A time-lag strong rock burst tunnel supporting structure dynamic load impact test method
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- SOUTHWEST JIAOTONG UNIV
- Filing Date
- 2026-01-19
- Publication Date
- 2026-06-12
Smart Images
Figure CN122192967A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of rock mechanics testing technology, specifically to a dynamic load impact test method for a rockburst tunnel support structure with strong time delay. Background Technology
[0002] During the excavation of deep-buried tunnel projects, rockbursts, as a typical dynamic disaster, seriously threaten the safety of construction workers, damage engineering equipment, and delay the construction progress. Among them, time-delayed rockbursts, due to their significant delay and uncertainty, have become the core challenge for the prevention and control of deep engineering.
[0003] Time-delayed rockbursts specifically refer to rock mass fracturing disasters that occur after tunnel excavation and unloading, following stress adjustment and balancing or long-term dynamic disturbance. Compared with instantaneous rockbursts, their core characteristics are: ① Strong spatiotemporal uncertainty, with more than half occurring within one month of excavation, a high-incidence area within 70 meters, and the furthest delay distance reaching hundreds of meters; ② Prominent disaster intensity, with most being medium to high intensity rockbursts, and extremely strong rockbursts causing long-term construction stoppages in a single incident; ③ Complex inducing factors, mainly stemming from stress redistribution after excavation and the cumulative expansion of rock mass fissures caused by multi-source dynamic disturbances (blasting vibration, TBM tunneling vibration, disturbance from adjacent tunnel construction, etc.), ultimately leading to the loss of surrounding rock bearing capacity; ④ The existence of a "dormant period," with some rockbursts occurring suddenly more than 6 days after the microseismic activity has subsided, further increasing the difficulty of early warning. Therefore, it is necessary to propose an experimental method that can simulate the impact of time-delayed rockbursts on tunnels. Summary of the Invention
[0004] To address the shortcomings of the prior art, this invention provides a dynamic load impact test method for rockburst tunnel support structures with strong time delay.
[0005] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows: A dynamic load impact test method for support structures of tunnels with strong time-delay rockbursts includes the following steps: S1: Similarity test design: Based on the actual engineering geological conditions, tunnel dimensions and laboratory conditions of the tunnel, determine the similarity ratio system for the model test; S2: Calculation and determination of test parameters: Based on the similarity ratio system determined in step S1, calculate the various similarity ratios required in the test, and then determine the geometric dimensions, material parameters, simulated impact energy and impact range of the tunnel lining model; S3: Test system fabrication and assembly: Based on the calculation results of step S2, fabricate a tunnel lining model, a surrounding rock similar model, a drop hammer and a force transmission plate. Design and fabricate a test frame according to the size of the surrounding rock similar model, and complete the assembly and debugging of the test equipment. At the same time, arrange strain and displacement monitoring components on the tunnel lining model. S4: Impact test implementation and data acquisition: By controlling the mass and drop height of the hammer, the simulated impact energy determined in step S2 is applied to the tunnel lining model to simulate the time-delayed rockburst impact energy, and the data of the monitoring components are collected simultaneously. S5: Data Analysis and Safety Assessment: Based on the data collected in step S4, calculate and analyze the changes in internal forces and displacements of the tunnel lining model during the impact process, and assess the safety status of the actual tunnel lining model under time-delayed rockburst impact.
[0006] As a preferred technical solution, the similarity ratio system uses geometric similarity ratio and bulk density similarity ratio as the basic similarity ratio.
[0007] As a preferred technical solution, in step S2, the method for determining the simulated impact energy of time-delayed rockburst is as follows: S21. Based on the theory of elasticity, calculate the energy stored per unit volume in the rock mass according to the stress state of the surrounding rock and the rock mass parameters; S22. Determine the kinetic energy conversion rate based on the rockburst tendency index, and calculate the kinetic energy of the rock ejected when the rockburst occurs; S23. Calculate the mass and kinetic energy of the rock burst blocks by combining the crater geometry parameters and rock density of different levels of rock bursts; S24. Based on the similarity ratio system, the energy similarity ratio is calculated from the basic similarity ratio. The weight and energy of the rockburst block calculated in step S23 are used to convert the kinetic energy of the rockburst block into the mass and impact energy of the falling hammer, and then the impact height of the falling hammer in the similarity test is calculated.
[0008] As a preferred technical solution, in step S2, the method for determining the impact range is as follows: based on the size of the rockburst fragments in existing similar projects or actual on-site rockbursts, and combined with the geometric similarity ratio, the rockburst impact range in the similar test is calculated.
[0009] As a preferred technical solution, the test system includes a tunnel lining model, a surrounding rock similarity model, a test frame, a force transmission plate, and a drop hammer. The tunnel lining model is installed on the inner periphery of the surrounding rock similarity model, which is installed inside the test frame. A force transmission plate is embedded in the top of the surrounding rock similarity model, with a flat top and direct contact with the tunnel lining model below. An impact window is located at the center of the top of the surrounding rock similarity model above the test frame, and the force transmission plate faces the impact window. The drop hammer is connected to a lifting rope, the other end of which passes over a pulley located at the top of the test frame. The lifting rope can pull up the drop hammer, and after the external force is released, the drop hammer falls freely under gravity to impact the force transmission plate.
[0010] As a preferred technical solution, monitoring components are arranged on the tunnel lining model, including strain gauges and laser displacement gauges.
[0011] As a preferred technical solution, the strain gauges are provided in multiple sets, with one set arranged at 22.5° intervals along the inner and outer sides of the tunnel lining model; the laser displacement gauges are arranged at 22.5° intervals along the circumference from the top of the tunnel lining model to both sides, for a total of 7 to 9.
[0012] As a preferred technical solution, step S4, the implementation of the impact test and data acquisition, includes: Step S41: Drop hammer lifting: Lift the drop hammer to the specified height according to the impact height of the drop hammer determined in step S24, ensuring that the drop hammer falls naturally and vertically, and that the lower action surface is parallel to the action surface of the force transmission block. Step S42: Drop hammer descent and data acquisition: After the drop hammer reaches the predetermined height, release the drop hammer and let it fall freely to impact the tunnel lining model. During the impact, an automatic data acquisition device is used to collect the test data. Step S43: Device Unloading: After confirming that the data has been saved correctly, proceed with the unloading process.
[0013] As a preferred technical solution, the internal force changes of the tunnel lining model during the impact process include changes in axial force and bending moment, and the calculation formulas are as follows: ; in: N For axial force, M For bending moment, For the inner surface stress of the tunnel lining model, For the stress on the outer surface of the tunnel lining model, A The cross-sectional area; I The moment of inertia of the cross section; y This is the distance from the measuring point to the centroid of the cross section.
[0014] As a preferred technical solution, step S5 further includes plotting the internal force change curve and displacement change curve of the lining structure during the impact process based on the calculated internal force and displacement data, and conducting a safety assessment based on the curves to provide a reference for the design and on-site construction of the tunnel lining.
[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention presents a dynamic load impact test method for tunnel support structures subjected to severe time-delay rockbursts. Addressing the shortcomings of existing long-term dynamic disturbance tests, such as the inability to accurately simulate real-world time-delay rockburst scenarios in tunnels and the difficulty in quantifying the impact of rockburst energy levels on the lining structure, this method designs a similar test, creating a scaled-down model similar to the engineering prototype. Sensors are deployed to monitor the displacement and strain of the lining model to analyze the deformation and internal forces of tunnel linings under different energy levels of time-delay rockbursts, analyzing their dynamic response. This allows for the assessment of the safety of actual tunnel linings under time-delay rockburst impacts, providing a basis for optimizing lining design and actual construction. This method is applicable to tunnels with a potential tendency for time-delay rockbursts and can quickly simulate the impact of time-delay rockbursts on tunnel linings based on the predicted rockburst levels from previous surveys and the actual tunnel design.
[0016] The present invention provides a dynamic load impact test method for tunnel support structures with strong time-delay rockburst. Based on similarity tests, it simulates the impact of different levels of time-delay rockburst on existing tunnel linings by setting different drop hammer impact energy levels. The method is simple in structure and easy to implement. Attached Figure Description
[0017] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.
[0018] Figure 1 This is a flowchart of the experimental method proposed in this invention; Figure 2 This is a three-dimensional schematic diagram of the simulation device in this invention; Figure 3 yes Figure 2 The front view; Figure 4 This is a schematic diagram of the measuring points set in a specific example of the present invention; Figure 5 shows the displacement curve and internal force curve of a certain measuring point under impact, as measured in a specific case of this patent.
[0019] Attached reference numerals: 1-Tunnel lining model, 2-Similar model of surrounding rock, 3-Test frame, 4-Force transmission plate, 5-Falling hammer, 6-Lifting rope, 7-Pulley. Detailed Implementation
[0020] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.
[0021] A dynamic load impact test method for support structures of tunnels with strong time delay rockburst, such as Figure 1 As shown, it includes the following steps: S1: Similarity test design: Based on the actual engineering geological conditions, tunnel dimensions and laboratory conditions of the tunnel, determine the similarity ratio system for the model test; S2: Calculation and determination of test parameters: Based on the similarity ratio system determined in step S1, calculate the various similarity ratios required in the test, and then determine the geometric dimensions, material parameters, simulated impact energy and impact range of the tunnel lining model; S3: Test system fabrication and assembly: Based on the calculation results of step S2, fabricate a tunnel lining model, a surrounding rock similar model, a drop hammer and a force transmission plate. Design and fabricate a test frame according to the size of the surrounding rock similar model, and complete the assembly and debugging of the test equipment. At the same time, arrange strain and displacement monitoring components on the tunnel lining model. S4: Impact test implementation and data acquisition: By controlling the mass and drop height of the hammer, the simulated impact energy determined in step S2 is applied to the tunnel lining model to simulate the time-delayed rockburst impact energy, and the data of the monitoring components are collected simultaneously. S5: Data Analysis and Safety Assessment: Based on the data collected in step S4, calculate and analyze the changes in internal forces and displacements of the tunnel lining model during the impact process, assess the safety status of the actual tunnel lining model under time-delayed rockburst impact, and provide a basis and suggestions for lining design and on-site construction.
[0022] Specifically, in step S1, the similarity ratio is determined by using a reasonable geometric similarity ratio and a bulk density similarity ratio as the basic similarity ratio of the system, based on the rockburst level predicted by geological exploration, the actual tunnel diameter, and laboratory conditions.
[0023] Based on the determined similarity coefficient, calculate the remaining similarity ratios. The calculation method is as follows: Formula 1: in: It is the stress similarity ratio; It is the volume similarity ratio; It is the geometric similarity ratio; It is the strain similarity ratio; It is the elastic modulus similarity ratio; It is a similarity ratio to Poisson's ratio; It is the similarity ratio of boundary forces; It is the displacement similarity ratio; It is the similarity ratio of bending stiffness; It is the energy similarity ratio; It is the density similarity ratio.
[0024] In practice, conducting experiments based solely on the similarity ratio calculations is insufficient to fully meet the requirements. Therefore, only key mechanical parameters under time-delayed rockburst impacts on tunnel linings are selected for similarity testing. This method involves calculating and designing the similarity ratio using geometric dimensions, unit weight, flexural stiffness, and energy during the similarity test. Based on the calculation results, the tunnel model dimensions, unit weight, similar surrounding rock materials, time-delayed rockburst impact range, and impact energy are determined for the test.
[0025] In step S2, the method for determining the time-delayed rockburst impact energy is as follows: S21. Based on the theory of elasticity, the energy stored per unit volume in the rock mass is calculated according to the stress state of the surrounding rock and the rock mass parameters. The calculation formula is as follows: Formula 2: In the formula: U Energy contained per unit volume 、 、 These are the first, second, and third principal stresses of the surrounding rock; v、 E These are Poisson's ratio and elastic modulus of the rock mass, respectively.
[0026] S22. Determine the kinetic energy conversion rate based on the rockburst tendency index, and calculate the kinetic energy of the rock ejected when the rockburst occurs; During a rockburst disaster, the energy stored in the surrounding rock... U Part of the energy is used as the destructive energy of the rock, and part is used as the kinetic energy of the rock ejected by the rockburst. The kinetic energy of the ejected rock is related to the total energy. U The ratio between them is defined as the kinetic energy conversion rate. Rockburst tendency index W et The calculation is as follows: Formula 3: .
[0027] S23. Calculate the mass and kinetic energy of the rock burst blocks by combining the crater geometry parameters and rock density of different levels of rock bursts; According to the depth of the crater under different levels of rockburst conditions in the "Railway Tunnel Design Code", the shape of the crater of a rockburst is approximately square pyramidal. Based on the average density of the rock known from the previous exploration, the weight and kinetic energy of the rock block under different levels of rockburst conditions are calculated.
[0028] S24. Finally, based on the similarity ratio system, the weight and momentum of the rockburst block calculated in step S23 are used to convert the kinetic energy of the rockburst block into the mass and impact energy of the falling hammer: and then the impact height of the falling hammer in the similarity test is calculated.
[0029] The method for determining the impact range is as follows: based on the size of the rockburst fragments in existing similar projects or actual on-site rockbursts, and combined with the geometric similarity ratio, the impact range of the rockburst in the similar test is calculated, that is, the size of the force transmission plate is determined.
[0030] S3. Construct a tunnel lining model 1, a surrounding rock similar model 2, a force transmission plate 4, and a drop hammer 5. Design and manufacture a test frame 3 according to the dimensions of the surrounding rock similar model 2, and complete the assembly and debugging of the test equipment. The tunnel lining model 1 is installed on the inner circumference of the surrounding rock similar model 2, and the surrounding rock similar model 2 is installed inside the test frame 3. The force transmission plate 4 is embedded on the top of the surrounding rock similar model 2. The top of the force transmission plate 4 is flat, and the bottom is in direct contact with the tunnel lining model 1. An impact window is provided at the top center of the test frame 3, directly opposite the similar model 2, and the force transmission plate 4 is located inside the impact window. A pulley 7 is set on the top of the test frame 3, and the drop hammer 5 is connected to a lifting rope 6. The other end of the lifting rope 6 passes around the pulley 7. The lifting rope 6 can pull up the drop hammer 5, and after the external force is released, the drop hammer 5 falls freely under the action of gravity to impact the force transmission plate 4. The force transmission plate 4 directly bears the impact of the drop hammer 5 and transfers the impact load to the tunnel lining model 1.
[0031] Strain and displacement monitoring components are arranged on the tunnel lining model 1. Specifically, strain gauges are attached and laser displacement meters are installed according to the test plan, and the strain gauges and laser displacement meters are then calibrated. Preferably, as follows: Figure 3 As shown, in the vicinity of the main influence area of the falling hammer dynamic load, a set of resistance strain gauges were symmetrically arranged at 22.5° intervals along the inner and outer circumference of the tunnel lining model 1. The strain gauges were used to collect the strain at each key point to obtain the stress at the key points of the structure, and then the internal forces on the structure during the test were calculated. Laser displacement gauges were arranged at 22.5° intervals along the circumference from the top of the tunnel to both sides, for a total of 7 gauges. The laser displacement gauges (accuracy 0.01mm, automatic acquisition) were used to measure the displacement of each key point in the core stress area of the lining arch.
[0032] Pre-test checks: Monitoring component inspection and debugging: Connect all monitoring component wires to the computer and perform a zeroing operation. Check for abnormal readings, poor contact, component damage, etc. If any problems are found, check and troubleshoot immediately to ensure that the monitoring components are in normal working condition; Pre-start equipment checks: Check whether the lining model and box are installed correctly and whether the fixing screws are loose, etc.
[0033] S4. The impact similarity test of time-delayed rockburst on the lining was carried out as follows: Step S41: Drop hammer lifting: Lift the drop hammer to the specified height according to the impact height of the drop hammer determined in step S24. During the lifting process, pay close attention to the posture to ensure that the drop hammer falls naturally and vertically, and the lower action surface is parallel to the action surface of the force transmission block.
[0034] Step S42: Drop hammer descent and data acquisition: After the drop hammer reaches the predetermined height, release it and let it fall freely to impact the tunnel lining model. During the impact, an automatic data acquisition device is used to collect the test data.
[0035] Step S43: Device unloading: After confirming that the data is saved correctly, unload the device until it is returned to its original position; collect and store the test components and test leads for use in the next test.
[0036] S5. After the test, the stress on the inner and outer surfaces of the tunnel lining model is calculated based on the measured strain data, thereby calculating the stress changes of the structure during the time-delayed rockburst impact process, including the changes in axial force and bending moment. The specific calculation formula is as follows: Formula 4: ; in: N For axial force, M For bending moment, For the inner surface stress of the tunnel lining model, For the stress on the outer surface of the tunnel lining model, A The cross-sectional area; I The moment of inertia of the cross section; y This is the distance from the measuring point to the centroid of the cross section.
[0037] Based on the monitoring and calculation results, the internal force curves of the tunnel lining model structure and the displacement curves of the monitoring points were plotted during the impact process. Based on the plotted curves, the influence of time-delayed rockburst on the lining displacement and internal forces was analyzed to determine whether the tunnel could remain in a safe state under the influence of the time-delayed rockburst.
[0038] The method of this application is described in detail below with a specific implementation case.
[0039] Based on a high-speed railway circular tunnel with a lining outer diameter of 10m, located in an area prone to rockburst disasters, this study examines the safety of the lining structure under time-delayed rockburst impact conditions. The tunnel has a maximum burial depth of 1453m and a maximum horizontal principal stress of 45.52MPa. The surrounding rock strata are relatively intact, primarily Class II and III rock, mainly granite with high hardness. During tunnel excavation, the original stress equilibrium was disrupted, causing the strain energy accumulated in the rock to be released as kinetic and destructive energy. This resulted in a large number of fragmented rock blocks being ejected at a certain speed, posing a significant safety threat to on-site personnel and equipment, severely delaying construction progress, and increasing construction costs. Therefore, it is necessary to analyze the safety of the lining structure under time-delayed rockburst impact conditions.
[0040] S1. Similar experimental design: In this experiment, a geometric similarity ratio was selected. C l =10 and similarity ratio of bulk density C γ A similarity ratio of 3 was used as the base ratio to achieve full similarity of all physical and mechanical parameters within the elastic range. After calculation, suitable materials were selected for the tunnel lining model 1 in this model test, and suitable materials were also selected for the surrounding rock similarity model.
[0041] S2. Calculation and determination of experimental parameters: S21. Based on Equation 2 and the specific rock mechanics parameters obtained from the engineering site, calculate the energy stored per unit volume in the rock mass.
[0042] S22. Based on Poland's current rockburst tendency index W et The prediction method, combined with Equation 3, can calculate the kinetic energy conversion rate under different rockburst levels, thereby calculating the kinetic energy generated per unit volume of rock block during rockburst.
[0043] S23. Based on the crater depths under different levels of rockburst conditions in the "Railway Tunnel Design Code" (depth of influence of minor rockburst ≤ 0.5m, depth of influence of minor rockburst < 1m, depth of influence of severe rockburst ≤ 3m, depth of influence of extremely severe rockburst > 3m), the shape of the rockburst crater is approximated as a square pyramid, and the average density of the rock is taken as 2.75t / m³. 3 The kinetic energy of rock blocks under different levels of rockburst conditions was calculated, and the results are shown in Table 1.
[0044] Table 1. Calculation of kinetic energy of rock blocks under different levels of rockburst conditions. S24. Given that the main rockburst hazard level during the tunnel construction was severe rockburst, this experiment primarily studies the impact resistance of the tunnel lining structure under severe rockburst conditions. Table 1 shows that the kinetic energy released during a severe rockburst is approximately 300 kJ, and the crater size is 3 m. 3m. Based on the principle of similarity tests and the selection of the similarity ratio, the impact energy of a strong rockburst impact on the lining structure in the indoor test is 10J. The mass of the rockburst fragment is approximately 8kg, and the impact range is a square area of 30×30cm. Considering that a force transmission plate needs to be installed in the actual impact to ensure that the impact energy covers the entire impact range, a force transmission plate needs to be installed. The weight of the force transmission plate is approximately 2kg. Therefore, the mass of the falling hammer is 6kg, and the impact height is 0.167m.
[0045] S3. Experimental System Fabrication and Assembly: After the specific test parameters were determined, the tunnel lining model 1, the surrounding rock similarity model 2, the drop hammer 5, and the force transmission plate 4 were fabricated. After fabrication, the tunnel lining model 1 was installed inside the surrounding rock similarity model 2. The test frame 3 was designed and fabricated according to the specific dimensions of the surrounding rock similarity model 2. The surrounding rock similarity model 2 was then installed on the test frame 3. The force transmission plate 4 was embedded in the surrounding rock similarity model 2 through the impact window of the test frame 3 and was in direct contact with the tunnel lining model 1. Specifically, as follows... Figure 2 , Figure 3 As shown.
[0046] According to the test plan, attach strain gauges, install laser displacement gauges, and debug the strain gauges and displacement gauges.
[0047] Specifically, near the main area affected by the falling hammer dynamic load, a set of resistance strain gauges was symmetrically arranged at 22.5° intervals along the inner and outer circumference of tunnel lining model 1. The strain gauges were used to collect strain at key points to obtain the stress at key structural points, and then the internal forces on the structure during the test were calculated. Seven laser displacement gauges were arranged at 22.5° intervals from the top of the tunnel outwards to both sides. These laser displacement gauges (accuracy 0.01mm, automatic data acquisition) were used to measure the displacement of key points in the core stress area of the lining arch, such as... Figure 4 As shown.
[0048] Before the test, an inspection is carried out, mainly monitoring the components and equipment before startup to ensure that the test can proceed normally.
[0049] S4. Impact Test Implementation and Data Acquisition: According to the plan, a 6kg drop hammer was raised to a height of 0.167m. After the hammer reached the predetermined height and stabilized, it was released and allowed to fall naturally, impacting the tunnel lining model. An automatic data acquisition device was activated before releasing the hammer to collect test data.
[0050] After the test is completed and the data is confirmed to be saved correctly, the equipment is unloaded until it is returned to its original position. The monitoring components and test lines are collected and stored for use in the next test.
[0051] S5. Calculate the stress on the inner and outer surfaces based on the measured strain data, and calculate the stress changes of the structure during the time-delayed rockburst impact process, including the changes in axial force and bending moment, using Equation 4.
[0052] Based on the monitoring and calculation results, the stress curve of the lining model structure and the displacement curve of the monitoring point were plotted during the impact process. Figure 5(a) shows the axial force curve and Figure 5(b) shows the displacement curve.
[0053] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the appended claims.
Claims
1. A method for dynamic load impact testing of support structures for tunnels with strong time-delay rockburst, characterized in that: Includes the following steps: S1: Similarity test design: Based on the actual engineering geological conditions, tunnel dimensions and laboratory conditions of the tunnel, determine the similarity ratio system for the model test; S2: Calculation and determination of test parameters: Based on the similarity ratio system determined in step S1, calculate the various similarity ratios required in the test, and then determine the geometric dimensions, material parameters, simulated impact energy and impact range of the tunnel lining model; S3: Test system fabrication and assembly: Based on the calculation results of step S2, fabricate the tunnel lining model, the surrounding rock similar model, the drop hammer and the force transmission plate, design and fabricate the test frame according to the size of the surrounding rock similar model, and complete the assembly and debugging of the test equipment. At the same time, arrange strain and displacement monitoring components on the tunnel lining model. S4: Impact test implementation and data acquisition: By controlling the mass and drop height of the drop hammer, the simulated impact energy determined in step S2 is applied to the tunnel lining model to simulate the time-delayed rockburst impact energy, and data from the monitoring components are collected simultaneously. S5: Data Analysis and Safety Assessment: Based on the data collected in step S4, calculate and analyze the changes in internal forces and displacements of the tunnel lining model during the impact process, and assess the safety status of the actual tunnel lining model under time-delayed rockburst impact.
2. The method for dynamic load impact test of support structure for tunnels with strong time-delay rockburst as described in claim 1, characterized in that: The similarity ratio system uses geometric similarity ratio and bulk density similarity ratio as the basic similarity ratios.
3. The method for dynamic load impact test of support structure for tunnels with strong time-delay rockburst as described in claim 2, characterized in that: In step S2, the method for determining the simulated impact energy of time-delayed rockburst is as follows: S21. Based on the theory of elasticity, calculate the energy stored per unit volume in the rock mass according to the stress state of the surrounding rock and the rock mass parameters; S22. Determine the kinetic energy conversion rate based on the rockburst tendency index, and calculate the kinetic energy of the rock ejected when the rockburst occurs; S23. Calculate the mass and kinetic energy of the rock burst blocks by combining the crater geometry parameters and rock density of different levels of rock bursts; S24. Based on the similarity ratio system, the energy similarity ratio is calculated from the basic similarity ratio. The weight and energy of the rockburst block calculated in step S23 are used to convert the kinetic energy of the rockburst block into the mass and impact energy of the falling hammer, and then the impact height of the falling hammer in the similarity test is calculated.
4. The method for dynamic load impact test of support structure for tunnels with strong time-delay rockburst as described in claim 2, characterized in that: In step S2, the impact range is determined by calculating the rockburst impact range in the similar test based on the size of the rockburst fragments from existing similar projects or actual rockbursts on site, combined with the geometric similarity ratio.
5. The method for dynamic load impact testing of support structures for tunnels with strong time-delay rockburst as described in claim 3, characterized in that: The test system includes a tunnel lining model, a surrounding rock similarity model, a test frame, a force transmission plate, and a drop hammer. The tunnel lining model is installed on the inner periphery of the surrounding rock similarity model, which is installed inside the test frame. A force transmission plate is embedded in the top of the surrounding rock similarity model, with a flat top and direct contact with the tunnel lining model below. An impact window is located at the center of the top of the surrounding rock similarity model above the test frame, and the force transmission plate faces the impact window. The drop hammer is connected to a lifting rope, the other end of which passes over a pulley located at the top of the test frame. The lifting rope can pull up the drop hammer, and after the external force is released, the drop hammer falls freely under the action of gravity to impact the force transmission plate.
6. The method for dynamic load impact test of support structure for tunnels with strong time-delay rockburst as described in claim 5, characterized in that: The tunnel lining model is equipped with monitoring components, including strain gauges and laser displacement meters.
7. The method for dynamic load impact testing of support structures for tunnels with strong time-delay rockburst as described in claim 6, characterized in that: The strain gauges are arranged in multiple sets, with one set every 22.5° along the inner and outer circumference of the tunnel lining model; the laser displacement gauges are arranged at 22.5° intervals along the circumference from the top of the tunnel lining model to both sides, for a total of 7 to 9.
8. The method for dynamic load impact test of support structure for tunnels with strong time-delay rockburst as described in claim 5, characterized in that: Step S4, the impact test and data acquisition, includes: Step S41: Drop hammer lifting: Lift the drop hammer to the specified height according to the impact height of the drop hammer determined in step S24, ensuring that the drop hammer falls naturally and vertically, and that the lower action surface is parallel to the action surface of the force transmission block. Step S42: Drop hammer descent and data acquisition: After the drop hammer reaches the predetermined height, release the drop hammer and let it fall freely to impact the tunnel lining model. During the impact, an automatic data acquisition device is used to collect the test data. Step S43: Device Unloading: After confirming that the data has been saved correctly, proceed with the unloading process.
9. The method for dynamic load impact test of support structure for tunnels with strong time-delay rockburst as described in claim 1, characterized in that: The internal force changes of the tunnel lining model during the impact process include changes in axial force and bending moment, and the calculation formulas are as follows: ； in: N For axial force, M For bending moment, For the inner surface stress of the tunnel lining model, For the stress on the outer surface of the tunnel lining model, A The cross-sectional area; I The moment of inertia of the cross section; y This is the distance from the measuring point to the centroid of the cross section.
10. The method for dynamic load impact testing of support structures for tunnels with strong time-delay rockburst as described in claim 9, characterized in that: Step S5 also includes plotting the internal force change curve and displacement change curve of the lining structure during the impact process based on the calculated internal force and displacement data, and conducting a safety assessment based on the curves to provide a reference for the design and on-site construction of the tunnel lining.