Method for determining mechanical parameters of surrounding rock of bulk material

Abstract

The present application provides a method for determining the mechanical parameters of bulk rock, belonging to the technical field of bulk rock mechanical parameter analysis, which comprises the following steps: obtaining geological basic data and estimating initial parameters, first conducting geological investigation and rock mass classification, conducting rock mechanics test indoors and outdoors, estimating initial parameters using Hoek-Brown criterion, constructing a three-dimensional tunnel construction model, monitoring the numerical value of displacement in the construction process for inversion analysis, conducting comparative analysis and parameter system correction, determining parameters and verifying calculation, inputting the corrected parameters into the initial parameter estimation again, updating the three-dimensional tunnel construction model, and obtaining the final mechanical parameters of bulk rock and construction parameters. The present application takes Hoek-Brown estimated parameters as input parameters for calculation as the input parameters for surrounding rock inversion analysis, solves the problem of strong subjectivity of geological strength index GSI through step-by-step approximation, and overcomes the problem of difficulty in obtaining high-credibility mechanical parameters due to the discontinuous and loose characteristics of bulk rock.

Description

Technical Field

[0001] This invention relates to the field of mechanical parameter analysis technology for granular surrounding rock, and more particularly to a method for determining the mechanical parameters of granular surrounding rock. Background Technology

[0002] With my country's rapid economic growth, highway construction has experienced a leapfrog development. Tunnels are playing an increasingly important role in highway construction. However, due to factors such as topography, geological structure, and highway alignment requirements, tunnel construction often involves traversing sections with unfavorable geological conditions, frequently encountering various geological hazards such as landslides, large-scale collapses, and surface subsidence. These hazards can affect construction progress, increase project costs, cause property and environmental damage, and in severe cases, even result in casualties. Therefore, ensuring construction safety during tunnel crossings of unfavorable geological sections remains a critical technical challenge that urgently needs to be overcome.

[0003] When tunnels traverse fault fracture zones and their influence zones, areas with intense tectonic movement in shallow buried sections, strongly weathered zones, accumulation sections, and loose sandy soil sections, they are highly susceptible to instability and collapse in the form of granular failure. Granular surrounding rock, a special type of unfavorable geological rock, is primarily composed of gravel and granular structures with an integrity coefficient <0.2. It is characterized by looseness, fracture, well-developed bedding, joints and fissures, and susceptibility to weathering, hydrolysis, expansion, and softening. Due to its loose structure and low strength, it is highly prone to instability and failure during tunnel construction when traversing granular surrounding rock sections. The main reason for this is the inability to accurately determine the mechanical parameters of the surrounding rock, thus hindering the development of effective excavation and support measures. The environment in which tunnel surrounding rock exists is extremely complex, and the determination of surrounding rock parameters is often uncertain and cannot be accurately described. Inaccurate parameter information has become a bottleneck problem in tunnel engineering theoretical analysis and excavation and support design. Therefore, it is necessary to design a method for determining the mechanical parameters of granular surrounding rock to ensure tunnel construction safety. Summary of the Invention

[0004] The purpose of this invention is to provide a method for determining the mechanical parameters of granular surrounding rock, thereby solving the technical problem that the determination of existing surrounding rock parameters often cannot be accurately described due to uncertainty, which leads to significant safety hazards in tunnel construction.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A method for determining the mechanical parameters of surrounding rock in granular materials, the method comprising the following steps: Step 1: Geological data acquisition and initial parameter estimation. First, conduct geological surveys and rock mass classification, and then conduct rock mechanics tests indoors and outdoors. Step 2: Estimate the initial parameters using the Hoek-Brown criterion; Step 3: Construct a three-dimensional tunnel construction model and perform inversion analysis by monitoring the displacement values ​​during the construction process; Step 4: Conduct comparative analysis and correct the parameter system; Step 5: Parameter determination and forward calculation verification. Input the corrected parameters back into Step 2, and repeat Step 2 and Step 3 to obtain the final mechanical parameters and construction parameters of the surrounding rock of the granular mass.

[0006] Furthermore, the specific process of geological investigation and rock mass classification in step 1 is as follows: conduct detailed engineering geological mapping to identify the rock mass structure type, structural surface development characteristics, weathering degree and groundwater conditions. Development characteristics include spacing, roughness and infill material. Quantitatively determine geological strength indicators, mark the degree of interlocking and alteration between rock blocks, conduct geological sketching and logging of the tunnel face and surrounding area, and use a standard record form with GSI quantitative charts to evaluate and score the structural surfaces and surface characteristics of the loose surrounding rock to obtain the GSI output value.

[0007] Furthermore, the specific process of conducting indoor and outdoor rock mechanics tests in step 1 is as follows: In indoor tests, uniaxial compressive strength tests are conducted on relatively intact rock blocks to obtain the uniaxial compressive strength and rock constants of intact rock, which are directly read from the peak stress of the test. During on-site evaluation of the experiment, the rock mass disturbance coefficient is determined based on the excavation method, the impact of blasting vibration, and the degree of stress release. The disturbance coefficient ranges from 0 to 1, and the larger the number, the more severe the disturbance.

[0008] Further, the specific process of step 2 is as follows: using the data from step 1 as input, the Hoek-Brown strength parameters of the rock mass are calculated using the Hoek-Brown criterion. Based on Mohr-Coulomb fitting, the equivalent cohesion, internal friction angle and tensile strength of the rock mass are derived. The initial elastic modulus of the rock mass is estimated using empirical formulas, thus obtaining the first complete set of rock mass mechanical parameters and the initial Poisson's ratio for deformation analysis.

[0009] Furthermore, in step 3, a model of the mountain's appearance is pre-captured using a drone equipped with a camera. The distribution of the rock strata throughout the mountain is analyzed using radar technology and geophysical exploration to obtain overall mountain data. Based on the collected data on the loose surrounding rock and the overall mountain data, a mountain model for the tunnel construction is constructed. Corresponding parameter data is matched according to the loose surrounding rock conditions at different depths of the mountain strata. Tunnel design drawings are consulted, and the tunnel design drawings are fused with the three-dimensional model of the mountain. Then, several stress and displacement sensors are installed at different locations at the upper end of the tunnel. The tunnel is simulated for excavation according to the initially set excavation method. Finally, data from the upper and lower ends of the already excavated tunnel are collected. The sensor data is collected and transmitted back to the mountain model to obtain a dynamic model of the excavation process. The dynamic model is labeled with time and corresponding construction parameters. Then, taking the upper end of the tunnel and the construction front area in the mountain model as the target area, the construction parameters and methods are continuously adjusted to obtain several dynamic models of the excavation process. The sensor values ​​at the same coordinates in each dynamic model are compared to obtain the minimum values ​​of stress change and displacement at different coordinate points. Then, the corresponding construction method is found in reverse. Finally, the data of all points are summarized to obtain the optimal excavation method and excavation parameters for different points of the tunnel. The construction method and construction parameters for each section are manually selected according to the construction requirements and conditions.

[0010] Furthermore, in step 3, based on the changes in sensor values ​​during construction dynamics, the settlement values ​​of the tunnel arch and front end, as well as the horizontal convergence values, are used as inversion targets. The deformation modulus and Poisson's ratio of the rock mass are used as the main inversion adjustment variables. The bisection method written in Fish language is used for optimization, and the deformation modulus and Poisson's ratio are continuously adjusted to minimize the error between the simulated displacement value and the field monitored displacement value. When the error between the simulated displacement and the measured displacement is less than the preset threshold, the inversion is considered to have converged. The parameters obtained at this time are the inversion deformation parameter set.

[0011] Furthermore, in step 4, the relative error between the estimated modulus and the inversion modulus is calculated. If the relative error is greater than 5%, it indicates that the GSI and rock mass disturbance coefficient values ​​on which the initial estimation is based deviate from the actual situation. If the inversion modulus is less than the estimated modulus, it indicates that the actual quality of the rock mass is worse or more severely disturbed. The GSI value should be appropriately lowered or the rock mass disturbance coefficient value should be increased, and vice versa.

[0012] Furthermore, in step 5, the GSI and rock mass disturbance coefficient values ​​are first input into step 2 to obtain the secondary parameter values. The secondary parameter values ​​are then put into the established three-dimensional tunnel construction model to obtain the final three-dimensional tunnel construction model.

[0013] The present invention, by adopting the above-described technical solution, has the following beneficial effects: This invention uses Hoek-Brown estimated parameters as input parameters for surrounding rock inversion analysis. Through a successive approximation method, it addresses the issue of the strong subjectivity of the Geological Strength Index (GSI) and overcomes the difficulty in obtaining highly reliable mechanical parameters for granular surrounding rocks due to their discontinuous and loose characteristics. Simultaneously, a construction dynamic model is designed during the mechanical parameter inversion process, and the accuracy of the granular surrounding rock mechanical parameters is verified by reverse engineering based on construction parameters. Then, construction personnel evaluate the parameters based on their experience and the simulated recommended construction methods, ultimately determining the granular surrounding rock mechanical parameters and subsequent construction methods. This achieves a dual benefit, providing data support for later construction. Attached Figure Description

[0014] Figure 1 This is a flowchart of the method of the present invention. Detailed Implementation

[0015] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and preferred embodiments. However, it should be noted that many details listed in the specification are merely to provide the reader with a thorough understanding of one or more aspects of the present invention, and these aspects of the invention can be implemented even without these specific details.

[0016] like Figure 1 As shown, a method for determining the mechanical parameters of surrounding rock in granular materials includes the following steps: Step 1: Geological Data Acquisition and Initial Parameter Estimation. This begins with geological surveys and rock mass classification, followed by indoor and outdoor rock mechanics tests. The specific process of geological surveys and rock mass classification involves detailed engineering geological mapping to identify the rock mass structure type, structural plane development characteristics, weathering degree, and groundwater conditions. Development characteristics include spacing, roughness, and infill materials. Geological strength indices are quantitatively determined. The degree of interlocking and alteration between rock blocks is marked. Geological sketches and logging of the tunnel face and surrounding area are conducted. Using a standard recording form with GSI quantitative charts, the structural planes and surface characteristics of the loose surrounding rock are evaluated and scored to obtain GSI output values.

[0017] The specific process of conducting rock mechanics tests indoors and outdoors is as follows: In indoor tests, uniaxial compressive strength tests are conducted on relatively intact rock blocks to obtain the uniaxial compressive strength and rock constants of intact rock, which are directly read from the peak stress of the test. During on-site evaluation of the test, the rock mass disturbance coefficient is determined based on the excavation method, the impact of blasting vibration, and the degree of stress release. The disturbance coefficient ranges from 0 to 1, and the larger the number, the more severe the disturbance.

[0018] Step 2: Estimate initial parameters using the Hoek-Brown criterion. Using the data from Step 1 as input, calculate the Hoek-Brown strength parameters of the rock mass using the Hoek-Brown criterion. Based on Mohr-Coulomb fitting, derive the equivalent cohesion, internal friction angle, and tensile strength of the rock mass. Estimate the initial elastic modulus of the rock mass using empirical formulas, obtaining the first complete set of rock mass mechanical parameters and the initial Poisson's ratio for deformation analysis.

[0019] Step 3: Construct a 3D tunnel construction model and perform inversion analysis on the displacement values ​​during the construction process. Beforehand, use a drone equipped with a camera to photograph the mountain's exterior model. Analyze the distribution of the entire mountain's rock strata using radar technology and geophysical exploration to obtain overall mountain data. Based on the collected data on the loose surrounding rock and the overall mountain data, construct a mountain model for the tunnel construction. Match corresponding parameter data according to the loose surrounding rock conditions at different depths of the mountain strata. Refer to the tunnel design drawings and integrate them with the 3D mountain model. Then, install several stress and displacement sensors at different locations at the upper end of the tunnel. Simulate excavation of the tunnel according to the initially set excavation method, and then collect the sensor stress data at the upper and lower ends of the excavated tunnel. The data changes, and the collected sensor data is then transmitted back to the mountain model to obtain a dynamic model of the excavation process. The dynamic model is labeled with time and corresponding construction parameters. Then, taking the upper end of the tunnel and the construction front area in the mountain model as the target area, the construction parameters and methods are continuously adjusted to obtain several dynamic models of the excavation process. The sensor values ​​at the same coordinates in each dynamic model are compared to obtain the minimum values ​​of stress change and displacement at different coordinate points. Then, the corresponding construction method is found in reverse. Finally, the data of all points are summarized to obtain the optimal excavation method and excavation parameters for different points of the tunnel. The construction method and construction parameters for each section are manually selected according to the construction requirements and conditions.

[0020] The drone carrying the camera is mainly used to obtain the overall structure and appearance of the mountain, such as whether there is any collapse. Geophysical exploration is mainly used to obtain the location of the rock strata, providing the location coordinates and orientation of the rock strata for the later construction of a 3D model.

[0021] Based on the changes in sensor values ​​during construction, the subsidence values ​​of the tunnel arch and front end, as well as the horizontal convergence values, are used as inversion targets. The deformation modulus and Poisson's ratio of the rock mass are used as the main inversion adjustment variables. A bisection method written in Fish language is used for optimization. The deformation modulus and Poisson's ratio are continuously adjusted to minimize the error between the simulated displacement value and the field monitored displacement value. When the error between the simulated displacement and the measured displacement is less than a preset threshold, the inversion is considered to have converged. The parameters obtained at this time are the inversion deformation parameter set.

[0022] Step 4: Perform comparative analysis and parameter system correction. Calculate the relative error between the estimated modulus and the inverted modulus. If the relative error is greater than 5%, it indicates that the initial estimation based on the GSI and rock mass disturbance coefficient values ​​deviates from the actual situation. If the inverted modulus is less than the estimated modulus, it indicates that the actual rock mass quality is worse or more severely disturbed, and the GSI value should be appropriately lowered or the rock mass disturbance coefficient value should be increased, and vice versa.

[0023] Step 5: Parameter Determination and Forward Calculation Verification. Input the corrected parameters back into Step 2, and repeat Steps 2 and 3 to obtain the final granular rock mass mechanical parameters and construction parameters. First, input the GSI and rock mass disturbance coefficient values ​​into Step 2 to obtain secondary parameter values. Then, input these secondary parameter values ​​into the established three-dimensional tunnel construction model to obtain the final three-dimensional tunnel construction model. In sub-step 3, update the parameter data of the internal rock strata of the three-dimensional model based on the updated parameters. Then, re-simulate the construction to continue obtaining the optimal construction parameters and methods.

[0024] In actual construction, if the collapse or displacement of the actual construction is found to be different from the simulation when the construction is halfway through or a part of it is found, the cause of the error should be identified in time. If the mechanical data of the rock has changed, the mechanical parameters and construction methods and parameters can be re-determined in the input steps 2 and 3. This can provide real-time data estimation for subsequent construction and better avoid construction accidents.

[0025] The rock mechanics parameter estimation method based on the Hoek-Brown strength criterion requires input geological strength indicators determined by GIS, which involves subjectivity, and the reliability of the estimated rock mechanics parameter values ​​is difficult to verify. Furthermore, the method for determining rock mechanics parameters based on displacement inversion suffers from the uniqueness problem in multi-parameter displacement inversion; two or more sets of parameter combinations may yield the same or similar objective function values.

[0026] First, the Hoek-Brown strength criterion is used to estimate the rock mass strength parameters of the granular surrounding rock, namely cohesion. internal friction angle ,tensile strength Estimated elastic modulus Then, the estimated strength parameters are used as constant parameters in the displacement inversion analysis process. Numerical analysis methods using FLAC3D modeling are employed to invert and optimize the deformation parameters (inverted elastic modulus EB and Poisson's ratio). Simultaneously, the estimated elastic modulus... By comparing and analyzing the inverted elastic modulus EB, the geological strength index GIS and engineering disturbance coefficient D are corrected to obtain rock mechanics parameters that are close to the actual values. The parameters determined by the new method are then used to perform forward inversion calculations using tunnel arch settlement and horizontal measurement data to verify the effectiveness, reliability, uniqueness, and standardization of the new method.

[0027] Matters not covered in this invention are common knowledge.

[0028] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for determining the mechanical parameters of surrounding rock in granular materials, characterized in that: The method includes the following steps: Step 1: Geological data acquisition and initial parameter estimation. First, conduct geological surveys and rock mass classification, and then conduct rock mechanics tests indoors and outdoors. Step 2: Estimate the initial parameters using the Hoek-Brown criterion; Step 3: Construct a three-dimensional tunnel construction model and perform inversion analysis by monitoring the displacement values ​​during the construction process; Step 4: Conduct comparative analysis and correct the parameter system; Step 5: Parameter determination and forward calculation verification. Input the corrected parameters back into Step 2, and repeat Step 2 and Step 3 to obtain the final mechanical parameters and construction parameters of the surrounding rock of the granular mass.

2. The method for determining the mechanical parameters of granular surrounding rock according to claim 1, characterized in that: The specific process of geological investigation and rock mass classification in step 1 is as follows: conduct detailed engineering geological mapping to identify the rock mass structure type, structural surface development characteristics, weathering degree and groundwater conditions. Development characteristics include spacing, roughness and infill material. Quantitatively determine geological strength indicators, mark the degree of interlocking and alteration between rock blocks, conduct geological sketching and logging of the tunnel face and surrounding area, and use a standard record form with GSI quantitative charts to evaluate and score the structural surfaces and surface characteristics of the loose surrounding rock to obtain the GSI output value.

3. The method for determining the mechanical parameters of granular surrounding rock according to claim 1, characterized in that: The specific process of conducting indoor and outdoor rock mechanics tests in step 1 is as follows: In the indoor test, a uniaxial compressive strength test is conducted on a relatively intact rock block to obtain the uniaxial compressive strength and rock constant of the intact rock. The results are directly read from the peak stress of the test. During the on-site evaluation of the experiment, the rock mass disturbance coefficient is determined based on the excavation method, the impact of blasting vibration, and the degree of stress release. The disturbance coefficient ranges from 0 to 1. The larger the number, the more severe the disturbance.

4. The method for determining the mechanical parameters of granular surrounding rock according to claim 1, characterized in that: The specific process of step 2 is as follows: using the data from step 1 as input, the Hoek-Brown strength parameters of the rock mass are calculated using the Hoek-Brown criterion. Based on Mohr-Coulomb fitting, the equivalent cohesion, internal friction angle and tensile strength of the rock mass are derived. The initial elastic modulus of the rock mass is estimated using empirical formulas, thus obtaining the first complete set of rock mass mechanical parameters and the initial Poisson's ratio for deformation analysis.

5. The method for determining the mechanical parameters of granular surrounding rock according to claim 1, characterized in that: In step 3, a drone equipped with a camera is used to photograph the mountain's exterior model beforehand. Radar technology and geophysical exploration are then used to analyze the distribution of the rock strata throughout the mountain to obtain overall mountain data. Based on the collected data on the loose surrounding rock and the overall mountain data, a mountain model for the tunnel construction is constructed. Corresponding parameter data is matched according to the loose surrounding rock conditions at different depths of the mountain strata. Tunnel design drawings are consulted and integrated with the three-dimensional mountain model. Then, several stress and displacement sensors are installed at different locations at the upper end of the tunnel. The tunnel is simulated for excavation according to the initially set excavation method. Finally, sensor data is collected from the upper and lower ends of the already excavated tunnel. The changes in force are detected, and the collected sensor data is then transmitted back to the mountain model to obtain a dynamic model of the excavation process. The dynamic model is labeled with time and corresponding construction parameters. Then, taking the upper end of the tunnel and the construction front area in the mountain model as the target area, the construction parameters and methods are continuously adjusted to obtain several dynamic models of the excavation process. The sensor values ​​at the same coordinate positions in each dynamic model are compared to obtain the minimum values ​​of stress change and displacement at different coordinate points. Then, the corresponding construction method is found in reverse. Finally, the data of all points are summarized to obtain the optimal excavation method and excavation parameters for different points of the tunnel. The construction method and construction parameters for each section are manually selected according to the construction requirements and conditions.

6. The method for determining the mechanical parameters of granular surrounding rock according to claim 1, characterized in that: In step 3, based on the changes in sensor values ​​during construction dynamics, the subsidence values ​​of the tunnel arch and front end, as well as the horizontal convergence values, are used as inversion targets. The deformation modulus and Poisson's ratio of the rock mass are used as the main inversion adjustment variables. The bisection method written in Fish language is used for optimization, and the deformation modulus and Poisson's ratio are continuously adjusted to minimize the error between the simulated displacement value and the field monitored displacement value. When the error between the simulated displacement and the measured displacement is less than the preset threshold, the inversion is considered to have converged, and the parameters obtained at this time are the inversion deformation parameter set.

7. The method for determining the mechanical parameters of granular surrounding rock according to claim 1, characterized in that: In step 4, the relative error between the estimated modulus and the inversion modulus is calculated. If the relative error is greater than 5%, it indicates that the GSI and rock mass disturbance coefficient values ​​on which the initial estimation is based deviate from the actual situation. If the inversion modulus is less than the estimated modulus, it indicates that the actual quality of the rock mass is worse or the disturbance is more severe. The GSI value should be appropriately lowered or the rock mass disturbance coefficient value should be increased, and vice versa.

8. The method for determining the mechanical parameters of granular surrounding rock according to claim 1, characterized in that: In step 5, the GSI and rock mass disturbance coefficient values ​​are first input into step 2 to obtain the secondary parameter values. The secondary parameter values ​​are then put into the established three-dimensional tunnel construction model to obtain the final three-dimensional tunnel construction model.

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