A device and method for monitoring in-situ shearing and cracks of a reservoir dam foundation rock mass in three dimensions

Abstract

The application relates to the technical field of hydraulic engineering, and particularly discloses a three-dimensional dynamic monitoring device for in-situ shearing and cracks of a reservoir dam foundation rock mass, which comprises a normal shearing composite loading system, a three-dimensional laminated acoustic emission collection system, a multi-directional displacement synchronous monitoring system and an analysis terminal, and specifically, the normal shearing composite loading system comprises a supporting base, a first hydraulic cylinder, a second hydraulic cylinder and a wedge-shaped force transmission module; the three-dimensional laminated acoustic emission collection system comprises a sensor array, a signal transmission module and a data processing unit; and the multi-directional displacement synchronous monitoring system comprises a laser displacement meter and a micrometer. The application further discloses a three-dimensional dynamic monitoring method for in-situ shearing and cracks of a reservoir dam foundation rock mass. The three-dimensional dynamic monitoring device and method for in-situ shearing and cracks of a reservoir dam foundation rock mass can solve the problems of insufficient dynamic coupling of the loading system, limited three-dimensional crack signal capturing capability and low positioning precision.

Description

Technical Field

[0001] This invention relates to the field of water conservancy engineering technology, and in particular to a device and method for in-situ three-dimensional dynamic monitoring of shear and cracks in the bedrock of a reservoir dam. Background Technology

[0002] In hydraulic engineering, the shear strength parameters of the structural planes within the dam foundation rock mass are core factors affecting dam foundation stability. These parameters directly determine the structural planes' ability to resist slippage, thus impacting the overall safety and reliability of the dam. The rock mass structural planes exposed on the adit sidewalls are easier to identify and accurately measure. Based on the stress characteristics of the dam foundation and the development of the structural planes, specimens in different orientations can be flexibly prepared.

[0003] However, conventional in-situ direct shear testing methods still suffer from bottlenecks such as insufficient dynamic coupling of the loading system, limited ability to capture three-dimensional crack signals, and low positioning accuracy, urgently requiring technological optimization and innovative breakthroughs. The main shortcomings are as follows:

[0004] (1) Poor adaptability of the loading system: Traditional in-situ direct shear tests mostly use independent normal and shear loading devices, which require applying normal force and shear force step by step. It is difficult to achieve synchronous loading on the vertical working surface of the adit sidewall, resulting in the loading path not matching the actual working conditions and insufficient stress field reconstruction capability. Especially in steep or inclined adit walls, the loading angle is limited, further weakening the accuracy of the test.

[0005] (2) Insufficient three-dimensional crack sensing capability: Existing in-situ tests mostly use two-dimensional acoustic emission or displacement sensors, which are mainly distributed on the surface or sides of the shear plane, ignoring the crack propagation characteristics behind the pre-set shear plane of the tunnel wall specimen. In tunnel walls with a thickness ≥0.5m and multiple sets of cleavage structures, cracks often propagate in an oblique, three-dimensional cross manner. The signal is easily affected by reflection and scattering from the cleavage plane during propagation, making it difficult to fully capture the internal crack development process, which seriously restricts the ability to dynamically grasp the instability process.

[0006] (3) Insufficient crack location accuracy: Traditional deployment methods do not optimize for the spatial stress state of the adit sidewall. Sensors are often only deployed near the shear surface, failing to form a three-dimensional spatial positioning network. This results in crack location errors often exceeding 5mm. Especially in adit walls with developed structural surfaces and uneven lithology, crack initiation points are easily misjudged, which is not conducive to high-precision safety assessment and early warning. Summary of the Invention

[0007] The present invention aims to solve at least one of the technical problems mentioned above, and provides a device and method for in-situ shear and crack three-dimensional dynamic monitoring of reservoir dam bedrock, so as to solve the problems of insufficient dynamic coupling of loading system, limited ability to capture three-dimensional crack signals and low positioning accuracy of conventional in-situ direct shear test methods.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is: a three-dimensional dynamic monitoring device for in-situ shearing and cracking of reservoir dam foundation rock mass, comprising:

[0009] A normal shear composite loading system includes a support base, a first hydraulic cylinder, a second hydraulic cylinder, and a wedge-shaped force transmission module. The support base is fixedly installed on the bedrock. The first and second hydraulic cylinders are installed on the support base and are used to apply normal force and shear force to the sample, respectively. The output ends of the first and second hydraulic cylinders are fixedly connected to the wedge-shaped force transmission module, and the end of the wedge-shaped force transmission module away from the output end abuts against the sample.

[0010] A three-dimensional stacked acoustic emission acquisition system includes a sensor array, a signal transmission module, and a data processing unit. The sensor array is arranged in three layers at equal intervals along the thickness direction of the sample, namely layer L1, layer L2, and layer L3. Each layer is equipped with 6 acoustic emission sensors, which are evenly distributed in a ring around the central axis of the sample. Layers L1 and L3 are symmetrically arranged at both ends of the sample, and layer L2 is located in the middle position between layers L1 and L3. The acoustic emission sensors on layer L2 are staggered with the acoustic emission sensors on layer L1.

[0011] A multi-directional displacement synchronous monitoring system includes a laser displacement meter and a dial gauge. The laser displacement meter includes a center displacement meter and a side displacement meter. The center displacement meter is vertically installed directly above the center of the top of the sample, and the side displacement meters are arranged on both sides of the sample to collect the three-dimensional deformation data of the sample in real time. Two sets of dial gauges are provided, and the probes of the two sets of dial gauges are respectively perpendicular to the side and top surfaces of the sample to measure the normal and tangential absolute displacement of the sample.

[0012] The analysis terminal acquires the acoustic emission signals from the three-dimensional stacked acoustic emission acquisition system and the displacement data from the multi-directional displacement synchronous monitoring system, and aligns the acoustic emission signals and displacement data according to timestamps.

[0013] Preferably, both the first hydraulic cylinder and the second hydraulic cylinder are connected to a pressure sensor and a servo controller. The pressure sensor can monitor the magnitude of the normal force and shear force of the first hydraulic cylinder and the second hydraulic cylinder, and the servo controller can adjust the loading ratio of the normal force and the shear force in real time to achieve dynamic coupling loading of the normal force and the shear force of the first hydraulic cylinder and the second hydraulic cylinder.

[0014] Preferably, the end of the wedge-shaped force transmission module is provided with a force application plate, and the contact surface between the force application plate and the sample is processed with a diamond-shaped anti-slip texture.

[0015] Preferably, the support base includes a first base and a second base, the first base is horizontally arranged, the second base is vertically fixed to one side edge of the first base, and the first hydraulic cylinder and the second hydraulic cylinder are respectively installed on the second base and the first base.

[0016] Preferably, the first base has a sliding groove along the horizontal direction, the bottom of the second hydraulic cylinder is fixedly provided with a sliding seat, the sliding seat slides with the sliding groove and is locked in the sliding groove by bolts, the second base has an adjustment groove along the vertical direction, and the first hydraulic cylinder is detachably fixed in the adjustment groove by bolts.

[0017] Preferably, the surface of the sample is provided with a mounting hole, a mounting bracket is provided at the mounting hole, the acoustic emission sensor is placed in the mounting hole, and a locking bolt is provided in the middle of the mounting bracket to lock and fix the acoustic emission sensor in the mounting hole.

[0018] Preferably, magnets are symmetrically fixedly mounted on both sides of the mounting hole on the surface of the sample, and the two ends of the mounting bracket are magnetically attracted to the magnets.

[0019] Preferably, one end of the acoustic emission sensor that contacts the sample is coated with a high thermal conductivity silicone grease coupling agent, and the other end is abutted against the locking bolt through a buffer pad.

[0020] Furthermore, this application also discloses a three-dimensional dynamic monitoring method for in-situ shear and cracking of the bedrock mass of a reservoir dam, employing any of the monitoring devices described above, and comprising the following steps:

[0021] (1) Loading is performed in 8 to 12 levels according to the ratio of normal stress to shear stress to simulate the gradual action of hydraulic load in water conservancy projects. Each level of loading is maintained for 5 minutes, and the next level is entered after the displacement rate is ≤0.01mm / min.

[0022] (2) The data processing unit acquires sensor signals at a sampling rate of 2MHz, triggers the built-in ray tracing technology, inputs the tilt angle of the structural surface and the three-dimensional coordinates of the sensor, calculates the signal arrival time difference, corrects the path deviation caused by the tilt of the structural surface, and outputs the crack source location result.

[0023] (3) Data from the laser displacement gauge and dial gauge are uploaded to the analysis terminal in real time via wireless transmission. The analysis terminal has a built-in data fusion algorithm to generate a three-dimensional deformation-acoustic emission energy-crack location correlation map.

[0024] (4) Based on existing ray tracing technology, after inputting the tilt angle of the structural surface and the three-dimensional coordinates of the sensor, the path deviation caused by the tilt of the structural surface is corrected by calculating the signal arrival time difference, and the crack source location result is output. The corrected crack source coordinates are aligned with the deformation data according to the timestamp, and the crack propagation rate curve and energy release accumulation diagram are drawn.

[0025] (5) Import the corrected acoustic emission location data into the analysis terminal, construct a three-dimensional model of shear plane failure evolution, and mark the main crack propagation path and secondary crack distribution;

[0026] (6) Output key mechanical parameters, including peak shear strength, failure energy threshold and crack propagation rate, and generate a comprehensive test report for use in the safety assessment of hydraulic engineering structures.

[0027] The beneficial effects are as follows: Compared with the prior art, the in-situ three-dimensional dynamic monitoring device and method for shearing and cracking of reservoir dam foundation rock mass of the present invention has the following advantages:

[0028] 1. The present invention arranges three layers of sensor array at equal intervals along the thickness direction of the sample, with the layer spacing being 1 / 3 of the sample thickness. Each layer has 6 acoustic emission sensors distributed in a ring array, and the acoustic emission sensors of the L2 layer are staggered with those of the L1 layer to form a three-dimensional signal capture network. This improves the signal reception rate of cracks inside the sample and can accurately identify complex failure modes such as tilting cracks and branch cracks. It is particularly suitable for crack monitoring in in-situ shear tests of rock mass on the sidewall of adit in water conservancy engineering exploration.

[0029] 2. This invention uses a combination of laser displacement meter and dial gauge to measure and cover the three-dimensional deformation field. It also uses wireless transmission to achieve data timestamp synchronization and alignment, generating a deformation-acoustic emission energy-crack location correlation map, thereby improving the data synchronization accuracy. It can quantitatively analyze the correspondence between shear displacement mutation and crack propagation rate, providing a multi-dimensional data fusion basis for the study of structural surface failure mechanisms in water conservancy projects. Attached Figure Description

[0030] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, wherein:

[0031] Figure 1 This is a schematic diagram of the structure of a three-dimensional dynamic monitoring device for in-situ shearing and cracking of the foundation rock mass of a reservoir dam according to the present invention;

[0032] Figure 2 This is a schematic diagram of the installation structure of a multi-directional displacement synchronous monitoring system;

[0033] Figure 3 This is a schematic diagram of the installation structure of an acoustic emission sensor;

[0034] Figure 4 This is a schematic diagram of the installation structure of the second hydraulic cylinder;

[0035] Figure 5 This is a schematic diagram of the installation structure of the first hydraulic cylinder.

[0036] In the diagram, 1-support base, 2-first hydraulic cylinder, 3-second hydraulic cylinder, 4-wedge force transmission module, 5-signal transmission module, 6-data processing unit, 7-acoustic emission sensor, 8-laser displacement gauge, 9-dial gauge, 10-servo controller, 11-first seat, 12-second seat, 13-slide groove, 14-slide block, 15-adjustment groove, 16-mounting hole, 17-mounting bracket, 18-locking bolt, 19-magnet, 20-force application plate, 21-buffer pad, 22-analysis terminal, 23-magnetic base, 24-steel bracket, 25-L1 layer, 26-L2 layer, 27-L3 layer. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0038] It should be noted that when a component is described as "fixed to" another component, it can be directly on the other component or may have a central component. When a component is described as "connected to" another component, it can be directly connected to the other component or may have a central component. When a component is described as "set on" another component, it can be directly set on the other component or may have a central component. When a component is described as "set in the middle," it is not simply set in the exact center, as long as it is not set within the area defined by both ends being in the middle. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0040] like Figures 1 to 5 As shown, this application discloses a three-dimensional dynamic monitoring device for in-situ shear and cracking of reservoir dam bedrock, including a normal shear composite loading system, a three-dimensional stacked acoustic emission acquisition system, a multi-directional displacement synchronous monitoring system, and an analysis terminal 22. Specifically:

[0041] The normal shear composite loading system includes a support base 1, a first hydraulic cylinder 2, a second hydraulic cylinder 3, and a wedge-shaped force transmission module 4. The support base 1 is fixedly installed on the bedrock. The first hydraulic cylinder 2 and the second hydraulic cylinder 3 are installed on the support base 1 and are used to apply normal force and shear force to the sample, respectively. The output ends of the first hydraulic cylinder 2 and the second hydraulic cylinder 3 are fixedly connected to the wedge-shaped force transmission module 4, and the end of the wedge-shaped force transmission module 4 away from the output end abuts against the sample. In one specific embodiment, the support base 1 includes a first seat body 11 and a second seat body 12. A concrete base is poured on the bedrock below the sample, and a steel plate is embedded in the concrete base. The first seat body 11 is horizontally fixedly installed on the steel plate. The second seat body 12 can be detachably and vertically fixed to one side edge of the first seat body 11 by bolts. The first hydraulic cylinder 2 is set on the vertical mounting plane of the second seat body 12, and the second hydraulic cylinder 3 is set on the horizontal mounting plane of the first seat body 11. In one specific installation structure, a groove 13 is provided on the first seat body 11 along the horizontal direction. The bottom of the second hydraulic cylinder 3 is fixedly provided with a slide block 14, which slides in conjunction with the slide groove 13. The side wall of the slide groove 13 is threaded with bolts. By tightening the bolts, the ends of the bolts abut against the side of the slide block 14, thereby locking the slide block 14 in the slide groove 13. The second seat body 12 is provided with an adjustment groove 15 along the vertical direction. The first hydraulic cylinder 2 is detachably fixed in the adjustment groove 15 by bolts. By adopting the bolt detachable installation method, the installation positions of the first hydraulic cylinder 2 and the second hydraulic cylinder 3 can be adjusted, thereby ensuring that the load is applied to the center of the loading surface. The output ends of the first hydraulic cylinder 2 and the second hydraulic cylinder 3 can be connected to wedge-shaped force transmission modules 4 via flanges. The wedge-shaped force transmission modules 4 are forged from TC4 titanium alloy, with the smaller end connected to the output end and the other end abutting against the sample surface. A force-applying plate 20 is provided at the end of the wedge-shaped force transmission module 4. The contact surface between the force-applying plate 20 and the sample is machined with diamond-shaped anti-slip patterns with a depth of 0.5 mm and a pattern spacing of 3 mm to prevent the wedge-shaped force transmission module 4 from moving relative to the sample when the first hydraulic cylinder 2 and the second hydraulic cylinder 3 apply force, ensuring accurate transmission of load along the normal and tangential directions of the structural surface. Both the first hydraulic cylinder 2 and the second hydraulic cylinder 3 are connected to pressure sensors and a servo controller 10. The pressure sensors can monitor the magnitude of the normal and shear forces of the first hydraulic cylinder 2 and the second hydraulic cylinder 3. The servo controller 10 can adjust the loading ratio of the normal and shear forces in real time to achieve dynamic coupling loading of the normal and shear forces of the first hydraulic cylinder 2 and the second hydraulic cylinder 3.

[0042] The three-dimensional stacked acoustic emission acquisition system includes a sensor array, a signal transmission module 5, and a data processing unit 6. The sensor array is arranged in three layers at equal intervals along the thickness direction of the sample, namely L1 layer 25, L2 layer 26, and L3 layer 27. Each layer is equipped with 6 acoustic emission sensors 7, which are evenly distributed in a ring around the central axis of the sample. The acoustic emission sensors 7 can be piezoelectric ceramic acoustic emission sensors with a diameter of 10 mm. L1 layer 25 and L3 layer 27 are symmetrically arranged at both ends of the sample, and L2 layer 26 is located in the middle position between L1 layer 25 and L3 layer 27. The acoustic emission sensors 7 on L2 layer 26 are staggered with the acoustic emission sensors 7 on L1 layer 25. Specifically, since one side of the sample is connected to the bedrock, acoustic emission sensors 7 are only set on its three sides. L1 layer 25 and L3 layer 27 are horizontally arranged with two acoustic emission sensors 7 on each side of the sample, and L2 layer 26 is vertically arranged with two acoustic emission sensors 7 on one side of the sample. In the mounting structure of the acoustic emission sensor 7, a mounting hole 16 with a depth of 15 mm and a diameter of 8 mm can be opened on the surface of the sample. A mounting bracket 17 is set at the mounting hole 16, and the acoustic emission sensor 7 is placed in the mounting hole 16. A locking bolt 18 is set in the middle of the mounting bracket 17 to lock the acoustic emission sensor 7 in the mounting hole 16. Furthermore, magnets 19 are symmetrically fixedly mounted on both sides of the mounting hole 16 on the surface of the sample. The bottom of the magnets 19 is coated with a 2 mm thick double-effect cement, which is a mixture of sulfoaluminate cement and epoxy resin in a 3:1 ratio. After curing, it forms a seamless contact with the bedrock. The two ends of the mounting bracket 17 are magnetically attracted to the magnets 19. The installation structure using magnetic attraction facilitates fine adjustment of the position of the mounting bracket 17, thereby adjusting the position of the locking bolt 18. One end of the acoustic emission sensor 7 that contacts the sample is coated with a high thermal conductivity silicone grease coupling agent, and the other end is abutted against the locking bolt 18 through a 5 mm thick nitrile rubber buffer pad 21 to effectively isolate external mechanical vibration interference. The signal from the acoustic emission sensor 7 is amplified by a preamplifier with a bandwidth of 10kHz~2MHz in the signal transmission module 5, and then transmitted to the acoustic emission host in the data processing unit 6 through a shielded cable. The acoustic emission host has a built-in signal correction module based on existing ray tracing technology. After inputting the tilt angle of the structural surface and the three-dimensional coordinates of the sensor, it calculates the signal arrival time difference, corrects the path deviation caused by the tilt of the structural surface, and outputs the crack source location result.

[0043] The multi-directional displacement synchronous monitoring system includes a laser displacement gauge 8 and a dial gauge 9. The laser displacement gauge 8 uses a semiconductor laser with a wavelength of 650nm and a sampling frequency of 1kHz. The laser displacement gauge 8 includes a central displacement gauge and a lateral displacement gauge. The central displacement gauge is vertically installed 50cm above the center of the top of the sample, and the lateral displacement gauges are arranged on both sides of the sample to collect the three-dimensional deformation data of the sample in real time. Two sets of dial gauges 9 are set up. They are mechanical gauges with a range of 10mm and a resolution of 0.001mm, and are fixed to independent steel brackets 24 on both sides of the sample by magnetic bases 23. The probes of the two sets of dial gauges 9 are perpendicular to the side and top surfaces of the sample, respectively, to measure the normal and tangential absolute displacement of the sample. The displacement data is wirelessly transmitted and synchronized to the analysis terminal 22. The analysis terminal 22 has a built-in data fusion algorithm. The analysis terminal 22 acquires the acoustic emission signal of the three-dimensional stacked acoustic emission acquisition system and the displacement data of the multi-directional displacement synchronous monitoring system, and aligns the acoustic emission signal and displacement data according to the timestamp.

[0044] In addition, this application also discloses a three-dimensional dynamic monitoring device for in-situ shear and cracking of the bedrock of a reservoir dam, which adopts the above-mentioned monitoring device and specifically includes the following steps:

[0045] 1. Assembly and debugging of the experimental setup

[0046] 1.1 Fixing the concrete base and support base 1

[0047] (1) A concrete base was poured at the test site, with a steel plate of 20mm thickness embedded inside. The surface flatness error of the steel plate was ≤0.05mm / m.

[0048] (2) Fix the support base 1 to the pre-embedded steel plate, and calibrate the level of the base by electronic tilt sensor to ensure that the level error is ≤0.1°.

[0049] 1.2 Installation of the Normal Shear Composite Loading System

[0050] (1) The first hydraulic cylinder 2 and the second hydraulic cylinder 3 are installed on the support base 1, and the output ends of the first hydraulic cylinder 2 and the second hydraulic cylinder 3 are connected to the wedge-shaped force transmission module 4 through the flange.

[0051] (2) M12 high-strength bolts are used to detachably connect the wedge-shaped force transmission module 4 to the output end. The contact surface of the wedge-shaped force transmission module 4 is machined with a diamond anti-slip pattern with a depth of 0.5mm and a pattern spacing of 3mm to ensure that the load is accurately transmitted along the normal and tangential directions of the structural surface.

[0052] (3) Start the servo controller 10, input the preset ratio of normal force and shear force, monitor in real time through a high-precision pressure sensor, and adjust the opening of the servo valve until the coupling error between normal force and shear force is <3%.

[0053] 2. Sample preparation and pretreatment

[0054] 2.1 Specimen Cutting and Reinforcement

[0055] (1) Select natural rock mass samples with structural surfaces, with dimensions of 0.5m×0.5m×0.3m (length×width×thickness). Cut the samples using a diamond wire saw. The parallelism error between the top and bottom surfaces of the sample after cutting is ≤0.1mm / m.

[0056] (2) For loose or cracked specimens, cast a C30 reinforced concrete protective sleeve around the specimen. The sleeve is 10cm thick and has a 2cm wide shear gap inside. The gap is filled with a neoprene rubber strip with an elastic modulus of 5MPa to prevent debris from interfering with the test.

[0057] 2.2 Structural Surface Inclination Calibration

[0058] The actual tilt angle of the sample structure surface is measured using a high-precision electronic inclinometer. If the deviation from the preset tilt angle is ≥0.5°, the bottom surface of the sample is finely ground using an angle grinder until the tilt angle deviation is ≤0.3°.

[0059] 3. Three-dimensional stacked acoustic emission sensor array arrangement

[0060] 3.1 Drilling and Fixture Installation

[0061] (1) Mark the drilling positions of the three layers L1, L2, and L3 along the thickness direction of the sample, with each layer spacing being 1 / 3 of the sample thickness; drill six mounting holes 16 in a ring around the central axis of the sample in each layer, with a diameter of 8 mm and a depth of 15 mm.

[0062] (2) Coat the bottom of magnet 19 with a 2mm thick double-effect cement. The double-effect cement is a mixture of sulfoaluminate cement and epoxy resin in a 3:1 ratio. After curing for 24 hours, it forms a seamless contact with the bedrock. Then, magnetically attach the two ends of mounting bracket 17 to magnet 19.

[0063] 3.2 Sensor Fixing and Signal Cable Laying

[0064] (1) Apply silicone grease coupling agent evenly to the contact surface between one end of the acoustic emission sensor 7 and the sample, and abut the other end with a 5mm thick nitrile rubber buffer pad 21 and a locking bolt 18 on the mounting bracket 17. Install the acoustic emission sensor 7 layer by layer to ensure that the acoustic emission sensor 7 of the L2 layer 26 is located between the L1 layer 25 and the L3 layer 27, and the L3 layer 27 is aligned with the L1 layer 25 to form a three-dimensional staggered array.

[0065] (2) A groove is pre-drilled along the side of the sample where the acoustic emission sensor 7 is fixed, and the signal line is laid. The groove is filled with epoxy resin for fixation. The preamplifier and the acoustic emission host are connected by a double-shielded cable.

[0066] 4. Configuration of Multi-directional Displacement Synchronous Monitoring System

[0067] 4.1 Installation of Laser Displacement Meter 8

[0068] (1) Install a laser displacement meter 8 vertically 50cm above the center of the top of the sample. The wavelength is 650nm, the sampling frequency is 1kHz, and the spot diameter is ≤1mm. The laser displacement meter is symmetrically arranged on both sides of the sample, 20cm away from the sample surface, to ensure that the laser beam is perpendicular to the measurement surface.

[0069] (2) Zero-point calibration of laser displacement meter 8 is performed using a calibration plate to eliminate ambient light interference, with an error ≤0.005mm.

[0070] 4.2 Dial gauge 9 Installation and Synchronization Test

[0071] (1) Install a mechanical dial indicator 9 with a range of 10 mm and a resolution of 0.001 mm in the shear direction and normal direction of the sample. Fix the dial indicator 9 to the independent steel bracket 24 through the magnetic base 23. The probe is perpendicular to the measuring point and the preload is set to 0.5 mm.

[0072] (2) Enable wireless transmission, synchronize the data of laser displacement meter 8 and dial gauge 9, verify the synchronization of timestamps, and ensure that the error is <1ms.

[0073] 5. Hierarchical loading and data acquisition process

[0074] 5.1 Loader Settings

[0075] (1) Loading is performed in 8 to 12 levels according to the ratio of normal stress to shear stress to simulate the gradual action of hydraulic load in water conservancy projects. Each level of loading is maintained for 5 minutes, and the next level is entered after the displacement rate is ≤0.01mm / min.

[0076] (2) The servo controller 10 controls the hydraulic cylinder output in real time, and the fluctuation range of normal force and shear force is ≤ ±1.5%.

[0077] 5.2 Data Synchronization Recording and Anomaly Handling

[0078] (1) The data processing unit 6 acquires sensor signals at a sampling rate of 2MHz, triggers the built-in ray tracing technology, inputs the tilt angle of the structural surface and the three-dimensional coordinates of the sensor, calculates the signal arrival time difference, corrects the path deviation caused by the tilt of the structural surface, and outputs the crack source location result.

[0079] (2) The data from the laser displacement meter 8 and the dial gauge 9 are uploaded to the analysis terminal 22 in real time via wireless transmission. The analysis terminal 22 has a built-in data fusion algorithm to generate a three-dimensional deformation-acoustic emission energy-crack location correlation map.

[0080] (3) If the acoustic emission event rate suddenly increases or the displacement rate is ≥0.1mm / min, immediately stop loading and record the current load status, analyze the failure mode of the sample, and provide data support for the safety early warning of water conservancy projects.

[0081] 6. Data Analysis and Reverse Modeling

[0082] 6.1 Crack initiation location and correction

[0083] (1) Based on existing ray tracing technology, after inputting the tilt angle of the structural surface and the three-dimensional coordinates of the sensor, the path deviation caused by the tilt of the structural surface is corrected by calculating the signal arrival time difference, and the crack source location result is output.

[0084] (2) Align the corrected crack source coordinates with the deformation data according to the timestamp, and draw the crack propagation rate curve and energy release accumulation diagram.

[0085] 6.2 Construction of a three-dimensional destruction evolution model

[0086] (1) Import the corrected acoustic emission location data into the analysis terminal 22, construct a three-dimensional model of shear plane failure evolution, and mark the main crack propagation path and secondary crack distribution.

[0087] (2) Output key mechanical parameters, including peak shear strength, failure energy threshold and crack propagation rate, and generate a comprehensive test report for use in the safety assessment of hydraulic engineering structures.

[0088] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of the technical solutions of the present invention.

Claims

1. A three-dimensional dynamic monitoring device for in-situ shearing and cracking of bedrock in a reservoir dam, characterized in that, include: A normal shear composite loading system includes a support base (1), a first hydraulic cylinder (2), a second hydraulic cylinder (3), and a wedge-shaped force transmission module (4). The support base (1) is fixedly installed on the bedrock. The first hydraulic cylinder (2) and the second hydraulic cylinder (3) are installed on the support base (1) and are used to apply normal force and shear force to the sample respectively. The output ends of the first hydraulic cylinder (2) and the second hydraulic cylinder (3) are fixedly connected to the wedge-shaped force transmission module (4). The end of the wedge-shaped force transmission module (4) away from the output end abuts against the sample. The first hydraulic cylinder (2) and the second hydraulic cylinder (3) are both connected to a pressure sensor and a servo controller (10). The pressure sensor can monitor the magnitude of the normal force and shear force of the first hydraulic cylinder (2) and the second hydraulic cylinder (3) in real time. The servo controller (10) can adjust the loading ratio of the normal force and the shear force in real time to realize the dynamic coupling loading of the normal force and the shear force of the first hydraulic cylinder (2) and the second hydraulic cylinder (3). A three-dimensional stacked acoustic emission acquisition system includes a sensor array, a signal transmission module (5), and a data processing unit (6). The sensor array is arranged in three layers at equal intervals along the thickness direction of the sample, namely L1 layer (25), L2 layer (26), and L3 layer (27). Each layer is equipped with 6 acoustic emission sensors (7), which are evenly distributed in a ring around the central axis of the sample. L1 layer (25) and L3 layer (27) are symmetrically arranged at both ends of the sample. L2 layer (26) is located in the middle position between L1 layer (25) and L3 layer (27). The acoustic emission sensors (7) on L2 layer (26) and L1 layer (25) are staggered to form a three-dimensional signal capture network. A multi-directional displacement synchronous monitoring system includes a laser displacement meter (8) and a dial gauge (9). The laser displacement meter (8) includes a central displacement meter and a lateral displacement meter. The central displacement meter is vertically installed directly above the center of the top of the sample, and the lateral displacement meters are arranged on both sides of the sample to collect the three-dimensional deformation data of the sample in real time. Two sets of dial gauges (9) are provided. The probes of the two sets of dial gauges (9) are respectively perpendicular to the side and top surfaces of the sample to measure the normal and tangential absolute displacement of the sample. Analysis terminal (22) acquires the acoustic emission signal of the three-dimensional stacked acoustic emission acquisition system and the displacement data of the multi-directional displacement synchronous monitoring system, and aligns the acoustic emission signal and displacement data according to the timestamp.

2. The three-dimensional dynamic monitoring device for in-situ shearing and cracking of reservoir dam bedrock as described in claim 1, characterized in that, The end of the wedge-shaped force transmission module (4) is provided with a force application plate (20), and the contact surface between the force application plate (20) and the sample is processed with a diamond-shaped anti-slip texture.

3. The three-dimensional dynamic monitoring device for in-situ shearing and cracking of reservoir dam bedrock as described in claim 1, characterized in that, The support base (1) includes a first base (11) and a second base (12). The first base (11) is horizontally arranged, and the second base (12) is vertically fixed to one side edge of the first base (11). The first hydraulic cylinder (2) and the second hydraulic cylinder (3) are respectively installed on the second base (12) and the first base (11).

4. The three-dimensional dynamic monitoring device for in-situ shearing and cracking of reservoir dam bedrock as described in claim 3, characterized in that, The first seat (11) is provided with a sliding groove (13) along the horizontal direction. The bottom of the second hydraulic cylinder (3) is fixedly provided with a sliding block (14). The sliding block (14) slides with the sliding groove (13) and is locked in the sliding groove (13) by bolts. The second seat (12) is provided with an adjustment groove (15) along the vertical direction. The first hydraulic cylinder (2) is detachably fixed in the adjustment groove (15) by bolts.

5. The three-dimensional dynamic monitoring device for in-situ shearing and cracking of reservoir dam bedrock as described in claim 1, characterized in that, The sample has a mounting hole (16) on its surface. A mounting bracket (17) is provided at the mounting hole (16). The acoustic emission sensor (7) is placed in the mounting hole (16). A locking bolt (18) is provided in the middle of the mounting bracket (17) to lock the acoustic emission sensor (7) in the mounting hole (16).

6. The three-dimensional dynamic monitoring device for in-situ shearing and cracking of reservoir dam bedrock as described in claim 5, characterized in that, Magnets (19) are symmetrically fixed on both sides of the mounting hole (16) on the surface of the sample, and the two ends of the mounting bracket (17) are magnetically attracted to the magnets (19).

7. The three-dimensional dynamic monitoring device for in-situ shearing and cracking of reservoir dam bedrock as described in claim 5, characterized in that, The acoustic emission sensor (7) is coated with a high thermal conductivity silicone grease coupling agent at one end that contacts the sample, and the other end is abutted against the locking bolt (18) through a buffer pad (21).

8. A three-dimensional dynamic monitoring method for in-situ shearing and cracking of bedrock in a reservoir dam, characterized in that, The monitoring device according to any one of claims 1 to 7 comprises the following steps: (1) Loading is performed in 8 to 12 levels according to the ratio of normal stress to shear stress to simulate the gradual action of hydraulic load in water conservancy projects. Each level of loading is maintained for 5 minutes, and the next level is entered after the displacement rate is ≤0.01mm / min. (2) The data processing unit (6) acquires the signal of the acoustic emission sensor (7) at a sampling rate of 2MHz. After inputting the tilt angle of the structural surface and the three-dimensional coordinates of the sensor through its built-in ray tracing technology, it calculates the signal arrival time difference, corrects the path deviation caused by the tilt of the structural surface, and outputs the crack source location result. (3) Data from the laser displacement meter (8) and the dial gauge (9) are uploaded to the analysis terminal (22) in real time via wireless transmission. The analysis terminal (22) has a built-in data fusion algorithm to generate a three-dimensional deformation-acoustic emission energy-crack location correlation map. (4) Based on the existing ray tracing technology, after inputting the tilt angle of the structural surface and the three-dimensional coordinates of the sensor, the path deviation caused by the tilt of the structural surface is corrected by calculating the signal arrival time difference, and the crack source location result is output. The corrected crack source coordinates are aligned with the deformation data according to the timestamp, and the crack propagation rate curve and energy release accumulation diagram are drawn. (5) Import the corrected acoustic emission location data into the analysis terminal (22), construct a three-dimensional model of shear plane failure evolution, and mark the main crack propagation path and secondary crack distribution; (6) Output key mechanical parameters, including peak shear strength, failure energy threshold and crack propagation rate, and generate a comprehensive test report for use in the safety assessment of hydraulic engineering structures.

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