CN111487128A - Device and method for describing compression shear damage of concrete-surrounding rock bonding surface - Google Patents
Device and method for describing compression shear damage of concrete-surrounding rock bonding surface Download PDFInfo
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Abstract
The invention discloses a device and a method for describing compression shear damage of a concrete-surrounding rock bonding surface, wherein the device comprises a concrete-surrounding rock test piece, a crack opening displacement meter and an axial extensometer; the concrete-surrounding rock test piece comprises a rock sample and sprayed concrete which are fixedly connected, the connecting surface of the rock sample and the sprayed concrete is an inclined plane, and the crack opening displacement meter is arranged at the connecting surface; and axial extensometers chucks are arranged at two ends of the concrete-surrounding rock test piece, and a plurality of axial extensometers are arranged between the two axial extensometer chucks. The method can be used for analyzing the strain rate effect of axial strain and shear displacement of the concrete-surrounding rock test piece, the mechanism of compression-shear damage, and the positioning and quantitative characterization of the compression-shear damage.
Description
Technical Field
The invention belongs to the technical field of concrete structures and materials, and particularly relates to a device and a method for describing compression-shear damage of a concrete-surrounding rock bonding surface.
Background
In the excavation process of the water delivery tunnel, in order to maintain the stability of surrounding rocks, a shotcrete supporting structure needs to be applied in time after excavation. The instability of the surrounding rock structure under the action of higher ground stress enables the sprayed concrete to be in a complex stress state after being bonded with the surrounding rock. In actual engineering, due to the limitation of a jet construction process, a concrete-surrounding rock bonding interface is often the weakest position, interface damage and damage are easy to occur under the action of dynamic loads of various frequencies of geological disasters, and due to the action of ground stress, the tunnel surrounding rock and jet concrete interface is often subjected to the combined action of compression stress and shearing stress. Therefore, the research on the damage mechanism, the damage position, the quantitative relation between the load and the damage value and the like of the concrete-surrounding rock bonding surface of the water delivery tunnel under the action of the compression-shear load is particularly important for evaluating the performance of the primary support structure of the water delivery tunnel for resisting geological disasters.
However, the present testing apparatus generally performs a direct shear test to test the shear strength while applying a certain axial compressive stress. The testing device and the method have the defects that the pressure stress and the shear stress can not be tested according to the change of the same strain rate, the cracking damage position in the loading process can not be positioned, and the damage mechanism of the water delivery tunnel concrete or the surrounding rock under the action of pressure shear loads with different strain rates is not analyzed.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provides a device and a method for describing the compression-shear damage of a concrete-surrounding rock bonding surface, which are used for analyzing the axial strain of a concrete-surrounding rock test piece, the strain rate effect of shear displacement, the compression-shear damage mechanism and the positioning and quantitative representation of the compression-shear damage.
The invention provides the following technical scheme:
a device for describing compression shear damage of a concrete-surrounding rock bonding surface comprises a concrete-surrounding rock test piece, a crack opening displacement meter and an axial extensometer;
the concrete-surrounding rock test piece comprises a rock sample and sprayed concrete which are fixedly connected, the connecting surface of the rock sample and the sprayed concrete is an inclined plane, and the crack opening displacement meter is arranged at the connecting surface;
and axial extensometers chucks are arranged at two ends of the concrete-surrounding rock test piece, and a plurality of axial extensometers are arranged between the two axial extensometer chucks.
Preferably, the test piece further comprises a steel hoop installed on the surface of the concrete-surrounding rock test piece, the steel hoop is provided with uniformly distributed fixed holes, and an acoustic emission probe is installed in each fixed hole.
Preferably, the acoustic emission probe is compacted in the fixed hole by a sensor cap.
Preferably, the steel hoop comprises a horizontal steel hoop installed in parallel with a horizontal plane and an oblique steel hoop installed in parallel with a connection surface of the rock sample and the shotcrete.
Preferably, the open end of the steel hoop is fixedly connected with a screw rod with a spring and a nut.
Preferably, the concrete-surrounding rock test piece is cylindrical and has a diameter-height ratio of 1: 2, the slope degree of the connecting surface of the rock sample and the sprayed concrete is 15-60 degrees.
Preferably, steel discs are arranged at two ends of the concrete-surrounding rock test piece, and the axial extensometer chuck is mounted on the steel discs; the number of the axial extensometers is 3 and the axial extensometers are uniformly arranged between the clamping heads of the axial extensometers.
Preferably, the crack opening displacement meter is arranged on a displacement meter chuck, and the displacement meter chuck comprises two displacement meter clamping pieces which are respectively arranged on the rock sample and the sprayed concrete; the displacement meter comprises a rock sample and a sprayed concrete connection surface, wherein the number of the displacement meter chucks is two, and the displacement meter chucks are respectively arranged at the lowest position and the highest position of the rock sample and the sprayed concrete connection surface.
A method for describing compression shear damage of a concrete-surrounding rock bonding surface, comprising the following steps:
manufacturing a rock sample with an inclined end face, and spraying sprayed concrete with the same thickness as the rock sample on the inclined face to obtain a concrete-surrounding rock test piece;
carrying out high-precision CT (computed tomography) test on the concrete-surrounding rock test piece before loading and recording interface fault data;
installing crack opening displacement meters at the connecting surfaces of the rock sample and the sprayed concrete, installing axial extensometer chucks at two ends of the concrete-surrounding rock test piece, and then installing a plurality of axial extensometers between the two axial extensometer chucks;
the method comprises the following steps of carrying out compression shear loading on a concrete-surrounding rock test piece by adopting an MTS testing machine, controlling the loading rate by using an axial extensometer to obtain a stress-strain curve, monitoring the shear displacement of the connecting surface of a rock sample and sprayed concrete in the loading process by using a crack opening displacement meter, carrying out high-precision CT (computed tomography) testing at different compression shear loading stages and recording interface fault data;
and analyzing the strain rate effects of the axial strain and the shear displacement of the concrete-surrounding rock test piece according to the measured relation among the axial strain, the shear displacement and the load, and performing fine nondestructive reconstruction on the internal structure of the test piece according to high-precision CT test data.
A method for describing compression shear damage of a concrete-surrounding rock bonding surface, comprising the following steps:
manufacturing a rock sample with an inclined end face, and spraying sprayed concrete with the same thickness as the rock sample on the inclined face to obtain a concrete-surrounding rock test piece;
installing crack opening displacement meters at the connecting surfaces of the rock sample and the sprayed concrete, installing axial extensometer chucks at two ends of the concrete-surrounding rock test piece, then installing a plurality of axial extensometers between the two axial extensometer chucks, installing a steel hoop, and installing an acoustic emission probe in a fixed hole;
the method comprises the following steps of (1) carrying out compression shear loading on a concrete-surrounding rock test piece by adopting an MTS testing machine, controlling the loading rate by using an axial extensometer to obtain a stress-strain curve, monitoring the shear displacement of a connecting surface of a rock sample and sprayed concrete in the loading process by using a crack opening displacement meter, and collecting an acoustic emission source signal in the compression shear failure process by using an acoustic emission probe;
and analyzing the strain rate effects of the axial strain and the shear displacement of the concrete-surrounding rock test piece according to the measured relationship among the axial strain, the shear displacement and the load, positioning the spatial position of an acoustic emission source according to the collected acoustic emission source signal in the compression-shear damage process, and analyzing the compression-shear damage value.
Compared with the prior art, the invention has the beneficial effects that:
(1) the device for describing the compression-shear damage of the concrete-surrounding rock bonding surface is characterized in that a rock sample and sprayed concrete are connected to form a concrete-surrounding rock test piece for simulating the real working condition in a water delivery tunnel, when an MTS (maximum temperature stress) testing machine is used for carrying out compression-shear loading on the concrete-surrounding rock test piece, the loading rate is controlled through an axial extensometer, and the shear displacement of the connecting surface of the rock sample and the sprayed concrete in the loading process is monitored through a crack opening displacement meter, so that the strain rate effects of the axial strain and the shear displacement of the concrete-surrounding rock test piece are analyzed;
(2) the method for describing the compression-shear damage of the concrete-surrounding rock bonding surface provided by the invention adopts the high-precision CT scanning to scan the concrete-surrounding rock test piece before and after loading, and carries out fine nondestructive reconstruction on the internal structure of the test piece, thereby analyzing the compression-shear damage mechanism of the concrete-surrounding rock bonding surface;
(3) according to the device and the method for describing the compression-shear damage of the concrete-surrounding rock bonding surface, the acoustic emission probes are installed through the steel hoop and the fixed cavities on the steel hoop, the relative positions of the probes are accurately measurable, the probes are well in contact coupling with the surface of a test piece, acoustic emission source signals in the compression-shear damage process can be accurately collected, and the positioning and quantitative characterization problems of the compression-shear damage of the concrete-surrounding rock bonding surface are conveniently analyzed and researched;
(4) the device for describing the compression-shear damage of the concrete-surrounding rock bonding surface provided by the invention has the advantages of simple structure and low manufacturing cost, and is suitable for experimental research.
Drawings
FIG. 1 is a schematic view of the structure of the present invention in example 1;
FIG. 2 is a schematic view of the installation structure of the crack opening displacement meter;
FIG. 3 is a schematic cross-sectional view of FIG. 1;
FIG. 4 is a schematic structural view of microcracks in example 1;
FIG. 5 is a schematic structural view of the present invention in example 2;
FIG. 6 is a schematic cross-sectional view of FIG. 5;
FIG. 7 is a schematic view of the mounting structure of the sensor cap of FIG. 5;
labeled as: 1. a steel disc; 2. concrete-surrounding rock test pieces; 21. a rock sample; 22. spraying concrete; 3. an axial extensometer; 4. an axial extensometer collet; 5. a crack opening displacement meter; 6. a displacement meter collet; 7. a sensor cap; 8. a horizontal steel hoop; 9. oblique steel hoop; 10. a screw; 11. a nut; 12. fixing the hole; 13. an acoustic emission probe.
Detailed Description
The invention is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
It should be noted that in the description of the present invention, the terms "front", "rear", "left", "right", "upper", "lower", "inner", "outer", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of describing the present invention but do not require that the present invention must be constructed and operated in a specific orientation, and thus, should not be construed as limiting the present invention.
Example 1
As shown in fig. 1-3, the device for describing the compression-shear damage of the concrete-surrounding rock bonding surface comprises a concrete-surrounding rock test piece 2, a crack opening displacement meter 5 and an axial extensometer 3; the concrete-surrounding rock test piece 2 comprises a rock sample 21 and sprayed concrete 22 which are fixedly connected, the connecting surface of the rock sample 21 and the sprayed concrete 22 is an inclined surface, and a crack opening displacement meter 5 is arranged at the connecting surface; the two ends of the concrete-surrounding rock test piece 2 are provided with axial extensometer chucks 4, and a plurality of axial extensometers 3 are arranged between the two axial extensometer chucks 4. The concrete-surrounding rock test piece 2 is cylindrical and has a diameter-height ratio of 1: 2, the slope of the connecting surface of the rock sample 21 and the sprayed concrete 22 is 15-60 degrees.
Both ends of the concrete-surrounding rock test piece 2 are provided with steel discs 1, and axial extensometers chucks 4 are arranged on the steel discs 1; the number of the axial extensometers 3 is 3 and the axial extensometers are evenly arranged between the axial extensometer chucks 4. The crack opening displacement meter 5 is arranged on a displacement meter chuck 6, and the displacement meter chuck 6 comprises two displacement meter clamping pieces which are respectively arranged on a rock sample 21 and sprayed concrete 22; the number of the displacement meter clamping heads 6 is two, and the two displacement meter clamping heads are respectively arranged at the lowest position and the highest position of the connecting surface of the rock sample 21 and the sprayed concrete 22.
High precision CT (computed tomography), that is, high precision computerized tomography, scans the layer of a test piece with a certain thickness by using X-rays, receives the X-rays projected through the layer by a detector, converts the X-rays into visible light, converts the visible light into electric signals by photoelectric conversion, converts the electric signals into digital signals by an analog/digital converter, and inputs the digital signals into a computer for processing. The technology is used for scanning the concrete-surrounding rock test piece, the X-ray attenuation change is caused by the change of different components and structures in the test piece, and the CT system reconstructs the X-ray information into an image to truly reflect the microscopic structure in the test piece. Therefore, the position and the form of the microcracks of the damaged part of the interface can be clearly shown in a picture form, and the damage mechanism of the interface is analyzed by analyzing the difference of the crack generating parts.
The MTS testing machine is mainly used for testing tensile and compressive properties of rock and concrete materials. And testing the shear stress-shear displacement full curve of the concrete-surrounding rock interface through an MTS testing machine axial compression test to realize shear damage analysis of the sprayed concrete-surrounding rock interface.
The method for describing the compression-shear damage of the concrete-surrounding rock bonding surface by adopting the device comprises the following steps:
s1, preparing a concrete-surrounding rock test piece
Manufacturing a rock sample 21 with an inclined end face, setting four slopes of 15 degrees, 30 degrees, 45 degrees and 60 degrees on the inclined face according to different proportions of compressive stress and shear stress, spraying concrete 22 with the same thickness as the rock sample 21 on the inclined face, and obtaining a cylindrical rock sample with the diameter-height ratio of 1: 2-concrete-surrounding rock test piece 2.
S2 high-precision CT test before loading
The manufactured concrete-surrounding rock test piece may have certain microcracks, and in order to accurately analyze the crack propagation mechanism under the action of the compression-shear load, high-precision CT test is carried out on all the test pieces before loading, and interface fault data are recorded.
S3, installing and describing device for pressure shearing damage of concrete-surrounding rock bonding surface
1) Using glue to paste two pairs of displacement meter chucks 6 on two sides of the connecting surface of the rock sample 21 and the sprayed concrete 22, wherein the concrete positions are the highest position and the lowest position of the inclined connecting surface; and then the two crack opening displacement meters 5 are respectively arranged on the stuck displacement meter chucks 6, and the crack opening displacement meters 5 are used for testing the shearing displacement of the interface in the compression shearing process.
2) The method comprises the steps of fixing two axial extensometer chucks 4 on an upper steel disc 1 and a lower steel disc 1 respectively, placing the lower steel disc 1 on the lower jaw of an MTS (maximum Transmission System) testing machine, placing a concrete-surrounding rock test piece 2 on the lower steel disc 1, placing the upper steel disc 1 on the top surface of the concrete-surrounding rock test piece, vertically fixing three axial extensometers 3 in the axial extensometer chucks 4, and controlling the loading rate by the axial extensometers 3.
S4, compression shear loading and high-precision CT test after loading
1) The loading process adopts axial strain to control the loading rate, and in order to research the compression-shear damage mechanism with different strain rates, 10 is selected-1、10-2、10-3、10-4The loading rate of the axial strain with four orders of magnitude and the loading mode of the axial strain control can obtain a complete stress-strain curve, and the crack opening displacement meter monitors the shear displacement of the connecting surface of the rock sample and the sprayed concrete in the loading process.
2) Scheme A: respectively suspending loading to different loading stages of peak load, 90% after peak, 80% after peak, 30% after peak and the like to perform high-precision CT scanning test;
scheme B: are respectively at 10-1、10-2、10-3、10-4And (4) carrying out high-precision CT scanning test after loading to damage under the axial strain rate of four orders of magnitude.
S5, result analysis
1) And analyzing the strain rate effects of the axial strain and the shear displacement of the concrete-surrounding rock test piece according to the measured relationship among the axial strain, the shear displacement and the load.
2) And carrying out fine nondestructive reconstruction on the internal structure of the test piece according to the high-precision CT test data. The test of the scheme A is used for analyzing the mechanism of the concrete-surrounding rock compression-shear damage at different load stages, and the test of the scheme B is used for analyzing the mechanism of the concrete-surrounding rock compression-shear damage at different strain rates.
The principle is that the changes of X-ray attenuation can be caused by cement matrixes, aggregates, interface transition areas, microcracks, rock mass particles and the like with different densities in a test piece, and a clear image of a microstructure is finally formed through reconstruction of a CT system. Furthermore, after the three-dimensional reconstruction image of the test piece is obtained, the test piece image can be cut in any plane, and the crack position can be tracked. Crack propagation in shotcrete can be divided into three cases: matrix cracks, aggregate cracks and interface transition zone cracks. The gray image analysis function of the Matlab software program can extract the lengths of the cement matrix cracks a, the aggregate cracks b and the interface transition zone cracks c with different widths respectively, as shown in fig. 4. By analyzing the proportion of damage cracks with different widths penetrating through a matrix, aggregate and an interface transition region, the mechanism of the concrete-surrounding rock pressure shear damage can be analyzed.
Example 2
As shown in fig. 2 and 5-7, the device for describing the compression-shear damage of the concrete-surrounding rock bonding surface comprises a concrete-surrounding rock test piece 2, a crack opening displacement meter 5 and an axial extensometer 3; the concrete-surrounding rock test piece 2 comprises a rock sample 21 and sprayed concrete 22 which are fixedly connected, the connecting surface of the rock sample 21 and the sprayed concrete 22 is an inclined surface, and a crack opening displacement meter 5 is arranged at the connecting surface; the two ends of the concrete-surrounding rock test piece 2 are provided with axial extensometer chucks 4, and a plurality of axial extensometers 3 are arranged between the two axial extensometer chucks 4. The concrete-surrounding rock test piece 2 is cylindrical and has a diameter-height ratio of 1: 2, the slope of the connecting surface of the rock sample 21 and the sprayed concrete 22 is 15-60 degrees.
The device for describing the compression-shear damage of the concrete-surrounding rock bonding surface provided by the embodiment further comprises a steel hoop arranged on the surface of the concrete-surrounding rock test piece 2, wherein the steel hoop is provided with uniformly distributed fixed holes 12, and an acoustic emission probe 13 is arranged in each fixed hole 12. The acoustic emission probe 13 is compacted in the fixed hole 12 through the sensor cap 7, and the sensor cap 7 contains a magnet and a spring pressing sheet, so that the acoustic emission probe 13 can be firmly pressed, the acoustic emission probe 13 is accurately positioned, and the acoustic emission probe is well in contact coupling with the surface of a test piece. The steel hoop comprises a horizontal steel hoop 8 which is arranged in parallel with the horizontal plane and an oblique steel hoop 9 which is arranged in parallel with the connecting surface of the rock sample 21 and the shotcrete 22. The open end of the steel hoop is fixedly connected with a screw rod 10 and a nut 11 with springs, and the springs are used for relieving radial expansion stress of the test piece.
Both ends of the concrete-surrounding rock test piece 2 are provided with steel discs 1, and axial extensometers chucks 4 are arranged on the steel discs 1; the number of the axial extensometers 3 is 3 and the axial extensometers are evenly arranged between the axial extensometer chucks 4. The crack opening displacement meter 5 is arranged on a displacement meter chuck 6, and the displacement meter chuck 6 comprises two displacement meter clamping pieces which are respectively arranged on a rock sample 21 and sprayed concrete 22; the number of the displacement meter clamping heads 6 is two, and the two displacement meter clamping heads are respectively arranged at the lowest position and the highest position of the connecting surface of the rock sample 21 and the sprayed concrete 22.
AE (acoustic emission), namely, the AE system can collect and record parameters such as amplitude, waveform, energy and arrival time of elastic waves generated in the internal damage process of the concrete material. The AE software system can accurately position the acoustic emission event source through the signal time difference acquired by the probes at different positions. The premise of accurate positioning is that the relative positions of the probes are accurate and measurable, and the contact coupling of each probe on the surface of the test piece is good.
The method for describing the compression-shear damage of the concrete-surrounding rock bonding surface by adopting the device comprises the following steps:
s1, preparing a concrete-surrounding rock test piece
Manufacturing a rock sample 21 with an inclined end face, setting four slopes of 15 degrees, 30 degrees, 45 degrees and 60 degrees on the inclined face according to different proportions of compressive stress and shear stress, spraying concrete 22 with the same thickness as the rock sample 21 on the inclined face, and obtaining a cylindrical rock sample with the diameter-height ratio of 1: 2-concrete-surrounding rock test piece 2.
S2, installing and describing device for pressure shearing damage of concrete-surrounding rock bonding surface
1) Using glue to paste two pairs of displacement meter chucks 6 on two sides of the connecting surface of the rock sample 21 and the sprayed concrete 22, wherein the concrete positions are the highest position and the lowest position of the inclined connecting surface; and then the two crack opening displacement meters 5 are respectively arranged on the stuck displacement meter chucks 6, and the crack opening displacement meters 5 are used for testing the shearing displacement of the interface in the compression shearing process.
2) Fixing the horizontal steel hoop 8 and the oblique steel hoop 9 on the concrete-surrounding rock test piece 2, installing an acoustic emission probe 13 in a fixed hole 12 of the horizontal steel hoop 8 and the oblique steel hoop 9, covering a sensor cover cap 7, measuring and recording the accurate position of the acoustic emission probe in the steel hoop, and inputting the position coordinate into the sensor position coordinate of an acoustic emission system for acoustic emission accurate positioning calculation.
3) The method comprises the steps of fixing two axial extensometer chucks 4 on an upper steel disc 1 and a lower steel disc 1 respectively, placing the lower steel disc 1 on the lower jaw of an MTS (maximum Transmission System) testing machine, placing a concrete-surrounding rock test piece 2 on the lower steel disc 1, placing the upper steel disc 1 on the top surface of the concrete-surrounding rock test piece 2, vertically fixing three axial extensometers 3 in the axial extensometer chucks 4, and controlling the loading rate by the axial extensometers 3.
S3, pressure shear loading and acoustic emission source signal acquisition
The loading process adopts a mode of controlling the loading rate by axial strain, a complete stress-strain curve can be obtained, a crack opening displacement meter monitors the shearing displacement of the connecting surface of the rock sample and the sprayed concrete in the loading process, and an acoustic emission probe and a system record and position acoustic emission source signals in the compression-shear damage process, such as amplitude, ringing count, impact number, energy, frequency and the like.
S4, result analysis
1) And analyzing the strain rate effects of the axial strain and the shear displacement of the concrete-surrounding rock test piece according to the measured relationship among the axial strain, the shear displacement and the load.
2) Microcracks and macrocracks generated at the damaged part in the pressing and shearing loading process can release elastic wave information of various different modes and different frequencies, and an acoustic emission source positioning function module in the acoustic emission system carries out post-processing positioning according to the acquired acoustic emission information. The positioning principle is as follows:
assuming an acoustic emission source position coordinate of (x, y, z), the acoustic emission wave propagates at a constant velocity along a straight line to the sensor, TiIs the ith sensor, TiHas a position coordinate of (x)i，yi，zi)，liIs the acoustic emission source to TiDistance of the sensor, tiIs the arrival time, t, of the acoustic emission recorded by the sensor0Is the starting moment of the acoustic emission source. Then:
where v is the acoustic emission wave velocity, which can be measured separately before the test. The combination of (1) and (2) can obtain:
in the formula (3), t is0X, y and z are 4 unknown quantities, so that the specific value of (x, y and z) can be calculated only by acoustic emission data of 4 probes, and the positioning accuracy can be improved by increasing the number of the probes.
In the embodiment, a 16-channel acoustic emission system is adopted, and more than or equal to 7 channels are arranged to acquire the same acoustic emission signal as an acoustic emission source, so that the positioning accuracy is improved.
3) Quantitatively analyzing a compression shear damage value loaded to any moment by a compression shear load based on acoustic emission energy in the compression shear damage process of the concrete-surrounding rock test piece acquired by an acoustic emission system, wherein the calculation formula is as follows:
in the formula, D is a damage index calculated based on acoustic emission energy, P is an acoustic emission energy value, T is a certain moment of test loading, and T is the moment of final failure and damage of the test beam.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (10)
1. A device for describing compression shear damage of a concrete-surrounding rock bonding surface is characterized by comprising a concrete-surrounding rock test piece, a crack opening displacement meter and an axial extensometer;
the concrete-surrounding rock test piece comprises a rock sample and sprayed concrete which are fixedly connected, the connecting surface of the rock sample and the sprayed concrete is an inclined plane, and the crack opening displacement meter is arranged at the connecting surface;
and axial extensometers chucks are arranged at two ends of the concrete-surrounding rock test piece, and a plurality of axial extensometers are arranged between the two axial extensometer chucks.
2. The device for describing the compression-shear damage of the concrete-surrounding rock bonding surface according to claim 1, further comprising a steel hoop installed on the surface of the concrete-surrounding rock test piece, wherein the steel hoop is provided with uniformly distributed fixed holes, and an acoustic emission probe is installed in each fixed hole.
3. The apparatus for describing the compression-shear damage of the concrete-surrounding rock bonding surface of claim 2, wherein the acoustic emission probe is compacted in the fixing hole through a sensor cap.
4. The apparatus for describing the compressive shear damage of a concrete-surrounding rock bonding surface according to claim 2, wherein the steel hoops comprise horizontal steel hoops installed in parallel with a horizontal plane and oblique steel hoops installed in parallel with a connecting surface of the rock sample and the shotcrete.
5. The apparatus for describing the compression-shear damage of the concrete-surrounding rock bonding surface of claim 2, wherein the open end of the steel hoop is fixedly connected with a screw rod and a nut with a spring.
6. The device for describing the compression-shear damage of the concrete-surrounding rock bonding surface according to claim 1 or 2, wherein the concrete-surrounding rock test piece is cylindrical and has a diameter-height ratio of 1: 2, the slope degree of the connecting surface of the rock sample and the sprayed concrete is 15-60 degrees.
7. The device for describing the compression-shear damage of the concrete-surrounding rock bonding surface according to claim 1 or 2, wherein steel discs are arranged at two ends of the concrete-surrounding rock test piece, and the axial extensometer chuck is mounted on the steel discs; the number of the axial extensometers is 3 and the axial extensometers are uniformly arranged between the clamping heads of the axial extensometers.
8. The apparatus for describing the compression-shear damage of the concrete-surrounding rock bonding surface according to claim 1 or 2, wherein the crack opening displacement meter is mounted on a displacement meter chuck, and the displacement meter chuck comprises two displacement meter jaws which are respectively mounted on the rock sample and the sprayed concrete; the displacement meter comprises a rock sample and a sprayed concrete connection surface, wherein the number of the displacement meter chucks is two, and the displacement meter chucks are respectively arranged at the lowest position and the highest position of the rock sample and the sprayed concrete connection surface.
9. A method for describing compression shear damage of a concrete-surrounding rock bonding surface is characterized by comprising the following steps:
manufacturing a rock sample with an inclined end face, and spraying sprayed concrete with the same thickness as the rock sample on the inclined face to obtain a concrete-surrounding rock test piece;
carrying out high-precision CT (computed tomography) test on the concrete-surrounding rock test piece before loading and recording interface fault data;
installing crack opening displacement meters at the connecting surfaces of the rock sample and the sprayed concrete, installing axial extensometer chucks at two ends of the concrete-surrounding rock test piece, and then installing a plurality of axial extensometers between the two axial extensometer chucks;
the method comprises the following steps of carrying out compression shear loading on a concrete-surrounding rock test piece by adopting an MTS testing machine, controlling the loading rate by using an axial extensometer to obtain a stress-strain curve, monitoring the shear displacement of the connecting surface of a rock sample and sprayed concrete in the loading process by using a crack opening displacement meter, carrying out high-precision CT (computed tomography) testing at different compression shear loading stages and recording interface fault data;
and analyzing the strain rate effects of the axial strain and the shear displacement of the concrete-surrounding rock test piece according to the measured relation among the axial strain, the shear displacement and the load, and performing fine nondestructive reconstruction on the internal structure of the test piece according to high-precision CT test data.
10. A method for describing compression shear damage of a concrete-surrounding rock bonding surface is characterized by comprising the following steps:
manufacturing a rock sample with an inclined end face, and spraying sprayed concrete with the same thickness as the rock sample on the inclined face to obtain a concrete-surrounding rock test piece;
installing crack opening displacement meters at the connecting surfaces of the rock sample and the sprayed concrete, installing axial extensometer chucks at two ends of the concrete-surrounding rock test piece, then installing a plurality of axial extensometers between the two axial extensometer chucks, installing a steel hoop, and installing an acoustic emission probe in a fixed hole;
the method comprises the following steps of (1) carrying out compression shear loading on a concrete-surrounding rock test piece by adopting an MTS testing machine, controlling the loading rate by using an axial extensometer to obtain a stress-strain curve, monitoring the shear displacement of a connecting surface of a rock sample and sprayed concrete in the loading process by using a crack opening displacement meter, and collecting an acoustic emission source signal in the compression shear failure process by using an acoustic emission probe;
and analyzing the strain rate effects of the axial strain and the shear displacement of the concrete-surrounding rock test piece according to the measured relationship among the axial strain, the shear displacement and the load, positioning the spatial position of an acoustic emission source according to the collected acoustic emission source signal in the compression-shear damage process, and analyzing the compression-shear damage value.
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