Method for evaluating stability of surrounding rock of cavern under earthquake action based on dynamic safety degree

Abstract

The invention provides a cavern surrounding rock stability evaluation method based on a dynamic safety degree under an earthquake effect. The method comprises the following steps: establishing an underground cavern three-dimensional numerical calculation model; applying an excavation load for static calculation to obtain the stress state of the surrounding rock after excavation; on the basis of keeping the stress state of the surrounding rock after excavation, the deformation of the surrounding rock is cleared, and the vibration acceleration time history is input for dynamic response calculation; feature points are arranged on the left and right side walls, the top arch and the bottom plate of the cavern, the displacement time history of each feature point in the earthquake process is monitored, and the relative dynamic displacement of the surrounding rock is calculated; counting the main stress time history extreme value of the surrounding rock unit to obtain surrounding rock peak stress; the surrounding rock plastic zone depth is counted; counting a supporting structure stress time history extreme value to obtain a supporting peak stress; respectively calculating a surrounding rock deformation dynamic safety degree, a surrounding rock stress dynamic safety degree, a surrounding rock plastic zone dynamic safety degree and a support stress dynamic safety degree; and when all the dynamic safety degrees are set to be threshold values, judging that the dynamic stability of the surrounding rock meets requirements.

Description

Technical Field

[0001] This invention relates to the field of geotechnical engineering technology, specifically to a method for evaluating the stability of surrounding rock in caverns under seismic loading based on dynamic safety factor. Background Technology

[0002] For the stability of surrounding rock during excavation and unloading in cavern construction, current research primarily employs numerical analysis methods. These methods comprehensively evaluate the stability of the surrounding rock based on calculated indicators such as the plastic zone, surrounding rock deformation, surrounding rock stress, and support load. Regarding the stability analysis and assessment of underground caverns under seismic loading, existing research mainly focuses on the deformation and failure characteristics of surrounding rock and seismic response properties under seismic loading, methods for calculating the overall safety factor of underground cavern groups under seismic loading, and methods for calculating point safety factors based on the Mohr-Coulomb yield criterion.

[0003] However, existing technologies have the following problems: (1) There are significant differences in the load nature, duration of action, and effects of excavation unloading and seismic vibration. Excavation load is essentially an internal load caused by the release of initial stress in the original rock, which is a static load with a long duration of action; while seismic load is essentially a seismic wave generated by crustal vibration propagating in the rock mass, which is a dynamic and periodic load, exhibiting pulse-like or reciprocating changes, with a short duration of action.

[0004] (2) The concepts of surrounding rock deformation and displacement under seismic loading cannot be used as in static analysis. In static analysis, since excavation unloading is a load acting on the excavation face of the tunnel and pointing into the tunnel, the displacement and deformation of the surrounding rock represent the same content; however, the dynamic displacement induced by seismic load includes both the spatial position change of the rock mass caused by the propagation of seismic waves and the deformation of the rock mass caused by dynamic additional stress. The dynamic stability of the surrounding rock cannot be directly evaluated based solely on the value of the dynamic displacement.

[0005] (3) The existing static stability evaluation system for surrounding rock cannot be directly applied to dynamic stability evaluation, and lacks quantitative evaluation indicators and criteria for dynamic stability of surrounding rock under seismic action.

[0006] Therefore, there is an urgent need to establish a quantitative evaluation method for the dynamic stability of the surrounding rock of underground caverns under seismic loading. Summary of the Invention

[0007] This invention proposes a method for evaluating the stability of surrounding rock in caverns under seismic loading based on dynamic safety factor, in order to solve the technical problem that existing technologies are unable to accurately characterize the impact of seismic loading on the stability of surrounding rock, resulting in the difficulty in providing quantitative evaluation in the construction of underground cavern projects in high seismic intensity areas.

[0008] To address the aforementioned technical problems, this invention provides a method for evaluating the stability of surrounding rock in caverns under seismic loading based on dynamic safety, comprising the following steps: Step S1: Establish a three-dimensional numerical calculation model of the underground cavern; Step S2: Apply excavation load to perform static calculations and obtain the stress state of the surrounding rock after excavation; Step S3: While maintaining the stress state of the surrounding rock after excavation, reset the deformation of the surrounding rock to zero and input the seismic acceleration time history to calculate the dynamic response; Step S4: Set feature points on the left and right side walls, roof arch and floor of the cavern, monitor the displacement time history of each feature point during the earthquake, calculate the relative dynamic displacement of the surrounding rock; statistically analyze the extreme values ​​of the principal stress time history of the surrounding rock unit to obtain the peak stress of the surrounding rock; statistically analyze the depth of the plastic zone of the surrounding rock; statistically analyze the extreme values ​​of the stress time history of the support structure to obtain the peak stress of the support. Step S5: Based on the relative dynamic displacement of the surrounding rock, the peak stress of the surrounding rock, the depth of the plastic zone of the surrounding rock, and the peak stress of the support, calculate the dynamic safety of the surrounding rock deformation, the dynamic safety of the surrounding rock stress, the dynamic safety of the plastic zone of the surrounding rock, and the dynamic safety of the support stress, respectively. Step S6: When all dynamic safety factors are set to the threshold, the dynamic stability of the surrounding rock is determined to meet the requirements.

[0009] Preferably, the method for calculating the relative dynamic displacement of the surrounding rock in step S4 is as follows: Set feature points on the left and right walls. m and n Feature points are set on the top arch and the bottom plate. p and q Obtain the displacement time history of the feature points during the earthquake process. m ( t ), n ( t ), p ( t ) and q(t); define the time history of the relative dynamic displacement between the left and right walls. Define the time history of the relative dynamic displacement between the arch and the base plate. .

[0010] Preferably, the method for calculating the peak stress of the surrounding rock in step S4 is as follows: Calculate the time history of the first principal stress for each surrounding rock unit. Minimum value and third principal stress time history The maximum value is used to obtain the peak stress of the surrounding rock element. and ,in , The duration of the earthquake action was determined; the maximum compressive stress in the surrounding rock was obtained by statistically analyzing all surrounding rock elements. and maximum tensile stress , among which only when Tensile stress is only formed when the stress is greater than 0. This represents all surrounding rock units.

[0011] Preferably, the method for calculating the depth of the plastic zone of the surrounding rock in step S4 is as follows: Based on the plastic strain state of the surrounding rock units, units that have entered the plastic state are identified, and the extent of the plastic zone from the excavation face towards the depth of the surrounding rock is statistically analyzed. The maximum depth of the plastic zone of the surrounding rock after the earthquake is obtained. .

[0012] Preferably, the method for calculating the peak support stress in step S4 is as follows: Calculate the stress time history of each anchor bolt Force history of anchor cables Obtain the extreme value of anchor bolt stress. and the extreme values ​​of anchor cable stress ,in .

[0013] Preferably, the dynamic safety factor of surrounding rock deformation in step S5 The calculation method is as follows: Calculate the displacement amplitude in the directions of the left and right walls. Displacement amplitude in the direction of the arch and the base plate ,in , , and These respectively indicate the spaces between the left and right walls, and between the arch and the base slab. Time history of relative dynamic displacement in the axial direction; calculation of maximum convergent deformation of the cavern. ,in For the span of the cavern, The height of the cavern; the dynamic safety factor of the surrounding rock deformation. ,in To allow for convergence deformation.

[0014] Preferably, the method for calculating the dynamic safety factor of surrounding rock stress in step S5 is as follows: Dynamic safety of surrounding rock under compressive strength Dynamic safety of surrounding rock under tensile stress ,in and These are the dynamic compressive strength and dynamic tensile strength of the rock mass, respectively.

[0015] Preferably, the dynamic safety factor of the surrounding rock plastic zone in step S5 The calculation method is as follows: ; In the formula, [L] represents the length of the anchorage support.

[0016] Preferably, the method for calculating the dynamic safety factor of the support force in step S5 is as follows: Anchor bolt stress safety Safety of anchor cable under stress ,in and These represent the allowable stress values ​​for the anchor bolt and the allowable force values ​​for the anchor cable, respectively.

[0017] Preferably, in step S1, an elastoplastic constitutive model is used to simulate the mechanical properties of the surrounding rock. The elastoplastic constitutive model is a Mohr-Coulomb ideal elastoplastic model with a tensile cutoff limit. The calculation model is solved numerically using the finite difference method or the finite element method.

[0018] Compared with the prior art, the present invention has at least the following beneficial effects: (1) This invention first distinguishes the differences in load properties, duration of action, range of influence and effect of excavation unloading and seismic vibration, clearly points out that the concepts of surrounding rock deformation and surrounding rock displacement under seismic action cannot be used as in static analysis, proposes the concept of relative dynamic displacement of surrounding rock, and eliminates the position change information unrelated to stress and strain contained in the dynamic displacement of surrounding rock.

[0019] (2) This invention proposes evaluation indicators such as relative dynamic displacement of surrounding rock, peak stress of surrounding rock, depth of plastic zone of surrounding rock and peak stress of support, and establishes a quantitative evaluation index system for dynamic stability of surrounding rock based on dynamic safety, including dynamic safety of surrounding rock deformation, dynamic safety of surrounding rock stress, dynamic safety of plastic zone of surrounding rock and dynamic safety of support force, providing quantitative criteria for evaluating the dynamic stability of surrounding rock of underground caverns under seismic action.

[0020] (3) The method of the present invention can effectively quantify the dynamic stability of the surrounding rock of underground caverns under seismic loads. It can be further applied to the quantitative analysis of the dynamic stability of the surrounding rock of underground caverns under different support measures and different seismic intensities, providing a scientific and reliable quantitative evaluation tool for the construction of underground caverns in high seismic intensity areas. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the method flow according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the computational model according to an embodiment of the present invention; Figure 3 This is a schematic diagram illustrating the action of excavation load and seismic load according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the deformation of the surrounding rock under excavation and unloading according to an embodiment of the present invention; Figure 5This is a schematic diagram of the dynamic displacement of the surrounding rock under seismic loading according to an embodiment of the present invention; Figure 6 This is a schematic diagram of the time history curve of ground motion acceleration according to an embodiment of the present invention; Figure 7 This is a schematic diagram of the time history of surrounding rock displacement during an earthquake, according to an embodiment of the present invention. Figure 8 This is a schematic diagram of the principal stress envelope of the surrounding rock during an earthquake, according to an embodiment of the present invention. Figure 9 This is a schematic diagram of the colored regions of plastic strain in the surrounding rock during an earthquake, according to an embodiment of the present invention. Figure 10 This is a schematic diagram illustrating the time history of support stress changes during an earthquake, according to an embodiment of the present invention. Detailed Implementation The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0022] This embodiment takes the underground cavern complex of a water source pumping station in a certain region as the research object. This underground cavern complex consists of the main pump house cavern, the main transformer cavern, and auxiliary tunnels. The excavation dimensions of the main cavern are 220m × 24.6m × 45.7m. The strata in the underground cavern area are mainly limestone, with most of the surrounding rock being Class II and III, exhibiting good stability. According to the seismic safety assessment results, the peak ground acceleration of the horizontal ground motion with a 50-year exceedance probability of 5% is 318 gal, and the basic intensity is 8 degrees.

[0023] like Figure 1 As shown, this embodiment of the invention provides a method for evaluating the stability of surrounding rock in caverns under seismic loading based on dynamic safety, including the following steps: Step S1: Establish a three-dimensional numerical calculation model of the underground cavern.

[0024] Specifically, in this embodiment, a three-dimensional numerical calculation model of the underground pump house cavern complex is established using FLAC3D software. The calculation model includes the main pump house cavern, main transformer cavern, maintenance valve chamber, and other main caverns, divided into 894,689 elements and 155,373 nodes. The Mohr-Coulomb ideal elastoplastic model with tensile cutoff limit is used to simulate the mechanical properties of the soil and rock materials. The rock mass deformation modulus is 10 GPa, cohesion is 1.0 MPa, internal friction coefficient is 1.0, and density is 2.98 g / cm³. The calculation model is as follows: Figure 2 As shown.

[0025] Step S2: Apply excavation load to perform static calculations and obtain the stress state of the surrounding rock after excavation.

[0026] Specifically, excavation loads are applied to the computational model to simulate the tunnel excavation process, and static calculations are performed to obtain the stress state of the surrounding rock after excavation. The excavation load is essentially an internal load caused by the release of initial stress within the original rock, and is a static load. Then, the deformation of the surrounding rock and the secondary stress field caused by excavation unloading are calculated.

[0027] Step S3: While maintaining the stress state of the surrounding rock after excavation, reset the deformation of the surrounding rock to zero and input the seismic acceleration time history to calculate the dynamic response.

[0028] Excavation load is essentially an internal load caused by the release of initial stress within the original rock, acting on the excavation face as follows: Figure 3 As shown in (a), the essence of seismic load is seismic waves generated by crustal vibration, which can be divided into longitudinal waves, transverse waves, and surface waves. These waves propagate within the rock mass and, upon entering the engineering area where the underground cavern is located, as shown in (a),... Figure 3 As shown in (b), dynamic additional stress is generated on the basis of the secondary stress field around the tunnel formed by excavation and unloading. This is an active external load applied to the surrounding rock, which is a dynamic and periodic load, exhibiting pulse-like or reciprocating changes. The load magnitude is related to the earthquake magnitude, focal distance, and spectral characteristics of the seismic waves. The seismic load has a short duration, with a single strong earthquake lasting 20-40 seconds, and the load peak only appears instantaneously.

[0029] The effect of excavation loads on the surrounding rock of a tunnel is primarily unloading. After excavation, the radial stress of the surrounding rock, i.e., the stress perpendicular to the tunnel wall, drops sharply to near zero near the excavation face, while the tangential stress concentrates. Under elastic response conditions, the tangential stress value is twice the initial stress, forming a stress concentration zone. The impact of excavation loads on the surrounding rock is limited to a local area around the tunnel. The stress disturbance range decreases rapidly with distance from the tunnel wall, generally being 2 to 3 times the tunnel diameter or span, forming a stress influence zone.

[0030] Seismic load is the dynamic additional stress exerted on rock masses with initial stress by seismic waves propagating through the strata. It manifests as additional shear stress induced by shear waves and additional compressive stress induced by longitudinal waves, exhibiting a reciprocating oscillating stress state. Although the seismic action covers the entire engineering area, its actual impact on the stability of the surrounding rock is limited to the vicinity of the surrounding rock. Based on the secondary stress field around the tunnel formed by excavation, the dynamic additional stress caused by seismic load will further evolve the stress state of the surrounding rock at the yield surface within the plastic zone, exacerbating the plasticity of the surrounding rock and potentially increasing the depth of the plastic zone.

[0031] Seismic loads manifest as dynamic additional stresses, which can increase the plastic strain within the plastic zone of the rock mass and expand the extent of the plastic zone. Further analysis of concepts such as surrounding rock deformation and displacement is as follows: (1) Surrounding rock displacement refers to the change of the rock mass relative to its original position, while surrounding rock deformation refers to the shape distortion of the rock mass caused by the load it bears. Although their physical meanings are different, in static analysis, since excavation unloading is a load acting on the excavation face of the tunnel and pointing towards the tunnel, the content represented by surrounding rock displacement and deformation is the same, both being the degree of displacement of the surrounding rock towards the tunnel. Figure 4 As shown, the black line represents the initial outline of the cavern, and the blue line represents the deformed outline. This is the effect of magnifying the deformation by 100 times, and it can be used for static stability analysis.

[0032] (2) The displacement induced by earthquake load is called dynamic displacement, which refers to the spatial positional change of the surrounding rock under earthquake action, such as... Figure 5 As shown. Dynamic displacement includes both the spatial positional change of the rock mass caused by the propagation of seismic waves and the deformation of the rock mass caused by dynamic additional stress. In dynamic analysis, the dynamic stability of the surrounding rock cannot be directly evaluated based solely on the magnitude of the dynamic displacement.

[0033] Therefore, in this embodiment, while maintaining the stress state of the surrounding rock after excavation, the deformation of the surrounding rock in the calculation model is reset to zero, and the seismic acceleration time history is input at the bottom boundary of the model as follows: Figure 6 As shown, dynamic response calculations are performed.

[0034] Step S4: Set feature points on the left and right side walls, top arch and bottom plate of the cavern, monitor the displacement time history of each feature point during the earthquake, calculate the relative dynamic displacement of the surrounding rock; statistically analyze the extreme values ​​of the principal stress time history of the surrounding rock unit to obtain the peak stress of the surrounding rock; statistically analyze the depth of the plastic zone of the surrounding rock; statistically analyze the extreme values ​​of the stress time history of the support structure to obtain the peak stress of the support.

[0035] The evaluation indicators for the stability of surrounding rock under excavation loads include surrounding rock deformation, stress, plastic zone, and support stress, among others. A relatively systematic static stability evaluation indicator system has been established. Therefore, this embodiment proposes dynamic stability evaluation indicators based on the analysis of static excavation evaluation indicators.

[0036] (1) Calculation of relative dynamic displacement of surrounding rock This embodiment proposes the concept of relative dynamic displacement to eliminate positional change information unrelated to stress and strain included in the dynamic displacement of surrounding rock. Feature points are set on the left and right walls. m and n Feature points are set on the top arch and the bottom plate. p and q The displacement time histories of various characteristic points during the earthquake were monitored. Based on the displacement time histories data, the relative dynamic displacement time histories between the left and right walls were calculated. and the time history of the relative dynamic displacement between the arch and the bottom plate. This index describes the degree of displacement of the maximum span and height of the cavern during an earthquake, characterizing the deformation of one point relative to another point (considered a fixed point).

[0037] Specifically, the data results are as follows: Figure 7 As shown, during the earthquake, the dynamic displacement time history curves of the surrounding rock in different sections of the tunnel were basically consistent, indicating that the overall integrity of the surrounding rock was good. The relative dynamic displacement time histories further revealed the influence of the earthquake on the deformation of the surrounding rock. The relative dynamic displacement between the monitoring points of the roof arch and the floor slab ranged from -1.24 cm to 1.26 cm, while the relative dynamic displacement between the monitoring points of the upstream and downstream sidewalls ranged from 0 to 0.95 cm. It can be seen that during the earthquake, the relative deformation of the surrounding rock was within 1.26 cm.

[0038] (2) Calculation of peak stress in surrounding rock Seismic loads induce dynamic additional stresses in the surrounding rock of the tunnel, causing fluctuations in the stress field of the surrounding rock elements. The time histories of the first principal stresses for each surrounding rock element during the seismic process are statistically analyzed. Minimum value and third principal stress time history The maximum value is calculated to obtain the peak stress of each element. Furthermore, principal stress envelope diagrams are plotted to characterize the extreme stress values ​​reached by the surrounding rock of the cavern during the earthquake.

[0039] ; Specifically, the principal stress envelope diagram of the surrounding rock is as follows: Figure 8 As shown, the maximum compressive stress in the surrounding rock over time was approximately 20 MPa, occurring in the rock column region between the main tunnel and the maintenance valve chamber; the maximum tensile stress was approximately 0.3 MPa, occurring in the lower part of the upstream sidewall of the main tunnel. Overall, the compressive stress in the surrounding rock increased only slightly compared to before the earthquake, while the range and value of tensile stress remained largely unchanged, indicating that the earthquake had a relatively small impact on the stress state of the surrounding rock.

[0040] (3) Statistical analysis of the depth of the plastic zone of the surrounding rock Based on the plastic strain state of the surrounding rock elements, identify the elements that have entered the plastic state. Specifically, such as... Figure 9 As shown, under seismic loading, the maximum depth of the plastic zone in the surrounding rock of the tunnel remained generally unchanged, with only local increases. Specifically, the depth of the plastic zone in the main tunnel's roof arch remained unchanged, while the maximum depth of the plastic zone in the upstream sidewall increased from 8m to 9m, and in the downstream sidewall from 14m to 15m. Therefore, the maximum depth of the plastic zone in the surrounding rock after seismic loading... =15m.

[0041] (4) Calculation of peak support stress Seismic loads can also cause fluctuations in the stress on anchor / cable structures placed in the surrounding rock. The stress time history of each anchor is statistically analyzed. extremum Force history of anchor cables extremum This represents the extreme stress value that the supporting structure has reached during an earthquake.

[0042] ; Specifically, the stress time history S(t) of each anchor rod and the force time history of the anchor cable are statistically analyzed. .from Figure 10 It is evident that the stress in the main tunnel arch anchor rods fluctuated between 28 MPa and 34 MPa during the earthquake, the stress in the upstream sidewall anchor rods fluctuated between 178 MPa and 205 MPa, and the stress in the downstream sidewall anchor rods fluctuated between 131 MPa and 171 MPa. This indicates that the anchor rod stress exhibited a certain degree of fluctuation, with the maximum time history value increasing by 3 MPa to 40 MPa compared to before the earthquake, but remaining below the anchor rod's tensile strength. The stress values ​​in the upstream sidewall anchor cables fluctuated between 1824 kN and 1877 kN, and the stress values ​​in the downstream sidewall anchor cables fluctuated between 1834 kN and 1882 kN.

[0043] Step S5: Based on the relative dynamic displacement of the surrounding rock, the peak stress of the surrounding rock, the depth of the plastic zone of the surrounding rock, and the peak stress of the support, calculate the dynamic safety of the surrounding rock deformation, the dynamic safety of the surrounding rock stress, the dynamic safety of the plastic zone of the surrounding rock, and the dynamic safety of the support stress, respectively.

[0044] (1) Dynamic safety degree of surrounding rock deformation Based on the time history of the relative dynamic displacement, the displacement amplitudes of the left wall-right wall and the top arch-bottom slab of the cavern are calculated. This represents the extreme value of the shortening of the distance between the characteristic points of the left and right walls during an earthquake, i.e., the maximum deformation value of the cavern sidewalls toward the inward side. This indicates the extreme value of the shortening of the distance between the characteristic points of the arch and the floor, which is the maximum deformation value of the cavern on the inward side of the arch and the floor.

[0045] ; in , , and These respectively indicate the spaces between the left and right walls, and between the arch and the base slab. Time history of relative dynamic displacement in the axial direction.

[0046] Further calculations were performed on the inward-facing side of the cavern during the earthquake. ε : ; In the formula: B For the span of the cavern, H The elevation of the cavern. The dynamic safety factor for surrounding rock deformation is defined. for: ; In the formula: [ ε To allow for convergence deformation, according to relevant specifications, the relative convergence value for Class III surrounding rock and caverns with a burial depth of 50~300m is 0.2%~0.5%. Taking the minimum value as brittle surrounding rock, the allowable convergence deformation [ε]=0.2%.

[0047] Therefore, the dynamic safety factor of surrounding rock deformation in this embodiment =0.2% / 0.051%=3.92>1, which meets the requirements.

[0048] (2) Dynamic safety factor of surrounding rock stress The stress extreme values ​​of each element during the earthquake were obtained. By evaluating all elements in the entire calculation model, the time-history maximum compressive stress of the surrounding rock of the cavern was further obtained. and maximum tensile stress Among them, only when the maximum value of the third principal stress of the surrounding rock is reached... Tensile stress is only formed when the value is positive.

[0049] ; The dynamic safety factor of surrounding rock stress includes compressive dynamic safety factor and tensile dynamic safety factor, defined as: ; In the formula: and These are the dynamic compressive and tensile strengths of the rock mass, respectively, and their values ​​can be determined based on the static strength parameters of the rock mass.

[0050] Based on geological data and relevant standards, the dynamic compressive strength of the rock mass =45MPa, dynamic tensile strength =1MPa.

[0051] Dynamic safety of surrounding rock under compressive strength =45MPa / 20MPa=2.25>1, which meets the requirements.

[0052] Surrounding rock tensile dynamic safety =1MPa / 0.3MPa=3.33>1, which meets the requirements.

[0053] (3) Dynamic safety of the plastic zone of the surrounding rock Define the dynamic safety factor of the plastic zone of the surrounding rock as: ; In the formula, This represents the maximum depth of the plastic zone in the rock surrounding the cave after an earthquake. In this embodiment, the length of the anchoring support is... =20m.

[0054] Dynamic safety of the plastic zone of the surrounding rock =20m / 15m=1.33>1, which meets the requirements.

[0055] (4) Dynamic safety of support under stress The support stress safety factor is defined as: ; In the formula: and These are the allowable values ​​for anchor bolt stress and anchor cable force, respectively.

[0056] In this embodiment, the anchor bolt yield strength =400MPa, the reasonable stress on the anchor cable is taken as 120% of the anchor cable tonnage. =2400kN.

[0057] Anchor bolt stress safety =400MPa / 205MPa=1.95>1, which meets the requirements.

[0058] Anchor cable stress safety =2400kN / 1877kN=1.28>1, which meets the requirements.

[0059] Step S6: When all dynamic safety factors are set to the threshold, the dynamic stability of the surrounding rock is determined to meet the requirements.

[0060] Specifically, based on the above calculation results, the dynamic safety factor of surrounding rock deformation is... =3.92, Dynamic safety factor of surrounding rock compressive strength =2.25, dynamic safety factor of surrounding rock under tensile stress =3.33, Dynamic safety factor of the plastic zone of the surrounding rock =1.33, anchor bolt stress safety factor =1.95, safety factor of anchor cable under stress =1.28, all dynamic safety factors are greater than the set threshold of 1, therefore it is determined that the dynamic stability of the surrounding rock of the underground cavern under seismic action meets the requirements.

[0061] This embodiment demonstrates that the method of the present invention can achieve a quantitative evaluation of the dynamic stability of the surrounding rock of underground caverns under seismic loads, providing a quantitative evaluation tool for the construction of underground cavern projects in high seismic intensity areas.

[0062] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described; only preferred embodiments of the present invention are illustrated. The descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. As long as the combination of these technical features does not contradict each other, it should be considered within the scope of this specification.

[0063] It should be noted that those skilled in the art can make various modifications and improvements without departing from the inventive concept, and these all fall within the scope of protection of this invention. Therefore, the scope of protection of this invention should be determined by the appended claims.

Claims

1. A method for evaluating the stability of surrounding rock in caverns under seismic loading based on dynamic safety factor, characterized in that: Includes the following steps: Step S1: Establish a three-dimensional numerical calculation model of the underground cavern; Step S2: Apply excavation load to perform static calculations and obtain the stress state of the surrounding rock after excavation; Step S3: While maintaining the stress state of the surrounding rock after excavation, reset the deformation of the surrounding rock to zero and input the seismic acceleration time history to calculate the dynamic response; Step S4: Set feature points on the left and right side walls, roof arch and floor of the cavern, monitor the displacement time history of each feature point during the earthquake, calculate the relative dynamic displacement of the surrounding rock; statistically analyze the extreme values ​​of the principal stress time history of the surrounding rock unit to obtain the peak stress of the surrounding rock; statistically analyze the depth of the plastic zone of the surrounding rock; statistically analyze the extreme values ​​of the stress time history of the support structure to obtain the peak stress of the support. Step S5: Based on the relative dynamic displacement of the surrounding rock, the peak stress of the surrounding rock, the depth of the plastic zone of the surrounding rock, and the peak stress of the support, calculate the dynamic safety of the surrounding rock deformation, the dynamic safety of the surrounding rock stress, the dynamic safety of the plastic zone of the surrounding rock, and the dynamic safety of the support stress, respectively. Step S6: When all dynamic safety factors are set to the threshold, the dynamic stability of the surrounding rock is determined to meet the requirements.

2. The method for evaluating the stability of cavern surrounding rock under seismic loading based on dynamic safety degree as described in claim 1, characterized in that: The calculation method for the relative dynamic displacement of the surrounding rock in step S4 is as follows: Set feature points on the left and right walls. m and n Feature points are set on the top arch and the bottom plate. p and q Obtain the displacement time history of the feature points during the earthquake process. m ( t ), n ( t ), p ( t ) and q(t); define the time history of the relative dynamic displacement between the left and right walls. Define the time history of the relative dynamic displacement between the arch and the base plate. .

3. The method for evaluating the stability of cavern surrounding rock under seismic loading based on dynamic safety degree as described in claim 2, characterized in that: The method for calculating the peak stress of the surrounding rock in step S4 is as follows: Calculate the time history of the first principal stress for each surrounding rock unit. Minimum value and third principal stress time history The maximum value is used to obtain the peak stress of the surrounding rock element. and ,in , The duration of the earthquake action; Statistical analysis of all surrounding rock elements yields the maximum compressive stress in the surrounding rock over time. and maximum tensile stress , among which only when Tensile stress is only formed when the stress is greater than 0. This represents all surrounding rock units.

4. The method for evaluating the stability of cavern surrounding rock under seismic loading based on dynamic safety degree as described in claim 1, characterized in that: The method for calculating the depth of the plastic zone in the surrounding rock in step S4 is as follows: Based on the plastic strain state of the surrounding rock units, units that have entered the plastic state are identified, and the extent of the plastic zone from the excavation face towards the depth of the surrounding rock is statistically analyzed. The maximum depth of the plastic zone of the surrounding rock after the earthquake is obtained. .

5. The method for evaluating the stability of cavern surrounding rock under seismic loading based on dynamic safety degree as described in claim 1, characterized in that: The calculation method for the peak support stress in step S4 is as follows: Calculate the stress time history of each anchor bolt Force history of anchor cables Obtain the extreme value of anchor bolt stress. and the extreme values ​​of anchor cable stress ,in .

6. The method for evaluating the stability of cavern surrounding rock under seismic loading based on dynamic safety degree as described in claim 2, characterized in that: Dynamic safety factor of surrounding rock deformation in step S5 The calculation method is as follows: Calculate the displacement amplitude in the directions of the left and right walls. Displacement amplitude in the direction of the arch and the base plate ,in , , and These respectively indicate the spaces between the left and right walls and between the arch and the base plate. Time history of relative dynamic displacement in the axial direction; Calculate the maximum convergence deformation of the cavern ,in For the span of the cavern, The height of the cavern; the dynamic safety factor of the surrounding rock deformation. ,in To allow for convergence deformation.

7. The method for evaluating the stability of cavern surrounding rock under seismic loading based on dynamic safety degree as described in claim 3, characterized in that: The calculation method for the dynamic safety factor of surrounding rock stress in step S5 is as follows: Dynamic safety of surrounding rock under compressive strength Dynamic safety of surrounding rock under tensile stress ,in and These are the dynamic compressive strength and dynamic tensile strength of the rock mass, respectively.

8. The method for evaluating the stability of cavern surrounding rock under seismic loading based on dynamic safety degree as described in claim 4, characterized in that: Dynamic safety factor of the surrounding rock plastic zone in step S5 The calculation method is as follows: ； In the formula, [L] represents the length of the anchorage support.

9. The method for evaluating the stability of cavern surrounding rock under seismic loading based on dynamic safety degree as described in claim 5, characterized in that: The calculation method for the dynamic safety factor of the support force in step S5 is as follows: Anchor bolt stress safety Safety of anchor cable under stress ,in and These represent the allowable stress values ​​for the anchor bolt and the allowable force values ​​for the anchor cable, respectively.

10. The method for evaluating the stability of cavern surrounding rock under seismic loading based on dynamic safety degree as described in claim 1, characterized in that: In step S1, an elastoplastic constitutive model is used to simulate the mechanical properties of the surrounding rock. The elastoplastic constitutive model adopts the Mohr-Coulomb ideal elastoplastic model with a tensile cutoff limit. The calculation model is solved numerically by the finite difference method or the finite element method.

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