provided by an embodiment of the present invention;

[0021] Figure 3 A side view of a loading transition cover provided by an embodiment of the present invention;

[0022] Figure 4 A schematic diagram of a top porous force transmission plate provided in an embodiment of the present invention;

[0023] Figure 5 A schematic diagram of a bottom porous force transmission plate provided in an embodiment of the present invention;

[0024] Figure 6 A schematic diagram of an electrode probe provided in an embodiment of the present invention.

[0025] In the figure, 1-piston block, 2-loading transition cover, 301-top porous force transmission plate, 302-bottom porous force transmission plate, 401-top permeable stone, 402-bottom permeable stone, 5-sample cylinder, 601-top electrode ring, 602-bottom electrode ring, 701-silicone sealing ring, 702-nylon gasket, 703-electrode probe, 704-locking bolt, 705-sieve hole, 8-bottom drainage hole, 9-top drainage hole, 10-triaxial loading piston. DETAILED DESCRIPTION

[0026] Exemplary embodiments will be described in detail herein, examples of which are illustrated in the accompanying drawings. In the following description, when referring to the drawings, like numbers in different figures represent like or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all possible embodiments consistent with the present invention. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present invention, as detailed in the appended claims.

[0027] The terms used in this invention are for the purpose of describing specific embodiments only and are not intended to limit the invention. The singular forms "a," "the," and "the" used in this invention and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise. It should also be understood that the term "and / or" as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0028] It should be understood that although the terms "first," "second," "third," etc. may be used in the present invention to describe various information, such information should not be limited to these terms. These terms are merely used to distinguish information of the same type from one another. For example, first information may also be referred to as second information, and similarly, second information may also be referred to as first information, without departing from the scope of the present invention. Depending on the context, the term "if" as used herein may be interpreted as "when," "when," or "in response to determining."

[0029] The present invention will be described in detail below with reference to the accompanying drawings. Unless there is any conflict, the features of the following embodiments and implementations may be combined with each other.

[0030] like Figure 1 As shown, an embodiment of the present invention provides a device for measuring the pore structure change of a porous medium material during a one-dimensional consolidation process based on a spectrum induced polarization method, the device comprising:

[0031] The sample tube 5 is provided with:

[0032] A loading transition cover 2, wherein the loading transition cover 2 accommodates a top electrode ring 601;

[0033] The sample soil body is provided with a top porous force transmission plate 301 on the upper part of the sample soil body, and a bottom porous force transmission plate 302 on the lower part of the sample soil body; at least two pairs of electrode probes 703 are provided on both sides of the sample soil body; the electrode probes 703 are used to measure the electrical parameters of the sample soil body within a certain height range.

[0034] The bottom electrode ring 602 is located below the bottom porous force transmission plate 302 and is coaxial with and identical in size to the top electrode ring 601. The top and bottom electrode rings 601 and 602 are connected to a spectrum induced polarization instrument to apply an alternating electric field to the soil sample.

[0035] Furthermore, in this example, the sample tube 5 is made of high-strength insulating nylon material, and the soil sample used for the consolidation test is directly made by layering and compacting in the container. The height of the container meets the space required by the electrode probe, and the height-to-diameter ratio meets the requirements of the consolidation test specification.

[0036] Furthermore, a piston block 1 is provided above the loading transition cover 2; the piston block 1 is made of high-strength acrylic material and is used to transmit axial pressure to the triaxial loading piston 10. The loading transition cover 2 is also made of high-strength acrylic material and is used to accommodate the top electrode ring 601 and transmit axial pressure.

[0037] Furthermore, the top of the sample tube 5 is provided with a plurality of top drainage holes 9, and the bottom is provided with at least one bottom drainage hole 8. During the experiment, a sodium chloride solution of a certain concentration can be introduced into the bottom drainage hole 8. Under the action of the water head pressure, the sodium chloride solution of a certain concentration flows through the bottom electrode ring 602, the bottom porous force transfer plate 302, and the bottom permeable stone 402, and flows from the bottom of the soil sample to the top, and then passes through the top permeable stone 401, the top porous force transfer plate 301, and the top electrode ring 601, and flows out from the top drainage hole 9 of the device. This process is maintained for a certain time to saturate the soil sample and the electrodes are in a sodium chloride solution environment of a certain concentration. Under the action of the alternating electric field, the electrical signal in the consolidation process of the sample soil is detected by the electrode probe 703. It should be noted that in this example, the sodium chloride solution of a certain concentration can be replaced by other salt solutions such as potassium chloride, magnesium chloride, calcium chloride, sodium carbonate, etc. Further, as Figure 2 and Figure 3 As shown, a circular groove is opened in the loading transition cover 2 for accommodating the top electrode ring 601; a pair of rectangular grooves are symmetrically opened on the side of the loading transition cover 2, and the depth of the rectangular grooves is the same as the depth of the circular groove, which is used to accommodate the top electrode ring 601 to ensure that the position of the top electrode ring 601 remains fixed during the vertical deformation of the sample soil and does not interfere with the loading transition cover 2, thereby ensuring the uniformity and consistency of the alternating electric field in the soil during the test.

[0038] Furthermore, the top electrode ring 601 is spiral-shaped (i.e., resembling a mosquito coil) in the portion located within the circular groove in the loading transition cover 2. Both ends of the top electrode ring 601 are straight, and both ends of the top electrode ring 601 are fixed to the sidewalls of the sample tube 5. A mounting groove for mounting the bottom electrode ring 602 is provided below the bottom porous force transmission plate 302 in the sample tube 5. One end of the bottom electrode ring 602 is fixed to the sidewall of the sample tube 5, and the other end is spiral-shaped (i.e., resembling a mosquito coil). The bottom electrode ring 602 and the spiral portion of the top electrode ring 601 are coaxial and have the same diameter, and are used to apply a uniform and stable alternating electric field to the soil. Furthermore, the mounting groove for the top electrode ring 601 in the loading transition cover 2 is coaxial and has the same diameter as the mounting groove for the bottom electrode ring 602 in the sample tube 5.

[0039] Furthermore, a top permeable stone 401 is provided between the sample soil and the top porous force transfer plate 301; a bottom permeable stone 402 is provided between the sample soil and the bottom porous force transfer plate 302. Due to the relatively high consolidation pressure, the top porous force transfer plate 301 and the bottom porous force transfer plate 302 are used to protect the top permeable stone 401 and the bottom permeable stone 402 while transmitting force and allowing water to pass through. This effectively avoids the damaging effects of the edges of the grooves in the loading transition cover on the permeable stone while ensuring sufficient water permeability. The bottom porous force transfer plate 302 also has a through hole, which is connected to the bottom drainage hole 8 through a drainage pipe, ensuring that a certain concentration of sodium chloride solution flows through the hole to the soil. The top permeable stone 401 and the bottom permeable stone 402 are in contact with the soil sample through filter paper, allowing water to pass through while preventing soil particles from being lost with the water flow.

[0040] Furthermore, if Figure 4 and Figure 5 As shown, the top porous force transmission plate 301 and the bottom porous force transmission plate 302 are provided with a circular hole array, wherein the radius R1 of the opening range is larger than the radius R2 of the installation groove of the bottom electrode ring 602 or the top electrode ring 601.

[0041] Furthermore, the sample tube 5 has a mounting slot for mounting the electrode probe 703; this slot is not connected to the inner wall of the sample tube, leaving a certain thickness to prevent lateral compression and deformation of the soil during the consolidation process. The bottom of the mounting slot has a plurality of sieve holes 705, which connect the electrode probe 703 to the sample soil while preventing soil loss. Specifically, a nylon mesh with a pore size smaller than the soil particle size is laid on the inner wall of the container to ensure that during the consolidation test, the electrode probe 703 is connected to the soil through a certain concentration of sodium chloride solution, while soil particles do not escape through the small holes.

[0042] Furthermore, in this embodiment, in order to avoid electrode polarization and reduce mutual influence between electrodes, the electrodes are all made of pure silver non-polarized metal material.

[0043] Furthermore, the top electrode ring 601, the bottom electrode ring 602, and the electrode probe 703 are fixed to the side wall of the sample tube 5 by a locking bolt 704. A silicone sealing ring 701 and a nylon gasket 702 are disposed within the locking bolt 704. The top electrode ring 601, the bottom electrode ring 602, and the electrode probe 703 are arranged at equal intervals.

[0044] On the other hand, an embodiment of the present invention provides a method for measuring changes in the pore structure of a porous medium material during a one-dimensional consolidation process based on the spectrum induced polarization method. The method is implemented based on the above-mentioned device for measuring changes in the pore structure of a porous medium material during a one-dimensional consolidation process based on the spectrum induced polarization method. The method includes:

[0045] Step S1: installing a device for measuring the change of the pore structure of a porous medium material during a one-dimensional consolidation process based on a spectrum induced polarization method.

[0046] Specifically, a 2mm diameter pure silver electrode rod is wound into a regular mosquito coil shape, slightly smaller than the circular groove at the bottom of the sample tube 5 that accommodates the bottom electrode ring 602. A certain length of the electrode rod is retained at the end of the electrode ring and installed into the reserved groove at the bottom of the sample tube 5. The bottom electrode ring 602 is sealed to the outer wall of the sample tube 5 using a locking bolt 704. The position of the bottom electrode ring 602 is adjusted to prevent it from contacting the sample tube 5. The bottom porous force transmission plate 302 is placed into the sample tube 5, and its position is adjusted so that the circular hole aligns with the bottom drainage hole 8 to ensure that a certain concentration of sodium chloride solution flows smoothly into the soil. Then, a bottom permeable stone 402 of appropriate size and filter paper are added.

[0047] The required soil sample mass is calculated based on the designed porosity ratio, and the soil sample to be tested is prepared in the sample cylinder 5 by the layered compaction method according to the specification requirements.

[0048] Place filter paper of appropriate size, top permeable stone 401 and top porous force transmission plate 301 in sequence on the prepared soil sample to be tested; wind a pure silver electrode rod with a diameter of 2 mm into a regular mosquito coil shape, the size of which is consistent with the bottom electrode ring 602, and retain a certain length of electrode rod at the starting and end of the top electrode ring 601, so that it passes through the reserved hole on the side wall of the sample tube 5, and the top electrode ring 601 is sealed on the outer wall of the sample tube with a locking bolt 704; place the loading transition cover 2 on the top of the soil sample to be tested, and adjust its position so that the internal circular groove matches the top electrode ring 601.

[0049] Four pure silver electrode rods of the same length and 2 mm in diameter are installed into the reserved holes of the electrode probe 703 and the electrode rods are sealed to the outer wall of the sample tube using locking bolts.

[0050] Step S2: introducing liquid into the sample soil through the bottom drainage hole 8.

[0051] Step S3 , aligning the central axis of the sample cylinder 5 and the three-axis loading piston 10 .

[0052] Step S4, setting the loading conditions, setting the signal acquisition frequency, performing graded loading on the sample soil, and recording the stress and deformation development of the sample soil.

[0053] Step S5: When the deformation of the sample soil tends to be stable under each level of consolidation pressure, a spectrum induced polarization test is performed to collect electrical signals.

[0054] Specifically, the top electrode ring 601 and the bottom electrode ring 602 are connected to an external power supply, and voltage is applied to form an alternating electric field between the two electrode rings; the spectrum excitation frequency is set to 0.01 Hz to 33.3 kHz, and the frequency spacing is logarithmic; when the soil deformation tends to be stable under each level of consolidation pressure, a spectrum excitation polarization test is performed, and the electrical signal of the soil sample to be tested within the height range near the electrode probes is obtained through two pairs of electrode probes, and the frequency domain response complex conductivity is derived. According to the test results, the real conductivity amplitude, imaginary conductivity amplitude and characteristic frequency are determined, which are correlated with the soil stress response and porosity ratio changes to analyze the evolution of the pore characteristics of the soil during the consolidation test.

[0055] In summary, the embodiment of the present invention, by setting the installation positions of the top electrode ring 601, the bottom electrode ring 602, and the electrode probe 703, can effectively measure the electrical parameters of the soil within a certain height range. The use of the loading transition cover 2 ensures that the spacing between the electrode rings remains unchanged during the consolidation test, and the electric field in the soil is uniformly and stably distributed, thereby processing and obtaining the evolution of the macro- and micro-pore characteristics of the soil under different stress levels. This testing device and method can obtain the electrical parameters of the soil using the spectrum excitation method during the consolidation test, providing a device for in-depth research on the coupling effect of particle compaction and structural failure in natural soft clay. It also provides technical support for monitoring the development of the soil spectrum excitation method electrical signal during the hardening process of cement-reinforced soil and exploring the quantitative relationship between the mechanical and electrical properties of cement-reinforced soil.

[0056] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the contents disclosed herein. This application is intended to cover any variations, uses, or adaptations of the present application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The description and examples are to be considered as exemplary only, and the true scope and spirit of the present application are indicated by the following claims.

[0057] It should be understood that the present application is not limited to the exact structures described above and shown in the drawings, and that various modifications and changes may be made without departing from the scope thereof. The scope of the present application is limited only by the appended claims.

Claims

1. A device for measuring the pore structure change of porous medium materials during one-dimensional consolidation based on spectral induced polarization method, characterized in that: The device comprises: A sample tube (5), wherein the sample tube (5) is provided with: A loading transition cover (2), wherein the loading transition cover (2) accommodates a top electrode ring (601); A sample soil body, wherein a top porous force transmission plate (301) is arranged on the upper part of the sample soil body, and a bottom porous force transmission plate (302) is arranged on the lower part of the sample soil body; at least two pairs of electrode probes (703) are arranged on both sides of the sample soil body; The bottom electrode ring (602) is arranged below the bottom porous force transmission plate (302), and the bottom electrode ring (602) is coaxial with the top electrode ring (601) and has the same size.

2. The device for measuring the pore structure change of porous medium materials during one-dimensional consolidation process based on spectrum induced polarization method according to claim 1, characterized in that: A piston block (1) is arranged above the loading transition cover (2), and the piston block (1) is used to transmit axial pressure to the triaxial loading piston (10).

3. The device for measuring the pore structure change of porous medium materials during one-dimensional consolidation process based on spectrum induced polarization method according to claim 1, characterized in that: The top of the sample tube (5) is provided with a plurality of top drainage holes (9), and the bottom is provided with at least one bottom drainage hole (8).

4. The device for measuring the pore structure change of porous medium materials during one-dimensional consolidation process based on spectrum induced polarization method according to claim 1, characterized in that: The loading transition cover (2) has a circular groove formed therein for accommodating the top electrode ring (601); a pair of rectangular grooves are symmetrically formed on the sides of the loading transition cover (2), and the depth of the rectangular grooves is the same as that of the circular groove.

5. The device for measuring the pore structure change of porous medium materials during one-dimensional consolidation process based on spectrum induced polarization method according to claim 4, characterized in that: The top electrode ring (601) is spiral-shaped at the portion located in the circular groove in the loading transition cover (2), and the two ends of the top electrode ring (601) are straight-line-shaped. The two ends of the top electrode ring (601) are fixed on the side wall of the sample tube (5).

6. The device for measuring the pore structure change of porous medium materials during one-dimensional consolidation process based on spectrum induced polarization method according to claim 1, characterized in that: A mounting groove for mounting a bottom electrode ring (602) is provided below the bottom porous force transmission plate (302) in the sample tube (5). One end of the bottom electrode ring (602) is fixed on the side wall of the sample tube (5), and the other end is spiral-shaped.

7. The device for measuring the pore structure change of porous medium materials during one-dimensional consolidation process based on spectrum induced polarization method according to claim 1, characterized in that: A top permeable stone (401) is arranged between the sample soil and the top porous force transmission plate (301); and a bottom permeable stone (402) is arranged between the sample soil and the bottom porous force transmission plate (302).

8. The device for measuring the pore structure change of porous medium materials during one-dimensional consolidation process based on spectrum induced polarization method according to claim 1, characterized in that: The top porous force transmission plate (301) and the bottom porous force transmission plate (302) are provided with a circular hole array, wherein the radius of the hole opening range is greater than the radius of the installation groove of the bottom electrode ring (602) or the top electrode ring (601).

9. The device for measuring the pore structure change of porous medium materials during one-dimensional consolidation process based on spectrum induced polarization method according to claim 1, characterized in that: The sample tube (5) is provided with an installation groove for installing an electrode probe (703); a plurality of sieve holes (705) are provided on the bottom surface of the installation groove, so that the electrode probe (703) is connected to the sample soil while ensuring that the sample soil will not be lost.

10. A method for measuring the pore structure change of porous medium materials during one-dimensional consolidation based on spectral induced polarization method, characterized in that: The device for measuring the change of pore structure of porous medium material during one-dimensional consolidation based on the spectrum induced polarization method according to any one of claims 1 to 9 is implemented, and the method comprises: Install a device for measuring the pore structure changes of porous media materials during one-dimensional consolidation based on the spectrum induced polarization method; Liquid is introduced into the sample soil through the drainage hole (8) at the bottom; Aligning the central axis of the sample cylinder (5) and the three-axis loading piston (10); Set the loading conditions, set the signal acquisition frequency, load the sample soil in stages, and record the stress and deformation development of the sample soil; When the deformation of the sample soil tends to be stable under each level of consolidation pressure, the spectrum induced polarization test is carried out to collect electrical signals.

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