Deep engineering true triaxial grouting simulation test system and test method thereof

Abstract

The invention discloses a deep engineering true triaxial grouting simulation test system and a test method thereof, and relates to the technical field of rock mechanics test equipment, and the deep engineering true triaxial grouting simulation test system comprises a true triaxial loading system, a servo control grouting system and a grouting process real-time monitoring system. The true triaxial loading system adopts a vertical and horizontal counter-force frame structure, three-dimensional principal stress is independently applied through an actuator, and true three-dimensional crustal stress of deep engineering is truly restored. The servo control grouting system achieves multi-mode grouting parameter output through linkage of a servo motor, a planetary reducer and a stepping piston. The grouting process real-time monitoring system is integrated with multi-source sensors such as distributed optical fibers and miniature thermocouple sensors, and slurry diffusion morphology, fracture deformation and splitting signals are captured in real time. The problems that a traditional simulation system is insufficient in crustal stress reduction, low in grouting parameter control precision and deficient in monitoring means under hidden conditions are solved, and a reliable basis is provided for deep grouting parameter design and critical splitting pressure analysis.

Description

Technical Field

[0001] The present invention relates to the technical field of rock mechanics testing equipment, and in particular to a deep engineering true triaxial grouting simulation test system and a test method thereof. Background Art

[0002] Grouting reinforcement is a convenient and effective support technique. It involves injecting inorganic or organic slurry into weak or fractured geological masses. Once the slurry solidifies, it effectively bonds and fills fractures in the broken rock mass, improving the overall bearing capacity of the rock mass and controlling the further development of fractures into deeper layers, thereby ensuring the stability of the surrounding rock mass of tunnels / roadways. However, it is worth noting that, to date, grouting theory has significantly lagged behind grouting practice. In particular, as geotechnical engineering projects have shifted from shallow to deep, the continued use of shallow grouting theory may not meet the needs of deep grouting reinforcement and provide inadequate guidance for on-site construction. In grouting projects, due to the hidden nature of the rock mass, it is difficult to monitor parameters such as the slurry diffusion morphology, diffusion distance, and changes in rock fracture aperture under the influence of grouting pressure in the field. However, these parameters provide valuable guidance for grouting parameter design and construction in on-site projects. Researchers have primarily used physical models, numerical simulations, and theoretical analysis to study the diffusion mechanism of the grouting process. Compared with numerical simulation and theoretical analysis, the physical model can more realistically reflect the entire grouting diffusion, penetration, splitting and other processes. Its experimental data is more reliable and can better reflect the actual working conditions. It is also the grouting simulation method most acceptable to scientific researchers.

[0003] At present, the innovations in physical model tests are mainly concentrated in grouting visualization, fracture model refinement, slurry-rock and soil coupling, etc., all of which are progressing in the direction of realism and refinement. However, the degree of true restoration of the current grouting physical simulation test is still lacking.

[0004] First, regarding the simulation of the grouting power system, indoor grouting simulation tests require high-precision control of the grouting flow rate and pressure, without pulse fluctuations, to more accurately reveal the laws governing the grouting diffusion process. On-site grouting, however, often utilizes high-pressure, high-flow reciprocating piston pumps. The pulsed grouting flow and pressure output can cause abrupt changes in the grouting diffusion morphology and range at specific time points. In particular, the pulsed grouting pressure cannot determine the actual allowable pressure that the rock mass can withstand during the grouting process, making quantitative analysis impossible. Furthermore, the high flow and pressure of on-site grouting pumps are unsuitable for indoor meter-scale grouting simulation tests. Currently, indoor grouting simulation systems often use air compressors, nitrogen cylinders, and small manual pumps as grouting power sources. These power sources have low precision, resulting in unstable grouting pressure and flow output during the test, which can lead to significant deviations in the experimental results. Furthermore, increasing the scale of the simulated object increases grouting time. Prolonged stagnant time within the pump can lead to water seepage and sedimentation. Inhomogeneous slurry can also affect the fidelity of the simulation results. Based on the above research results analysis and test requirements, the development of a large-capacity grouting simulation system with high-precision control that can ensure slurry homogeneity is a problem that needs to be solved at present.

[0005] Secondly, in terms of geostress environment simulation, the process of slurry diffusion in the crack is actually the coupling of slurry stress and geostress field. It is very necessary to consider the influence of geostress on grouting diffusion during the test process. Existing physical simulation tests only impose a one-dimensional or two-dimensional stress environment on the crack model during the test process. Moreover, most crack models are made of acrylic or resin materials, and their deformation and failure characteristics do not conform to the similarity theory of physical simulation tests. It is worth mentioning that as geotechnical engineering gradually moves into deep areas, one-dimensional or two-dimensional geostress simulation is no longer in line with actual working conditions, and it is necessary to truly reproduce a three-dimensional, high-precision triaxial stress environment.

[0006] Finally, regarding grouting simulation and signal monitoring during the grouting process, most studies use transparent flat plate fractures to simulate the diffusion and filling processes, using video equipment to record the grouting morphology. Currently, simulation of the entire grouting process—from grouting diffusion within the fracture, filling, to splitting and expansion—is relatively rare in existing rock fracture grouting physical models. Particularly under true triaxial stress, studying the maximum allowable grouting pressure that the rock mass can withstand at the critical splitting state during grouting is crucial. This provides important guidance for designing parameters such as grouting pressure, flow rate, and time in deep grouting treatment projects. As mentioned above, transparent acrylic or resin materials do not conform to the fracture failure deformation characteristics, necessitating the development of similar fluid-structure interaction materials. However, these materials are generally non-transparent, and particularly at the specimen boundary after true triaxial stress application, making it impossible to record information using video equipment. Therefore, when conducting grouting simulation tests under true triaxial stress, a monitoring system is needed that can monitor grouting diffusion, filling, and even splitting fractures in real time.

[0007] Based on the above needs, the present invention has designed and developed a grouting system and test method that can highly reproduce the grouting process of deep engineering. It can simulate the true triaxial stress environment of deep engineering, and at the same time, it can control the parameters such as grouting pressure and flow in real time with high precision. It can also simulate grouting parameters such as pulse grouting pressure, constant / variable grouting pressure and constant / variable grouting rate. Summary of the Invention

[0008] Based on the technical problems raised above, the present invention provides a true triaxial grouting simulation test system and a test method for deep engineering. Through true triaxial loading, servo grouting control and real-time monitoring system, the grouting diffusion and rock mass response under three-dimensional stress in deep engineering are simulated to optimize the grouting parameter design.

[0009] To achieve the above purpose, the technical means adopted by the present invention are as follows:

[0010] A true triaxial grouting simulation test system for deep engineering, comprising:

[0011] A true triaxial loading system comprises a vertical reaction frame and a horizontal reaction frame, wherein the vertical reaction frame provides the second and third principal stresses via an actuator, and the horizontal reaction frame provides the first principal stress via an actuator. The horizontal reaction frame is provided with a semi-open pressure chamber for placing a physical model specimen. After the specimen is installed, it is pushed into the vertical reaction frame along a serrated guide rail by a driving motor to form a true triaxial loading structure.

[0012] A servo-controlled grouting system includes a servo motor, a planetary reducer, a synchronous pulley, a rotating screw, a stepping piston, a hollow pump body, and a built-in stirring basket. The servo motor is connected to the synchronous pulley via the planetary reducer, and the synchronous pulley is connected to the rotating screw. The stepping piston achieves axial displacement through the engagement of the rotating screw threads. The stirring basket is driven by the rotating motor to stir the slurry in real time. The system achieves constant pressure, variable pressure, constant rate, variable rate, and pulse pressure grouting parameter outputs through servo motor control.

[0013] A real-time monitoring system for the grouting process includes distributed optical fibers pre-buried in the upper and lower walls of the specimen crack, an acoustic emission sensor disposed on the specimen surface, a temperature-difference-based micro-thermocouple sensor, an earth pressure cell sensor, and a mud pressure sensor. The distributed optical fibers, acoustic emission sensor, micro-thermocouple sensor, earth pressure cell sensor, and mud pressure sensor are connected to a computer control system via a signal path for real-time monitoring of slurry diffusion morphology, crack deformation, and rupture signals.

[0014] The true triaxial loading system is connected to a hydraulic oil source via a hydraulic oil circuit, the servo-controlled grouting system is connected to a physical model specimen via a grouting pipeline, and the grouting process real-time monitoring system is connected to a computer control system via a signal path.

[0015] Furthermore, the true triaxial loading system includes four loading surfaces, wherein the first loading surface is provided by the actuator on the left side of the horizontal reaction frame; the second loading surface and the third loading surface are provided by the upper actuator and the lower actuator of the vertical reaction frame; the fourth loading surface is provided by the actuator on the right side of the vertical reaction frame; the left and back sides of the vertical reaction frame are loaded through the frame reaction force, and the vertical reaction frame is provided with an excavation window and an observation window, and the horizontal reaction frame is provided with an excavation window.

[0016] Furthermore, the mixing basket of the servo-controlled grouting system is a hollow structure, located inside the hollow pump body and connected to the rotating motor through a bearing. The tail end of the stepping piston is provided with a fixed seat that engages with the rotating screw thread, and the power transmission between the servo motor and the rotating screw is realized through a synchronous pulley drive.

[0017] Furthermore, the distributed optical fiber is pre-buried along the upper and lower plates of the sample crack to monitor crack deformation, the acoustic emission sensor captures microseismic signals of crack splitting, and the micro-thermocouple sensor provides real-time feedback on the diffusion range through the temperature difference between the slurry and the crack surface.

[0018] Furthermore, the grouting pipe channel passes through the raised pad on the side of the interlocking pad, and the grouting pipeline is connected to the servo-controlled grouting system after a 90° turn. A height difference space is reserved between the raised pad and the interlocking pad for the pipeline to be led out.

[0019] The present invention also provides a test method for a deep engineering true triaxial grouting simulation test system, comprising the following steps:

[0020] S1. Place the physical model sample of the embedded grouting pipeline and sensor on the bottom pad of the working platform of the true triaxial loading system, and push the sample into the pressure chamber through the ball bearing;

[0021] S2. Start the drive motor to push the horizontal reaction frame into the vertical reaction frame, and apply the load to the surface of the physical model specimen through the actuator to form a true triaxial stress environment and maintain the load;

[0022] S3. Close the slurry outlet and discharge port of the servo-controlled grouting system, drive the stepping piston backward to suck the slurry into the hollow pump body, start the stirring basket to prevent the slurry from settling, exhaust the air in the pipeline, and then connect the grouting pipeline of the physical model specimen;

[0023] S4. Start the real-time monitoring system for the grouting process, perform the grouting simulation test according to the set grouting parameters and collect data simultaneously;

[0024] S5. After grouting is completed, stop the servo control grouting system, disconnect the grouting pipeline, remove the boundary stress of the true triaxial loading system, reverse drive the motor to withdraw the horizontal reaction frame, take out the physical model sample, analyze the crack diffusion morphology and sensor data, and clean the residual slurry in the hollow pump body and pipeline.

[0025] Furthermore, the specific steps in S3 include:

[0026] S31, close the slurry outlet and the slurry discharge port, and open the grouting port;

[0027] S32, driving the stepping piston backward by the servo motor to absorb the slurry;

[0028] S33, starting the rotary motor to drive the stirring basket to continuously stir the slurry;

[0029] S34, after closing the grouting port, drive the stepping piston forward to expel the air until slurry flows out of the slurry outlet.

[0030] Furthermore, the grouting parameters include achieving a constant pressure, a variable rate or a pulse pressure mode by adjusting the servo motor speed and the rotation screw stroke;

[0031] Combined with the built-in pressure sensor feedback signal, the grouting pressure output is calibrated in real time.

[0032] Furthermore, the real-time monitoring system for the grouting process includes: synchronously monitoring the changes in the fluid-solid coupling stress field in the cracks through distributed optical fibers and soil pressure box sensors; locating the crack expansion position using acoustic emission sensors and combining with micro-thermocouple sensors to generate a three-dimensional morphology map of slurry diffusion.

[0033] Due to the adoption of the above technical solution, the present invention has the following advantages compared with the prior art:

[0034] 1. The present invention provides a true triaxial grouting simulation test system for deep engineering. Through the combined design of separate vertical and horizontal reaction frames, it independently applies three-dimensional principal stresses and accurately simulates the true three-dimensional ground stress conditions of deep engineering. This solves the defect that traditional one-dimensional or two-dimensional stress simulation does not conform to actual working conditions, and significantly improves the data reliability of grouting diffusion mechanism research.

[0035] 2. The present invention provides a true three-axis grouting simulation test system and test method for deep engineering, which are based on the linkage control of a servo motor, a planetary reducer and a stepping piston to achieve multi-mode grouting parameter output such as constant pressure, change rate and pulse pressure. Combined with the real-time stirring function of the stirring basket, it effectively avoids slurry sedimentation and water seepage problems, ensures the stability of the grouting process and the homogeneity of the slurry, and solves the deviation of experimental results caused by the insufficient accuracy of traditional power sources.

[0036] 3. The present invention provides a true triaxial grouting simulation test system and test method for deep engineering. Through the coordinated monitoring of multiple-source sensors such as distributed optical fibers, acoustic emission sensors, and micro-thermocouple sensors, the system can capture the slurry diffusion morphology, crack deformation, and splitting signals in real time. This overcomes the limitation that non-transparent specimens cannot use video equipment in a true triaxial stress environment, and provides comprehensive and dynamic data support for deep grouting parameter design and critical splitting pressure analysis. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0038] Figure 1 This is an overall layout diagram of a grouting simulation test platform of a true triaxial grouting simulation test system for deep engineering according to an embodiment of the present invention;

[0039] Figure 2 A three-dimensional view of a true triaxial loading system of a deep engineering true triaxial grouting simulation test system according to an embodiment of the present invention;

[0040] Figure 3 A top view of a true triaxial loading system of a deep engineering true triaxial grouting simulation test system according to an embodiment of the present invention;

[0041] Figure 4 A side view of a true triaxial loading system of a true triaxial grouting simulation test system for deep engineering according to an embodiment of the present invention;

[0042] Figure 5 This is a front view of a true triaxial loading system of a deep engineering true triaxial grouting simulation test system according to an embodiment of the present invention;

[0043] Figure 6 This is a three-dimensional view of a servo-controlled grouting system of a true triaxial grouting simulation test system for deep engineering according to an embodiment of the present invention;

[0044] Figure 7 This is a cross-sectional view of a servo-controlled grouting system of a true triaxial grouting simulation test system for deep engineering according to an embodiment of the present invention;

[0045] Figure 8 This is a bottom schematic diagram of a servo-controlled grouting system of a true triaxial grouting simulation test system for deep engineering according to an embodiment of the present invention;

[0046] Figure 9 This is a schematic diagram of the installation of a physical model specimen of a true triaxial grouting simulation test system for deep engineering according to an embodiment of the present invention;

[0047] Figure 10 This is a schematic diagram of the rear installation of a physical model specimen of a deep engineering true triaxial grouting simulation test system according to an embodiment of the present invention;

[0048] Figure 11 This is a flow chart of a test method for a true triaxial grouting simulation test system for deep engineering according to an embodiment of the present invention.

[0049] Figure: 1. True triaxial loading system; 2. Servo-controlled grouting system; 3. Hydraulic oil source; 4. Computer control system; 5. Grouting pipeline; 6. Hydraulic oil circuit; 7. Signal path; 8. Vertical reaction frame; 9. Horizontal reaction frame; 10. Actuator; 11. Working platform; 12. Ball bearing; 13. Drive motor; 14. Sawtooth guide rail; 15. Excavation window; 16. Observation window; 17. Hollow pump body; 18. Servo motor; 19. Planetary reducer; 20. Synchronous pulley; 21. Power distribution Box; 22. Base; 23. Pulley; 24. Fixed base; 25. Rotating screw; 26. Stepping piston; 27. Piston position fishbone; 28. Slurry outlet; 29. ​​Grouting port; 30. Built-in pressure sensor; 31. Slurry outlet; 32. Mixing flower basket; 33. Rotating motor; 34. Physical model specimen; 35. Bottom pad; 36. Front pad; 37. Left pad; 38. Upper pad; 39. Rear pad; 40. Raised pad; 41. Interlocking pads; 42. Grouting pipe channel. DETAILED DESCRIPTION

[0050] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0051] In order to make the purpose, technical solutions and advantages of the implementation of the present invention clearer, the technical solutions in the embodiments of the present invention will be described in more detail below in conjunction with the drawings in the embodiments of the present invention. In the drawings, the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions; the embodiments described are part of the embodiments of the present invention, not all of the embodiments; the embodiments and directional terms described below with reference to the drawings are exemplary and intended to be used to explain the present invention, and cannot be understood as limitations on the present invention; based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. The parts and equipment all adopt conventional models in the prior art, and the circuit connections adopt conventional connection methods in the prior art, which will not be described in detail here. The contents not described in detail in this specification belong to the prior art known to professional and technical personnel in this field. The embodiments of the present invention are described in detail below in conjunction with the drawings:

[0052] Example

[0053] like Figures 1 to 10 As shown, a deep engineering true triaxial grouting simulation test system includes:

[0054] The true triaxial loading system 1 comprises a vertical reaction frame 8, a horizontal reaction frame 9, a work platform 11, a drive motor 13, an actuator 10, and interlocking pads 41. The horizontal reaction frame 9 is internally designed with a semi-open pressure chamber for placing a physical model specimen 34. The front of the horizontal reaction frame 9 is connected to the work platform 11, on which a bottom pad 35 is placed. A ball bearing 12 is designed between the bottom pad 35 and the work platform 11. Once the physical model specimen 34 is placed on the bottom pad 35, the friction-reducing effect of the ball bearing 12 pushes the physical model specimen 34 into the pressure chamber of the horizontal reaction frame 9. A drive motor 13 is also provided at the rear of the horizontal reaction frame 9, which pushes the horizontal reaction frame 9 into the interior of the vertical reaction frame 8 along a designed serrated guide rail 14. The actuator 10 is installed on two reaction frames, and a total of four loading surfaces are designed, which are located above, below and on the right of the vertical reaction frame 8, and on the left of the horizontal reaction frame 9. That is, the vertical reaction frame 8 applies the second and third direction principal stresses, and the horizontal reaction frame 9 applies the first direction principal stress. The application of the stress boundaries of the other two surfaces is provided by the reaction force. After the sample is installed, the loading of true triaxial stress is realized. At the same time, in order to realize the connection between the grouting pipeline 5 inside the sample and the servo-controlled grouting system 2, a raised pad 40 is designed on the side of the interlocking pad 41. The grouting pipeline 5 is led out from the inside of the sample, passes through the grouting pipe channel, and then it is turned 90°. The true triaxial loading system 1 is led out in the height difference space between the raised pad 40 and the interlocking pad 41, and finally the connection with the servo-controlled grouting system 2 is realized. In addition, in order to further expand the application scenarios of physical model tests, excavation windows 15 are designed on the reaction frame of the true triaxial loading system 1, which are located in the middle of the vertical reaction frame 8 and the horizontal reaction frame 9 respectively. At the same time, observation windows 16 are designed on both sides of the excavation window 15 of the vertical reaction frame 8, which can be used to simulate deep engineering tunnel excavation simulation tests.

[0055] The servo-controlled grouting system 2 includes a servo motor 18, a planetary reducer 19, a synchronous pulley 20, a rotating screw 25, a stepping piston 26, a hollow pump body 17, a stirring basket 32, a rotating motor 33, a distribution box 21, a base 22, a pulley 23, and a built-in pressure sensor 30. The servo motor 18 is connected to the grouting control system to provide and control the grouting output parameters; the planetary reducer 19 is connected to the servo motor 18, and its function is to reduce the speed, increase the torque and reduce the motor's moment of inertia ratio on the basis of ensuring the precise transmission of the servo motor 18; the distribution box 21 is fixed to the side of the base 22, the pulley 23 is installed at the bottom of the base 22, and the built-in pressure sensor 30 is arranged on the inner wall of the hollow pump body 17; a synchronous pulley 20 is connected to the tail end of the planetary reducer 19, and the upper and lower synchronous pulleys 20 are respectively connected to the planetary reducer 19 and the rotating screw 25, and the power transmission between the servo motor 18 and the rotating screw 25 is realized through the transmission of the synchronous pulley 20. The rotating screw 25 is designed with threads, and a stepping piston 26 is assembled on the rotating screw 25. The stepping piston 26 is a hollow structure design, and a fixed base 24 is designed at the tail end. The fixed base 24 and the rotating screw 25 are engaged with each other through threads. When the rotating screw 25 rotates, it can drive the stepping piston 26 to move, and the specific position of the stepping piston 26 is displayed by the piston position fishbone 27, thereby realizing the stroke control of the stepping piston 26 inside the pump body. The mixing basket 32 ​​is a hollow design, located inside the hollow pump body 17, and is connected to the external rotary motor 33 through a bearing. Driven by the rotary motor 33, the mixing basket 32 ​​can rotate in real time to stir the slurry contained in the hollow pump body 17.

[0056] The real-time monitoring system for the grouting process includes the following sensors: micro-thermocouple sensors, distributed optical fibers, hydraulic pressure sensors, earth pressure cell sensors, acoustic emission sensors, and mud pressure sensors. The micro-thermocouple sensors are embedded in the surface of the model's internal fractures. They use the temperature difference between the slurry and the fracture surface to capture temperature change signals, used to monitor the diffusion range and morphology of the slurry under concealed conditions. Distributed optical fibers are embedded in the upper and lower walls of the fractures to monitor fracture deformation under the changing fluid-solid coupling stress field during grouting. Hydraulic pressure sensors and earth pressure cell sensors are embedded in the surface and interior of the upper and lower walls of the fractures within the model to monitor stress changes in the fluid-solid coupling field within the fractures. Acoustic emission sensors are embedded in the model's surface to monitor microseismic signals indicating cracking and expansion under grouting pressure. The mud pressure sensor is installed at the interface of the model's grouting pipeline 5 to monitor changes in grouting pressure signals and compare them with the grouting system's pressure output. The combination of the above sensors can monitor the diffusion information of the slurry inside the cracks as well as the rupture and deformation information of the cracks in real time, so as to achieve transparent monitoring of the entire grouting process under concealed conditions.

[0057] The true triaxial loading system 1 is connected to the hydraulic oil source 3 through the hydraulic oil circuit 6, the servo-controlled grouting system 2 is connected to the physical model specimen 34 through the grouting pipeline 5, and the real-time monitoring system of the grouting process is connected to the computer control system 4 through the signal path 7 to drive the actuator 10 to apply three-dimensional principal stress.

[0058] like Figure 11 As shown, the present invention also provides a test method for a true triaxial grouting simulation test system for deep engineering, comprising the following steps:

[0059] S1. Preparation and installation of the physical model specimen 34: Cast the physical model specimen 34, embed the grouting pipeline 5 and sensors inside, including:

[0060] Distributed optical fiber: arranged along the upper and lower walls of the fracture to monitor changes in the fluid-solid coupling stress field;

[0061] Acoustic emission sensor: installed on the surface of the sample to capture the microseismic signal of crack expansion;

[0062] Micro thermocouple sensor: pre-buried on the crack surface, generates diffusion topography through the temperature difference between slurry and crack;

[0063] Soil pressure cell sensor and mud pressure sensor: monitor internal stress of cracks and grouting pressure.

[0064] The physical model specimen 34 is placed on the bottom pad 35 of the working platform 11 of the true triaxial loading system 1. A ball 12 is provided between the bottom pad 35 and the working platform 11 to reduce friction.

[0065] The front pad 36, the left pad 37, the upper pad 38, and the rear pad 39 are interlocked on the surface of the sample through the interlocking pads 41 to form a complete loading surface;

[0066] The physical model specimen 34 is pushed to slide along the ball 12 and sent into the semi-open pressure chamber inside the horizontal reaction force frame 9 .

[0067] S2. Assembling and applying stress to the true triaxial loading system 1: Start the drive motor 13 at the rear of the horizontal reaction frame 9 and push the horizontal reaction frame 9 into the middle of the vertical reaction frame 8 along the serrated guide rail 14 to form a closed loading structure;

[0068] Start the hydraulic oil source 3 and drive the actuator 10 to apply three-dimensional principal stress, among which the first direction principal stress (horizontal direction) is provided by the actuator 10 on the left side of the horizontal reaction frame 9; the second direction principal stress (vertical direction) is provided by the upper actuator 10 of the vertical reaction frame 8; the third direction principal stress (transverse direction) is provided by the right actuator 10 of the vertical reaction frame 8; the remaining two surfaces are loaded through the frame reaction force to ensure that the sample is in a true three-dimensional stress state; load to the target value according to the set parameters and maintain the load until the stress field of the sample is stable.

[0069] S3. Preparation of the servo-controlled grouting system 2 and slurry injection: Slurry suction and stirring: Close the slurry outlet 28 and slurry discharge port 31 of the servo-controlled grouting system 2, and open the grouting port 29; the servo motor 18 drives the rotary screw 25 to rotate through the planetary reducer 19 and the synchronous pulley 20, and the stepping piston 26 retreats, sucking the slurry from the grouting port 29 into the hollow pump body 17; start the rotary motor 33, driving the hollow stirring basket 32 ​​to continuously stir the slurry to prevent water seepage or sedimentation;

[0070] Close the grouting port 29, drive the stepping piston 26 forward, and discharge the air from the external pipeline of the slurry outlet 28 until the slurry flows out steadily; connect the grouting pipeline 5 of the slurry outlet 28 with the grouting pipeline 5 inside the sample through the grouting pipe channel 42, and ensure that the pipeline turns 90° through the height difference space between the raised pad 40 and the interlocking pad 41 to avoid pressure damage to the pipeline during loading.

[0071] S4. Grouting process simulation and real-time monitoring: grouting parameter mode is set through computer control system 4:

[0072] Constant pressure / rate: adjust the speed of the servo motor 18 and the stroke of the rotating screw 25;

[0073] Variable pressure / rate: Dynamically adjust motor speed and screw stroke;

[0074] Pulse pressure: periodically switch pressure output mode;

[0075] The grouting pressure is calibrated in real time in combination with the feedback signal from the built-in pressure sensor 30;

[0076] Real-time data acquisition is carried out through distributed optical fibers, acoustic emission sensors, micro-thermocouple sensors, earth pressure cells, and mud pressure sensors. All sensor signals are transmitted to the computer control system 4 through the signal path 7 to achieve full-process monitoring. Among them, the distributed optical fibers monitor the deformation of the upper and lower walls of the fracture and the changes in the fluid-solid coupling stress field; the acoustic emission sensors capture the microseismic signals of the fracture splitting and locate the expansion position; the micro-thermocouple sensors generate a three-dimensional morphology of the slurry diffusion through the temperature difference; the earth pressure cell sensors and the mud pressure sensors provide feedback on the internal stress of the fracture and the grouting pressure data.

[0077] S5, test termination and system reset: After the grouting is completed, the servo control grouting system 2 is stopped, the grouting pipeline 5 is disconnected, the boundary stress of the true triaxial loading system 1 is unloaded, and the reverse drive motor 13 is withdrawn from the horizontal reaction frame 9;

[0078] The physical model sample 34 is taken out, the crack diffusion morphology and sensor data are analyzed, and the residual slurry in the hollow pump body 17 and the pipeline is cleaned to ensure that there is no pollution in the next test.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A true triaxial grouting simulation test system for deep engineering, characterized by: include: A true triaxial loading system comprises a vertical reaction frame and a horizontal reaction frame, wherein the vertical reaction frame provides the second and third principal stresses via an actuator, and the horizontal reaction frame provides the first principal stress via an actuator. The horizontal reaction frame is provided with a semi-open pressure chamber for placing a physical model specimen. After the specimen is installed, it is pushed into the vertical reaction frame along a serrated guide rail by a driving motor to form a true triaxial loading structure. A servo-controlled grouting system includes a servo motor, a planetary reducer, a synchronous pulley, a rotating screw, a stepping piston, a hollow pump body, and a built-in stirring basket. The servo motor is connected to the synchronous pulley via the planetary reducer, and the synchronous pulley is connected to the rotating screw. The stepping piston achieves axial displacement through the engagement of the rotating screw threads. The stirring basket is driven by the rotating motor to stir the slurry in real time. The system achieves constant pressure, variable pressure, constant rate, variable rate, and pulse pressure grouting parameter outputs through servo motor control. A real-time monitoring system for the grouting process includes distributed optical fibers pre-buried in the upper and lower walls of the specimen crack, an acoustic emission sensor disposed on the specimen surface, a temperature-difference-based micro-thermocouple sensor, an earth pressure cell sensor, and a mud pressure sensor. The distributed optical fibers, acoustic emission sensor, micro-thermocouple sensor, earth pressure cell sensor, and mud pressure sensor are connected to a computer control system via a signal path for real-time monitoring of slurry diffusion morphology, crack deformation, and rupture signals. The true triaxial loading system is connected to a hydraulic oil source via a hydraulic oil circuit, the servo-controlled grouting system is connected to a physical model specimen via a grouting pipeline, and the grouting process real-time monitoring system is connected to a computer control system via a signal path.

2. A deep engineering true triaxial grouting simulation test system according to claim 1, characterized in that: The true triaxial loading system includes four loading surfaces, wherein the first loading surface is provided by the actuator on the left side of the horizontal reaction frame; the second loading surface and the third loading surface are provided by the upper actuator and the lower actuator of the vertical reaction frame; the fourth loading surface is provided by the actuator on the right side of the vertical reaction frame; the left and rear sides of the vertical reaction frame are loaded through the frame reaction force, and the vertical reaction frame is provided with an excavation window and an observation window, and the horizontal reaction frame is provided with an excavation window.

3. A deep engineering true triaxial grouting simulation test system according to claim 1, characterized in that: The stirring basket of the servo-controlled grouting system is a hollow structure, located inside the hollow pump body and connected to the rotating motor through a bearing. The tail end of the stepping piston is provided with a fixed seat that engages with the rotating screw thread, and the power transmission between the servo motor and the rotating screw is realized through a synchronous pulley drive.

4. A deep engineering true triaxial grouting simulation test system according to claim 1, characterized in that: The distributed optical fiber is pre-buried along the upper and lower plates of the sample crack to monitor crack deformation, the acoustic emission sensor captures microseismic signals of crack splitting, and the micro-thermocouple sensor provides real-time feedback on the diffusion range through the temperature difference between the slurry and the crack surface.

5. A deep engineering true triaxial grouting simulation test system according to claim 2, characterized in that: The grouting pipe channel passes through the raised pad on the side of the interlocking pad, and the grouting pipeline is connected to the servo-controlled grouting system after a 90° turn. A height difference space is reserved between the raised pad and the interlocking pad for the pipeline to be led out.

6. A test method based on a deep engineering true triaxial grouting simulation test system according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Place the physical model sample of the embedded grouting pipeline and sensor on the bottom pad of the working platform of the true triaxial loading system, and push the sample into the pressure chamber through the ball bearing; S2. Start the drive motor to push the horizontal reaction frame into the vertical reaction frame, and apply the load to the surface of the physical model specimen through the actuator to form a true triaxial stress environment and maintain the load; S3. Close the slurry outlet and discharge port of the servo-controlled grouting system, drive the stepping piston backward to suck the slurry into the hollow pump body, start the stirring basket to prevent the slurry from settling, exhaust the air in the pipeline, and then connect the grouting pipeline of the physical model specimen; S4. Start the real-time monitoring system for the grouting process, perform the grouting simulation test according to the set grouting parameters and collect data simultaneously; S5. After grouting is completed, stop the servo control grouting system, disconnect the grouting pipeline, remove the boundary stress of the true triaxial loading system, reverse drive the motor to withdraw the horizontal reaction frame, take out the physical model sample, analyze the crack diffusion morphology and sensor data, and clean the residual slurry in the hollow pump body and pipeline.

7. The test method of a deep engineering true triaxial grouting simulation test system according to claim 6, characterized in that: The specific steps in S3 include: S31, close the slurry outlet and the slurry discharge port, and open the grouting port; S32, driving the stepping piston backward by the servo motor to absorb the slurry; S33, starting the rotary motor to drive the stirring basket to continuously stir the slurry; S34, after closing the grouting port, drive the stepping piston forward to expel the air until slurry flows out of the slurry outlet.

8. The test method of a deep engineering true triaxial grouting simulation test system according to claim 6, characterized in that: The grouting parameters include achieving constant pressure, variable rate or pulse pressure mode by adjusting the servo motor speed and the rotation screw stroke; Combined with the built-in pressure sensor feedback signal, the grouting pressure output is calibrated in real time.

9. The test method of a deep engineering true triaxial grouting simulation test system according to claim 6, characterized in that: The real-time monitoring system for the grouting process includes: synchronously monitoring the changes in the fluid-solid coupling stress field in the cracks through distributed optical fibers and soil pressure box sensors; locating the crack expansion position using acoustic emission sensors and combining them with micro-thermocouple sensors to generate a three-dimensional morphology map of slurry diffusion.

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