Apparatus and method for cross-fault measurement in experimental earthquakes

Abstract

This application relates to the field of seismic measurement technology, and provides an apparatus and method for measuring cross-fault motion in experimental earthquakes. The apparatus includes a metal rod, an elastic compression spring installed at the first end of the metal rod, and a rod axial force gauge installed on the metal rod. The method involves installing the apparatus on a fault model and calculating fault motion. Based on the tensile stiffness K1 of the apparatus for measuring cross-fault motion in experimental earthquakes and the data recorded by the rod axial force gauge, the axial displacement of the metal rod, the shear displacement in the fault shear direction, and the real-time velocity and acceleration of the fault motion at time t are calculated. The apparatus for measuring cross-fault motion in experimental earthquakes of this application has a simple structure, is easy to manufacture, and can capture vibration information during fault instability without the need for complex field equipment deployment. It is not easily affected by the environment, and the test results are accurate. The method can accurately describe the instability process of experimental earthquakes.

Description

Technical Field

[0001] This application relates to the field of seismic measurement technology, and in particular to an apparatus and method for measuring cross-faults in experimental earthquakes. Background Technology

[0002] Natural earthquakes are difficult to capture, but they can be attributed to the shearing motion of two rock masses, releasing energy through friction at the interface and causing ground vibrations. Although natural earthquakes are elusive, this process can be simulated on a laboratory scale using experimental earthquakes. The principle behind experimental earthquake simulations is the friction between rock interfaces or the fracturing and instability of rock bridges. By measuring the fault instability process in indoor experiments, we can understand the strain distribution and variation patterns of the rock mass under stress.

[0003] Currently, various methods exist for measuring fault instability processes in the laboratory. For example, digital imaging technology can acquire the full-field strain of the rock mass, acoustic emission technology can obtain vibration information during fault instability, and monitoring the force and displacement of loading instruments can reveal the bearing state of the test rock mass. However, these methods are often difficult to apply directly in the field. For instance, digital imaging technology may be affected by factors such as lighting conditions and terrain obstruction in the field, leading to decreased measurement accuracy; acoustic emission technology may be affected by various background noises in noisy environments, making it difficult to accurately capture weak seismic signals; and monitoring loading instruments are difficult to apply directly in the field because the rock cannot be loaded and controlled with the same precision as in the laboratory. Therefore, it is essential to develop a reliable fault motion measurement method applicable to faults in the field. Summary of the Invention

[0004] The purpose of this application is to provide an apparatus and method for cross-fault measurement in experimental earthquakes, so as to solve or alleviate the problems existing in the prior art.

[0005] To achieve the above objectives, this application provides the following technical solution: An apparatus for measuring cross-faults in experimental earthquakes includes a metal rod, an elastic compression spring mounted on a first end of the metal rod, and a rod axial force gauge mounted on the metal rod.

[0006] Furthermore, the yield force of the metal rod is not less than the ultimate elastic compressive force of the elastic spring; the ultimate compressive force of the metal rod is between 1-2 kN; the ultimate displacement of the metal rod is adjusted by changing the length of the elastic spring, and the ultimate displacement of the metal rod is within 1-10 mm.

[0007] Furthermore, the minimum diameter of the metal rod is 1 mm, and the length is matched according to the size of the sample.

[0008] Furthermore, the minimum outer diameter of the elastic compression spring is 10mm, and the inner diameter is 2-4mm larger than the diameter of the metal rod; the length of the elastic compression spring is 5-20mm, and the compression amount is adjustable within 1-10mm.

[0009] This application also proposes a method for cross-fault measurement in experimental earthquakes, using the aforementioned apparatus for cross-fault measurement in experimental earthquakes, comprising the following steps: Step 1: Prepare the fault model; the fault model is a simulated rock mass with simulated faults inside; Step 2: Create a vertical rod groove on the surface of the fault model. The rod groove penetrates the simulated fault and extends to the first and second end faces of the fault model. Install the device for measuring the fault span during the experimental earthquake in the rod groove. The inner side of the elastic compression spring and the rod axial force gauge rests against the first and second end faces, respectively. Step 3: Apply a constant load vertically to the fault model on which the experimental earthquake cross-fault measurement device is installed, and record the mechanical growth of the metal rod in real time using the rod axial force gauge; A constant load constraint is applied to the fault model in the horizontal direction to which the device for measuring cross-faults in the experimental earthquake is installed. The loading force in this direction can vary, but the displacement is consistently applied at a fixed rate to drive the simulated fault to accumulate and release elastic energy. The axial force gauge of the rod records the mechanical growth of the metal rod in real time. Step 4: Calculate the fault motion; based on the tensile stiffness K1 of the cross-fault measurement device during the experimental earthquake and the data recorded by the rod axial force gauge, calculate the axial displacement of the metal rod, the shear displacement in the fault shear direction, and the real-time velocity and acceleration of the fault motion at time t.

[0010] Furthermore, step four, the calculation steps for fault motion, include: (1) Based on the axial force increase ΔF of the metal rod and the tensile stiffness K1 of the device for measuring across the fault in the experimental earthquake, calculate the displacement u in the axial direction of the metal rod, u=ΔF / K1; (2) Project the axial displacement u of the metal rod onto the fault plane and calculate the shear displacement s in the fault shear direction, s=u×cos , The angle between the rod groove and the simulated fault; (3) Calculate the real-time velocity v and acceleration a of the fault motion using differentiation, v = ds / dt, a = d 2 v / dt 2 .

[0011] Furthermore, the elastic limit pressure of the elastic spring does not exceed 2% of the lower limit of all loading forces; the ultimate tensile displacement of the metal rod is greater than the maximum design displacement of the simulated fault in step three.

[0012] Furthermore, the depth of the groove is not less than half the thickness of the simulated rock mass material, and the width of the groove is not less than the range of the simulated fault shear displacement in step three.

[0013] Furthermore, in step one, preliminary tests are conducted on the simulated rock mass material and the device for cross-fault measurement during experimental earthquakes. Stick-slip tests were conducted on simulated rock mass materials without experimental earthquake cross-fault measurement devices. The critical value of stress accumulation in the stick-slip test was used as the upper limit of the applied axial force, and the stable value of stress release in the stick-slip test was used as the lower limit of the applied axial force.

[0014] For a metal rod, the tensile stiffness K1 and elastic limit tensile force F of the device used for measuring fault spans in experimental earthquakes are tested using a universal testing machine at a rate on the order of mm / s. max and ultimate tensile displacement u max ; and by changing the radius and length of the elastic compression spring, K1 and F are adjusted. max u max The value of the elastic limit pressure F ultimately makes the elastic limit pressure F max The ultimate tensile displacement u should not exceed 2% of the lower limit of the axial force in the stick-slip test. max The test displacement is greater than that of the stick-slip test.

[0015] Furthermore, the simulated fault is the contact interface between two rock materials or rock-like materials, and the simulated fault includes a mature interface, an interface with a rock bridge, or an interface with fault gouge interlayers in the middle.

[0016] Furthermore, the rock material types include granite, sandstone, marble, basalt, gabbro, etc.; the rock-like material types include plexiglass, cast concrete, artificial bricks, etc.

[0017] The technical solution of this application has the following beneficial effects: The experimental seismic trans-fault measurement device of this application has a simple structure, is easy to manufacture, and can capture vibration information during fault instability without the need for complex field equipment deployment. It is not easily affected by the environment and the test results are accurate. The device is in direct contact with the rock sample during the experiment, ensuring mechanical boundary stability and convenient analysis of calculation results. It can also be adaptably applied to the measurement of fault instability processes in the field. Furthermore, this device can simultaneously observe fault instability with other methods such as acoustic emission and digital imaging.

[0018] The method of this application is applicable to experimental earthquakes with a lower limit loading force of 20kN or more. Based on the tensile stiffness K1 of the cross-fault measurement device and the data recorded by the rod axial force gauge during the experimental earthquake, it can calculate the axial displacement of the metal rod, the shear displacement in the fault shear direction, and the real-time velocity and acceleration of the fault movement at time t, thereby achieving an accurate description of the instability process of the experimental earthquake. Attached Figure Description

[0019] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. Wherein: Figure 1 This is a schematic diagram of the structure of an embodiment of the present invention.

[0020] Figure 2 This is a schematic diagram of the installation of the present invention in a simulated fault according to an embodiment of the invention.

[0021] Figure 3 This is a schematic diagram of the structure of a simulated fault according to an embodiment of the present invention.

[0022] Figure 4 This is a schematic diagram of the tensile testing fixture for a universal testing machine.

[0023] Figure 5 This is a schematic diagram of the installation of a cross-fault measuring device without elastic compression springs in a simulated fault, as described in an embodiment of the present invention.

[0024] Figure 6 This is a schematic diagram illustrating the application of the present invention in field rock mass fault measurement.

[0025] Figure 7 This is a schematic diagram of the component installation on the pier for field rock mass fault measurement according to the present invention.

[0026] Figure 8 Test results of a universal testing machine when the number of springs installed at the end of a metal rod is different.

[0027] Figure 9 The results are from tests conducted using a universal testing machine that only stretches a metal rod.

[0028] In the diagram, 1-elastic compression spring, 2-metal rod, 3-rod axial force gauge, 4-rod groove, 5-simulated fault, 6-first rock mass, 7-second rock mass, 8-first clamping fixture, 9-second clamping fixture, 10-nut, 11-washer, 12-loading rod, 13-tensile testing fixture, 21-steel cable, 22-field axial force gauge, 23-field compression spring, 24-anchor, 25-pier, 26-grouting area. Detailed Implementation

[0029] The present application will now be described in detail with reference to the accompanying drawings and embodiments. Various examples are provided by way of interpretation and not by way of limitation. In fact, those skilled in the art will recognize that modifications and variations can be made to the present application without departing from the scope or spirit thereof. For example, a feature shown or described as part of one embodiment may be used in another embodiment to produce yet another embodiment. Therefore, it is desirable that the present application encompass such modifications and variations that fall within the scope of the appended claims and their equivalents.

[0030] An apparatus for measuring cross-faults in experimental earthquakes includes a metal rod 2, an elastic compression spring 1 mounted on the first end of the metal rod 2, and a rod axial force gauge 3 mounted on the metal rod 2. The elastic compression spring 1 includes a spring and washers 11 located at both ends of the spring length. The metal rod 2 is anchored to or outside the washers 11 located on the outer side by fasteners, so that the spring can be compressed by pulling the metal rod 2. The fasteners can be anchors 24 or nuts 10.

[0031] Furthermore, the yield force of the metal rod 2 is not less than the ultimate elastic compressive force of the elastic spring 1. This is to ensure that the elastic spring 1, with its adjustable stiffness and elastic compressive displacement, plays the core role in the cross-fault measurement device of this application, rather than relying on the metal rod 2 with its relatively small elastic ultimate displacement. The ultimate compressive force of the metal rod 2 is between 1 and 2 kN, meeting the slip requirements for the entire cycle in current experimental earthquakes. This method is applicable to experimental earthquakes with a lower limit loading force of 20 kN or higher. The ultimate displacement of the metal rod 2 is adjusted according to the length of the elastic spring 1, and is within 1-10 mm. The diameter of the metal rod 2 is kept as small as possible, typically 1-2 mm, and its length is matched to the sample size.

[0032] Furthermore, the outer diameter of the elastic spring 1 is 10-20 mm, and the inner diameter is 2-4 mm larger than the diameter of the metal rod. To ensure the stability of the elastic spring 1 during compression, its length is 5-20 mm, and the compression amount is adjustable within 1-10 mm to meet the displacement requirements of the experimental earthquake. In use, one end of the elastic spring 1 is secured with a nut 10, and the other end is pressed against the side of the simulated rock to achieve the tension of the metal rod and the compression of the spring. Even with large compression displacements, the elastic spring 1 can still maintain a linear force-displacement relationship, provided that the ultimate compressive force is much smaller than the hydraulic cylinder loading force during the rock instability measurement process, ensuring that the cross-fault measurement equipment only serves a monitoring function.

[0033] Furthermore, the rod axial force gauge 3 is used to monitor the axial force change of the metal rod 2 in real time during the experiment. Its range should be slightly smaller than the ultimate elastic stress of the metal rod 2, because generally, the smaller the range of the axial force gauge, the higher the accuracy. The rod axial force gauge 3 is a through-type compression axial force gauge, and its maximum force range is not less than the ultimate force of the metal rod 2 and the elastic compression spring 1. To ensure the stability of the through-type axial force gauge, during the simulated earthquake test, it is fixed to the other end of the rod, with the outer side tightened with nut 10 and the inner side in close contact with the sample; the inner diameter of the through-type axial force gauge should be as small as possible, only 1-2 mm larger than the outer diameter of the rod.

[0034] In another embodiment, the device for cross-fault measurement during experimental earthquakes does not include the elastic compression spring 1, but consists only of a metal rod 2 and an axial force gauge. In this case, it is suitable for test samples with small instability slip. The displacement is calculated using the linear elastic stiffness of the elastic segment of the metal rod 2. The yield force is between 1-2 kN. The diameter of the metal rod 2 should be as small as possible, preferably within 2 mm, and the length can be matched according to the size of the sample.

[0035] This application also proposes a method for cross-fault measurement in experimental earthquakes, using the aforementioned apparatus for cross-fault measurement in experimental earthquakes, comprising the following steps: Step 1: Prepare the fault model; the fault model is a simulated rock mass with simulated fault 5 inside; Figure 3 This is an example of a fault model, shown in the figure. The angle between the groove 4 and the simulated fault 5; Step 2: A vertical rod groove 4 is made on the surface of the fault model. The rod groove 4 penetrates the simulated fault 5 and extends to the first and second end faces of the fault model. The device for measuring the fault across the experimental earthquake is installed in the rod groove 4. The inner sides of the elastic compression spring 1 and the rod axial force gauge 3 abut against the first and second end faces, respectively. Step 3: Apply constant loads from four directions (up, down, left, and right) to the fault model on which the experimental earthquake cross-fault measurement device is installed vertically. The load is a constant normal stress of 2-5 MPa and a shear loading rate of 1-3 μm / s. The axial force gauge 3 records the mechanical growth of the metal rod 2 in real time. A constant load constraint is applied to the fault model in which the experimental earthquake cross-fault measurement device is installed in the horizontal direction. The loading force in this direction can vary, but the displacement is consistently applied at a fixed rate to drive the simulated fault 5 to accumulate and release elastic energy. The axial force gauge 3 records the mechanical growth of the metal rod 2 in real time. Figure 2 A fault model for installing a device for cross-fault measurement during experimental earthquakes; Step 4: Calculate the fault motion; based on the tensile stiffness K1 of the cross-fault measurement device during the experimental earthquake and the data recorded by the rod axial force gauge, calculate the axial displacement of the metal rod, the shear displacement in the fault shear direction, and the real-time velocity and acceleration of the fault motion at time t.

[0036] Furthermore, step four, the calculation steps for fault motion, include: (1) Calculate the axial displacement u of the metal rod based on the axial force increase ΔF of the metal rod and the tensile stiffness K1 of the device used for cross-fault measurement during the experimental earthquake, u=ΔF / K1; (2) Project the axial displacement u of the metal rod onto the fault plane and calculate the shear displacement s in the fault shear direction, s=u×cos , The angle between the rod groove and the simulated fault; (3) Calculate the real-time velocity v and acceleration a of the fault motion using differentiation, v = ds / dt, a = d 2 v / dt 2 .

[0037] Furthermore, the elastic limit pressure of the elastic spring 1 does not exceed 2% of the lower limit of all loading forces; the ultimate tensile displacement of the metal rod 2 is greater than the maximum design displacement of the simulated fault 5 in step three.

[0038] Furthermore, to ensure the strength of the simulated fault 5, the depth of the rod groove 4 is not less than half the thickness of the simulated rock mass material. The purpose of the groove is to place the rod in the center of the sample during installation, which facilitates the installation of the anchor rod in the rock sample. The width of the rod groove 4 is not less than the shear displacement range of the simulated fault 5 in step three, so as to ensure that the cross-fault measuring rod will not be subjected to shear force during the cross-fault test.

[0039] Furthermore, in step one, preliminary tests are conducted on the simulated rock mass material and the device for cross-fault measurement during experimental earthquakes. Stick-slip tests were conducted on simulated rock mass materials without experimental earthquake cross-fault measurement devices. The critical value of stress accumulation in the stick-slip test was used as the upper limit of the applied axial force, and the stable value of stress release in the stick-slip test was used as the lower limit of the applied axial force. For metal rods, such as Figure 4 As shown, the tensile stiffness K1 and elastic limit tensile force F of the device used for measuring faults during experimental earthquakes are tested at a rate of 0.05-5 mm / s using a tensile testing machine or a universal testing machine. max and ultimate tensile displacement u max ; and by changing the radius and length of the elastic compression spring, the tensile stiffness K1 and the elastic limit tensile force F are adjusted. max Ultimate tensile displacement u maxThe value of the elastic limit pressure F ultimately makes the elastic limit pressure F max The ultimate tensile displacement u should not exceed 2% of the lower limit of the axial force in the stick-slip test. max The test displacement is greater than that of the stick-slip test.

[0040] Specifically, the elastic compression spring and the metal rod form the core component of the device for cross-fault measurement in experimental earthquakes, referred to simply as the measurement core component. For example... Figure 4 As shown, the core measurement component was calibrated using a standard laboratory universal testing machine. The core measurement component was mounted on a tensile testing fixture. Washers were placed on both sides of the elastic spring. The first end of the metal rod passed through the elastic spring and was secured with a nut. A loading rod was fixed to one end of the tensile testing fixture, and the second end of the metal rod extended beyond the other end of the fixture to serve as the force application section. During the tensile test, the universal testing machine transmitted force to the washers and elastic spring through the loading rod and the metal rod. The tensile displacement and tensile force were recorded, and data graphs and linear fitting were performed. The slope of the fitted line in the graph represents the tensile stiffness K1 of the core measurement component.

[0041] The simulated fault 5 is the contact interface between two rock materials or rock-like materials. The simulated fault 5 includes mature interfaces, interfaces with rock bridges, or interfaces with fault gouge interlayers. The rock materials include granite, sandstone, marble, basalt, gabbro, etc.; the rock-like materials include plexiglass, cast concrete, artificial brick, etc. In this embodiment, the simulated fault 5 is formed by piecing together two right-angled triangular sub-modules, suitable for biaxial shearing instruments for fault instability. It can also be configured with other shapes to suit other specifications of shearing instruments. Figure 2 , Figure 3 , Figure 5 In this context, the two sub-modules are the first rock mass 6 and the second rock mass 7, respectively.

[0042] When conducting experimental earthquakes, this device needs to be installed in a fault model. In order to facilitate the application of loading force to the fault model, a groove for installing the axial force gauge / elastic spring 1 is specially provided on the end face of the fault model; or, a first clamping fixture 8 and a second clamping fixture 9 that can cover the axial force gauge / elastic spring 1 are designed to make the surface bearing the loading force plane.

[0043] The following is a complete method for cross-fault measurement in experimental earthquakes.

[0044] First, before the formal experiment, the metal rod 2, the elastic spring 1, and the core measurement component composed of the two need to be calibrated. The metal rod 2 has a diameter of 2mm, and the elastic spring 1 has an outer diameter of 14mm and a height of 20mm. like Figure 8-9 The image shown is a diagram of the results of the preliminary tests conducted by the inventor. Figure 8 The figure shows the test results of a universal testing machine when the number of springs installed at the ends of the metal rod 2 varies. A single spring indicates that the core measuring component has an elastic compression spring 1 installed only at one end of the metal rod 2, while a double spring indicates that the core measuring component has elastic compression springs 1 installed at both ends of the metal rod 2. Figure 8 The results show that within the tensile force loading range of 0-0.7kN, regardless of whether the core measurement component uses a single spring or a double spring, the lines connecting the tensile test data are all oblique lines, indicating a linear growth relationship between tensile force and tensile displacement. Calculations show that in this embodiment, the tensile stiffness K1 of the core measurement component composed of a single spring and a metal rod is 0.25kN / mm.

[0045] Figure 9 The test data for the universal testing machine only stretched the metal rod 2 shows that the tensile stiffness of the metal rod 2 exhibits a trend of first increasing, then remaining constant, and finally decreasing. During the increasing phase, which corresponds to the elastic phase of the metal material, we use the elastic tensile stiffness of this phase to calculate the relationship between the tensile displacement and the axial force of the metal rod 2. In this embodiment, the effective gauge length of the metal rod 2 is 280 mm. During the elastic deformation phase, its linear elastic modulus is 210 GPa. Using the tensile stiffness formula, the tensile stiffness of the metal rod 2 is calculated to be 2.356 kN / mm.

[0046] The above results demonstrate that there is a good linear relationship between the tensile force and tensile displacement of the core component, which can be used to measure the displacement of the simulated fault 5 in the experimental earthquake; alternatively, the displacement of the simulated fault 5 in the experimental earthquake can be measured solely using the elastic segment of the metal rod 2. Therefore, in this embodiment, two schemes are adopted for the cross-fault measurement device in the experimental earthquake: a complete scheme using the elastic spring 1, the metal rod 2, and the axial force gauge (Scheme 1), and a cross-fault measurement device using only the metal rod 2 and the axial force gauge without using the elastic spring 1 (Scheme 2).

[0047] A method for cross-fault measurement in experimental earthquakes includes the following steps: Step 1: Prepare the fault model. In this embodiment, a biaxial shear instrument is used to provide the loading force. The fault model consists of two sub-modules that are essentially right-angled triangles. These two sub-models are designated as the first rock mass 6 and the second rock mass 7, respectively. A stick-slip test is conducted on the simulated rock mass material without the experimental earthquake cross-fault measurement device. The upper and lower limits of the loading axial force of the granite fault model containing the rock bridge are 550kN and 150kN, respectively. The upper and lower limits of the loading axial force of the acrylic fault model containing the smooth simulated fault 5 are 60kN and 20kN, respectively. After calibration, the tensile stiffness K1 of the core component is 0.25kN / mm, and the elastic stiffness K2 of the metal rod is 2.356kN / mm. Step 2: Create vertical grooves 4 on the surface of the fault model. The grooves 4 penetrate the simulated fault 5 and extend to the first and second end faces of the fault model. Option 1 involves installing a metal rod 2 in a fault model made of granite containing a rock bridge. The inner sides of the elastic spring 1 and the rod axial force gauge 3 abut against the first and second end faces of the fault model, respectively. This fault model exhibits a relatively large instability displacement. Option 2, without a spring, involves installing a device in a fault model composed of two acrylic thick plates. The two acrylic thick plates form a smooth simulated fault 5. A metal rod 2 is installed in the rod groove 4. One end of the metal rod 2 is fixed in a groove on the first end face of the acrylic thick plate, and the rod axial force gauge 3 is installed in a groove on the second end face of the acrylic thick plate. This fault model exhibits a smaller instability displacement. Step 3: Apply constant loads from four directions (up, down, left, and right) to the fault model on which the experimental earthquake cross-fault measurement device is installed vertically. The load is a constant normal stress of 4 MPa and a shear loading rate of 2 μm / s. The axial force gauge 3 records the mechanical growth of the metal rod 2 in real time. A constant load constraint is applied horizontally to the fault model on which the experimental earthquake cross-fault measurement device is installed. The loading force in this direction can vary, but the displacement is consistently applied at a fixed rate to drive the simulated fault 5 to accumulate and release elastic energy, resulting in spontaneous instability. The shear direction of the simulated fault 5 is as follows: Figure 2 As shown by the middle arrow, the elastic spring 1 is under compression and the metal rod 2 is under tension; the rod axial force gauge 3 records the mechanical growth of the metal rod 2 in real time. Step 4: Calculate fault motion: (1) Based on the tensile stiffness K1 of the core component measured / the elastic stiffness K2 of the metal rod and the axial force increase ΔF measured by the axial force gauge, the axial displacement u1 of the metal rod in Scheme 1 is calculated as ΔF / K1, and the axial displacement u2 of the metal rod in Scheme 2 is calculated as ΔF / K2. (2) Project the axial displacement u of the metal rod onto the fracture surface, and calculate the shear displacement s1 = u1 × cos θ in the shear direction of the fracture in Scheme 1. Scheme 2: The shear displacement in the shear direction of the interrupted layer is s2 = u2 × cos , The angle between the rod groove and the simulated fault; (3) Calculate the real-time velocity v1=ds1 / dt and acceleration a1=dt of the simulated fault motion using Scheme 1 by differentiation. 2 v1 / dt 2 Using Scheme 2, the real-time velocity of the simulated fault motion is v2=ds2 / dt, and the acceleration is a2=d 2v2 / dt 2 ; d is the differentiation operator. The test results of the loading experiment using the fault model of Scheme 1 show that when the fault in the rock bridge test occurs, the anchor rod is stretched, the axial force increases, and the corresponding loading force decreases. The anchor rod force is consistent with the loading force of the testing machine.

[0048] For the loading test of Scheme 2, the results of the loading test using the fault model of Scheme 2 show that the absolute value of the displacement changes in both are consistent, and the axial force of the anchor bolt is more stable than that of the extensor displacement gauge.

[0049] Application examples The device for cross-fault measurement in experimental seismic testing of this application, after adjusting the component parameters, can also be used for field rock mass fault measurement. The measurement steps are as follows: S1. Determine the location and orientation of the fault through geological data and field investigation; S2. Set up piers 25 on the ground surface and conduct geological drilling on the fault to ensure that the drilling crosses the fault. S3. Place the steel anchor bolt or steel cable 21 into the borehole; S4. Grout the bottom of the borehole to anchor the bottom of the steel anchor rod or steel cable 21. S5. Install the field axial force gauge 22, field compression spring 23 and anchor 24 (nut 10 or wedge type anchor 24) in sequence on the pier 25. Figure 5 This is a schematic diagram of the field measurement installation of the device. The diagram schematically shows the grouting area 26 at the bottom of the borehole, faults, etc. In this application example, since the axial force gauge cannot be installed underground, the field axial force gauge 22 is also adapted to be installed on the surface. Figure 6 This is a schematic diagram of the installation of the field axial force gauge 22, field compression spring 23, and anchor 24 on the pier 25. In field measurement, a measurement scheme that does not include the field compression spring 23 and only installs the field axial force gauge 22 and anchor 24 on the pier 25 can also be selected according to the actual situation. S6. Prestress the steel anchor bolts or anchor cables to put them into a monitoring and service state from the beginning; S7. The axial force gauge monitors the axial force of the steel anchor rod or steel cable 21 and transmits it to the background monitoring center via the data transmission unit. If the axial force increases, it proves that the fault has undergone shearing motion, causing the steel anchor rod or steel cable 21 to be subjected to tension, resulting in fault activity.

[0050] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A device for cross-fault measurement in experimental earthquakes, characterized in that: It includes a metal rod, an elastic compression spring mounted on the first end of the metal rod, and a rod axial force gauge mounted on the metal rod.

2. The apparatus and method for cross-fault measurement in experimental earthquakes according to claim 1, characterized in that: The yield force of the metal rod is not less than the ultimate elastic compressive force of the elastic spring; the ultimate compressive force of the metal rod is between 1-2 kN; the ultimate displacement of the metal rod is adjusted by changing the length of the elastic spring, and the ultimate displacement of the metal rod is within 1-10 mm.

3. The apparatus for cross-fault measurement in experimental earthquakes according to claim 1, characterized in that: The minimum diameter of the metal rod is 1 mm, and the length is matched according to the size of the sample.

4. The apparatus for cross-fault measurement in experimental earthquakes according to claim 1, characterized in that: The minimum outer diameter of the elastic compression spring is 10mm, and the inner diameter is 2-4mm larger than the diameter of the metal rod; the length of the elastic compression spring is 5-20mm, and the compression amount is adjustable within 1-10mm.

5. A method for cross-fault measurement in experimental earthquakes, characterized in that, The apparatus for cross-fault measurement in experimental earthquakes as described in any one of claims 1-4 includes the following steps: Step 1: Prepare the fault model; the fault model is a simulated rock mass with simulated faults inside; Step 2: Create a vertical rod groove on the surface of the fault model. The rod groove penetrates the simulated fault and extends to the first and second end faces of the fault model. Install the device for measuring the fault span during the experimental earthquake in the rod groove. The inner side of the elastic compression spring and the rod axial force gauge rests against the first and second end faces, respectively. Step 3: Apply a constant load vertically to the fault model on which the experimental earthquake cross-fault measurement device is installed, and record the mechanical growth of the metal rod in real time using the rod axial force gauge; A constant load constraint is applied to the fault model in the horizontal direction to which the device for measuring cross-faults in the experimental earthquake is installed. The loading force in this direction can vary, but the displacement is consistently applied at a fixed rate to drive the simulated fault to accumulate and release elastic energy. The axial force gauge of the rod records the mechanical growth of the metal rod in real time. Step 4: Calculate the fault motion; based on the tensile stiffness K1 of the cross-fault measurement device during the experimental earthquake and the data recorded by the rod axial force gauge, calculate the axial displacement of the metal rod, the shear displacement in the fault shear direction, and the real-time velocity and acceleration of the fault motion at time t.

6. The method for cross-fault measurement in experimental earthquakes according to claim 5, characterized in that: Step four, the calculation steps for fault motion, include: (1) Based on the axial force increase ΔF of the metal rod and the tensile stiffness K1 of the device for measuring across the fault in the experimental earthquake, calculate the displacement u in the axial direction of the metal rod, u=ΔF / K1; (2) Project the axial displacement u of the metal rod onto the fault plane and calculate the shear displacement s in the fault shear direction, s=u×cos , The angle between the rod groove and the simulated fault; (3) Calculate the real-time velocity v and acceleration a of the fault motion using differentiation, v = ds / dt, a = d 2 v / dt 2 .

7. The method for cross-fault measurement in experimental earthquakes according to claim 5, characterized in that: The elastic limit pressure of the elastic compression spring does not exceed 2% of the lower limit of all loading forces; the ultimate tensile displacement of the metal rod is greater than the maximum design displacement of the simulated fault in step three.

8. The method for cross-fault measurement in experimental earthquakes according to claim 5, characterized in that: The depth of the groove is not less than half the thickness of the simulated rock mass material, and the width of the groove is not less than the range of the simulated fault shear displacement in step three.

9. The method for cross-fault measurement in experimental earthquakes according to claim 5, characterized in that: In step one, preliminary tests are conducted on the simulated rock mass material and the device for cross-fault measurement during experimental earthquakes; Stick-slip tests were conducted on simulated rock mass materials without experimental earthquake cross-fault measurement devices. The critical value of stress accumulation in the stick-slip test was used as the upper limit of the applied axial force, and the stable value of stress release in the stick-slip test was used as the lower limit of the applied axial force. For a metal rod, the tensile stiffness K1 and elastic limit tensile force F of the device used for measuring fault spans in experimental earthquakes are tested using a universal testing machine at a rate on the order of mm / s. max and ultimate tensile displacement u max ; and by changing the radius and length of the elastic compression spring, K1 and F are adjusted. max u max The value of the elastic limit pressure F ultimately makes the elastic limit pressure F max The ultimate tensile displacement u should not exceed 2% of the lower limit of the axial force in the stick-slip test. max The test displacement is greater than that of the stick-slip test.

10. The method for cross-fault measurement in experimental earthquakes according to claim 5, characterized in that: The simulated fault is the contact interface between two rock materials or rock-like materials. The simulated fault includes a mature interface, an interface with a rock bridge, or an interface with fault gouge interlayers in the middle.

Images