Coal rock sample volume strain measuring device and measuring method

Abstract

The invention discloses a coal rock sample volume strain measuring device which comprises a rotary table, a sample clamping unit, an axial pressure loading pipeline and a CT ray source. Wherein the sample clamping unit is arranged on the rotary table, the sample clamping unit comprises a transparent measuring cylinder, an upper bearing cylinder, a lower bearing cylinder and a loading cylinder, the upper bearing cylinder and the lower bearing cylinder are arranged at the two ends of the inner side of the measuring cylinder respectively, and the loading cylinder is arranged on the upper side of the lower bearing cylinder in a sliding mode; a gap is reserved between the loading cylinder and the lower bearing cylinder in a sliding mode, a cavity used for containing a sample is formed between the loading cylinder and the upper bearing cylinder, and scales are further arranged on the side wall of the measuring cylinder. The outlet end of the axial pressure loading pipeline penetrates through the lower bearing cylinder and then faces the gap, and the inlet end of the axial pressure loading pipeline is connected with a pressure source; the CT ray source is arranged on one side of the sample clamping unit; and the flat panel detector is arranged on the other side of the sample clamping unit.

Description

Technical Field

[0001] The present invention belongs to the technical field of volume strain measurement of coal and rock samples, and in particular relates to a device and a method for measuring volume strain of coal and rock samples. Background Art

[0002] Volumetric strain refers to the ratio of the volume change of an object under the action of force to its original volume. This physical quantity has important academic value in the fields of materials science, rock mechanics, geological engineering, etc. Volumetric strain is closely related to the elastic modulus and Poisson's ratio of the material. By measuring the volumetric strain, the elastic modulus and Poisson's ratio of the material can be determined more accurately, thereby better understanding the mechanical properties of the material. Volumetric strain can help study the volume change of the material during plastic deformation, which is very important for understanding the plasticity and fracture behavior of the material. In addition, volumetric strain is also of great value in studying the compression and expansion characteristics of coal and rock samples and evaluating the bearing capacity and sample permeability.

[0003] The existing coal rock sample volume strain measurement device includes a press, a strain gauge attached to the measured object, and a data acquisition system collection unit and a data analysis unit connected to the strain gauge in sequence.

[0004] When using the above-mentioned measuring device to measure the volume strain of coal rock samples, the coal rock samples are first processed into the required size and shape, and transverse strain gauges and axial strain gauges are respectively installed at specific positions of the samples. After the samples are placed in the base or mold of the press, pressure is started to be loaded. During the pressure loading process, the transverse strain gauge and the axial strain gauge can respectively record the transverse strain and axial strain of the sample. After these data are collected and transmitted to the data analysis unit through the data acquisition system, the data analysis unit simply multiplies the axial strain and the transverse strain to calculate the theoretical volume change when calculating the volume strain. This calculation method is only applicable to the volume strain calculation of linear elastic materials (i.e., the stress and strain are in a linear relationship within the elastic range). For coal rock samples, the stress and strain relationship is often not completely linear, especially at higher stress levels, the coal rock may exhibit plastic deformation. Therefore, there must be measurement errors when the above-mentioned device measures the volume strain of coal rock samples. Summary of the invention

[0005] The purpose of the present invention is to provide a method for quantitatively measuring the volume strain of coal rock samples, which solves the problem of measurement error when the existing measuring device measures the volume strain of coal rock samples.

[0006] The technical solution adopted by the present invention is a method for quantitatively measuring the volume strain of coal rock samples, comprising:

[0007] Turntable;

[0008] The sample clamping unit is arranged on the turntable, and the sample clamping unit comprises a transparent measuring cylinder and a loading cylinder. The loading cylinder is slidably arranged inside the measuring cylinder and can slide along the axial direction of the measuring cylinder. A cavity for placing the sample to be measured is formed on the upper side of the loading cylinder, and a scale is also arranged on the side wall of the measuring cylinder.

[0009] An axial pressure loading pipeline, whose liquid outlet end passes through the lower side wall of the measuring cylinder and faces the bottom of the loading cylinder, and whose liquid inlet end is connected to the first external pressure source;

[0010] A CT ray source is arranged on one side of the sample holding unit;

[0011] A flat panel detector is arranged at the other side of the sample holding unit, and scans the sample to be tested through a CT ray source and obtains a two-dimensional cross-sectional image of the sample to be tested at each stage on the flat panel detector;

[0012] The computer is connected to the flat panel detector, and the computer can perform three-dimensional reconstruction on the obtained two-dimensional cross-sectional image, and finally obtain the volume strain curve of the measured sample.

[0013] Preferably, the measuring device further comprises a pore pressure loading pipeline, the liquid outlet of the pore pressure loading pipeline sequentially passes through the side wall of the measuring tube and the loading cylinder and then faces the bottom of the cavity, and the liquid inlet of the pore pressure loading pipeline is connected to the second external pressure source.

[0014] Preferably, the measuring device also includes a confining pressure loading pipeline, which includes a liquid inlet pipeline and a liquid outlet pipeline connected to the interior of the measuring cylinder, the liquid outlet end of the liquid inlet pipeline points to the upper end of the inner side of the measuring cylinder, the liquid inlet end of the liquid inlet pipeline is connected to a third external pressure source, the liquid inlet end of the liquid outlet pipeline points to the lower end of the inner side of the measuring cylinder, and the liquid outlet end of the liquid outlet pipeline is located on the outside of the measuring cylinder.

[0015] Preferably, an upper load-bearing cylinder and a lower load-bearing cylinder are respectively provided in the measuring cylinder. The upper load-bearing cylinder is located on the upper side of the loading cylinder and a cavity is formed between the two. The lower load-bearing cylinder is located on the lower side of the loading cylinder and a gap is left between the two. The liquid outlet end of the axial pressure loading pipeline passes through the side wall of the measuring cylinder and the lower load-bearing cylinder in sequence and then points to the gap.

[0016] Preferably, a hollow base is also provided at the lower end of the measuring cylinder, and the lower end of the measuring cylinder passes through the upper side wall of the hollow base. A lower sealing plug capable of sealing the lower end of the measuring cylinder is also provided in the hollow base, and an upper sealing plug capable of sealing the upper end of the measuring cylinder is also provided on the side of the upper supporting cylinder away from the cavity.

[0017] Preferably, the liquid outlet end of the liquid inlet pipeline points to the side wall of the upper sealing plug, and the liquid inlet end of the liquid outlet pipeline points to the loading cylinder.

[0018] Preferably, the hollow base is arranged on a turntable, a clamp is also arranged on the turntable, and a clamping cylinder for facilitating clamping by the clamp is also arranged at the bottom of the hollow base.

[0019] Another technical solution disclosed in the present invention is a method for measuring volume strain of a coal rock sample, based on the above-mentioned device for measuring volume strain of a coal rock sample, and specifically comprising the following steps:

[0020] Fixing the sample holding unit to the rotating table, and placing the coal and rock sample to be tested in the cavity;

[0021] Axial pressure is applied to the coal and rock samples through an axial pressure loading pipeline, and a CT ray source is activated to perform CT scanning in stages while the pressure is applied, so that two-dimensional tomographic images of each stage are obtained on a flat panel detector;

[0022] The two-dimensional tomographic images obtained at each stage are reconstructed into a three-dimensional model by computer;

[0023] Delimiting the boundaries of the reconstructed three-dimensional model using sample feature points and scales, and obtaining voxel points at each stage;

[0024] The volume of each stage is calculated based on the voxel points combined with the resolution;

[0025] Plot the stress and volumetric strain curves.

[0026] While loading the axial pressure, the pore pressure can also be loaded onto the sample through the pore pressure loading pipeline, or the confining pressure can be loaded onto the surrounding of the sample through the confining pressure loading pipeline.

[0027] The beneficial effects of the present invention are:

[0028] The present invention provides a coal rock sample volume strain measuring device. When measuring the volume strain of the coal rock sample, first, the sample clamping unit is fixed to the turntable, and the coal rock sample to be measured is placed in the cavity, and then the axial pressure is loaded on the coal rock sample through the axial pressure loading pipeline. While loading the pressure, the CT ray source is enabled to perform CT scanning in stages. During the scanning, a two-dimensional tomographic image is obtained on the flat panel detector, and then a three-dimensional model is reconstructed for the two-dimensional tomographic image obtained in each stage by a computer, and several sample feature points are taken on the reconstructed three-dimensional model. Then, the boundaries of the reconstructed three-dimensional model are defined by using the sample feature points and the scale, and the voxel points of each stage are obtained. Then, the volume of each stage is calculated based on the voxel points combined with the resolution, and finally, the stress and volume strain curve is drawn. In summary, when the volume strain measuring device disclosed in the present invention measures the volume strain of the coal rock sample, the actual volume and volume change of each stage when the coal salt sample is deformed under pressure can be obtained, and the volume can be accurately calibrated even when the pressure is too large and the coal rock sample is plastically deformed, thereby avoiding the problem of error in the measurement of the current measuring device. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of a coal rock sample volume strain measurement device of the present invention;

[0030] Figure 2 It is a top view of a device for measuring volume strain of coal and rock samples according to the present invention;

[0031] Figure 3 It is a schematic diagram of a sample clamping unit on a coal rock sample volume strain measurement device of the present invention;

[0032] Figure 4 Stress and volumetric strain curves after volume measurement using this method.

[0033] In the figure, 1. turntable; 2. measuring cylinder; 3. upper bearing cylinder; 4. lower bearing cylinder; 5. loading cylinder; 6. pore pressure loading pipeline; 7. confining pressure loading pipeline; 8. axial pressure loading pipeline; 9. liquid inlet pipeline; 10. liquid outlet pipeline; 11. hollow base; 12. lower sealing plug; 13. upper sealing plug; 14. clamping cylinder; 15. CT ray source; 16. flat panel detector. DETAILED DESCRIPTION

[0034] The present invention is described in detail below in conjunction with the accompanying drawings and specific implementation methods. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection solution of the present invention.

[0035] Volumetric strain refers to the ratio of the volume change of an object under the action of force to its original volume. This physical quantity has important academic value in the fields of materials science, rock mechanics, geological engineering, etc. Volumetric strain is closely related to the elastic modulus and Poisson's ratio of the material. By measuring the volumetric strain, the elastic modulus and Poisson's ratio of the material can be determined more accurately, thereby better understanding the mechanical properties of the material. Volumetric strain can help study the volume change of the material during plastic deformation, which is very important for understanding the plasticity and fracture behavior of the material. In addition, volumetric strain is also of great value in studying the compression and expansion characteristics of coal and rock samples and evaluating the bearing capacity and sample permeability.

[0036] The existing coal rock sample volume strain measurement device includes a press, a strain gauge attached to the measured object, and a data acquisition system collection unit and a data analysis unit connected to the strain gauge in sequence.

[0037] When using the above-mentioned measuring device to measure the volume strain of coal rock samples, the coal rock samples are first processed into the required size and shape, and transverse strain gauges and axial strain gauges are respectively installed at specific positions of the samples. After the samples are placed in the base or mold of the press, pressure is started to be loaded. During the pressure loading process, the transverse strain gauge and the axial strain gauge can respectively record the transverse strain and axial strain of the sample. After these data are collected and transmitted to the data analysis unit through the data acquisition system, the data analysis unit simply multiplies the axial strain and the transverse strain to calculate the theoretical volume change when calculating the volume strain. This calculation method is only applicable to the volume strain calculation of linear elastic materials (i.e., the stress and strain are in a linear relationship within the elastic range). For coal rock samples, the stress and strain relationship is often not completely linear. Especially at higher stress levels, the coal rock may show plastic deformation and damage accumulation. Therefore, there must be measurement errors when the above-mentioned device measures the volume strain of coal rock samples.

[0038] The present invention discloses a coal rock sample volume strain measurement device, such as Figure 1-3 As shown, it includes: a turntable 1, a sample clamping unit, an axial pressure loading pipeline 8, a CT ray source 15, a flat panel detector 16 and a computer; wherein the sample clamping unit is arranged on the turntable 1, and the sample clamping unit includes a transparent measuring cylinder 2, an upper bearing cylinder 3, a lower bearing cylinder 4 and a loading cylinder 5, the upper bearing cylinder 3 and the lower bearing cylinder 4 are respectively arranged at the two ends of the inner side of the measuring cylinder 2, the loading cylinder 5 is slidably arranged between the lower bearing cylinder 4 and the upper bearing cylinder 3, the loading cylinder 5 can slide along the axial direction of the measuring cylinder 2, a cavity for placing the sample is formed between the loading cylinder 5 and the upper bearing cylinder 3, and the loading cylinder 5 and the lower bearing cylinder 4, and a scale is also provided on the side wall of the measuring cylinder 2; the liquid outlet end of the axial pressure loading pipeline 8 passes through the lower side wall of the measuring cylinder 2 and faces the bottom of the loading cylinder 5, and the liquid inlet end thereof is connected to the first external pressure source; the CT ray source 15 is arranged on one side of the sample clamping unit; the flat panel detector 16 is arranged on the other side of the sample clamping unit; the sample to be tested is scanned by the CT ray source 15 and a two-dimensional cross-sectional view of the sample to be tested at each stage is obtained on the flat panel detector 16; a computer is connected to the flat panel detector 16, and the computer can perform three-dimensional reconstruction on the obtained two-dimensional cross-sectional view, and finally obtain the volume strain curve of the sample to be tested.

[0039] The upper bearing cylinder 3 and the lower bearing cylinder 4 provided therein can ensure the sealing of the interior of the entire measuring cylinder 2, thereby ensuring the accuracy of its measurement.

[0040] When the volume strain measuring device for coal rock samples disclosed in the present invention measures the volume strain of coal rock samples, first, the sample clamping unit is fixed to the turntable 1, and the coal rock sample to be measured is placed in the cavity, and then the axial pressure is applied to the coal rock sample through the axial pressure loading pipeline 8, and the CT ray source 15 is enabled to perform CT scanning in stages while the pressure is loaded; a two-dimensional tomographic image is obtained on the flat panel detector 16 during scanning; then, a three-dimensional model is reconstructed for the two-dimensional tomographic image obtained in each stage by a computer, and then the boundaries of the reconstructed three-dimensional model are demarcated using the sample feature points and scales, and the voxel points of each stage are obtained at the same time; then the volume of each stage is calculated based on the voxel points combined with the resolution; finally, the stress and volume strain curve is drawn. In summary, when the volume strain measuring device disclosed in the present invention measures the volume strain of coal rock samples, the actual volume and volume change of each stage when the coal salt sample is deformed under pressure can be obtained, and the volume can be accurately calibrated even when the pressure is too large and the coal rock sample undergoes plastic deformation, thereby avoiding the problem of errors in the current measurement device during measurement.

[0041] Furthermore, the measuring device disclosed in the present invention includes a pore pressure loading pipeline 6, the liquid outlet end of the pore pressure loading pipeline 6 passes through the side wall of the measuring tube 2, the lower bearing cylinder 4 and the loading cylinder 5 in sequence and then faces the bottom of the cavity, and the liquid inlet end of the pore pressure loading pipeline 6 is connected to a second external pressure source. The pore pressure loading pipeline 6 is set to meet the requirements of various experimental conditions, such as gas-bearing oil shale, high-gas coal seams, etc., the internal pores and fracture structures contain high-pressure fluids, and the pore pressure is used to simulate similar environments.

[0042] The measuring device also includes a confining pressure loading pipeline 7, which includes a liquid inlet pipeline 9 and a liquid outlet pipeline 10 connected to the measuring cylinder 2. The liquid outlet end of the liquid inlet pipeline 9 points to the upper end of the inner side of the measuring cylinder 2, and the liquid inlet end of the liquid inlet pipeline 9 is connected to a third external pressure source. The liquid inlet end of the liquid outlet pipeline 10 points to the lower end of the inner side of the measuring cylinder 2, and the liquid outlet end of the liquid outlet pipeline 10 is located outside the measuring cylinder 2. The confining pressure loading pipeline 7 is set to simulate the three-dimensional stress state of actual rock formations and coal seams. Therefore, in addition to the uniaxial environment, a confining pressure environment is also set.

[0043] Furthermore, in order to ensure the sealing of the entire measuring device, a hollow base 11 is also provided at the lower end of the measuring tube 2 disclosed in the present embodiment, and the lower end of the measuring tube 2 passes through the upper side wall of the hollow base 11, and a lower sealing plug 12 capable of sealing the lower end of the measuring tube 2 is also provided in the hollow base 11, and an upper sealing plug 13 capable of sealing the upper end of the measuring tube 2 is also provided on the side of the upper supporting cylinder 3 away from the cavity; therefore, the two ends of the measuring tube 2 can be completely sealed by the lower sealing plug 12 and the upper sealing plug 13, so when pressure is applied, the pressure completely acts on the coal and rock samples to be measured, which is beneficial to reduce the error of the measurement results.

[0044] Furthermore, the inner end of the liquid inlet pipeline 9 disclosed in this embodiment points to the side wall of the upper sealing plug 13, and the inner end of the liquid outlet pipeline 10 points to the loading cylinder 5. This is to ensure that after the pressure is loaded through the confining pressure loading pipeline 7, the confining pressure formed can fully cover the sample under test. Because the upper sealing plug 13 and the loading cylinder 5 themselves are supported by metal materials, they will not affect the loading cylinder 5 and the upper sealing plug 13 themselves.

[0045] In order to conveniently clamp the hollow base 11 during measurement, a clamp is also provided on the turntable 1 disclosed in the present embodiment, and a clamping cylinder 14 is also provided at the bottom of the hollow base 11 for convenient clamping by the clamp. After the clamp clamps the clamping cylinder 14, the hollow base 11 and the sample clamping unit thereon can be driven to rotate, so that normal measurement can be performed.

[0046] A method for measuring volume strain of a coal rock sample, based on the above-mentioned device for measuring volume strain of a coal rock sample, is characterized in that it specifically comprises the following steps:

[0047] Placing the coal and rock samples in the cavity, and fixing the sample clamping unit to the turntable 1;

[0048] Applying axial pressure to the coal and rock samples through the axial pressure loading pipeline 8, while applying pressure, activating the CT ray source 15 to perform CT scanning in stages;

[0049] Reconstruct a three-dimensional model based on the image information obtained at each stage;

[0050] Delimiting the boundaries of the reconstructed three-dimensional model using sample feature points and scales, and obtaining voxel points at each stage;

[0051] Calculating the volume of each stage according to the voxel points combined with the resolution;

[0052] Plot the stress and volumetric strain curves.

[0053] While loading the axial pressure, the pore pressure can also be loaded onto the sample through the pore pressure loading pipeline 6 , or the confining pressure can be loaded onto the periphery of the sample through the confining pressure loading pipeline 6 .

[0054] High reliability. Especially for samples with various anisotropies, high-precision resolution and efficient regional segmentation methods (accurate delineation of the measurement space boundary) ensure the reliability of the volume strain results; third, it is helpful for subsequent research. The accurate determination of volume strain is of great value for the study and improvement of mechanical properties, instability failure, compression and expansion characteristics, permeability, deformation characteristics of surrounding rocks in underground engineering, and constitutive models of solid materials. For example, the study of coal and gas outbursts requires accurate determination of the volume expansion of coal samples. The traditional method of measuring volume strain is difficult to accurately determine the turning point from contraction to expansion. This method can achieve accurate determination, which is conducive to related research.

[0055] The present invention discloses a method for quantitatively measuring the volume strain of coal and rock samples. CT scanning can accurately calibrate the internal structure of the sample in a non-destructive manner with high resolution. The present invention utilizes the advantages of the CT scanning system to achieve quantitative characterization of the deformation of the sample during the scanning process of the sample at different loading stages, thereby avoiding the problem of errors in measurement by current measuring devices.

[0056] The embodiments described above are only preferred specific implementation methods of the present invention, and the protection scope of the present invention is not limited thereto. Any simple changes or equivalent replacements of the technical solutions that can be obviously obtained by any technician familiar with the field within the technical scope disclosed in the present invention belong to the protection scope of the present invention.

Claims

1. A coal rock sample volume strain measurement device, characterized in that: include: Turntable (1); A sample clamping unit is arranged on the turntable (1), the sample clamping unit comprises a transparent measuring cylinder (2) and a loading cylinder (5), the loading cylinder (5) is slidably arranged inside the measuring cylinder (2) and can slide along the axial direction of the measuring cylinder (2), a cavity for placing a sample to be measured is formed on the upper side of the loading cylinder (5), and a scale is also arranged on the side wall of the measuring cylinder (2); An axial pressure loading pipeline (8), the liquid outlet of which passes through the lower side wall of the measuring cylinder (2) and faces the bottom of the loading cylinder (5), and the liquid inlet of which is connected to a first external pressure source; A CT ray source (15) is arranged on one side of the sample holding unit; A flat panel detector (16) is arranged on the other side of the sample clamping unit, and scans the sample to be tested through the CT ray source (15) and obtains a two-dimensional cross-sectional image of the sample to be tested at each stage on the flat panel detector (16); A computer is connected to the flat panel detector (16), and the computer can perform three-dimensional reconstruction on the obtained two-dimensional cross-sectional image and finally obtain a volume strain curve of the measured sample.

2. A coal rock sample volume strain measurement device according to claim 1, characterized in that: The measuring device further comprises a pore pressure loading pipeline (6), the liquid outlet end of the pore pressure loading pipeline (6) sequentially passes through the side wall of the measuring tube (2) and the loading cylinder (5) and then faces the bottom of the cavity, and the liquid inlet end of the pore pressure loading pipeline (6) is connected to a second external pressure source.

3. A coal rock sample volume strain measurement device according to claim 2, characterized in that: The measuring device further comprises a confining pressure loading pipeline (7), wherein the confining pressure loading pipeline (7) comprises a liquid inlet pipeline (9) and a liquid outlet pipeline (10) which are in communication with the interior of the measuring cylinder (2), wherein the liquid outlet end of the liquid inlet pipeline (9) points to the upper end of the inner side of the measuring cylinder (2), the liquid inlet end of the liquid inlet pipeline (9) is connected to a third external pressure source, the liquid inlet end of the liquid outlet pipeline (10) points to the lower end of the inner side of the measuring cylinder (2), and the liquid outlet end of the liquid outlet pipeline (10) is located outside the measuring cylinder (2).

4. A coal rock sample volume strain measurement device according to claim 3, characterized in that: An upper bearing cylinder (3) and a lower bearing cylinder (4) are also provided in the measuring cylinder (2), respectively; the upper bearing cylinder (3) is located on the upper side of the loading cylinder (5) and the cavity is formed therebetween; the lower bearing cylinder (4) is located on the lower side of the loading cylinder (5) and a gap is left therebetween; the liquid outlet end of the axial pressure loading pipeline (8) passes through the side wall of the measuring cylinder (2) and the lower bearing cylinder (4) in sequence and then points to the gap.

5. A coal rock sample volume strain measurement device according to claim 4, characterized in that: The lower end of the measuring cylinder (2) is also provided with a hollow base (11), the lower end of the measuring cylinder (2) passes through the upper side wall of the hollow base (11), a lower sealing plug (12) capable of sealing the lower end of the measuring cylinder (2) is also provided in the hollow base (11), and an upper sealing plug (13) capable of sealing the upper end of the measuring cylinder (2) is also provided on the side of the upper bearing cylinder (3) away from the cavity.

6. A coal rock sample volume strain measurement device according to claim 5, characterized in that: The liquid outlet end of the liquid inlet pipeline (9) points to the side wall of the upper sealing plug (13), and the liquid inlet end of the liquid outlet pipeline (10) points to the loading cylinder (5).

7. The device for measuring volume strain of coal and rock samples according to claim 5, characterized in that: The hollow base (11) is arranged on a turntable (1), a clamp is also arranged on the turntable (1), and a clamping cylinder (14) is also arranged at the bottom of the hollow base (11) for facilitating clamping by the clamp.

8. A method for measuring volume strain of a coal rock sample, based on the device for measuring volume strain of a coal rock sample as claimed in claim 3, characterized in that: The specific steps include: The sample clamping unit is fixed to the turntable (1), and the coal and rock sample to be tested is placed in the cavity; The axial pressure is applied to the coal rock sample through the axial pressure loading pipeline (8), and while the pressure is applied, the CT ray source (15) is activated to perform CT scanning in stages, so that two-dimensional tomographic images of each stage are obtained on the flat panel detector (16); The two-dimensional tomographic images obtained at each stage are reconstructed into a three-dimensional model by computer; Delimiting the boundaries of the reconstructed three-dimensional model using sample feature points and scales, and obtaining voxel points at each stage; Calculate the volume of each stage according to the voxel points combined with the resolution; Plot the stress and volumetric strain curves.

9. A method for measuring volume strain of coal rock samples according to claim 8, characterized in that: While loading the axial pressure, the pore pressure can also be loaded onto the sample through the pore pressure loading pipeline (6), and / or the confining pressure can be loaded onto the periphery of the sample through the confining pressure loading pipeline (7).

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