Fault slip experiment device

Abstract

The invention discloses a fault slippage experimental device which can realize controllable roughness processing of a fault plane and continuously monitor strain and displacement spatial and temporal distribution rules of the fault plane in a laboratory. The device comprises a fault model, a loading device, a data acquisition and processing unit and a control and monitoring unit, and can further improve the research precision and breadth of a fault experiment by controlling the roughness of a fault plane. By introducing a parameterized roughness design and processing technology, high-precision and controllable roughness processing of the fault surface is realized; according to the invention, the multi-channel transient strain acquisition module based on the strain gauges and the full-field displacement observation module based on a digital image correlation method are utilized to realize high-precision observation of a fault plane. The device is a further supplement for an existing fault slip experiment device, and a new technical means can be provided for exploring a basic mechanism of fault slip behaviors.

Description

Technical Field

[0001] The invention belongs to the technical field of rock and soil mechanics experimental equipment, and in particular relates to a fault slip experimental device. Background Art

[0002] Fault slip behavior is one of the core issues in seismology and rock mechanics research, and the roughness of the fault surface plays a key role in this process. The rough surface of a natural fault is formed by the combined action of a variety of geological processes, including shearing, rock crushing, and chemical precipitation. The rough surface is highly complex and multi-scale, ranging from local protrusions at the micron level to wavy shapes at the meter level. This multi-scale roughness directly affects the mechanical behavior of the fault, such as friction characteristics, slip triggering thresholds, and slip rates. For example, higher roughness usually leads to greater friction, and when the fault slips, the geometric characteristics of the roughness may cause unstable slip or even vibration slip.

[0003] However, in experimental research, how to accurately control the roughness characteristics of the fault surface remains an unresolved problem. Traditional experimental devices usually use natural fault samples or simply hand-processed models to study fault slip behavior. For example, although natural fault samples can truly reflect the geometric characteristics and material properties of the fault, there is a large uncertainty in their geometric shape and mechanical properties, making them difficult to use for rigorous comparative experiments. In addition, the acquisition and preparation of natural fault samples are expensive, and are limited by the sampling location, fault type and scale, which further limits the breadth of the experiment.

[0004] On the other hand, hand-processed fault models are usually prepared by grinding, sawing or random scratching. Although these methods are simple and easy to use, the roughness characteristics they generate often lack controllability and it is difficult to accurately describe the multi-scale characteristics of the surface morphology. Such simply processed models are usually only suitable for qualitative studies, but are insufficient for exploring the quantitative mechanisms of fault mechanical behavior. For example, the grinding processed models usually tend to be too smooth and cannot reproduce the true friction characteristics of the rough surface of natural faults, while the distribution of random scratches may not represent the stress concentration pattern of natural faults.

[0005] In recent years, as 3D printing continues to mature, this technology has also been applied to the rough surface processing of fault models. However, since the surface quality of 3D printing is usually limited by the printing resolution, the printed surface often has a distinct sense of layering, and it is difficult to achieve the micron-level precision of laser etching. In addition, the choice of 3D printing materials is relatively limited, and more post-processing is required to obtain the ideal roughness characteristics, which limits its application in precision surface processing.

[0006] In summary, the current fault slip experimental device still has many deficiencies in its ability to control roughness. Therefore, it is urgent to develop an experimental device that can accurately process and control the roughness of the fault surface, providing a new technical means for exploring the basic mechanism of fault slip behavior. Summary of the invention

[0007] The present invention aims to solve one of the technical problems in the related art at least to a certain extent.

[0008] Therefore, the purpose of the present invention is to provide a fault slip experimental device to solve the problems of difficult control of the roughness characteristics of the fault surface and low precision in existing fault experiments.

[0009] In order to achieve the above object, the present invention adopts the following technical solution:

[0010] The present invention provides a fault slip experimental device, comprising:

[0011] A fault model, comprising a first sub-model and a second sub-model, wherein the first sub-model and the second sub-model use the same right-angled triangle plate, and the inclined surfaces of the first sub-model and the second sub-model are bonded to each other to form a laboratory fault surface at the bonding point, and the inclined surface of each sub-module has a micron-level roughness feature, and the roughness feature is formed by using a parametric laser etching process, that is, using a parametric laser beam to perform micron-level precision engraving on the originally smooth inclined surface of each sub-model;

[0012] A loading device is arranged around the fault model to realize biaxial loading of the fault model and simulate fault slip conditions;

[0013] Data acquisition and processing unit, including a multi-channel transient strain acquisition module based on strain gauges and a full-field displacement observation module based on digital image correlation method, to achieve all-round observation of the entire fault experiment;

[0014] The control and monitoring unit is connected to the loading device and the data acquisition and processing unit, and is used to control the parameters of the laser beam during the laser etching process, and is also used to control the stability of the experiment, and observe and analyze the experimental results.

[0015] In some embodiments, the first sub-model and the second sub-model are made of the same material, and an acrylic material having a wave velocity close to that of an actual rock formation is selected; each corner of the fault model is chamfered to reduce stress concentration at the end.

[0016] In some embodiments, before laser etching is performed, a fixture is used to fix and clamp the submodule to ensure that the submodule is stable and does not shift during the processing. The fixture is compatible with submodules of different shapes and sizes.

[0017] In some embodiments, the laser etching process uses a focused laser beam through a precisely controlled scanning system to gradually melt, vaporize or evaporate the surface of the material locally along a predetermined trajectory to form a fine texture or a concave-convex structure. The energy density, pulse width, repetition frequency and scanning speed of the laser are set according to the depth, morphology and distribution density of the texture on the fault surface; the laser source is selected as an ultraviolet laser or a fiber laser.

[0018] In some embodiments, the fault slip experimental device also includes a roughness sensing unit connected to the control and monitoring unit, and the roughness sensing unit includes a fault surface roughness sensor, a laser power sensor, and a position and speed sensor; the fault surface roughness sensor is used to detect the roughness of the etched surface in real time to ensure that the surface texture meets the design requirements; the laser power sensor is used to detect the output power of the laser beam to ensure that it meets the set range; the position and speed sensor is used to monitor the scanning speed and position of the laser beam to ensure the accuracy of the scanning path; the control and monitoring unit establishes a mapping relationship between roughness and laser beam parameters, and adjusts the laser beam parameters in real time to accurately achieve the required surface roughness and simulate the micron-level features of the real fault surface.

[0019] In some embodiments, after the laser etching process is completed, a high-pressure airflow of 0.3Mpa-1Mpa is used to clean the fault surface to remove residual particles on the fault surface.

[0020] In some embodiments, the loading device includes a main structure, which is a U-shaped integral casting frame. Servo cylinders and servo control valves supported on corresponding side walls of the main structure are respectively provided around the fault model, and are equipped with corresponding digital closed-loop servo controllers, load sensors and displacement sensors. A loading plate is fixed to the end of the piston rod of each servo cylinder. During the loading process, the loading plate contacts the corresponding side of the fault model. The digital closed-loop servo controller, the load sensor and the displacement sensor are connected to the control and monitoring unit.

[0021] In some embodiments, the strain gauge-based multi-channel transient strain acquisition module includes a strain amplifier, a storage recorder, and a plurality of strain rosettes, Wheatstone bridges, and wires. The strain rosettes are arranged on one side surface of the fault model and along the fault plane. Each strain rosette is connected to a corresponding one of the Wheatstone bridges through the wire. The Wheatstone bridge adopts a half-bridge connection mode. The difference of the principal strain is measured by the voltage difference output by the Wheatstone bridge, and then the shear strain near the fault plane is obtained according to the strain gauge-Wheatstone bridge measurement principle. The strain amplifier supplies power to all the Wheatstone bridges through the wire, amplifies the voltage difference output by each Wheatstone bridge, and transmits it to the storage recorder.

[0022] In some embodiments, the full-field displacement observation module based on the digital image correlation method includes a camera and a speckle pattern arranged on the other side surface of the fault model and arranged along the fault plane. The camera is used to collect the speckle image of the target area during the recording process, and then the digital image correlation method is used to perform iterative calculations to find the extreme value of the correlation coefficient, thereby obtaining the full-field displacement information of the laboratory fault plane.

[0023] In some embodiments, the control and monitoring unit includes a connected control module and a monitoring platform, wherein the control module is used to control the loading device and data acquisition, and is also used to control the laser beam parameters of the laser etching process to ensure the stability and repeatability of the experiment; the monitoring platform provides real-time monitoring and data display functions of the experimental process.

[0024] A fault slip experimental device provided by an embodiment of the present invention has the following characteristics and beneficial effects:

[0025] 1) Introduce parametric roughness design and processing technology to achieve high-precision and controllable roughness processing of the fault surface.

[0026] 2) Utilize the multi-channel transient strain acquisition module and the ultra-high-speed full-field displacement observation module to achieve high-precision observation of the fault plane. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 A schematic diagram of the back side of a fault slip experimental device based on controllable roughness processing provided by an embodiment of the present invention;

[0028] Figure 2 A front schematic diagram of a fault slip experimental device based on controllable roughness processing provided by an embodiment of the present invention;

[0029] Numbers in the figure: 1—first sub-model; 2—second sub-model; 3—loading device; 4—strain rosette; 5—speckle pattern. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application. The following scheme is only used as an explanation of the inventive concept, and the specific scheme is not limited thereto. In addition, for ease of description, only the parts related to the present invention are shown in the accompanying drawings, rather than the entire process.

[0031] On the contrary, the present application covers any substitution, modification, equivalent method and scheme made on the essence and scope of the present application as defined by the claims. Further, in order to make the public have a better understanding of the present application, some specific details are described in detail in the detailed description of the present application below. Those skilled in the art can fully understand the present application without the description of these details.

[0032] See also Figure 1 , Figure 2 , a fault slip experimental device provided by an embodiment of the present invention comprises:

[0033] The fault model includes a first sub-model 1 and a second sub-model 2. The first sub-model 1 and the second sub-model 2 use the same right-angled triangle plate. The inclined surfaces of the first sub-model 1 and the second sub-model 2 are bonded to each other to form a laboratory fault surface at the bonding point. The inclined surfaces of each sub-module have a micron-level roughness feature. The roughness feature is formed by using a parametric laser etching process, that is, using a high-energy laser beam of 50mJ to 500mJ to perform micron-level precision engraving on the originally smooth inclined surface of each sub-model;

[0034] The loading device 3 is arranged around the fault model to realize biaxial loading of the fault model and simulate fault slip conditions;

[0035] Data acquisition and processing unit, including a multi-channel transient strain acquisition module based on strain gauges and a full-field displacement observation module based on the Digital Image Correlation (DIC) method, to achieve all-round observation of the entire fault experiment;

[0036] The control and monitoring unit is connected to the loading device 3 and the data acquisition and processing unit, and is used to control the parameters of the laser beam during the laser etching process, and is also used to control the stability of the experiment, and observe and analyze the experimental results.

[0037] In some embodiments, the fault model is a rectangular plate structure formed by splicing a first sub-model 1 and a second sub-model 2. The two sub-models have exactly the same shape and size, and the laboratory fault plane formed between the first sub-model 1 and the second sub-model 2 is located exactly on a diagonal line of the fault model.

[0038] Optionally, the first sub-model 1 and the second sub-model 2 both use isosceles right-angled triangle plates, the right-angled side length of each sub-model is about 50 cm, and the thickness of each sub-model is about 2 cm.

[0039] In some embodiments, the first sub-model 1 and the second sub-model 2 are made of the same material, and an acrylic material having a wave velocity close to that of the actual rock formation is selected. In addition, the acrylic material is easy to process and can better simulate different roughnesses.

[0040] In some embodiments, before the submodule is laser-etched, a fixture is used to fix and clamp the submodule so that the submodule is stable and does not shift during the processing. In addition, the size of the fixture is adjustable and can be compatible with sub-models of different shapes and sizes. After the sub-model is fixed, a high-energy laser beam of 50mJ to 500mJ is used to precisely engrave the surface of the sub-model to generate micron-level roughness features. The laser etching process uses a focused high-power laser beam through a precisely controlled scanning system to gradually melt, vaporize or evaporate the surface of the material locally along a predetermined trajectory to form a fine texture or concave-convex structure. Parameters such as the energy density, pulse width, repetition frequency and scanning speed of the laser can be adjusted as needed to control the depth, morphology and distribution density of the surface texture. The laser source is selected as an ultraviolet laser or a fiber laser. The roughness parameters are input into the control and monitoring unit to achieve controllable roughness processing and simulate the real fault surface.

[0041] Furthermore, in order to ensure that the parameters in the laser etching process always meet the predetermined roughness requirements, the fault slip experimental device of this embodiment also includes a roughness sensing unit connected to the control and monitoring unit, and the roughness sensing unit includes a fault surface roughness sensor, a laser power sensor, a position and speed sensor, etc., and each sensor is connected to the control and monitoring unit, wherein the fault surface roughness sensor is used to detect the roughness of the etched surface in real time to ensure that the surface texture meets the design requirements; the laser power sensor is used to detect the output power of the laser beam to ensure that it meets the set range; the position and speed sensor is used to monitor the scanning speed and position of the laser beam to ensure the accuracy of the scanning path. During the laser etching process, the control and monitoring unit calculates the appropriate laser beam parameters based on the input roughness parameters. Larger roughness usually requires higher laser power and longer pulse width to ensure deep etching and form a more obvious surface texture, while smaller roughness requires lower power, short pulse width and faster scanning speed to obtain fine and uniform texture. The control and monitoring unit establishes a mapping relationship between roughness and laser beam parameters through experimental data and theoretical models, and adjusts the laser beam parameters in real time to accurately achieve the required surface roughness and simulate the micron-level features of the real fault surface.

[0042] Furthermore, after the roughness of the fault surface is processed, a 0.3Mpa-1Mpa high-pressure airflow is used to clean the fault surface to remove the residual particles on the fault surface.

[0043] Furthermore, the four top corners of the fault model are chamfered to reduce stress concentration at the ends.

[0044] In some embodiments, the loading device 3 includes a main structure, which is a U-shaped integral casting frame, the inner side wall of the main structure does not contact the outer side wall of the fault model, and the fault model is surrounded by ( Figure 1 The upper, lower, left and right sides are shown in the figure. Each of the servo cylinders and servo control valves supported on the corresponding side walls of the main structure is provided with a corresponding digital closed-loop servo controller, a high-precision load sensor and a high-precision displacement sensor. A loading plate is fixed to the piston rod end of each servo cylinder. The loading plate contacts the corresponding side of the fault model during loading. The digital closed-loop servo controller, the high-precision load sensor and the high-precision displacement sensor are connected to the control module in the control and monitoring unit. When applying pressure load to the fault model, the control module is operated to load the horizontal and vertical forces to the preset load value at the same time, and then the horizontal pressure is kept unchanged, and the vertical direction is switched to displacement control. The loading speed is 1μm / s. The high-precision sensor measures and feeds back the current load or displacement. The digital closed-loop servo controller performs double closed-loop PID calculation, outputs control signals, drives the servo cylinder control valve, and realizes high-precision displacement control and load control of the servo cylinder.

[0045] In some embodiments, the multi-channel transient strain acquisition module based on strain gauges is mainly composed of a strain amplifier, a storage recorder, a plurality of strain gauges 4, a Wheatstone bridge and a wire. Each strain gauge 4 is provided with two strain gauges, each strain gauge is used as a resistor, and the Wheatstone bridge adopts a half-bridge connection mode. The resistance difference of the two strain gauges in the strain gauge 4 connected to the Wheatstone bridge can be obtained by the voltage difference of the collected Wheatstone bridge, and the difference of the principal strain is further calculated by the resistance difference, and then the shear strain near the fault plane is obtained according to the strain gauge-Wheatstone bridge measurement principle. Each strain gauge 4 is connected to a corresponding Wheatstone bridge through a wire, and the strain amplifier supplies power to all Wheatstone bridges through the wire, and amplifies the voltage difference of the collected Wheatstone bridge, and transmits it to the storage recorder, and the storage recorder outputs the measured strain value to the control and monitoring unit. The strain gauge 4 is arranged on the back of the fault model and arranged along the fault plane. The distance between adjacent strain gauges 4 is 80 mm, and the center position of the strain gauge is 2 mm away from the fault plane.

[0046] In some embodiments, the full-field displacement observation module includes a camera, and the full-field displacement of the laboratory fault plane is observed and analyzed in combination with the DIC method. First, the surface opposite to the fault where the strain rosette 4 is set (in this embodiment, the surface of the fault on the front of the fault model) is selected as the target area, and the speckle pattern 5 is arranged along the target area. The camera is used to collect the speckle image of the target area during the loading process, and then the DIC method is used for iterative calculation to find the extreme value of the correlation coefficient, thereby obtaining the corresponding displacement field information.

[0047] 1) In some embodiments, the control and monitoring unit includes a control module and a monitoring platform connected to each other, which is convenient for controlling the stability of the experiment, observing and analyzing the experimental results; wherein the control module is connected to the loading device 3 and the data acquisition and processing unit, and is used to control the loading device 3 and data acquisition to ensure the stability and repeatability of the experiment. Specifically, the control module is connected to the digital closed-loop servo controller, the high-precision load sensor and the high-precision displacement sensor in the loading device 3. The control module is also connected to the roughness sensing unit to control the laser parameters to meet the predetermined roughness requirements. The monitoring platform provides real-time monitoring and data display functions of the experimental process, and can display the curves of strain, displacement and other data changes, and realize the monitoring of the spatiotemporal continuous change law of the strain field and displacement field of the fault surface, which is convenient for the analysis of subsequent experimental data.

[0048] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "install", "connect", "connect", and "set" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0049] In the description of the present application, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In the description of the present application, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0050] Although embodiments of the present disclosure have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and alterations may be made to the embodiments without departing from the principles and spirit of the present disclosure, the scope of which is defined by the claims and their equivalents.

Claims

1. A fault slip experimental device, characterized in that: include: A fault model, comprising a first sub-model and a second sub-model, wherein the first sub-model and the second sub-model use the same right-angled triangle plate, and the inclined surfaces of the first sub-model and the second sub-model are bonded to each other to form a laboratory fault surface at the bonding point, and the inclined surface of each sub-module has a micron-level roughness feature, and the roughness feature is formed by using a parametric laser etching process, that is, using a parametric laser beam to perform micron-level precision engraving on the originally smooth inclined surface of each sub-model; A loading device is arranged around the fault model to realize biaxial loading of the fault model and simulate fault slip conditions; Data acquisition and processing unit, including a multi-channel transient strain acquisition module based on strain gauges and a full-field displacement observation module based on digital image correlation method, to achieve all-round observation of the entire fault experiment; The control and monitoring unit is connected to the loading device and the data acquisition and processing unit, and is used to control the parameters of the laser beam during the laser etching process, and is also used to control the stability of the experiment, and observe and analyze the experimental results.

2. The fault slip experimental device according to claim 1, characterized in that: The first sub-model and the second sub-model are made of the same material, an acrylic material having a wave velocity close to that of the actual rock formation; each corner of the fault model is chamfered to reduce stress concentration at the end.

3. The fault slip experimental device according to claim 1, characterized in that: Before laser etching, the submodule is fixed and clamped by a fixture to ensure that the submodule is stable and does not shift during the processing. The fixture is compatible with submodules of different shapes and sizes.

4. The fault slip experimental device according to claim 1, characterized in that: The laser etching process uses a focused laser beam through a precisely controlled scanning system to gradually melt, vaporize or evaporate the surface of the material locally along a predetermined trajectory to form a fine texture or concave-convex structure. The energy density, pulse width, repetition frequency and scanning speed of the laser are set according to the depth, shape and distribution density of the fault surface texture; the laser source is selected as an ultraviolet laser or a fiber laser.

5. The fault slip experimental device according to claim 1, characterized in that: The fault slip experimental device also includes a roughness sensing unit connected to the control and monitoring unit, and the roughness sensing unit includes a fault surface roughness sensor, a laser power sensor, and a position and speed sensor; the fault surface roughness sensor is used to detect the roughness of the etched surface in real time to ensure that the surface texture meets the design requirements; the laser power sensor is used to detect the output power of the laser beam to ensure that it meets the set range; the position and speed sensor is used to monitor the scanning speed and position of the laser beam to ensure the accuracy of the scanning path; the control and monitoring unit establishes a mapping relationship between the roughness and the laser beam parameters, and adjusts the laser beam parameters in real time to accurately achieve the required surface roughness and simulate the micron-level characteristics of the real fault surface.

6. The fault slip experimental device according to claim 4, characterized in that: After the laser etching process is completed, a high-pressure airflow of 0.3Mpa-1Mpa is used to clean the fault surface to remove the residual particles on the fault surface.

7. The fault slip experimental device according to claim 1, characterized in that: The loading device includes a main structure, which is a U-shaped integral casting frame. Servo cylinders and servo control valves supported on the corresponding side walls of the main structure are respectively arranged around the fault model, and are equipped with corresponding digital closed-loop servo controllers, load sensors and displacement sensors. A loading plate is fixed to the end of the piston rod of each servo cylinder. During the loading process, the loading plate contacts the corresponding side of the fault model. The digital closed-loop servo controller, the load sensor and the displacement sensor are connected to the control and monitoring unit.

8. The fault slip experimental device according to claim 1, characterized in that: The multi-channel transient strain acquisition module based on strain gauges includes a strain amplifier, a storage recorder, and a plurality of strain rosettes, Wheatstone bridges and wires. The strain rosettes are arranged on one side surface of the fault model and along the fault plane. Each strain rosette is connected to a corresponding one of the Wheatstone bridges through the wire. The Wheatstone bridge adopts a half-bridge connection mode. The difference of the principal strain is measured by the voltage difference output by the Wheatstone bridge, and then the shear strain near the fault plane is obtained according to the strain gauge-Wheatstone bridge measurement principle. The strain amplifier supplies power to all the Wheatstone bridges through the wire, amplifies the voltage difference output by each Wheatstone bridge, and transmits it to the storage recorder.

9. The fault slip experimental device according to claim 8, characterized in that: The full-field displacement observation module based on the digital image correlation method includes a camera and a speckle pattern arranged on the other side surface of the fault model and arranged along the fault plane. The camera is used to collect the speckle image of the target area during the recording process, and then the digital image correlation method is used to perform iterative calculation to find the extreme value of the correlation coefficient and obtain the full-field displacement information of the laboratory fault plane.

10. The fault slip experimental device according to claim 1, characterized in that: The control and monitoring unit includes a control module and a monitoring platform connected to each other. The control module is used to control the loading device and data acquisition, and is also used to control the laser beam parameters of the laser etching process to ensure the stability and repeatability of the experiment; the monitoring platform provides real-time monitoring and data display functions of the experimental process.

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