Simulation loading test method suitable for cross-creep fault tunnel

Abstract

The invention discloses a test method suitable for simulation loading of a cross-creeping fault tunnel, and aims to solve the problem that most of existing indoor simulation loading devices for the cross-creeping fault tunnel are mainly based on a stick-slip fault and can only be used for test research on the aspects of damage mechanism and prevention and control of a tunnel structure caused by the stick-slip fault. The invention aims at carrying out research on the interaction mechanism between the creep fault and the tunnel structure, catastrophe prevention and control and monitoring and early warning through indoor test simulation. Free contraction and shear deformation of the fixed model box and the movable model box are achieved through the spring and the telescopic connecting belt, and shear dislocation simulation of the creep fault crossing tunnel is achieved. And dislocation loading of the movable model box can be realized through a second jack and a third jack which can move freely.

Description

Technical Field

[0001] The invention belongs to the technical field of geotechnical test methods, and in particular relates to a test method suitable for simulating loading of a tunnel across a creep fault. Background Art

[0002] A large number of tunnel construction projects in the western mountainous areas often inevitably cross active fault areas, which adds great difficulty to tunnel construction. The adverse effects of faults on mountain tunnels are mainly manifested as follows: on the one hand, the existence of active faults will have an adverse effect on the geostress field in mountainous areas. Specifically, the stress redistribution effect causes the original stress state of the surrounding rock to be destroyed, resulting in stress concentration in the surrounding rock, which is the root cause of tunnel structure damage or surrounding rock instability; on the other hand, tunnel excavation induces fault activation, resulting in a significant reduction in the strength of the surrounding rock, which in turn has an adverse effect on the tunnel lining. If the fault area is not pre-reinforced before construction, tunnel excavation and completion are prone to engineering disasters such as collapse, large lining deformation, and water inrush, which poses a huge safety hazard to the tunnel structure itself. In serious cases, it will cause casualties or even the failure of the tunnel project.

[0003] Fault dislocation can be divided into creep and stick-slip according to the speed of time. Creep is usually a slow sliding of the fault over time, that is, the deformation has a strong timeliness (rheology) and usually does not induce earthquakes or only induces small earthquakes. Stick-slip is usually accompanied by the rapid release of a large amount of elastic energy, which is transmitted to the surrounding rock in the form of seismic waves. In severe cases, it may cause disasters such as rock bursts, earthquakes, cracking of existing structures, and even collapse accidents, making repair work difficult and causing serious economic losses. Looking at the current research status at home and abroad, it can be seen that scholars are currently focusing on the failure mechanism, support and monitoring of stick-slip faults. In actual engineering, creep faults are not easily taken seriously due to their rheological characteristics, but the degree of damage they cause cannot be ignored. Therefore, studying the mechanism of action and deformation response characteristics of creep active faults on tunnel structures, and then improving the anti-dislocation performance of long and large tunnel projects crossing active faults can provide reference and reference for their design and construction.

[0004] Due to various factors and objective conditions, it is very difficult to directly observe the surrounding rock damage and movement laws caused by fault activation. However, similar material simulation tests can simulate the impact of fault activation on tunnel structure and surrounding rock stress distribution by artificially changing the test conditions based on the actual geological data on site. The test results can roughly reproduce the catastrophic evolution process and activation law of the fault. Therefore, an easy-to-operate, accurate and reasonably designed model test device is particularly important to achieve the above goals. However, the current research and development of such test devices is still concentrated in the field of stick-slip faults based on shaking tables, and there is still a lack of devices that can realize the rheological simulation loading function of creep fault tunnels. Summary of the invention

[0005] In order to study the stress and deformation of a tunnel model in a stick-slip fault area, the present invention provides a test method suitable for simulating loading of a tunnel across a creep fault.

[0006] To this end, the present invention adopts the following technical solutions: A test method for simulating loading of a tunnel across a creep fault includes the following methods: Step 1: Prototype Engineering Generalization Generalize the prototype project according to the research purpose and establish a generalized model that meets the test requirements; Step 2: Determine the test parameters Determine the fault parameters according to the generalized model obtained in step 1, including the inclination parameter, the width parameter of the fault fracture zone, and the angle between the fault and the tunnel; select a suitable similarity ratio for experimental design according to the prototype engineering profile and the geometric dimensions of the model box, and then derive the physical and mechanical parameters of the model material according to the similarity relationship theory; Step 3: Build the model box It comprises two model boxes arranged in parallel, the left side is a fixed model box, the right side is a movable model box, and a gap is left between the two model boxes; the left side, front side, rear side and bottom surface of the fixed model box are closed surfaces, and the right side is a hollow surface; the right side, front side, rear side and bottom surface of the movable model box are closed surfaces, and the left side is a hollow surface, and the hollow surfaces of the fixed model box and the movable model box are opposite to each other; the movable model box is connected with a horizontal moving component and a vertical moving component, which are used to drive the movable model box to realize horizontal and vertical movement; A telescopic connecting belt is connected between the hollow surfaces of the two model boxes, and the telescopic connecting belt is connected between the side surfaces and the bottom surfaces of the two model boxes, and the telescopic connecting belt is used to seal the test soil in the model boxes; the two model boxes are internally connected, and the model boxes are used to fill the surrounding rock and the tunnel model; It also includes a frame, which is a rigid structure, and the fixed model box and the movable model box are placed in the frame; it also includes a bearing foundation, which is placed under the fixed model box and is used to raise the fixed model box; The bottom of the movable model box is connected with a vertical third jack, the bottom of the third jack is connected with a horizontal moving assembly, the horizontal moving assembly includes a third horizontal guide rail, a third frame and a third roller, the third jack is fixedly connected to the third frame, the third roller is connected to the third frame, and the third roller can move along the third horizontal guide rail; The top of the movable model box is connected to a vertical second jack, the top of the second jack is connected to a second frame, the second frame is connected to a second roller, the top of the frame is connected to a second horizontal guide rail, and the second roller can move along the second horizontal guide rail; the bottom of the second jack is fixedly connected to a horizontal pressure plate, which is embedded in the top of the movable model box and is used to apply pressure to the surrounding rock in the movable model box; Step 4: Sensor layout The sensors used in this test include strain gauges, earth pressure gauges, and dial indicators. The strain gauges and some earth pressure gauges are attached to the outer surface of the tunnel model, including the invert, arch crown, arch feet on both sides, and characteristic parts of the arch feet. They are arranged in multiple sections to monitor the stress and deformation response data of tunnel support structures at different depths. The remaining earth pressure gauges are arranged in the surrounding rock and fault zone to monitor the stress state of the surrounding rock and fault zone. The dial indicator is arranged at the top or bottom of the active model box to monitor the vertical displacement. Step 5: Loading rate design The extension or contraction rate of the jack is set according to the ground stress state of the prototype project; before the test, the second jack is kept in contact with the active model box and a fixed load is applied to achieve vertical stress compensation of the deep buried tunnel, and the third jack is in an extension state to support the active model box; after the test starts, the second jack and the third jack are kept extending and contracting at the same rate to achieve loading of the tunnel across the creep fault, while ensuring that the stress state of the surrounding rock during the test is consistent with that before the test; in addition, according to the loading rate of the second jack and the third jack, their sliding rate is controlled by computer to achieve shear and contraction movement of the active model box; Step 6: Filling the model Fill the tunnel model with a layer of 10 cm according to the designed fault and tunnel model positions. The density is determined by the ring knife method. When the tunnel model and corresponding sensors are placed at the designated position, Step 7: Experimental implementation The test is carried out at the loading rate preset in step five, and the deformation and force response data of the surrounding rock and tunnel model are recorded during the test. During the test, since the second jack and the third jack maintain the same rate of extension, contraction and sliding, the spring will extend or contract accordingly, and the third roller will move horizontally by itself, further realizing the tensile and shear deformation between the fixed model box and the movable model box, and finally realizing the simulated loading of the tunnel across the creep fault.

[0007] Furthermore, a vertical first jack is connected to the top of the fixed model box, the top of the first jack is fixed to the frame, and a horizontal pressure plate is connected to the bottom of the first jack. The pressure plate is embedded in the top of the fixed model box, and the pressure plate is used to apply pressure to the surrounding rock in the fixed model box.

[0008] Furthermore, it also includes an elastic support component, which is connected between the sides of the two model boxes and is located outside the telescopic connecting belt. The elastic support component includes two obliquely arranged rotating rods, the two rotating rods are parallel and close to the sides of the model box, and the two rotating rods are respectively a first rotating rod and a second rotating rod; the upper end of the first rotating rod is hinged to the top of the fixed model box, and the lower end of the second rotating rod is hinged to the bottom of the movable model box, and a plurality of springs are connected between the first rotating rod and the second rotating rod at intervals, and each spring is arranged in parallel.

[0009] Furthermore, the lower end of the first rotating rod is hinged with a first telescopic rod, the first telescopic rod is close to the side of the model box, and the other end of the first telescopic rod is hinged to the bottom of the fixed model box; the upper end of the second rotating rod is hinged with a second telescopic rod, the second telescopic rod is close to the side of the model box, and the other end of the second telescopic rod is hinged to the top of the movable model box.

[0010] Design principle of the present invention: The spring and telescopic connecting belt are used to realize the free contraction and shear deformation of the fixed model box and the movable model box, so as to realize the shear displacement simulation of the tunnel across the creep fault. The movable model box can be loaded with displacement by the freely movable second and third jacks. Under the action of the second and third jacks, the movable model box has not only vertical movement but also horizontal movement, thus simulating the real fault movement.

[0011] The beneficial effects of the present invention are: 1. The present invention can simulate the loading of a tunnel across a creep fault and intuitively reproduce the influence of the rheological characteristics of the creep fault on the tunnel structure; 2. By setting a second jack on the top of the movable model box, the second jack applies pressure to the surrounding rock inside the top of the movable model box to achieve vertical stress compensation of the deep buried tunnel and more realistically invert the original rock stress state of the deep buried tunnel; 3. By setting springs and telescopic connecting belts, the contraction and shear deformation between the two model boxes can be achieved. Compared with the previous model boxes that can only achieve shear displacement, it can more accurately reflect the stress and deformation of the creep fault; 4. The side walls of the two model boxes can be made of plexiglass, which is convenient for test personnel to observe and record the deformation and damage of the surrounding rock at any time; 5. The device of the present invention can be connected to a deformation and stress monitoring system, which can realize the continuous deformation and stress state monitoring of the tunnel structure and surrounding rock under the action of fault creep, and provide a reliable device and method for the study of large deformation mechanism of tunnel structure; 6. The device of the present invention has a simple principle and is easy to operate. It meets the test requirements under different fault parameter conditions, is easy to reuse, and has good versatility. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1It is a schematic diagram of the structure of the test device of the present invention; Figure 2 It is a structural schematic diagram of a fixed model box of the test device of the present invention; Figure 3 It is a structural schematic diagram of a movable model box of a test device of the present invention; Figure 4 It is a schematic diagram of the structure of the telescopic connecting belt and the elastic support assembly of the present invention; Figure 5 is a schematic structural diagram of the elastic support assembly of the present invention; Figure 6 It is a structural schematic diagram of the telescopic connecting belt of the present invention; In the figure: fixed model box 1, movable model box 2, frame 3, bearing foundation 4, first jack 5, second jack 6, third jack 7, second roller 8, second horizontal guide rail 9, third roller 10, third horizontal guide rail 11, first rotating rod 12, column 13, hinge shaft 14, first telescopic rod 16, spring 17, telescopic connecting belt 18. DETAILED DESCRIPTION

[0013] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments: Step 1: Prototype Engineering Generalization Rock and soil bodies are characterized by discreteness, multiphase and variability. Before the model test, the prototype project needs to be generalized according to the research purpose. The first is to fully understand the specific geological conditions of the rock and soil bodies and establish a reasonable geological model. Secondly, on this basis, the non-essential factors that are essentially irrelevant or have little correlation with the research purpose are excluded, and then a reasonable conceptual model is established. Finally, the essential properties of the rock and soil bodies are refined, idealized and abstracted, so as to establish a reasonable conceptual model, and then the problem is analyzed and quantified by means of model tests. The specific approach is to ignore some minor factors, such as vegetation, small valleys, micro-topography, etc., based on the current status of the prototype project and the purpose of the research. Then a model scheme with experimental operability and real objectivity is abstracted, and quantitative research is carried out through indoor experimental means.

[0014] Step 2: Determine the test parameters Determine the fault parameters according to the generalized model obtained in step 1, including the inclination parameter, the width parameter of the fault fracture zone, the angle between the fault and the tunnel, etc. Select a suitable similarity ratio for experimental design based on the prototype project profile and the geometric dimensions of the model box, and then derive the physical and mechanical parameters of the model material according to the similarity relationship theory. In this embodiment, the fault parameters are determined based on the geometric characteristics of the creep fault simulated by the specific project. Set the geometric similarity ratio to 1:40, the required simulated fault inclination to 60°, the tunnel and the fault are parallel (the tunnel axis is parallel to the fault inclination), and the width of the fault fracture zone is about 50 cm.

[0015] Step 3: Build the model box It comprises two model boxes arranged in parallel, the left side is a fixed model box 1, the right side is a movable model box 2, and a gap is left between the two model boxes; the left side, front side, rear side and bottom surface of the fixed model box 1 are closed surfaces, and the right side is a hollow surface; the right side, front side, rear side and bottom surface of the movable model box 2 are closed surfaces, and the left side is a hollow surface, and the hollow surfaces of the fixed model box 1 and the movable model box 2 are opposite to each other; the movable model box 2 is connected with a horizontal moving component and a vertical moving component, which are used to drive the movable model box 2 to realize horizontal movement and vertical movement; A telescopic connecting belt 18 is connected between the hollow surfaces of the two model boxes. The telescopic connecting belt 18 is connected between the side surfaces and the bottom surfaces of the two model boxes. The telescopic connecting belt 18 is used to seal the test soil in the model box. The telescopic connecting belt 18 is made of elastic rubber sheet material. The two model boxes are internally connected, and the model boxes are used to fill the surrounding rock and tunnel model. It also includes a frame 3, which is a rigid structure, and the fixed model box 1 and the movable model box 2 are placed in the frame 3; it also includes a bearing foundation 4, which is placed under the fixed model box 1 and is used to raise the fixed model box 1; The bottom of the movable model box 2 is connected with a vertical third jack 7, the bottom of the third jack 7 is connected with a horizontal moving assembly, the horizontal moving assembly includes a third horizontal guide rail 11, a third frame and a third roller 10, the third jack 7 is fixedly connected to the third frame, the third roller 10 is connected to the third frame, and the third roller 10 can move along the third horizontal guide rail 11; A vertical second jack 6 is connected to the top of the movable model box 2, a second frame is connected to the top of the second jack 6, a second roller 8 is connected to the second frame, a second horizontal guide rail 9 is connected to the top of the frame 3, and the second roller 8 can move along the second horizontal guide rail 9; a horizontal pressure plate is fixedly connected to the bottom of the second jack 6, and the pressure plate is embedded in the top of the movable model box 2, and the pressure plate is used to apply pressure to the surrounding rock in the movable model box 2.

[0016] A vertical first jack 5 is connected to the top of the fixed model box 1, and the top of the first jack 5 is fixed to the frame 3. A horizontal pressure plate is connected to the bottom of the first jack 5, and the pressure plate is embedded in the top of the fixed model box 1. The pressure plate is used to apply pressure to the surrounding rock in the fixed model box 1.

[0017] It also includes an elastic support component, which is connected between the sides of the two model boxes and is located outside the telescopic connecting belt 18. The elastic support component includes two inclined rotating rods, which are parallel and close to the sides of the model boxes. The two rotating rods are respectively a first rotating rod 12 and a second rotating rod; the upper end of the first rotating rod 12 is hinged to the top of the fixed model box 1, and the lower end of the second rotating rod is hinged to the bottom of the movable model box 2. A plurality of springs 17 are connected between the first rotating rod 12 and the second rotating rod at intervals, and each spring 17 is arranged in parallel.

[0018] The lower end of the first rotating rod 12 is hinged with a first telescopic rod 16, which is close to the side of the model box, and the other end of the first telescopic rod 16 is hinged to the bottom of the fixed model box 1; the upper end of the second rotating rod is hinged with a second telescopic rod, which is close to the side of the model box, and the other end of the second telescopic rod is hinged to the top of the movable model box 2.

[0019] Step 4: Sensor layout The sensors used in this test include strain gauges, earth pressure gauges, and dial indicators. The strain gauges and some earth pressure gauges are pasted on the outer surface of the tunnel model, including the invert, arch crown, arch feet on both sides, and characteristic parts of the arch feet. They are arranged in multiple sections to monitor the stress and deformation response data of tunnel support structures at different depths; the remaining earth pressure gauges are arranged in the surrounding rock and fault zone to monitor the stress state of the surrounding rock and fault zone; the dial indicator is arranged at the top or bottom of the active model box 2 to monitor the vertical displacement.

[0020] Selection of similar materials: The surrounding rock simulated in this test is mainly made of river sand, quartz sand, and fly ash, with waste oil and vaseline as cementing materials, and barite powder and diatomaceous earth as auxiliary materials, mixed in a certain ratio to form a stratum-similar material. The tunnel model can be made of gypsum, and its cross-section shape is horseshoe-shaped, with a length and height of 25 cm and 18 cm respectively, and an axial length of 200 cm.

[0021] Step 5: Loading rate design The extension or contraction rate of the jack is set according to the ground stress state of the prototype project; before the test, the second jack 6 keeps in contact with the movable model box 2 and applies a fixed load to achieve vertical stress compensation of the deep buried tunnel, and the third jack 7 is in an extension state to support the movable model box 2; after the test starts, the second jack 6 and the third jack 7 keep extending and contracting at the same rate (0.1 ~ 0.5 cm / h according to the research purpose), so as to achieve loading of the tunnel across the creep fault, while ensuring that the stress state of the surrounding rock during the test is consistent with that before the test; in addition, according to the loading rate of the second jack 6 and the third jack 7, their sliding rate is controlled by computer to achieve shear and contraction movement of the movable model box 2.

[0022] Step 6: Filling the model According to the designed fault and tunnel model positions, filling is carried out with a 10 cm per layer. The density is determined by the ring knife method. When filling to the specified position, the tunnel model and corresponding sensors are placed.

[0023] Step 7: Experimental implementation The test is carried out at the loading rate preset in step five, and the deformation and force response data of the surrounding rock and tunnel model are recorded during the test. During the test, since the second jack 6 and the third jack 7 maintain the same rate of elongation, contraction and sliding, the spring 17 will elongate or contract accordingly, further realizing the tensile and shear deformation between the fixed model box 1 and the movable model box 2, and finally realizing the simulated loading of the tunnel across the creep fault.

Claims

1. A test method suitable for simulating loading in a tunnel across a creep fault, characterized in that: The following methods are included: Step 1: Prototype Engineering Generalization Generalize the prototype project according to the research purpose and establish a generalized model that meets the test requirements; Step 2: Determine the test parameters Determine the fault parameters according to the generalized model obtained in step 1, including the inclination parameter, the width parameter of the fault fracture zone, and the angle between the fault and the tunnel; select a suitable similarity ratio for experimental design according to the prototype engineering profile and the geometric dimensions of the model box, and then derive the physical and mechanical parameters of the model material according to the similarity relationship theory; Step 3: Build the model box The invention comprises two model boxes arranged in parallel, the left side being a fixed model box (1) and the right side being a movable model box (2), with a gap between the two model boxes; the left side, front side, rear side and bottom surface of the fixed model box (1) are closed surfaces, and the right side is a hollow surface; the right side, front side, rear side and bottom surface of the movable model box (2) are closed surfaces, and the left side is a hollow surface, and the hollow surfaces of the fixed model box (1) and the movable model box (2) are opposite to each other; the movable model box (2) is connected to a horizontal moving component and a vertical moving component for driving the movable model box (2) to achieve horizontal and vertical movement; A telescopic connecting belt (18) is connected between the hollow surfaces of the two model boxes. The telescopic connecting belt (18) is connected between the side surfaces and the bottom surfaces of the two model boxes. The telescopic connecting belt (18) is used to seal the test soil in the model boxes. The two model boxes are internally connected, and the model boxes are used to fill the surrounding rock and the tunnel model. It also includes a frame (3), which is a rigid structure, and the fixed model box (1) and the movable model box (2) are placed in the frame (3); it also includes a bearing foundation (4), which is placed under the fixed model box (1), and the bearing foundation (4) is used to raise the fixed model box (1); The bottom of the movable model box (2) is connected to a vertical third jack (7), the bottom of the third jack (7) is connected to a horizontal moving assembly, the horizontal moving assembly comprises a third horizontal guide rail (11), a third frame and a third roller (10), the third jack (7) is fixedly connected to the third frame, the third roller (10) is connected to the third frame, and the third roller (10) can move along the third horizontal guide rail (11); The top of the movable model box (2) is connected to a vertical second jack (6), the top of the second jack (6) is connected to a second frame, the second frame is connected to a second roller (8), the top of the frame (3) is connected to a second horizontal guide rail (9), and the second roller (8) can move along the second horizontal guide rail (9); the bottom of the second jack (6) is fixedly connected to a horizontal pressure plate, the pressure plate is embedded in the top of the movable model box (2), and the pressure plate is used to apply pressure to the surrounding rock in the movable model box (2); Step 4: Sensor layout The sensors used in this test include strain gauges, earth pressure gauges, and dial indicators. The strain gauges and some earth pressure gauges are attached to the outer surface of the tunnel model, including the invert, arch crown, arch feet on both sides, and characteristic parts of the arch feet. They are arranged in multiple sections to monitor the stress and deformation response data of tunnel support structures at different depths. The remaining earth pressure gauges are arranged in the surrounding rock and fault zone to monitor the stress state of the surrounding rock and fault zone. The dial indicator is arranged at the top or bottom of the active model box (2) to monitor the vertical displacement. Step 5: Loading rate design The extension or contraction rate of the jack is set according to the ground stress state of the prototype project; before the test, the second jack (6) is in contact with the movable model box (2) and a fixed load is applied to achieve vertical stress compensation of the deep buried tunnel, and the third jack (7) is in an extension state to support the movable model box (2); after the test begins, the second jack (6) and the third jack (7) maintain the same rate of extension and contraction, thereby achieving loading of the tunnel across the creep fault, while ensuring that the stress state of the surrounding rock during the test is consistent with that before the test; in addition, according to the loading rate of the second jack (6) and the third jack (7), their sliding rate is controlled by a computer to achieve shear and contraction movement of the movable model box (2); Step 6: Filling the model Fill the tunnel model with a layer of 10 cm according to the designed fault and tunnel model positions. The density is determined by the ring knife method. When the tunnel model and corresponding sensors are placed at the designated position, Step 7: Experimental implementation The test is carried out at the loading rate preset in step 5, and the deformation and force response data of the surrounding rock and the tunnel model are recorded during the test. During the test, since the second jack (6) and the third jack (7) maintain the same rate of extension, contraction and sliding, the third roller (10) moves horizontally by self-drive, and the spring (17) will extend or contract accordingly, further realizing the tensile and shear deformation between the fixed model box (1) and the movable model box (2), and finally realizing the simulated loading of the tunnel across the creep fault.

2. The test method for simulating loading in a tunnel across a creep fault according to claim 1, characterized in that: The top of the fixed model box (1) is connected to a vertical first jack (5), the top of the first jack (5) is fixed to the frame (3), and the bottom of the first jack (5) is connected to a horizontal pressure plate, which is embedded in the top of the fixed model box (1). The pressure plate is used to apply pressure to the surrounding rock in the fixed model box (1).

3. The test method for simulating loading in a tunnel across a creep fault according to claim 1, characterized in that: The invention also includes an elastic support component, which is connected between the sides of the two model boxes and is located outside the telescopic connection belt (18). The elastic support component includes two tilted rotating rods, which are parallel to and close to the sides of the model boxes. The two rotating rods are respectively a first rotating rod (12) and a second rotating rod. The upper end of the first rotating rod (12) is hinged to the top of the fixed model box (1), and the lower end of the second rotating rod is hinged to the bottom of the movable model box (2). A plurality of springs (17) are connected between the first rotating rod (12) and the second rotating rod at intervals, and each spring (17) is arranged in parallel.

4. The test method for simulating loading in a tunnel across a creep fault according to claim 3, characterized in that: The lower end of the first rotating rod (12) is hingedly connected to a first telescopic rod (16), the first telescopic rod (16) is in close contact with the side of the model box, and the other end of the first telescopic rod (16) is hingedly connected to the bottom of the fixed model box (1); the upper end of the second rotating rod is hingedly connected to a second telescopic rod, the second telescopic rod is in close contact with the side of the model box, and the other end of the second telescopic rod is hingedly connected to the top of the movable model box (2).

Images