Method and device for testing stress distribution in a cemented filling body

Abstract

The present application belongs to the technical field of mine engineering filling body testing, in particular to a cemented filling body internal stress distribution testing method and equipment. In order to solve the problems that the existing test cannot simulate the actual working condition, covers up the early damage mechanism and the safety factor test is inaccurate, the testing method is to make a test block, pre-bury monitoring elements, arrange an observation system, carry out compression test and analyze data. The detection equipment workbench has a supporting table, a hydraulic cylinder I is arranged to drive a pressing plate, an extrusion mechanism for locking a cylinder is arranged in the pressing plate, which can conform to the topography of the sample top and lock, capture the local high stress of the top point; horizontal impact mechanisms are arranged on both sides of the workbench, which can apply horizontal impact inertia force; there is also a side direction surrounding rock rebound mechanism, which can simulate surrounding rocks with different hardness. The equipment can accurately simulate the actual working condition and obtain the internal stress distribution and deformation data of the filling body.

Description

Technical Field

[0001] This invention relates to the field of testing technology for backfill bodies in mining engineering, and in particular to a method and equipment for testing the internal stress distribution of cemented backfill bodies. Background Technology

[0002] Cemented backfill materials are widely used in engineering fields such as mining, and their internal stress distribution directly affects the stability and safety of the engineering structure. Accurately obtaining the internal stress distribution and deformation patterns of cemented backfill materials is of great significance for optimizing backfilling process parameters and ensuring construction safety. Currently, testing methods and related detection equipment for the internal stress distribution of cemented backfill materials have been studied, but many shortcomings still exist in practical applications: 1. In the existing technology, the standard mold used in laboratory testing is a steel plate with extremely high rigidity, which restricts all lateral displacements of the filling body (lateral strain ε2=ε3=0), simulating the "infinitely rigid" surrounding rock. However, in actual engineering, the surrounding rock often deforms. Existing equipment cannot simulate this dynamic equilibrium process of "the filling body pushing the surrounding rock and the surrounding rock reacting on the filling body", resulting in the internal stress value measured being generally higher than the actual working conditions. 2. During the filling process, due to the shrinkage of the grout due to bleeding, the top of the filling body often cannot completely adhere to the upper layer, and only makes point contact with some protruding rocks. This point contact will generate extremely high local stress, leading to local crushing of the filling body. Existing pressure testing machines all use finely ground flat pressure plates for loading. This idealized boundary condition completely masks the early failure mechanism of the filling body caused by "non-uniform contact". 3. Existing uniaxial compression tests can only measure the static peak strength of the filling material. However, downhole accidents often occur when the static stress has not yet reached its limit, but is triggered by the blasting vibration. Conventional equipment cannot introduce this lateral dynamic inertial force, resulting in an overestimation of the safety factor and potential engineering hazards. Summary of the Invention

[0003] Existing tests for cemented infill bodies have limitations in simulating actual non-uniform roof contact, surrounding rock deformation, and dynamic disturbances, easily masking early failure mechanisms and leading to an overestimation of the safety factor. This invention addresses these issues by developing a testing method and equipment capable of realistically reproducing complex working conditions.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A method for testing the internal stress distribution of a cemented infill body includes the following steps: S1. The test uses a casting mold with a length × width × height of 18.0cm × 18.0cm × 18.0cm. Before making the test block, the mold is cleaned and a layer of mineral oil or other release agent is applied to its inner wall. S2. Install resistance-type steel stress gauges on the reinforcement model to monitor the stress distribution of the steel reinforcement in the top slab and sidewalls during the excavation of the model. S3. Weigh out a certain amount of aggregate, cementitious material and water according to the ingredient list and mix them thoroughly. The casting is done manually with a spoon. First, pour a filling slurry to a height of about 1.5cm, and then place different reinforcement models. To prevent the slurry from settling, stir while pouring and quickly take out the slurry and pour it into the test mold. The slurry height should exceed the test mold by 2-3mm. During the casting process, place small earth pressure boxes at the corresponding locations and lead out the wires. S4. After demolding at the end of the model curing period, set the front of the model as the DIC observation surface, dry the surface with a hot air gun, and manually spray spots randomly to form a cemented filling sample. S5. Before applying pressure to the model, connect the wires of the pre-embedded monitoring elements to the monitoring equipment; set up the DIC observation system, and adjust the aperture and focal length of the left and right cameras to ensure the clarity of the captured images; S6. Use testing equipment to perform compression tests on the cured cemented filling sample. Apply pressure to the model gradually at a rate of 0.05 kN per second. Record the images of the stress process on the side surface where the speckle is located throughout the process, and record the stress and strain data of each point inside the model provided by the micro earth pressure cell and the resistance steel stress gauge. S7. The stress value at the test point measured by the resistance-type steel bar stress gauge is compared with the stress in the vertical direction of the filling body measured by the micro earth pressure cell; then the displacement of the observation point of the reinforcement model measured by it is compared and analyzed with the displacement and strain cloud map observed by the DIC system, so as to obtain the stress distribution inside the filling body and the displacement before and after deformation, and then calculate the stress and strain of the whole field.

[0005] A testing device, applied to the above-mentioned method for testing the internal stress distribution of a cemented infill body, includes: A workbench, the top of which is provided with a support platform for placing cemented filler samples; A support plate is fixed above the worktable by multiple vertical rods; Hydraulic cylinder I is fixed inside the support plate, with its output end facing the support platform; The pressure plate assembly is connected to the output end of the hydraulic cylinder I. The pressure plate assembly includes a pressure plate and multiple cylinders. The bottom of the pressure plate is provided with multiple sliding grooves. Each cylinder is slidably disposed in one of the sliding grooves, and the bottom end of each cylinder is provided with a pressure sensor for contacting the top of the sample and sensing local contact stress during testing. Two sets of horizontal impact components are symmetrically arranged on both sides of the support platform. Each set of horizontal impact components includes a vertical plate and an impact generator. The vertical plate is provided with at least one impact pin. The impact generator is used to drive the impact pin to reciprocate in the horizontal direction, and to apply dynamic disturbance to the side of the cemented filling sample. Two sets of lateral rock rebound components are symmetrically arranged on both sides of the support platform. Each set of lateral rock rebound components includes a reaction plate and an elastic simulation mechanism. The reaction plate is hinged to the worktable through a rotating arm. The elastic simulation mechanism is located on the side of the reaction plate facing the support platform. The equivalent stiffness of the elastic simulation mechanism can be changed by adjusting the internal pressure to simulate the lateral constraint of surrounding rocks of different hardness on the sample.

[0006] In one possible design, the pressure plate assembly further includes a locking mechanism, which includes a cavity disposed within the pressure plate, a plurality of circular grooves communicating with the slide groove, locking pins slidably disposed in each of the circular grooves, and a communication channel connecting the cavity and each of the circular grooves; when high-pressure gas is introduced into the cavity, the gas pushes all the locking pins against the corresponding cylinders through the communication channel, thereby locking the plurality of cylinders.

[0007] In one possible design, each of the grooves is provided with a spring I, the two ends of which are respectively connected to the top inner wall of the groove and the top of the cylinder.

[0008] In one possible design, the impact generator of the horizontal impact assembly includes a fixed cylinder I fixed to the vertical plate, a striker slidably disposed within the fixed cylinder I, a connecting rod connected to the end of the striker away from the support platform, a spring II sleeved on the connecting rod, a cam rotatably connected to the vertical plate, and a drive motor for driving the cam to rotate; the spring II provides an elastic force that causes the striker to strike the support platform, and the cam periodically compresses and releases the spring II through the connecting rod during rotation, thereby causing the striker to generate reciprocating impacts.

[0009] In one possible design, the horizontal impact assembly further includes a vibration transmission plate located between the impact pin and the cemented filler specimen.

[0010] In one possible design, the elastic simulation mechanism includes multiple fixed cylinders II arranged vertically, a sliding column sealed and slidably disposed within each fixed cylinder II, and a connecting pipe connecting adjacent fixed cylinders II vertically. One end of all the sliding columns is connected to an inner layer plate, which is used to contact the cemented filler sample. It also includes a collection box communicating with the uppermost fixed cylinder II. By filling or venting gas into the collection box, the pressure inside each fixed cylinder II is changed, thereby adjusting the overall equivalent stiffness of the elastic simulation mechanism.

[0011] In one possible design, the inner layer is a Teflon film.

[0012] In one possible design, a hydraulic cylinder II is also included, which is fixed to the support plate and its output end is connected to a lifting plate. The vertical plate is slidably connected to the support plate via a slide rod and is fixedly connected to the lifting plate. The hydraulic cylinder II is used to drive the horizontal impact assembly to lift as a whole.

[0013] In one possible design, the bottom of the vertical plate is hinged to the reaction plate via a connecting rod. When the hydraulic cylinder II drives the vertical plate to rise, the reaction plate is pulled around its hinge point to rotate to a vertical position via the connecting rod.

[0014] Compared with existing technologies, this solution achieves real-world working condition reproduction through the combination of an adaptive cylindrical group, a high-pressure gas locking mechanism to simulate non-uniform top contact, a cam-driven striker horizontal impact to simulate dynamic disturbance, and an adjustable air pressure elastic mechanism to simulate surrounding rock rebound. It eliminates the need for additional fans, water cooling, or rigid boundary equipment, significantly reducing test energy consumption and complexity.

[0015] Beneficial effects: In this invention, multiple cylinders in the extrusion mechanism can be displaced according to the uneven terrain of the top of the cemented filling sample under the action of spring I. Then, the cylinders are locked into a rigid integral pressure head by the locking column driven by high pressure inert gas. This ensures that the pressure head is fully in contact with the top of the sample, so that the applied extrusion force is evenly distributed and the test accuracy is improved. At the same time, the pressure sensor at the bottom of the cylinder can capture the local high stress concentration phenomenon at the joint, which makes up for the deficiency of conventional earth pressure cells that can only measure uniform stress, making the test data more comprehensive. Spring I can provide stable elastic force to ensure the contact effect between the cylinder and the top of the sample. In this invention, the cam is driven by a drive motor to rotate, and the spring force of spring II is used to realize the reciprocating impact motion of the impact pin. This can apply a vertical static pressure to the cemented filling sample while simultaneously applying a horizontal impact inertial force. It can reproduce the rockburst process induced by high static pressure and enhanced disturbance in the laboratory, making the test scenario closer to the actual engineering situation and the test results more valuable. The design of the trapezoidal plate and the base plate can store the impact pin in the fixed cylinder I when the vertical plate moves up, avoiding interference between the impact pin and the pressure plate and ensuring the normal operation of the equipment. The cooperation between the limiting groove on the baffle and the vertical rod improves the stability of the vertical plate lifting process and ensures the stability of the impact force. In this invention, the equivalent elastic modulus of the sidewall can be precisely adjusted by regulating the pressure of the high-pressure inert gas in the collection box, which can simulate the stress changes of cemented filling bodies in surrounding rock environments with different hardness, thus expanding the applicability of the equipment. The inner plate is made of Teflon film, which can directly contact the filling slurry and prevent adhesion, ensuring the sample molding quality and testing accuracy. The observation port on the reaction plate facilitates the DIC camera to photograph the bulging deformation of the inner plate, providing convenience for obtaining sample sidewall deformation data. In this invention, the vertical plate and the reaction plate are connected by a connecting rod, realizing the coordinated linkage between the horizontal impact mechanism and the lateral surrounding rock rebound mechanism. When the vertical plate moves up to be stored, it can drive the reaction plate to rotate to a vertical state, so that the inner plate fits against the side wall of the sample. When the vertical plate moves down, it can drive the reaction plate to reset, which simplifies the operation process and improves the testing efficiency.

[0016] This invention can more realistically simulate the complex mechanical environment of downhole filling bodies. By using a group of cylinders that can be locked to form concave and convex pressure surfaces, it reproduces the phenomenon of local high stress concentration caused by point contact during top contact. The reaction plate with adjustable lateral stiffness simulates the elastic deformation of the surrounding rock, reflecting the interaction between the filling body and the surrounding rock. The horizontal impact mechanism introduces dynamic disturbance loads, simulating blasting vibrations and other inducements, making the test conditions closer to engineering practice. The obtained data on stress distribution, failure mode, and strength of the filling body are more accurate and reliable, and have higher guiding value for safety design and disaster prevention in actual engineering. Attached Figure Description

[0017] Figure 1 This is a three-dimensional structural schematic diagram of a detection device provided by the present invention; Figure 2 This is a schematic diagram of the front view structure of a detection device provided by the present invention; Figure 3 A three-dimensional cross-sectional view of the pressure plate of a testing device provided by the present invention; Figure 4 for Figure 3 Enlarged structural diagram at point A in the middle; Figure 5A three-dimensional structural diagram of the lifting plate, vertical plate, and reaction plate of a detection device provided by the present invention; Figure 6 A three-dimensional exploded view of the base plate, vertical plate, and cam of a detection device provided by the present invention; Figure 7 This is a three-dimensional cross-sectional view of the fixed cylinder I of the detection device provided by the present invention; Figure 8 A three-dimensional exploded structural diagram of the baffle and vertical plate of a detection device provided by the present invention; Figure 9 This is a three-dimensional exploded structural diagram of the reaction plate, fixed cylinder II, and inner layer plate of a detection device provided by the present invention. Figure 10 A three-dimensional structural diagram of the fixed cylinder II, sliding column, and connecting pipe of a detection device provided by the present invention; Figure 11 A three-dimensional exploded structural diagram of the reaction plate, vertical plate, and connecting rod of a detection device provided by the present invention; Figure 12 A schematic diagram of the reinforcement model and monitoring instrument arrangement for a method of testing the internal stress distribution of cemented infill bodies provided by the present invention; Figure 13 This is a schematic diagram of the structure of a cemented filler sample used in a method for testing the internal stress distribution of a cemented filler provided by the present invention.

[0018] In the diagram: 1. Workbench; 2. Support platform; 3. Cemented filler sample; 4. Vertical rod; 5. Support plate; 6. Hydraulic cylinder I; 7. Pressure plate; 8. Slide groove; 9. Cylinder; 10. Spring I; 11. Cavity; 12. Connecting channel; 13. Locking post; 14. Circular groove; 15. Air inlet pipe; 16. Air outlet pipe; 17. Air pressure sensor; 18. Hydraulic cylinder II; 19. Lifting plate; 20. Slide rod; 21. Vertical plate; 22. Fixed cylinder I; 23. Strike pin; 24. 25. Connecting rod; 26. Spring II; 27. Base plate; 28. Rotating shaft; 29. ​​Cam; 20. Drive motor; 31. Trapezoidal plate; 32. Crossbar; 33. Baffle; 34. Limiting groove; 35. Fixed shaft; 36. Rotating arm; 37. Reaction plate; 38. Fixed cylinder II; 39. Sliding column; 40. Connecting pipe; 41. Collection box; 42. Top pipe; 43. Air guide pipe; 44. Inner plate; 45. Limiting plate; 46. Observation port; 47. Fixed seat; 48. Connecting rod. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0020] In one embodiment: a method and equipment for testing the internal stress distribution of cemented backfill, relating to the field of testing backfill in mining engineering, includes the following steps: S1. Mold preparation: The test uses a casting mold with dimensions of 18.0cm×18.0cm×18.0cm (length×width×height). Before making the test block, the mold is cleaned to ensure that there are no impurities or oil stains on the inner wall. Then, a layer of mineral oil is evenly applied to the inner wall as a release agent. The coating thickness is controlled between 0.1mm and 0.2mm to ensure that all parts of the inner wall of the mold are covered with the release agent, so as to avoid the subsequent filling slurry from sticking to the mold and affecting the molding quality of the test block. S2. Stress gauge installation: Install resistance-type rebar stress gauges on the reinforcement model. Determine the installation points of the stress gauges based on the specific locations of the top slab and sidewalls during the excavation of the model. Install one resistance-type rebar stress gauge at each point. During installation, ensure that the stress gauge is in close contact with the rebar and that the lead wire is led out in a reasonable direction to avoid damage or entanglement of the lead wire during subsequent pouring. After installation, perform preliminary debugging of the resistance-type rebar stress gauges to check whether they can work properly and ensure the accuracy of the monitoring data. S3. Slurry Preparation and Pouring: Weigh out a certain amount of aggregate, cementitious material, and water according to the batching list. The aggregate should be quartz sand with a particle size of 0.5mm to 5mm, and the cementitious material should be ordinary Portland cement. The water-cement ratio should be controlled between 0.5 and 0.6. Place the weighed aggregate, cementitious material, and water into a mixing device and mix thoroughly for 3 to 5 minutes to ensure the slurry is uniform and free of lumps. Pouring should be done manually using a ladle. First, pour a filling slurry to a height of approximately 1.5cm to the bottom of the mold. Then, slowly place different reinforcement models, pre-installed with resistance-type rebar stress gauges, into the mold, ensuring the reinforcement models are accurately positioned during placement. To ensure the slurry remains within a certain distance from the inner wall of the mold, and to prevent sedimentation, the slurry must be stirred while pouring. The stirring direction should follow the rotation direction of the slurry, and the stirring speed should be controlled at 60 r / min to 80 r / min. During the stirring process, the slurry should be quickly removed and poured into the mold, with the slurry height exceeding the top of the mold by 2 mm to 3 mm. During the pouring process, small earth pressure cells should be placed at corresponding positions inside the cemented filling body. The number of small earth pressure cells is determined according to the testing requirements, generally 3 to 5 on the top plate, side walls, and bottom. When placing them, ensure that the small earth pressure cells are in full contact with the slurry, with no air bubbles remaining, and orderly lead their wires out of the mold and mark them. S4. Sample Pretreatment: After demolding at the end of the model curing period, the front of the model is set as the DIC observation surface. The observation surface is dried using a hot air gun at a temperature of 60℃ to 80℃ for 20 to 30 minutes to ensure no moisture residue remains on the observation surface. Then, spots are sprayed onto the observation surface manually and randomly. The spot material is black matte paint, with a spot diameter of 2mm to 3mm and a spot spacing of 5mm to 8mm to ensure uniform spot distribution, no overlap, and no omissions, forming a cemented filling sample. After spraying, the observation surface is dried again with a hot air gun for 5 to 10 minutes to ensure that the spots are firmly bonded to the sample surface. S5. Monitoring System Setup: Before applying pressure to the model, connect the wires of the pre-embedded monitoring elements to the monitoring equipment. During the connection process, ensure that the wires are firmly connected, have good contact, and are free from loosening or short circuits. At the same time, set up the DIC observation system, symmetrically arranging two cameras on both sides of the DIC observation surface of the cemented filling sample. The distance between the camera and the observation surface should be controlled between 1.5m and 2m. Adjust the aperture and focal length of the left and right cameras. Set the aperture value between f / 5.6 and f / 8, and adjust the focal length to make the captured image clearly show the speckle details. Ensure that the clarity and contrast of the captured image meet the requirements of DIC analysis. S6. Compression Test and Data Acquisition: The cured cemented infill sample is subjected to a compression test using testing equipment. The hydraulic cylinder I6 of the testing equipment is activated to gradually apply pressure to the model at a speed of 0.05 kN per second. The speed is kept stable during the pressure application process. During this time, the camera of the DIC observation system is activated to record the images of the stress process on the side surface where the speckle is located. The shooting frame rate is set to 10 fps to 20 fps to ensure that the deformation process of the sample can be completely captured. At the same time, the monitoring equipment records the stress and strain data of each point inside the model provided by the micro earth pressure cell and the resistance steel stress gauge in real time. The data acquisition frequency is consistent with the camera shooting frame rate to ensure the synchronization of stress and strain data and image data. S7. Data Processing and Analysis: The stress values ​​at the test points measured by the resistance-type steel bar stress gauge are compared with the stress values ​​in the vertical direction of the filling body measured by the micro earth pressure cell to check the consistency and rationality of the two sets of data. Then, the displacement values ​​at the observation points of the reinforcement model measured by the resistance-type steel bar stress gauge are compared and analyzed with the displacement and strain cloud maps observed by the DIC system. The DIC image data is processed by professional data processing software to extract the displacement field and strain field information of the sample surface. Combined with the monitoring data of the micro earth pressure cell and the resistance-type steel bar stress gauge, the stress distribution inside the filling body and the displacement before and after deformation are obtained, and then the stress and strain of the whole field are calculated.

[0021] Reference Figure 1 and Figure 2 A testing device is used in the above-mentioned method for testing the internal stress distribution of cemented filler. The device includes a workbench 1, which is a rigid and heavy steel structure platform that provides the foundation for the entire testing system. A support platform 2 is fixed at the center of the top of the workbench 1. The support platform 2 is used to place the prepared cemented filler sample 3. The surface of the support platform 2 is flat and has sufficient rigidity to avoid deformation during loading. Around the support platform 2, multiple vertical rods 4 are vertically fixed to the top of the workbench 1. These vertical rods 4 are symmetrically distributed around the perimeter of the support platform 2. An integral support plate 5 is fixed to the upper part of the outer wall of all the vertical rods 4 by welding or high-strength bolts. The support plate 5 is horizontally set and parallel to the workbench 1, forming a stable portal frame structure.

[0022] Furthermore, referring to Figure 1 and Figure 2 A hydraulic cylinder I6 is fixedly installed through the center of the support plate 5. The cylinder body of the hydraulic cylinder I6 is rigidly connected to the support plate 5 by high-strength bolts. The output rod of the hydraulic cylinder I6 extends vertically downward. The bottom end of the output rod is fixedly connected to a pressure plate 7 through a flange. The pressure plate 7 is a rectangular thick steel plate. Its planar dimensions are slightly larger than the top surface dimensions of the cemented filling sample 3. The pressure plate 7 is equipped with a set of extrusion mechanism. This extrusion mechanism is used to adapt to the uneven surface morphology that may exist on the top of the cemented filling sample 3 and to apply uniform or pre-distributed extrusion force.

[0023] Furthermore, referring to Figure 3 and Figure 4 The extrusion mechanism includes multiple arrayed grooves 8 machined on the bottom of the pressure plate 7. Each groove 8 is a blind hole with its opening facing downwards. A cylinder 9 is disposed within each groove 8. A limiting groove is vertically formed on the inner wall of the groove 8. A limiting protrusion, adapted to the limiting groove, is provided on the side wall of the cylinder 9. The limiting protrusion slides into the limiting groove, guiding and assisting in limiting the cylinder 9. The diameter of the cylinder 9 is slightly smaller than the inner diameter of the groove 8, allowing it to slide freely vertically within the groove 8. A spring is installed at the opening of the groove 8. A dust cover is provided, with its two ends sealed to the edge of the slide 8 and the side wall of the cylinder 9, respectively. A spring I10 is installed between the top of the cylinder 9 and the top inner wall of the slide 8. The two ends of the spring I10 are fixed to the top of the cylinder 9 and the top wall of the slide 8, respectively, through spring seats, allowing the cylinder 9 to retract smoothly when it encounters a protrusion on the sample surface. A miniature pressure sensor is embedded at the bottom of each cylinder 9. This pressure sensor is used to directly measure the local pressure at the contact point between the cylinder 9 and the sample.

[0024] Furthermore, referring to Figure 3 and Figure 4To achieve collective locking of the cylinders 9, a cavity 11 is provided inside the pressure plate 7. The cavity 11 is located in the middle of the pressure plate 7 and is a sealed cavity. Multiple connecting channels 12 are led out from the cavity 11. The bottom end of each connecting channel 12 is connected to a circular groove 14. The circular groove 14 is horizontally set and communicates with the side of the corresponding sliding groove 8. A locking post 13 is sealed and slidably set in each circular groove 14. One end of the locking post 13 can slide in the circular groove 14, and the other end retracts into the circular groove 14 when not pressurized. The protruding end of the locking post 13 is provided with a friction block made of a high friction coefficient material (such as engineering rubber or polyurethane), or designed as a wedge head that can engage with the groove of the side wall of the cylinder 9. When high-pressure gas is introduced into cavity 11, locking pin 13 is pushed out. Through the strong friction of friction blocks or the mechanical engagement of wedge heads, cylinder 9 is tightly pressed against the inner wall of slide groove 8, thus firmly restricting the relative movement of all cylinders 9 in the vertical direction. This makes them act as a single rigid pressure head during loading. At this time, multiple cylinders 9 are locked and can no longer produce relative displacement between them in the vertical direction. They move downward as a whole. Since each cylinder 9 has adaptively conformed to the top terrain of the sample before locking, after locking, the pressure head assembly... The load applied by the hydraulic cylinder I6 can be distributed and transmitted to each contact point on the top of the sample through the pressure sensors at the bottom of each cylinder 9, thereby simulating non-uniform contact loading conditions. At this time, the bottom surfaces of multiple cylinders 9 together form a rigid pressure head that matches the top top terrain of the sample. The top of the pressure plate 7 is also provided with an air outlet pipe 16, which is used to release the gas in the cavity 11 after the test. Solenoid valves are installed on both the air inlet pipe 15 and the air outlet pipe 16 to achieve automatic control. A pressure sensor 17 is installed on the top of the pressure plate 7 to monitor the real-time pressure in the cavity 11.

[0025] Furthermore, referring to Figure 2 and Figure 5 Two sets of horizontal impact mechanisms are symmetrically arranged on both sides of the support platform 2. The horizontal impact mechanisms are used to apply a dynamic impact load in the horizontal direction while performing static compression on the sample in the vertical direction. Each set of horizontal impact mechanisms includes a vertical plate 21. The vertical plate 21 is a vertically set steel plate with a height greater than the height of the cemented filling sample 3. The side of the vertical plate 21 facing the cemented filling sample 3 is the action surface. Multiple sliding rods 20 are vertically fixed to the top of the vertical plate 21. The sliding rods 20 extend upward and slide through the corresponding guide holes on the support plate 5. This allows the vertical plate 21 to be driven smoothly up and down in the vertical direction by the drive mechanism. At the top of the support plate 5, multiple hydraulic cylinders II 18 are fixedly installed above the vertical plate 21. The output rods of all hydraulic cylinders II 18 are fixedly connected upward to a lifting plate 19. The lifting plate 19 is rigidly connected to the sliding rods 20 by bolts. Through the synchronous extension and retraction of the hydraulic cylinders II 18, the vertical plate 21 and the entire horizontal impact mechanism can be driven to rise or fall.

[0026] Furthermore, referring to Figures 5-7 The core impact component of the horizontal impact mechanism is mounted on the vertical plate 21. On the side of the vertical plate 21 facing the cemented filler sample 3, multiple fixed cylinders I 22 are horizontally fixed and penetrate through it. The axis of the fixed cylinders I 22 is horizontal and perpendicular to the plane of the vertical plate 21. Each fixed cylinder I 22 has a slidingly fitted impact pin 23. The opening of each fixed cylinder I 22 is equipped with a folded dust cover or sealing ring. The impact pin 23 passes through the folded dust cover or sealing ring to reduce the entry of test debris. The impact pin 23 is a rod-shaped body made of high-strength alloy steel. The end of the impact pin 23 closest to the sample is the impact end, which can be designed as a hemispherical shape to reduce contact stress. The other end of the impact pin 23... The end is fixed with a connecting rod 24 and is fixedly connected to a base plate 26 through a connecting rod 24. The base plate 26 is parallel to the vertical plate 21 and is located on the side of the vertical plate 21 facing away from the cemented filling sample 3. Inside the fixed cylinder I 22, a spring II 25 is sleeved on the fixed connecting rod 24. One end of the spring II 25 is pressed against one end of the impact pin 23 through a spring seat, and the other end is pressed against the inner end face of the fixed cylinder I 22 through a spring seat. The elastic coefficient of the spring II 25 can ensure that the impact pin 23 has sufficient impact speed and energy after release. In the natural state, the preload of the spring II 25 causes the impact end of the impact pin 23 to protrude from the working surface of the vertical plate 21.

[0027] Furthermore, referring to Figure 6 and Figure 7 The reset and impact of the striking pin 23 are driven by a cam 28 mechanism. On the back of the vertical plate 21, a horizontally set rotating shaft 27 is installed through a bearing seat. The axis of the rotating shaft 27 is parallel to the plane of the base plate 26. Multiple cams 28 are fixedly sleeved on the rotating shaft 27. The outline of the cam 28 is designed as an eccentric circle. A drive motor 29 is fixedly installed on the back of the vertical plate 21. The output shaft of the drive motor 29 is connected to one end of the rotating shaft 27 through a coupling. The speed of the drive motor 29 can be precisely controlled.

[0028] Specifically, when the cam 28 rotates, its protruding part pushes the base plate 26 to move away from the vertical plate 21. The base plate 26 drives all the impact pins 23 to compress their respective springs II 25 through the connecting rod 24, so that the impact end of the impact pin 23 retracts into the fixed cylinder I 22. After the protruding part of the cam 28 rotates past the base plate 26, the compressed spring II 25 quickly releases its elastic potential energy. The spring II 25 pushes the impact pin 23 to rush towards the side of the sample at high speed, completing one impact. The impact frequency can be adjusted by controlling the speed of the drive motor 29.

[0029] Furthermore, referring to Figure 2 , Figure 5 and Figure 8To ensure the stability of the vertical plate 21 under impact, multiple horizontal bars 31 are fixed to the back of the vertical plate 21. One end of the bars 31 is fixed to the vertical plate 21, and the other end is fixed to a vertical baffle 32. The baffle 32 is parallel to the side of the support plate 5, and a vertical limiting groove 33 is provided on the baffle 32. The vertical bar 4 on the side of the support plate 5 passes through this limiting groove 33. When the vertical plate 21 moves up and down, the vertical bar 4 slides in the limiting groove 33, effectively preventing the vertical plate 21 from swaying or tilting back and forth when subjected to the periodic action of the cam 28, and ensuring the accuracy of the impact direction.

[0030] Furthermore, referring to Figure 2 , Figure 5 and Figure 9 To simulate the lateral constraint of surrounding rocks with different stiffness on the filling body, two sets of lateral surrounding rock rebound mechanisms are also set on both sides of the support platform 2. These mechanisms are adjacent to the horizontal impact mechanism but have independent functions. Each set of mechanisms includes a reaction plate 36, which is a rectangular steel plate with a size sufficient to cover the side surface of the sample. On the inner side of the reaction plate 36, i.e. the side facing the cemented filling sample 3, there is an inner plate 43. The inner plate 43 is made of Teflon film material, which has an extremely low surface friction coefficient. It can be tightly attached to the side of the cast sample and slide when the sample expands laterally under pressure, while preventing it from sticking to the sample. The inner plate 43 and the reaction plate 36 are connected by an elastic component.

[0031] Furthermore, referring to Figure 9 and Figure 10 The elastic component provides adjustable lateral stiffness and consists of multiple vertically arranged fixed cylinders II 37. The fixed cylinders II 37 are horizontally fixed to the inside of the reaction plate 36. The axes of all fixed cylinders II 37 are parallel to each other and perpendicular to the reaction plate 36. The upper and lower adjacent fixed cylinders II 37 are fixedly connected by connecting pipes 39, so that their internal cavities are connected in series. Each fixed cylinder II 37 has a sliding column 38 sealed and slidably fitted inside. The opening of the fixed cylinder II 37 is provided with a sealing ring. The sliding column 38 passes through the sealing ring to ensure the sealing performance of the sliding column 38 during movement. One end of the sliding column 38 extends out of the fixed cylinder II 37 and is fixedly connected to the outer surface of the inner layer plate 43. The inner cavity of the fixed cylinder II 37, the connecting pipe 39 and related pipelines form a sealed gas volume system.

[0032] Furthermore, referring to Figure 9 and Figure 10A collection box 40 is fixed to the outside of the reaction plate 36. The collection box 40 is a sealed container. The bottom of the collection box 40 is connected to the tail of the uppermost fixed cylinder II 37 through the top pipe 41. The top of the collection box 40 is connected to a gas guide pipe 42. The gas guide pipe 42 is connected to a high-pressure gas source and is equipped with a solenoid valve and a pressure sensor 17. High-pressure inert gas is injected into the collection box 40 through the gas guide pipe 42. The gas then enters the sealing system of the entire elastic component. The gas pressure in the system acts on the end faces of all sliding columns 38, generating a uniform pressure that pushes the inner plate 43 towards the sample. By precisely controlling the gas pressure in the collection box 40, the equivalent elastic modulus of the entire elastic component can be linearly adjusted. The higher the pressure, the greater the lateral constraint stiffness, which is used to simulate different surrounding rock conditions from soft mudstone to hard granite. The bottom of the collection box 40 is also equipped with an exhaust hose with a solenoid valve to release gas and reduce stiffness.

[0033] Furthermore, referring to Figure 2 , Figure 5 and Figure 9 The lateral rock rebound mechanism is connected to the workbench 1 via a rotating mechanism. At the top of the workbench 1, a vertical fixed shaft 34 is fixed on each side of the support platform 2. Multiple rotating arms 35 are fitted around the fixed shaft 34. The rotating arms 35 can rotate around the axis of the fixed shaft 34. The other end of all the rotating arms 35 is fixedly connected to the reaction plate 36. This allows the reaction plate 36 to swing around the fixed shaft 34 like a door, thus moving closer to or away from the side of the sample. To limit the rotation amplitude, a limiting plate 44 is also fixed at the top of the workbench 1. When the rotating arm 35 rotates to the vertical position, its side is blocked by the limiting plate 44. At this time, the reaction plate 36 is in a vertical closed state, and the inner plate 43 is in close contact with the side wall of the sample. Multiple observation ports 45 are provided on the reaction plate 36. The observation ports 45 are transparent windows or direct openings, which facilitate the DIC camera to observe the bulging deformation of the inner plate 43 under the side pressure of the sample through the observation ports 45.

[0034] Furthermore, referring to Figure 2 , Figures 5-7 In addition, on both sides of the bottom of the support plate 5, corresponding to the position of the rising path of the vertical plate 21, there is a trapezoidal plate 30 fixed. The inclined surface of the trapezoidal plate 30 faces outward and downward. When the vertical plate 21 rises, the base plate 26 on its back rises accordingly and contacts the inclined surface of the trapezoidal plate 30. The inclined surface will guide the base plate 26 to move outward horizontally. The base plate 26 drives all the impact pins 23 to compress the spring II 25 through the connecting rod 24, so that the impact pins 23 are completely retracted into the fixed cylinder I 22. This design ensures that during the lifting process of the vertical plate 21, the protruding impact pins 23 will not interfere with the pressure plate 7 or other components.

[0035] The testing equipment also includes an integrated controller (such as a PLC or industrial computer). This controller is electrically connected to the electro-hydraulic servo valve of hydraulic cylinder I6, the solenoid directional valve of hydraulic cylinder II18, the driver of drive motor 29, the solenoid valves on the inlet pipe 15 and outlet pipe 16, the solenoid valves on the air guide pipe 42 and exhaust hose, and all pressure sensors and air pressure sensors 17. The controller is configured to receive sensor signals and, according to a preset program or instructions from the tester, control the sequential operation of each actuator. For example, first, drive hydraulic cylinder II18 to raise and lower the vertical plate 21 and link it with the reaction plate 36; then adjust the air pressure of the collection box 40; subsequently, control hydraulic cylinder I6 to press down and lock the pressure plate 7; finally, start drive motor 29 to perform the impact test, thereby achieving automation and synchronous data acquisition of the entire testing process.

[0036] In another embodiment: Refer to Figure 5 and Figure 11 There is a linkage between the horizontal impact mechanism and the lateral rock rebound mechanism. A fixed seat 46 is fixed on each side of the bottom of the vertical plate 21. A connecting rod 47 is hinged to the fixed seat 46. The other end of the connecting rod 47 is hinged to the lower outer part of the reaction plate 36. When the hydraulic cylinder II 18 drives the vertical plate 21 to rise, the vertical plate 21 pulls the reaction plate 36 through the connecting rod 47, causing it to rotate inward around the fixed axis 34 until it is restricted to the vertical closed position by the limiting plate 44. When the vertical plate 21 descends to the working position, the connecting rod 47 pushes the reaction plate 36 to rotate outward and downward, so that it is placed flat on the worktable 1, thereby making room so that the impact pin 23 on the vertical plate 21 can directly act on the side of the sample. This linkage design simplifies the operation process.

[0037] A method of using a testing device includes the following steps: S1. When implementing the test method, firstly, prepare cemented filling sample 3. The test uses a cubic steel casting mold with an inner cavity size of 18 cm long, 18 cm wide, and 18 cm high. Before making the sample, clean the inner wall of the mold and evenly coat it with a layer of mineral oil as a release agent. According to the batching table determined by the indoor mix proportion test, accurately weigh the aggregate, cementitious material, and water, and use a mixer to fully mix them to form a uniform filling slurry. The casting is done manually. First, pour a slurry of about 1.5 cm thick into the mold as the bottom layer, and then place the pre-made reinforced model stably on the bottom slurry. The reinforced model is made of welded steel bars to simulate the support structure in the actual mine pillar. At critical points of the reinforcing steel, such as stress concentration areas in the top slab and sidewalls, resistance-type steel stress gauges are pre-installed. The wires of the stress gauges are carefully led out of the test mold. To prevent sedimentation and segregation of the slurry, it is stirred while pouring during the casting process. The slurry is slowly stirred in the direction of rotation and quickly scooped into the test mold with a spoon. When the slurry is poured to near the top of the test mold, the micro earth pressure cells are carefully placed at the corresponding spatial location where they are planned to be embedded. The membrane of the earth pressure cell faces the predetermined stress direction, and its wires are gently led out of the test mold. The pouring continues until the slurry height exceeds the upper edge of the test mold by two to three millimeters. The test mold is slightly vibrated to remove large air bubbles. The test mold is then placed under standard curing conditions and cured to the specified age. S2. After curing, demolding is carried out. One side of the cemented infill specimen 3 after demolding is set as the digital image correlation observation surface. The surface is dried at low temperature using a hot air gun. Then, black spots are randomly sprayed on the surface with a spray gun to form a high-contrast speckle field. Before the test begins, the equipment and specimen are positioned. The cemented infill specimen 3 is placed in the center of the support platform 2 of the testing equipment. The wires of all the resistance steel stress gauges and micro earth pressure cells embedded in the specimen are connected to the external static strain acquisition instrument. The digital image correlation observation system is set up. Two high-resolution cameras are fixed on a tripod, aligned with the observation surface of the specimen, and the aperture, focal length and angle of the cameras are adjusted to ensure that the speckle image of the entire observation surface can be clearly captured. The system calibration is then completed. S3. Adjust the test boundary conditions, operate the control system, start the hydraulic cylinder II 18, and raise the vertical plates 21 on both sides to the highest position. During this process, the vertical plates 21 pull the reaction plate 36 to rotate to the vertical closed state through the connecting rod 47, so that the Teflon inner layer plate 43 is tightly attached to the two sides of the sample. At the same time, the inclined surface of the trapezoidal plate 30 forces the base plate 26 to move outward, and completely retracts the impact pin 23 into the fixed cylinder I 22. Inert gas is injected into the two collection boxes 40 through the gas guide pipe 42. The gas pressure value is set according to the simulated surrounding rock hardness. The pressure value is monitored by the gas pressure sensor 17. After the pressure stabilizes, the elastic component provides the set lateral constraint stiffness for the sample. S4. Pre-locking and centering are performed. The hydraulic cylinder I6 is slowly lowered so that the array of cylinders 9 at the bottom of the pressure plate 7 contacts the top of the sample. Since the top surface of the sample may be uneven, each cylinder 9 moves independently under the action of the spring I10 until the pressure sensors at the bottom of all cylinders 9 have a weak contact signal. At this time, high-pressure inert gas is injected into the cavity 11 of the pressure plate 7 through the air inlet pipe 15. The gas pressure rises to the set value, such as one MPa. The high-pressure gas pushes the locking pins 13 in all the circular grooves 14 to extend out and rub to lock the corresponding cylinders 9. All cylinders 9 are rigidly connected into a pressure head that is completely in contact with the top surface of the sample. S5. Simultaneously, a high-toughness metal vibration plate is installed on each side of the cemented filling sample 3 beforehand. When the pressure plate 7 applies extrusion pressure to the cemented filling sample 3, the output end of the hydraulic cylinder II 18 drives the lifting plate 19 and the two vertical plates 21 to move downward as a whole. When the base plate 26 moves to below the trapezoidal plate 30, the base plate 26 loses the limitation of the trapezoidal plate 30 and moves towards the cemented filling sample 3 under the elastic force of the spring II 25, and abuts against the metal vibration plate on the side of the cemented filling sample 3. Then, the drive motor... 29 drives cam 28 and rotating shaft 27 to rotate. The protrusion of cam 28 pushes base plate 26 and multiple impact pins 23 to move away from cemented filling sample 3. When the protrusion of cam 28 is misaligned with base plate 26, the impact pins 23 strike the metal vibration plate on the side of cemented filling sample 3 again under the elastic force of spring II 25. The stress wave generated by the impact is transmitted into the filling through the metal vibration plate. At this time, with the addition of static load in the vertical direction, the rockburst process of high static pressure enhanced disturbance induced by the collapse of the filling can be reproduced in the laboratory. S6. During the entire loading process, multi-source data is collected synchronously. The static strain acquisition instrument continuously records the electrical signals output by all micro earth pressure cells and resistance steel stress gauges. These signals are converted to obtain the stress and steel strain at key points inside the filling body. Two cameras of the digital image correlation system continuously capture speckle images of the specimen observation surface at a fixed frame rate. The micro pressure sensors on each cylinder 9 at the bottom of the pressure plate 7 record the local contact pressure in real time. The load and displacement data of the hydraulic cylinder I6 are recorded by the controller. The speed and angle of the drive motor 29 are monitored. S7. Data Analysis Process: After loading, the collected data is processed. The data from the resistance steel bar stress gauge reflects the stress history of key points in the reinforcement model under complex stress. The data from the micro earth pressure cell provides the vertical stress response at different depths and locations inside the filling body. The stress values ​​measured by the steel bar stress gauge at the same time are compared and mutually verified with the stress values ​​measured by the adjacent earth pressure cell. The full-field displacement cloud map and strain cloud map obtained by the digital image correlation system are analyzed. The deformation characteristics of the sample surface shown in the cloud map, especially the displacement field of the sidewall, are correlated with the stress change trend at the corresponding internal location. Combined with the top contact stress concentration area captured by the local pressure sensor of cylinder 9 and the dynamic response of internal stress under lateral impact, the three-dimensional stress distribution evolution law inside the cemented filling sample 3 under simulated complex boundary conditions is comprehensively calculated.

[0038] However, as is well known to those skilled in the art, the working principles and wiring methods of the pressure sensor 17, drive motor 29, hydraulic cylinder II 18 and hydraulic cylinder I 6 are all conventional means or common knowledge, and will not be described in detail here. Those skilled in the art can make any selections according to their needs or convenience.

[0039] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for testing the internal stress distribution of a cemented infill body, characterized in that, Includes the following steps: S1. The test uses a casting mold with a length × width × height of 18.0cm × 18.0cm × 18.0cm. Before making the test block, the mold is cleaned and a layer of mineral oil or other release agent is applied to its inner wall. S2. Install resistance-type steel stress gauges on the reinforcement model to monitor the stress distribution of the steel reinforcement in the top slab and sidewalls during the excavation of the model. S3. Weigh out a certain amount of aggregate, cementitious material and water according to the ingredient list and mix them thoroughly. The casting is done manually with a spoon. First, pour a filling slurry to a height of about 1.5cm, and then place different reinforcement models. To prevent the slurry from settling, stir while pouring and quickly take out the slurry and pour it into the test mold. The slurry height should exceed the test mold by 2-3mm. During the casting process, place small earth pressure boxes at the corresponding locations and lead out the wires. S4. After demolding at the end of the model curing period, the front of the model is set as the DIC observation surface. The surface is dried with a hot air gun and spots are randomly sprayed manually to form a cemented filling sample (3). S5. Before applying pressure to the model, connect the wires of the pre-embedded monitoring elements to the monitoring equipment; set up the DIC observation system, and adjust the aperture and focal length of the left and right cameras to ensure the clarity of the captured images; S6. Use testing equipment to perform compression tests on the cured cemented filling sample (3), gradually apply pressure to the model at a speed of 0.05kN per second, record the image of the stress process on the side surface where the speckle is located throughout the process, and record the stress and strain data of each point inside the model provided by the micro-small earth pressure cell and the resistance steel stress gauge. S7. The stress value at the test point measured by the resistance-type steel bar stress gauge is compared with the stress in the vertical direction of the filling body measured by the micro earth pressure cell; then the displacement of the observation point of the reinforcement model measured by it is compared and analyzed with the displacement and strain cloud map observed by the DIC system, so as to obtain the stress distribution inside the filling body and the displacement before and after deformation, and then calculate the stress and strain of the whole field.

2. A testing device, applied to the method for testing the internal stress distribution of a cemented infill body as described in claim 1, characterized in that, include: The workbench (1) has a support platform (2) on top for placing the cemented filler sample (3). The support plate (5) is fixed above the workbench (1) by multiple vertical rods (4); Hydraulic cylinder I (6) is fixed inside the support plate (5), with its output end facing the support platform (2); The pressure plate assembly is connected to the output end of the hydraulic cylinder I (6). The pressure plate assembly includes a pressure plate (7) and a plurality of cylinders (9). The bottom of the pressure plate (7) is provided with a plurality of grooves (8). Each cylinder (9) is slidably disposed in one of the grooves (8). The bottom end of each cylinder (9) is provided with a pressure sensor for contacting the top of the sample and sensing local contact stress during testing. Two sets of horizontal impact components are symmetrically arranged on both sides of the support platform (2). Each set of horizontal impact components includes a vertical plate (21) and an impact generator. The vertical plate (21) is provided with at least one impact pin (23). The impact generator is used to drive the impact pin (23) to reciprocate in the horizontal direction and to apply dynamic disturbance to the side of the cemented filling sample (3). Two sets of lateral rock rebound components are symmetrically arranged on both sides of the support platform (2). Each set of lateral rock rebound components includes a reaction plate (36) and an elastic simulation mechanism. The reaction plate (36) is hinged to the worktable (1) through a rotating arm (35). The elastic simulation mechanism is located on the side of the reaction plate (36) facing the support platform (2). The equivalent stiffness of the elastic simulation mechanism can be changed by adjusting the internal pressure to simulate the lateral constraint of surrounding rocks of different hardness on the sample.

3. The detection device according to claim 2, characterized in that, The pressure plate assembly also includes a locking mechanism, which includes a cavity (11) disposed in the pressure plate (7), a plurality of circular grooves (14) communicating with the slide groove (8), a locking pin (13) slidably disposed in each of the circular grooves (14), and a communication channel (12) connecting the cavity (11) and each of the circular grooves (14); when high-pressure gas is introduced into the cavity (11), the gas pushes all the locking pins (13) against the corresponding cylinders (9) through the communication channel (12), thereby locking the plurality of cylinders (9).

4. The detection device according to claim 3, characterized in that, Each of the grooves (8) is provided with a spring I (10), and the two ends of the spring I (10) are respectively connected to the top inner wall of the groove (8) and the top of the cylinder (9).

5. The detection device according to claim 4, characterized in that, The impact generator of the horizontal impact assembly includes a fixed cylinder I (22) fixed to the vertical plate (21), a striker (23) slidably disposed in the fixed cylinder I (22), a connecting rod (24) connected to the end of the striker (23) away from the support platform (2), a spring II (25) sleeved on the connecting rod (24), a cam (28) rotatably connected to the vertical plate (21), and a drive motor (29) for driving the cam (28) to rotate; the spring II (25) provides an elastic force that causes the striker (23) to strike the support platform (2), and the cam (28) periodically compresses and releases the spring II (25) through the connecting rod (24) during rotation, thereby causing the striker (23) to generate reciprocating impact.

6. The detection device according to claim 5, characterized in that, The horizontal impact assembly also includes a vibration transmission plate located between the impact pin (23) and the cemented filler sample (3).

7. The detection device according to claim 6, characterized in that, The elastic simulation mechanism includes multiple fixed cylinders II (37) arranged vertically, a sliding column (38) that is sealed and slidably disposed in each fixed cylinder II (37), and a connecting pipe (39) that connects the upper and lower adjacent fixed cylinders II (37). One end of all the sliding columns (38) is connected to an inner plate (43), which is used to contact the cemented filler sample (3). It also includes a collection box (40) that is connected to the uppermost fixed cylinder II (37). By filling or venting gas into the collection box (40), the pressure in each fixed cylinder II (37) is changed, thereby adjusting the overall equivalent stiffness of the elastic simulation mechanism.

8. The detection device according to claim 7, characterized in that, The inner layer plate (43) is a Teflon film.

9. The detection device according to claim 8, characterized in that, It also includes a hydraulic cylinder II (18), which is fixed on the support plate (5) and its output end is connected to the lifting plate (19). The vertical plate (21) is slidably connected to the support plate (5) through the slide rod (20) and fixedly connected to the lifting plate (19). The hydraulic cylinder II (18) is used to drive the horizontal impact assembly to lift as a whole.

10. A testing device according to claim 9, characterized in that, The bottom of the vertical plate (21) is hinged to the reaction plate (36) via a connecting rod (47).

Images