CN114547746A - Discrete element method and system for simulating creep instability of roadway surrounding rock - Google Patents

Discrete element method and system for simulating creep instability of roadway surrounding rock Download PDF

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CN114547746A
CN114547746A CN202210179692.5A CN202210179692A CN114547746A CN 114547746 A CN114547746 A CN 114547746A CN 202210179692 A CN202210179692 A CN 202210179692A CN 114547746 A CN114547746 A CN 114547746A
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creep
block
model
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roadway
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李国栋
刘洪林
杭银建
马述起
刘金虎
王宏志
张卫东
李剣峰
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Xuzhou Mining Business Group Co ltd
China University of Mining and Technology CUMT
Southwest Jiaotong University
Xinjiang University
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Xuzhou Mining Business Group Co ltd
China University of Mining and Technology CUMT
Southwest Jiaotong University
Xinjiang University
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Abstract

The invention relates to a discrete element method and a discrete element system for simulating creep instability of roadway surrounding rock. The method comprises the following steps: according to the stress-strain curve, inverting the compression splitting model to obtain parameter values of a reasonable contact surface and a reasonable block; inverting the first uniaxial creep numerical model established according to the parameter values according to the rock creep curve to obtain reasonable block creep parameter values; inverting a second uniaxial creep numerical model constructed according to the parameter values of the reasonable contact surface and the reasonable block creep according to the rock creep curve to obtain a reasonable block creep parameter degradation equation; carrying out mesh division on a simulation model constructed based on a reasonable block creep parameter degradation equation; simulating the divided simulation model to obtain the accumulated length of the tension fracture and the accumulated length of the shear fracture of each grid; and determining the range of the creep instability of the surrounding rock of the roadway to be simulated based on the accumulated length of the tension fracture and the accumulated length of the shear fracture. The method can improve the accuracy of the simulation tunnel surrounding rock creep instability research result.

Description

Discrete element method and system for simulating creep instability of roadway surrounding rock
Technical Field
The invention relates to the technical field of surrounding rock supporting, in particular to a discrete element method and a discrete element system for simulating creep instability of surrounding rock of a roadway.
Background
The external manifestation of tunnel rock mass damage is usually represented by cracking, spalling, buckling, sliding, rock burst and the like of an excavation face rock mass, and the internal cause is the process of initiation, expansion and communication of primary cracks or secondary cracks in the rock mass under the action of stress, so that an excavation damage area or an excavation disturbance area is formed in a certain range of the rock mass. Therefore, the damage condition of the surrounding rock under the disturbance action of the surrounding rock excavation can be accurately described and predicted, and the method has important significance for ensuring the safety and stability of the surrounding rock when the underground engineering is carried out.
At present, finite difference and discrete element numerical simulation methods are commonly adopted for predicting and describing damage and damage caused by rock excavation, and the damage area range of the surrounding rock is predicted and calculated by utilizing the Mohr-Coulomb strength criterion. In the prior art, an analysis model is established by using a finite difference method, an energy release process induced by cavern excavation is simulated, the magnitude of an energy release coefficient is calculated, and the relation between surrounding rock damage and surrounding rock energy release in the excavation process is determined, so that the surrounding rock damage range is predicted. The surrounding rock damage prediction method based on the energy release coefficient is suitable for researching the macroscopic damage of the surrounding rock of the roadway, but the essence of the damage of rock fracture expansion to the surrounding rock of the roadway cannot be revealed. In the prior art, the essence of roadway surrounding rock damage is disclosed from the aspect of crack expansion by using UDEC discrete element numerical simulation software, however, 8 creep models such as a Viscous model, a Burgers model and a Cvisc model are used for creep characteristic analysis of rocks in the UDEC discrete element software, but the creep models do not consider the influence of deformation and stress of the rocks along with time factors, and micro-crack expansion in the accelerated creep stage and the creep process of the rocks cannot be realized, so that the research result of simulating creep instability of the roadway surrounding rock is inaccurate.
Disclosure of Invention
The invention aims to provide a discrete element method and a discrete element system for simulating the creep instability of surrounding rock of a roadway, which can improve the accuracy of a research result of the creep instability of the surrounding rock of the roadway.
In order to achieve the purpose, the invention provides the following scheme:
a discrete element method for simulating creep instability of roadway surrounding rock comprises the following steps:
acquiring occurrence conditions of surrounding rocks of a roadway to be simulated, physical and mechanical parameters of a rock stratum within a set range of the roadway to be simulated and a curve of deformation of the surrounding rocks of the roadway to be simulated along with time; the occurrence conditions include: the size of the roadway, the burial depth, the excavation condition around the roadway and rock mass parameters within a set range; the rock mass parameters include: the dip angle, thickness, lithology and bedding structure of the rock mass; the physical-mechanical parameters include: stress-strain curves of uniaxial pressure tests, stress-strain curves of Brazilian splitting tests and creep curves of rocks;
establishing a compression splitting model by using UDEC discrete element simulation software, and inverting the contact parameters and the block parameters of the compression splitting model according to the uniaxial pressure test stress-strain curve and the Brazilian splitting test stress-strain curve to obtain reasonable contact surface parameter values and reasonable block parameter values; the compression splitting model comprises a single-axis compression numerical model and a Brazilian splitting numerical model;
establishing a first uniaxial creep numerical model with a block unit being a Cvisc creep model by using UDEC discrete element simulation software according to the reasonable block parameter values and the reasonable contact surface parameter values, and inverting the block creep parameters of the first uniaxial creep numerical model according to the rock creep curve to obtain reasonable block creep parameter values;
constructing a second uniaxial creep numerical model of a block unit as an improved Cvisc creep model by using UDEC discrete element simulation software according to the reasonable contact surface parameter value and the reasonable block creep parameter value, and inverting a block creep parameter degradation equation of the second uniaxial creep numerical model according to the rock creep curve to obtain a reasonable block creep parameter degradation equation; the block unit of the second uniaxial creep numerical model is an improved Cvisc creep model; the improved Cvisc creep model is a Cvisc creep model of which the degradation equation is a block creep parameter degradation equation;
constructing a tunnel discrete element numerical simulation model according to the curve of the deformation of the tunnel surrounding rock to be simulated along with the change of time, the occurrence condition and the reasonable block creep parameter degradation equation, and performing grid division on the tunnel discrete element numerical simulation model by adopting a discrete method to obtain a tunnel discrete element numerical simulation model subjected to discrete grid processing;
according to occurrence conditions of the surrounding rocks of the roadway to be simulated, physical and mechanical parameters of rock strata in a set range of the roadway to be simulated and a curve of deformation of the surrounding rocks of the roadway to be simulated along with time, simulating and excavating the discrete element numerical simulation model of the roadway subjected to discrete gridding treatment to obtain the length of an accumulated tensioning fracture and the length of an accumulated shearing fracture of each grid; the accumulated length of the tension fracture is the sum of the lengths of all the tension fractures in the grid; the accumulated shearing fracture length is the sum of all the shearing fracture lengths in the grid;
and determining the creep instability range of the surrounding rock of the roadway to be simulated according to the accumulated length of the tension fracture, the accumulated length of the shear fracture and the critical creep damage value of each grid.
A discrete element system for simulating creep instability of surrounding rock of a roadway comprises:
the acquisition module is used for acquiring occurrence conditions of the surrounding rocks of the roadway to be simulated, physical and mechanical parameters of rock layers in a set range of the roadway to be simulated and a curve of deformation of the surrounding rocks of the roadway to be simulated along with time; the occurrence condition includes: the size of the roadway, the burial depth, the excavation condition around the roadway and rock mass parameters within a set range; the rock mass parameters include: the dip angle, thickness, lithology and bedding structure of the rock mass; the physical-mechanical parameters include: stress-strain curves of uniaxial pressure tests, stress-strain curves of Brazilian splitting tests and creep curves of rocks;
a reasonable contact surface parameter value and reasonable block parameter value determining module, configured to establish a compressive splitting model by using UDEC discrete element simulation software, and perform inversion on the contact parameters and the block parameters of the compressive splitting model according to the uniaxial pressure test stress-strain curve and the brazilian splitting test stress-strain curve to obtain reasonable contact surface parameter values and reasonable block parameter values; the compression splitting model comprises a single-axis compression numerical model and a Brazilian splitting numerical model;
the reasonable block creep parameter value determining module is used for establishing a first uniaxial creep numerical model with a block unit being a Cvisc creep model by using UDEC discrete element simulation software according to the reasonable block parameter value and the reasonable contact surface parameter value and inverting the block creep parameters of the first uniaxial creep numerical model according to the rock creep curve to obtain the reasonable block creep parameter value;
the reasonable block creep parameter degradation equation determining module is used for constructing a second single-axis creep numerical model of which a block unit is an improved Cvisc creep model by using UDEC discrete element simulation software according to the reasonable contact surface parameter value and the reasonable block creep parameter value and inverting the block creep parameter degradation equation of the second single-axis creep numerical model according to the rock creep curve to obtain a reasonable block creep parameter degradation equation; the block unit of the second uniaxial creep numerical model is an improved Cvisc creep model; the improved Cvisc creep model is a Cvisc creep model of which the degradation equation is a block creep parameter degradation equation;
the roadway discrete element numerical simulation model determining module is used for constructing a roadway discrete element numerical simulation model according to a curve of deformation of the roadway surrounding rock to be simulated along with time, the occurrence condition and the reasonable block creep parameter degradation equation and performing grid division on the roadway discrete element numerical simulation model by adopting a discrete method to obtain a discrete grid-processed roadway discrete element numerical simulation model;
the fracture length determining module is used for performing simulated excavation on the discrete element numerical simulation model of the roadway subjected to the discrete gridding treatment according to occurrence conditions of the surrounding rock of the roadway to be simulated, physical and mechanical parameters of rock strata in a set range of the roadway to be simulated and a curve of deformation of the surrounding rock of the roadway to be simulated along with time to obtain the accumulated length of the tensioned fracture and the accumulated length of the sheared fracture of each grid; the accumulated length of the tensioned fracture is the sum of the lengths of all the tensioned fractures in the grid; the accumulated shear fracture length is the sum of all shear fracture lengths in the grid;
and the instability range determining module is used for determining the range of the creep instability of the surrounding rock of the roadway to be simulated according to the accumulated length of the tension fracture, the accumulated length of the shear fracture and the critical creep damage value of each grid.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects: the method comprises the steps of obtaining occurrence conditions of surrounding rocks of a roadway to be simulated, physical and mechanical parameters of rock strata in a set range of the roadway to be simulated and a curve of deformation of the surrounding rocks of the roadway to be simulated along with time; establishing a compression splitting model and inverting the contact parameters and the block parameters of the compression splitting model according to the uniaxial pressure test stress-strain curve and the Brazilian splitting test stress-strain curve to obtain reasonable contact surface parameter values and reasonable block parameter values; establishing a first uniaxial creep numerical model with a Cvisc creep model as a block unit according to the reasonable block parameter values and the reasonable contact surface parameter values, and inverting the block creep parameters of the first uniaxial creep numerical model according to the rock creep curve to obtain the reasonable block creep parameter values; constructing a second uniaxial creep numerical model of which the block unit is an improved Cvisc creep model according to the reasonable contact surface parameter value and the reasonable block creep parameter value, and inverting a block creep parameter degradation equation of the second uniaxial creep numerical model according to the rock creep curve to obtain a reasonable block creep parameter degradation equation; constructing a tunnel discrete element numerical simulation model according to a curve of deformation of tunnel surrounding rock to be simulated along with time change, occurrence conditions and a reasonable block creep parameter degradation equation, and performing grid division on the tunnel discrete element numerical simulation model by adopting a discrete method to obtain a tunnel discrete element numerical simulation model subjected to discrete grid processing; simulating and excavating the discrete element numerical simulation model of the roadway subjected to discrete gridding treatment according to occurrence conditions of surrounding rocks of the roadway to be simulated, physical and mechanical parameters of rock strata in a set range of the roadway to be simulated and a curve of deformation of the surrounding rocks of the roadway to be simulated along with time to obtain the accumulated length of the tensioned fracture and the accumulated length of the sheared fracture of each grid; the creep instability range of the roadway surrounding rock to be simulated is determined according to the accumulated length of the tension fracture, the accumulated length of the shear fracture and the critical creep damage value of each grid.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
FIG. 1 is a flowchart of a discrete element method for simulating creep instability of roadway surrounding rock according to an embodiment of the present invention;
FIG. 2 is a stress-strain diagram of uniaxial rock compression test in steps S1 and S2 according to an embodiment of the invention;
FIG. 3 is a graph of stress-strain curves in the Brazilian rock split test in steps S1 and S2 according to an embodiment of the present invention;
FIG. 4 is a graph of rock creep in steps S1, S2 according to an embodiment of the present invention;
FIG. 5 is a time-strain curve of uniaxial creep degradation test of rock in step S3 according to an embodiment of the present invention;
FIG. 6 is a diagram illustrating a model for discrete element numerical simulation in step S4 according to the present invention;
fig. 7 is a schematic diagram of the discretization grid of the roadway surrounding rock in step S4 according to the embodiment of the present invention;
FIG. 8 is a graph illustrating creep damage evolution of roadway surrounding rock at different times in step S6 according to the embodiment of the present invention;
FIG. 9 is a diagram illustrating the damage range of the surrounding rock at step S6 according to the embodiment of the present invention;
fig. 10 is a general flowchart of a discrete element method for simulating creep instability of roadway surrounding rock according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
The invention discloses a discrete element method for simulating creep instability of roadway surrounding rock, which comprises the following specific steps as shown in figure 1:
step 101: acquiring occurrence conditions of the surrounding rock of the roadway to be simulated, physical and mechanical parameters of the rock stratum within a set range of the roadway to be simulated and a curve of the deformation of the surrounding rock of the roadway to be simulated along with the change of time. The occurrence condition includes: the size of the roadway, the burial depth, the excavation condition around the roadway and rock mass parameters within a set range; the rock mass parameters include: the dip angle, thickness, lithology and bedding structure of the rock mass; the physical-mechanical parameters include: the stress-strain curve of the uniaxial pressure test, the stress-strain curve of the Brazilian split test and the rock creep curve, wherein the set range can be a width range three times that of the roadway.
Step 102: establishing a compression splitting model by using UDEC discrete element simulation software, and inverting the contact parameters and the block parameters of the compression splitting model according to the uniaxial pressure test stress-strain curve and the Brazilian splitting test stress-strain curve to obtain reasonable contact surface parameter values and reasonable block parameter values; the compression splitting model comprises a single-axis compression numerical model and a Brazilian splitting numerical model.
Step 103: and establishing a first uniaxial creep numerical model with a block unit as a Cvisc creep model by using UDEC discrete element simulation software according to the reasonable block parameter values and the reasonable contact surface parameter values, and inverting the block creep parameters of the first uniaxial creep numerical model according to the rock creep curve to obtain the reasonable block creep parameter values.
Step 104: constructing a second uniaxial creep numerical model of a block unit as an improved Cvisc creep model by using UDEC discrete element simulation software according to the reasonable contact surface parameter value and the reasonable block creep parameter value, and inverting a block creep parameter degradation equation of the second uniaxial creep numerical model according to the rock creep curve to obtain a reasonable block creep parameter degradation equation; the block unit of the second uniaxial creep numerical model is an improved Cvisc creep model; the improved Cvisc creep model is a Cvisc creep model with a degradation equation being a block creep parameter degradation equation.
Step 105: and constructing a tunnel discrete element numerical simulation model according to the curve of the deformation of the tunnel surrounding rock to be simulated along with the change of time, the occurrence condition and the reasonable block creep parameter degradation equation, and performing grid division on the tunnel discrete element numerical simulation model by adopting a discrete method to obtain the tunnel discrete element numerical simulation model subjected to discrete grid processing.
Step 106: according to occurrence conditions of the surrounding rocks of the roadway to be simulated, physical and mechanical parameters of rock strata in a set range of the roadway to be simulated and a curve of deformation of the surrounding rocks of the roadway to be simulated along with time, simulating and excavating the discrete element numerical simulation model of the roadway subjected to discrete gridding treatment to obtain the length of an accumulated tensioning fracture and the length of an accumulated shearing fracture of each grid; the accumulated length of the tension fracture is the sum of the lengths of all the tension fractures in the grid; the cumulative shear fracture length is the sum of all shear fracture lengths in the grid.
Step 107: and determining the creep instability range of the surrounding rock of the roadway to be simulated according to the accumulated length of the tension fracture, the accumulated length of the shear fracture and the critical creep damage value of each grid.
In practical application, step 101 specifically includes:
step 1.1: collecting occurrence conditions of surrounding rocks of the roadway to be simulated, including the size of the roadway, the burial depth, the mining conditions around the roadway and the rock inclination angle, the thickness, the lithology and the bedding structure within the triple width range of the roadway.
Step 1.2: the method for measuring and obtaining the physical and mechanical parameters of the rock stratum within the triple width range of the roadway to be simulated by the indoor experiment comprises the following steps: rock stress-strain curves (uniaxial pressure test stress-strain curve and brazilian split test stress-strain curve), rock creep curves.
Step 1.3: and observing the evolution rule of the deformation of the surrounding rocks of the roadway to be simulated along with time to obtain a curve of the deformation of the surrounding rocks of the roadway to be simulated along with the change of time.
In practical applications, step 102 specifically includes:
and (3) constructing a single-axis compression numerical model and a Brazilian split numerical model by using UDEC discrete element simulation software. Inverting the bulk and contact parameters of the uniaxial compressive numerical model using an iterative trial and error method from the uniaxial pressure test stress-strain curve to arrive at the uniaxial compressive numerical modelMatching with the uniaxial pressure test stress-strain curve, inverting the block parameters and the contact surface parameters of the Brazilian splitting numerical model according to the Brazilian splitting experiment stress-strain curve to match the Brazilian splitting numerical model with the Brazilian splitting experiment stress-strain curve to obtain reasonable contact surface parameter values and reasonable block parameter values (specifically, in step 2.1, establishing a uniaxial compression numerical model with the diameter of 50mm and the height of 100mm and a Brazilian splitting numerical model with the diameter of 50mm by using UDEC discrete element simulation software, wherein the model block adopts a triangular block or a Voronoi polygonal block, the block unit and the contact surface both adopt a Mohr-Coulomb model, and the block parameters comprise a volume modulus K, a shear modulus G and an internal friction angle thetaZCohesive force CZAnd tensile strength TZThe contact surface parameter comprises normal phase stiffness knAnd shear stiffness ksAngle of internal friction of contact surface thetajContact surface cohesion CjTensile strength T of contact surfacejAnd (3) inverting the block parameters and the contact surface parameters by adopting an iterative trial and error method, so that the uniaxial compression numerical model and the Brazilian splitting numerical model are matched with the rock stress-strain curves (the uniaxial pressure test stress-strain curve and the Brazilian splitting test stress-strain curve) obtained in the step 1.2, and thus reasonable model block parameters and reasonable contact surface parameters are obtained.
In practical application, step 103 specifically includes:
and establishing a first uniaxial creep numerical model with a block unit being a Cvisc creep model, a block parameter being the reasonable block parameter value and a contact surface parameter being the reasonable contact surface parameter value by using UDEC discrete element simulation software. And (2) inverting the block creep parameters of the first uniaxial creep numerical model according to the rock creep curve by using an iterative trial and error method to enable the first uniaxial creep numerical model to be matched with the rock creep curve to obtain reasonable block creep parameter values (specifically, step 2.2: establishing a first uniaxial creep numerical model with the diameter of 50mm and the height of 100mm, wherein the shape and the size of the model block are the same as those of step 2.1, the block unit adopts a Cvisc creep model of a software self-carrying block unit, and the block creep parameters comprise Maxwell shearing modelQuantity GmMaxwell viscosity coefficient etamKelvin shear modulus GkKelvin viscosity coefficient ηkInternal angle of friction thetazCohesive force CZAnd tensile strength TzAnd the contact surface parameters are the same as those in the step 2.1, and block creep parameters are inverted by adopting an iterative trial and error method, so that the initial creep and constant-speed creep stages of the first uniaxial creep numerical model are matched with the rock creep curve obtained in the step 1.2, and reasonable block creep parameter values are obtained).
The Cvisc creep model with the software can well simulate the initial creep stage and the constant-speed creep stage of the rock, but the Cvisc creep model does not consider the process that the mechanical parameters of the rock are continuously deteriorated along with time under the action of constant load, so that the micro-crack rapid expansion of the accelerated creep stage and the accelerated creep stage in the rock creep process cannot be realized. Therefore, the block creep parameter degradation equation needs to be customized on the basis of the Cvisc creep model, so in practical application, step 104 specifically includes:
and establishing a second uniaxial creep numerical model with the block unit as an improved Cvisc creep model, the contact surface parameters as the reasonable contact surface parameter values and the block creep parameters as the reasonable block creep parameter values by using UDEC discrete element simulation software. Inverting the creep constant in the block creep parameter degradation equation in the improved Cvisc creep model of the second uniaxial creep numerical model according to the rock creep curve by using an iterative trial and error method so as to enable the second uniaxial creep numerical model to be matched with the rock creep curve to obtain a reasonable block creep parameter degradation equation (specifically, step 3: establishing a second uniaxial creep numerical model with the diameter of 50mm and the height of 100mm, referencing the reasonable contact surface parameter value calibrated in step 2.1 and the reasonable block creep parameter value calibrated in step 2.2, embedding the customized initial creep parameter degradation equation into a main program, inverting the block creep parameter degradation equation by adopting an iterative trial and error method so as to enable the initial creep stage, the constant-speed creep stage and the accelerated creep stage of the second uniaxial creep numerical model to be matched with the rock creep curve obtained in step 1.2, and realizing the rapid expansion of the microcracks in the creep process, thereby obtaining a reasonable creep parameter degradation equation).
In practical applications, the initial creep parameter degradation equation is:
Figure BDA0003520002660000091
wherein t is the life of the test piece; t is t0For short-term strength time, from load to uniaxial strength σcDetermining the uniaxial creep rupture time; cz(t) block cohesion at creep time t; sigmacdA uniaxial resistance strength of about 1/2 times, which is a creep damage threshold; sigma1Is the maximum principal stress to which the block is actually subjected; k is a creep constant and is determined by adopting an iterative trial and error method.
In practical applications, step 105 specifically includes:
and constructing an initial simulation model with the contact surface parameters as the reasonable contact surface parameter values, the block parameters as the reasonable block parameter values, the block creep parameters as the reasonable block creep parameter values and the degradation equation as the reasonable block creep parameter degradation equation according to the occurrence conditions by using UDEC discrete element simulation software. Simulating excavation is carried out on the initial simulation model, and an iterative trial and error method is adopted to carry out inversion on contact surface parameters, block parameters and block creep parameters of the initial simulation model so as to enable the initial simulation model to be matched with a curve of the deformation of the roadway surrounding rock to be simulated along with the change of time to obtain a roadway discrete element numerical simulation model (specifically, the step 4.1 is that the occurrence conditions of the roadway surrounding rock obtained according to the step 1.1 comprise roadway buried depth, roadway surrounding excavation conditions and rock inclination angle, thickness, lithology and bedding structure in a roadway width triple range, a roadway numerical simulation geometric model conforming to the occurrence conditions of the roadway surrounding rock is established by using UDEC software, triangular blocks or Voronoi polygonal blocks are adopted for the surrounding rock in the roadway width triple range, the side length of each block is not more than 1/10 times of the roadway width, boundary conditions are applied, and the reasonable contact surface parameter values, the block parameters and the block creep parameters determined in the step 2.1 are subjected to inversion, And (3) carrying out initial parameter assignment on the tunnel numerical simulation geometric model by using the reasonable block parameter values and the reasonable block creep parameter values determined in the step 2.2, and carrying out initial balance on the model. Step 4.2: embedding a reasonable block creep parameter degradation equation into a main program of a tunnel numerical simulation geometric model, performing simulated excavation on the model after initial balance in the step 4.1, and adjusting creep parameters (block creep parameters, model block parameters and contact surface parameters) by adopting a trial-and-error iteration method to enable the tunnel numerical simulation geometric model to be matched with the evolution rule of tunnel surrounding rock deformation along with time in the step 1.3, so as to obtain the creep parameters matched with the actual engineering. Step 4.3: and (4) re-parametrizing the model in the step (4.1) by using the creep parameters adjusted in the step (4.2) to obtain a re-valued roadway numerical simulation model. The roadway discrete element numerical simulation model is discretized into regular grids (grid discretization is to better analyze the damage of surrounding rocks, a research area is divided by using an abstracted regular grid, the development condition of rock mass fractures in a grid range can be monitored in real time by programming through a Fish language carried by software), unique identification marks are carried out on each grid, and unique identification data (for conveniently distinguishing different areas, the grids are numbered, the number of each grid is not repeated, and the number is unique) are marked on each grid for later use).
In practical applications, the process of determining the critical creep damage value specifically includes:
and constructing a third uniaxial creep numerical model according to the contact surface parameter value, the block creep parameter value and the block creep parameter degradation equation of the tunnel discrete element numerical simulation model. Performing uniaxial creep numerical simulation according to the third uniaxial creep numerical model by adopting a step loading mode, and taking a critical creep damage value when the test piece undergoes accelerated creep in the uniaxial creep numerical simulation process as the critical creep damage value (specifically, in the step 5.1, establishing a third uniaxial creep numerical model with the diameter of 2m and the height of 4m, the shape and the size of a model block are the same as those in the step 4.1, the creep parameters adopt the parameters determined in the step 4.2, and a reasonable creep parameter degradation equation is embedded into a numerical model main program through a Fish language, and in the step 5.2, performing uniaxial creep numerical simulation by adopting a step loading mode until the test piece undergoes accelerated creep ruptureCounting fracture evolution conditions in the uniaxial creep simulation process by using a Fish language, wherein the fracture evolution conditions comprise the number of tension fractures, the number of shear fractures, the length of the tension fractures and the change condition of the length of the shear fractures along with time; step 5.3: critical creep damage D when accelerated creep occurs in a test piece during uniaxial creep numerical simulationminAs criterion for creep instability of rock mass).
In practical applications, step 106 specifically includes:
step 6.1: and (3) according to the actual condition of the mine collected in the step 1.1, simulating excavation on the roadway discrete element numerical simulation model subjected to discrete gridding in the step 4.4, and counting the time-space evolution rule of the tension fracture and the shear fracture in each grid under the roadway creep condition through a Fish language to obtain the length of the tension fracture and the length of the shear fracture.
In practical application, step 107 specifically includes:
and determining the rock creep damage of each grid according to the accumulated length of the tension fracture and the accumulated length of the shear fracture of each grid.
According to the rock creep damage of each grid and the critical creep damage value D of each gridminAnd determining the creep instability range of the surrounding rock of the roadway to be simulated.
In practical application, the concrete steps of determining the rock creep damage of each grid according to the accumulated length of the tension fracture and the accumulated length of the shear fracture of each grid are as follows: step 6.2: substituting the conditions of creep tension fracture and shear fracture counted in the step 6.1 into a formula
Figure BDA0003520002660000111
Calculating creep damage D of the rock in each grid in the calculation of the creep damage of the rock of the gridiCreep rock to damage DiAnd DminPerforming comparison, if Di>DminDetermining the instability time and the damage range of the surrounding rock of the roadway by determining the creep damage of the rock mass in the grid and stabilizing the rock mass in the grid if the creep damage of the rock mass in the grid is not stable, wherein DiFor creep damage of rock, LsFor cumulative length of tensioned fracture, LnFor cumulative shear fracture length, L is theoryThe cumulative fracture length is obtained by Fish language statistics.
The embodiment of the invention also provides a discrete element system for simulating the creep instability of the surrounding rock of the roadway, which comprises the following components:
the acquisition module is used for acquiring occurrence conditions of the surrounding rocks of the roadway to be simulated, physical and mechanical parameters of rock strata in a set range of the roadway to be simulated and a time-varying curve of deformation of the surrounding rocks of the roadway to be simulated. The occurrence condition includes: the size of the roadway, the burial depth, the excavation condition around the roadway and rock mass parameters within a set range; the rock mass parameters include: the dip angle, thickness, lithology and bedding structure of the rock mass; the physical-mechanical parameters include: uniaxial pressure test stress-strain curves, brazilian split test stress-strain curves, and rock creep curves.
The reasonable contact surface parameter value and reasonable block parameter value determining module is used for establishing a compression splitting model by using UDEC discrete element simulation software and inverting the contact parameters and the block parameters of the compression splitting model according to the uniaxial pressure test stress-strain curve and the Brazilian splitting test stress-strain curve to obtain a reasonable contact surface parameter value and a reasonable block parameter value; the compression splitting model comprises a single-axis compression numerical model and a Brazilian splitting numerical model.
And the reasonable block creep parameter value determining module is used for establishing a first uniaxial creep numerical model with a block unit being a Cvisc creep model by using UDEC discrete element simulation software according to the reasonable block parameter values and the reasonable contact surface parameter values and inverting the block creep parameters of the first uniaxial creep numerical model according to the rock creep curve to obtain the reasonable block creep parameter values.
The reasonable block creep parameter degradation equation determining module is used for constructing a second single-axis creep numerical model of which a block unit is an improved Cvisc creep model by using UDEC discrete element simulation software according to the reasonable contact surface parameter value and the reasonable block creep parameter value and inverting the block creep parameter degradation equation of the second single-axis creep numerical model according to the rock creep curve to obtain a reasonable block creep parameter degradation equation; the block unit of the second uniaxial creep numerical model is an improved Cvisc creep model; the improved Cvisc creep model is a Cvisc creep model with a degradation equation being a block creep parameter degradation equation.
And the roadway discrete element numerical simulation model determining module is used for constructing a roadway discrete element numerical simulation model according to the curve of the deformation of the roadway surrounding rock to be simulated along with the change of time, the occurrence condition and the reasonable block creep parameter degradation equation and carrying out grid division on the roadway discrete element numerical simulation model by adopting a discrete method to obtain the discrete gridded roadway discrete element numerical simulation model.
The fracture length determining module is used for performing simulated excavation on the discrete element numerical simulation model of the roadway subjected to the discrete gridding treatment according to occurrence conditions of the surrounding rock of the roadway to be simulated, physical and mechanical parameters of rock strata in a set range of the roadway to be simulated and a curve of deformation of the surrounding rock of the roadway to be simulated along with time to obtain the accumulated length of the tensioned fracture and the accumulated length of the sheared fracture of each grid; the accumulated length of the tensioned fracture is the sum of the lengths of all the tensioned fractures in the grid; the cumulative shear fracture length is the sum of all shear fracture lengths within the grid.
And the instability range determining module is used for determining the range of the creep instability of the surrounding rock of the roadway to be simulated according to the accumulated length of the tension fracture, the accumulated length of the shear fracture and the critical creep damage value of each grid.
As an optional implementation, the module for determining the reasonable contact surface parameter value and the reasonable block parameter value specifically includes:
and the single-axis compression numerical model and Brazilian split numerical model constructing unit is used for constructing the single-axis compression numerical model and the Brazilian split numerical model by using UDEC discrete element simulation software.
And the reasonable contact surface parameter value and reasonable block parameter value determining unit is used for inverting the block parameters and the contact surface parameters of the uniaxial compression numerical model according to the uniaxial pressure test stress-strain curve by using an iterative trial-and-error method so as to enable the uniaxial compression numerical model to be matched with the uniaxial pressure test stress-strain curve, and inverting the block parameters and the contact surface parameters of the Brazilian splitting numerical model according to the Brazilian splitting test stress-strain curve so as to enable the Brazilian splitting numerical model to be matched with the Brazilian splitting test stress-strain curve, so as to obtain reasonable contact surface parameter values and reasonable block parameter values.
As an optional implementation, the reasonable block creep parameter value determination module specifically includes:
and the first uniaxial creep numerical model construction unit is used for establishing a first uniaxial creep numerical model with a block unit being a Cvisc creep model, a block parameter being the reasonable block parameter value and a contact surface parameter being the reasonable contact surface parameter value by using UDEC discrete element simulation software.
And the reasonable block creep parameter value determining unit is used for inverting the block creep parameters of the first uniaxial creep numerical model according to the rock creep curve by using an iterative trial and error method so as to enable the first uniaxial creep numerical model to be matched with the rock creep curve to obtain the reasonable block creep parameter values.
As an alternative embodiment, the rational block creep parameter degradation equation determining module specifically includes:
and the second uniaxial creep numerical model construction unit is used for establishing a second uniaxial creep numerical model with the block unit as an improved Cvisc creep model, the contact surface parameters as the reasonable contact surface parameter values and the block creep parameters as the reasonable block creep parameter values by using UDEC discrete element simulation software.
And the reasonable block creep parameter degradation equation determining unit is used for inverting a creep constant in a block creep parameter degradation equation in the improved Cvisc creep model of the second uniaxial creep numerical model according to the rock creep curve by using an iterative trial and error method so as to enable the second uniaxial creep numerical model to be matched with the rock creep curve to obtain a reasonable block creep parameter degradation equation.
As an optional implementation manner, the module for determining a tunnel discrete element numerical simulation model specifically includes:
and the initial simulation model building unit is used for building an initial simulation model with the contact surface parameters as the reasonable contact surface parameter values, the block parameters as the reasonable block parameter values, the block creep parameters as the reasonable block creep parameter values and the degradation equations as the reasonable block creep parameter degradation equations according to the occurrence conditions by using UDEC discrete element simulation software.
And the roadway discrete element numerical simulation model determining unit is used for simulating excavation of the initial simulation model and inverting the contact surface parameters, the block parameters and the block creep parameters of the initial simulation model by adopting an iterative trial and error method so as to enable the initial simulation model to be matched with a curve of the deformation of the roadway surrounding rock to be simulated along with time to obtain the roadway discrete element numerical simulation model.
As an optional implementation manner, the instability range determining module specifically includes:
and the rock creep damage determining unit is used for determining the rock creep damage of each grid according to the accumulated length of the tension fracture and the accumulated length of the shear fracture of each grid.
And the instability range determining unit is used for determining the range of the creep instability of the surrounding rock of the roadway to be simulated according to the rock creep damage of each grid and the critical creep damage value of each grid.
As an optional implementation manner, the discrete element system for simulating creep instability of the roadway surrounding rock further includes:
and the third uniaxial creep numerical model building module is used for building a third uniaxial creep numerical model according to the contact surface parameter value, the block creep parameter value and the block creep parameter degradation equation of the roadway discrete element numerical simulation model.
And the critical creep damage value determining module is used for adopting a grading loading mode, carrying out uniaxial creep numerical simulation according to the third uniaxial creep numerical model, and taking the critical creep damage value when the test piece generates accelerated creep in the uniaxial creep numerical simulation process as the critical creep damage value.
The embodiment of the invention also provides a more specific process for processing by adopting the method, as shown in fig. 10, the method comprises six steps of roadway surrounding rock geomechanical test, rock creep parameter calibration, block creep degradation equation inversion, construction of a roadway discrete element numerical simulation model, establishment of rock creep instability criterion and roadway surrounding rock creep instability prediction, and the specific process is as follows:
engineering background: a certain mine owner adopts a 3# coal seam, and a No. 33 working face is positioned in the 3# coal seam underground. The average buried depth of the No. 3 coal seam is 350m, the thickness is 4.50 m-6.30 m, and the average thickness is 5.90 m; the dip angle of the coal seam is 1-9 degrees, the average dip angle is 5 degrees, and the coal seam is a nearly horizontal coal seam. The thickness of the direct roof is 1.4-3.0 m, the average thickness is 2.0m, and the lithology is mostly grey white siltstone. The basic top is sandy mudstone with relatively developed bedding, the thickness is 2-10 m, and the average thickness is 5.0 m. The direct bottom was sandy mudstone with an average thickness of 4.0 m. The No. 33 air inlet crossheading serves the air inlet task of the working face, and simultaneously serves as an auxiliary return air crossheading of the next working face, and belongs to a secondary multiplexing roadway.
Step S1: and (5) performing geomechanical test on the surrounding rock of the roadway.
Step S1.1: the method is characterized in that 33 air inlet crossroads are taken as research objects, the net height of a roadway is 2.6m, the net width of the roadway is 4.2m, the roadway is tunneled along the bottom plate of the coal seam, the average buried depth of the coal seam is 350m, the roadway is located in the northeast part and is a mining area large roadway, the southeast part is a 3201 working face, the southwest part is a well field boundary, the northwest part is an unexplored area, and the occurrence condition of rock strata in the roadway triple width range is shown in table 1.
TABLE 1 rock stratum occurrence table in roadway triple width range
Figure BDA0003520002660000151
Step S1.2: the physical and mechanical parameters of the rock stratum within the range of three times of the width of the roadway obtained by indoor experiment measurement comprise: the stress-strain curve in the rock uniaxial compression test is shown in fig. 2, the stress-strain curve in the rock brazilian splitting test is shown in fig. 3, and the rock creep curve (rock uniaxial creep test time-strain curve) is shown in fig. 4.
Step S1.3: and during the tunneling, a surface displacement measuring station is arranged every 50m from the beginning of the tunneling, and the relative deformation of the tunnel is monitored by using a measuring tape or a measuring rod.
Step S2: and calibrating the rock creep parameters.
Step S2.1: the method comprises the following steps of establishing a uniaxial compression numerical model with the diameter of 50mm and the height of 100mm and a Brazilian split numerical model with the diameter of 50mm by using UDEC discrete element simulation software, wherein the model block adopts a triangular block generated by software with a Trigon algorithm, the maximum side length of the triangular block is not more than 5mm, block units and contact surfaces adopt Mohr-Coulomb models, and block parameters are as follows: bulk modulus K1.2 e9Pa, shear modulus G0.78 e9Pa, internal friction angle θZ30 ° cohesion CZ6.3e6Pa and tensile strength Tz4.4e6Pa, contact surface parameters: normal phase stiffness kn2.56e11Pa, shear stiffness ks1.02e11Pa, contact surface internal friction angle thetaj30 ° contact surface cohesion Cj3.2e6Pa and contact surface tensile strength Tj1.2e6Pa, compared with the numerical model through laboratory experiments of uniaxial compression and Brazilian splitting, as shown in figures 2 and 3, the error of the rock elastic modulus and the compressive strength is less than 10%, which indicates that the determined block parameters and the contact surface parameters are reasonable.
Step S2.2: establishing a first uniaxial creep numerical model with the diameter of 50mm and the height of 100mm, wherein the shape and the size of the model block are the same as those in the step S2.1, the block unit adopts a Cvisc creep model carried by software, and the block creep parameters are as follows: maxwell shear modulus Gm5.97e8Pa, Maxwell viscosity coefficient etam2.9e13 Kelvin shear modulus Gk0.78e9Pa, Kelvin viscosity coefficient etak1.0e3, internal friction angle θz30 ° cohesion CZ6.3e6Pa and tensile strength Tz4.4e6Pa, the contact surface model and parameters are the same as those in step S2.1, and through comparison of a single-axis creep indoor experiment with a numerical model, as shown in fig. 4, the initial creep stage and the constant-speed creep stage of numerical simulation are better matched with the results of the indoor experiment, and the initial creep stage and the constant-speed creep stage of the rock can be better simulated by adopting the software-carried Cvisc creep model, and the creep damage process of the rock is not considered by the Cvisc creep modelNamely, the process that the mechanical parameters of the rock are continuously deteriorated along with time under the action of constant load, and the accelerated creep stage cannot be realized.
Step S3: and inverting a creep degradation equation. Establishing a second uniaxial creep numerical model with the diameter of 50mm and the height of 100mm, assigning parameters to contact surface parameters and block creep parameters calibrated in the step S2, embedding a customized initial block creep parameter degradation equation into a main program, and comparing the numerical model with a rock creep curve obtained in the step S1.2, wherein as can be seen from a figure 4, the initial creep, constant-speed creep and accelerated creep stages of the rock are reproduced through numerical simulation, and as can be seen from a figure 5, the method can also realize micro-crack expansion in the creep process, and the method is roughly divided into three stages: the method is characterized in that the method comprises the following steps of slow expansion in an initial creep stage, uniform expansion in a constant-speed creep stage and rapid expansion in an accelerated creep stage, when microcracks are continuously expanded and communicated, macroscopic deformation failure behaviors, namely rupture instability, are formed, and a large number of indoor uniaxial creep acoustic emission experiments also verify the point.
Creep parameter initial degradation equation in step S3:
Figure BDA0003520002660000171
wherein t is the life of the test piece; t is t0For short-term intensity-time, t is determined after inversion0＝0.04s；Cz(t) block cohesion at creep time t; sigmacdDetermining σ after inversion for creep damage thresholdcd＝6.72MPa；σ1Is the maximum principal stress to which the block is actually subjected; k is a creep constant, and k is determined to be 0.05 after inversion.
Step S4: and constructing a tunnel discrete element numerical simulation model.
Step S4.1: the occurrence conditions of the surrounding rocks of the roadway obtained according to the step S1.1 comprise the buried depth of the roadway, the mining conditions around the roadway and the rock inclination angle, the thickness, the lithology and the bedding structure within the triple width range of the roadway, a numerical simulation geometric model of the roadway is established as shown in figure 6, and the numerical simulation model has the following dimensions: the x direction is 250m, the y direction is 50m, and the side length of the surrounding rock of the roadway is not more than 0.2mThe angular block is refined, the vertical stress of the upper boundary of the model is 350m according to the depth and 25kN/m of volume weight3Considering that the pressure is 8.75MPa, initial parameters are given to the respective formation creep parameters determined in step S2, and initial balance of the model is performed.
Step S4.2: embedding the creep parameter degradation equation obtained in the step S3 into a main program of the numerical model, and adjusting creep parameters by adopting a trial-and-error iteration method to enable the numerical model to be matched with the evolution rule of the roadway surrounding rock deformation in the step S1.3 along with time, so as to obtain the creep parameters matched with the actual engineering.
Step S4.3: and step 4.2, re-parametrizing the model in the step 4.1 by the creep parameters adjusted in the step 4.2, dispersing the surrounding rock of the roadway to be researched into regular grids, carrying out unique identification marking on each grid, and marking unique identification data at each grid for later use as shown in fig. 7.
Step S5: and establishing a criterion of creep instability of the rock mass.
Step 5.1: and (3) establishing a third uniaxial creep numerical model with the diameter of 2m and the height of 4m, wherein the shape and the size of the model block are the same as those in the step (S4.1), the creep parameters adopt the parameters determined in the step (4.2), and the creep parameter degradation equation in the step (3) is embedded into the main program of the numerical model through a Fish language.
Step 5.2: the model adopts a grading loading mode, and the uniaxial compressive strength sigma of the test piececAnd (2) sequentially loading 8.5, 9.5, 10.5, 11.5 and 12.5MPa on the same test piece, wherein each stress level is loaded for 2h until the test piece is subjected to accelerated creep failure, and counting the fracture evolution conditions in the uniaxial creep simulation process by using a Fish language, wherein the fracture evolution conditions comprise the number of tension fractures, the number of shear fractures, the length of the tension fractures and the change condition of the length of the shear fractures along with time.
Step 5.3: the rock creep damage (Di) is represented by the microcrack development density in the creep process, and the critical damage D when the test piece undergoes accelerated creep in the process is simulated by a uniaxial creep numerical valuemin59.5 percent is used as the criterion of the rock mass creep instability.
Step S6: and predicting creep instability of the surrounding rock of the roadway.
Step 6.1: according to the mine actual situation collected in the step S1.1, simulating excavation is carried out on the roadway discrete element numerical simulation model subjected to discrete gridding processing in the step S4.3, and the spatial-temporal evolution rule of tension cracks and shear cracks in each grid under the roadway creep condition is counted through a Fish language;
step S6.2: substituting the creep tension crack and the shear crack conditions monitored in the step S6.1 into a formula
Figure BDA0003520002660000181
Calculating to obtain rock creep damage D in each gridiAs shown in fig. 8, the rock was damaged by creep DiCriterion D of creep instabilityminPerforming comparison, if Di>DminCreep failure occurs to the rock mass in the grid, and the rock mass is stable, so that the instability time and the failure range of the surrounding rock of the roadway are determined as shown in fig. 9.
The invention has the beneficial effects that:
1. the method is based on UDEC discrete element simulation software, simulates the initial creep stage, the constant-speed creep stage and the accelerated creep stage of the rock, realizes the micro-crack expansion in the rock creep process, realizes the disclosure of the creep instability process and mechanism of the surrounding rock of the roadway from a microscopic view, can quantitatively predict the creep instability time and the damage range of the surrounding rock of the roadway by establishing a criterion of the creep instability of the rock mass, and provides a theoretical basis for the creep control of the high-ground-stress soft rock roadway. The method is particularly suitable for determining the creep damage degree of the surrounding rock in geotechnical engineering, coal mine underground and tunnel engineering.
2. The initial creep stage, the constant-speed creep stage and the accelerated creep stage of the rock can be obtained through the method, the creep instability process and mechanism of the surrounding rock of the roadway are revealed from the micro-crack expansion angle, and a theoretical basis is provided for roadway support design.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.

Claims (10)

1. A discrete element method for simulating creep instability of roadway surrounding rock is characterized by comprising the following steps:
acquiring occurrence conditions of surrounding rocks of a roadway to be simulated, physical and mechanical parameters of a rock stratum within a set range of the roadway to be simulated and a curve of deformation of the surrounding rocks of the roadway to be simulated along with time; the occurrence condition includes: the size of the roadway, the burial depth, the excavation condition around the roadway and rock mass parameters within a set range; the rock mass parameters include: the dip angle, thickness, lithology and bedding structure of the rock mass; the physical-mechanical parameters include: stress-strain curves of uniaxial pressure tests, stress-strain curves of Brazilian splitting tests and creep curves of rocks;
establishing a compression splitting model by using UDEC discrete element simulation software, and inverting the contact parameters and the block parameters of the compression splitting model according to the uniaxial pressure test stress-strain curve and the Brazilian splitting test stress-strain curve to obtain reasonable contact surface parameter values and reasonable block parameter values; the compression splitting model comprises a single-axis compression numerical model and a Brazilian splitting numerical model;
establishing a first uniaxial creep numerical model with a block unit being a Cvisc creep model by using UDEC discrete element simulation software according to the reasonable block parameter values and the reasonable contact surface parameter values, and inverting the block creep parameters of the first uniaxial creep numerical model according to the rock creep curve to obtain reasonable block creep parameter values;
constructing a second uniaxial creep numerical model of a block unit as an improved Cvisc creep model by using UDEC discrete element simulation software according to the reasonable contact surface parameter value and the reasonable block creep parameter value, and inverting a block creep parameter degradation equation of the second uniaxial creep numerical model according to the rock creep curve to obtain a reasonable block creep parameter degradation equation; the block unit of the second uniaxial creep numerical model is an improved Cvisc creep model; the improved Cvisc creep model is a Cvisc creep model of which the degradation equation is a block creep parameter degradation equation;
constructing a tunnel discrete element numerical simulation model according to the curve of the deformation of the tunnel surrounding rock to be simulated along with the change of time, the occurrence condition and the reasonable block creep parameter degradation equation, and performing grid division on the tunnel discrete element numerical simulation model by adopting a discrete method to obtain a tunnel discrete element numerical simulation model subjected to discrete grid processing;
according to occurrence conditions of the surrounding rocks of the roadway to be simulated, physical and mechanical parameters of rock strata in a set range of the roadway to be simulated and a curve of deformation of the surrounding rocks of the roadway to be simulated along with time, simulating and excavating the discrete element numerical simulation model of the roadway subjected to discrete gridding treatment to obtain the length of an accumulated tensioning fracture and the length of an accumulated shearing fracture of each grid; the accumulated length of the tension fracture is the sum of the lengths of all the tension fractures in the grid; the accumulated shearing fracture length is the sum of all the shearing fracture lengths in the grid;
determining the creep instability range of the surrounding rock of the roadway to be simulated according to the accumulated length of the tension fracture, the accumulated length of the shear fracture and the critical creep damage value of each grid;
and determining the creep instability range of the surrounding rock of the roadway to be simulated according to the rock creep damage and the critical creep damage value of each grid.
2. The discrete element method for simulating creep instability of roadway surrounding rock according to claim 1, wherein the method for establishing the compressive splitting model by using the UDEC discrete element simulation software and inverting the contact parameters and the block parameters of the compressive splitting model according to the uniaxial pressure test stress-strain curve and the brazilian splitting test stress-strain curve to obtain reasonable contact surface parameter values and reasonable block parameter values specifically comprises:
constructing a single-axis compression numerical model and a Brazilian split numerical model by using UDEC discrete element simulation software;
and inverting the block parameters and the contact surface parameters of the uniaxial compression numerical model according to the uniaxial pressure test stress-strain curve by using an iterative trial and error method so as to enable the uniaxial compression numerical model to be matched with the uniaxial pressure test stress-strain curve, and inverting the block parameters and the contact surface parameters of the Brazilian splitting numerical model according to the Brazilian splitting test stress-strain curve so as to enable the Brazilian splitting numerical model to be matched with the Brazilian splitting test stress-strain curve, so as to obtain reasonable contact surface parameter values and reasonable block parameter values.
3. The discrete element method for simulating roadway surrounding rock creep instability according to claim 1, wherein the establishing a first uniaxial creep numerical model with a block unit being a Cvisc creep model by using UDEC discrete element simulation software according to the reasonable block parameter values and the reasonable contact surface parameter values and inverting the block creep parameters of the first uniaxial creep numerical model according to the rock creep curve to obtain the reasonable block creep parameter values specifically comprises:
establishing a first uniaxial creep numerical model with a block unit being a Cvisc creep model, a block parameter being a reasonable block parameter value and a contact surface parameter being a reasonable contact surface parameter value by using UDEC discrete element simulation software;
and inverting the block creep parameters of the first uniaxial creep numerical model according to the rock creep curve by using an iterative trial and error method so as to enable the first uniaxial creep numerical model to be matched with the rock creep curve to obtain reasonable block creep parameter values.
4. The discrete element method for simulating roadway surrounding rock creep instability according to claim 1, wherein the constructing a second uniaxial creep numerical model of a block unit, which is an improved Cvisc creep model, by using UDEC discrete element simulation software according to the reasonable contact surface parameter value and the reasonable block creep parameter value and inverting a block creep parameter degradation equation of the second uniaxial creep numerical model according to the rock creep curve to obtain a reasonable block creep parameter degradation equation specifically comprises:
establishing a second uniaxial creep numerical model with a block unit as an improved Cvisc creep model, a contact surface parameter as the reasonable contact surface parameter value and a block creep parameter as the reasonable block creep parameter value by using UDEC discrete element simulation software;
and inverting the creep constant in the block creep parameter degradation equation in the improved Cvisc creep model of the second uniaxial creep numerical model according to the rock creep curve by using an iterative trial and error method so as to enable the second uniaxial creep numerical model to be matched with the rock creep curve to obtain a reasonable block creep parameter degradation equation.
5. The discrete element method for simulating creep instability of roadway surrounding rocks according to claim 1, wherein the constructing of the roadway discrete element numerical simulation model according to the curve of the deformation of the roadway surrounding rocks to be simulated over time, the occurrence condition and the reasonable block creep parameter degradation equation specifically comprises:
utilizing UDEC discrete element simulation software to construct an initial simulation model with contact surface parameters as the reasonable contact surface parameter values, block parameters as the reasonable block parameter values, block creep parameters as the reasonable block creep parameter values and a degradation equation as the reasonable block creep parameter degradation equation according to the occurrence conditions;
and simulating excavation is carried out on the initial simulation model, and contact surface parameters, block parameters and block creep parameters of the initial simulation model are inverted by adopting an iterative trial and error method so that the initial simulation model is matched with a curve of the deformation of the surrounding rock of the roadway to be simulated along with the change of time to obtain a roadway discrete element numerical simulation model.
6. The discrete element method for simulating creep instability of roadway surrounding rock according to claim 1, wherein the determination process of the critical creep damage value specifically comprises:
constructing a third uniaxial creep numerical model according to the contact surface parameter value, the block creep parameter value and the block creep parameter degradation equation of the tunnel discrete element numerical simulation model;
and adopting a grading loading mode, carrying out uniaxial creep numerical simulation according to the third uniaxial creep numerical model, and taking a critical creep damage value when the test piece undergoes accelerated creep in the uniaxial creep numerical simulation process as the critical creep damage value.
7. The discrete element method for simulating roadway surrounding rock creep instability according to claim 1, wherein the determining of the range of the roadway surrounding rock creep instability to be simulated according to the accumulated length of the tension fracture, the accumulated length of the shear fracture and the critical creep damage value of each grid specifically comprises:
determining rock creep damage of each grid according to the accumulated length of the tension fracture and the accumulated length of the shear fracture of each grid;
and determining the creep instability range of the surrounding rock of the roadway to be simulated according to the rock creep damage of each grid and the critical creep damage value of each grid.
8. A discrete element system for simulating creep instability of roadway surrounding rock is characterized by comprising:
the acquisition module is used for acquiring occurrence conditions of the surrounding rocks of the roadway to be simulated, physical and mechanical parameters of rock strata in a set range of the roadway to be simulated and a curve of deformation of the surrounding rocks of the roadway to be simulated along with time; the occurrence condition includes: the size of the roadway, the burial depth, the excavation condition around the roadway and rock mass parameters within a set range; the rock mass parameters include: the dip angle, thickness, lithology and bedding structure of the rock mass; the physical-mechanical parameters include: stress-strain curves of uniaxial pressure tests, stress-strain curves of Brazilian splitting tests and creep curves of rocks;
the reasonable contact surface parameter value and reasonable block parameter value determining module is used for establishing a compression splitting model by using UDEC discrete element simulation software and inverting the contact parameters and the block parameters of the compression splitting model according to the uniaxial pressure test stress-strain curve and the Brazilian splitting test stress-strain curve to obtain a reasonable contact surface parameter value and a reasonable block parameter value; the compression splitting model comprises a single-axis compression numerical model and a Brazilian splitting numerical model;
the reasonable block creep parameter value determining module is used for establishing a first uniaxial creep numerical model with a block unit being a Cvisc creep model by using UDEC discrete element simulation software according to the reasonable block parameter value and the reasonable contact surface parameter value and inverting the block creep parameters of the first uniaxial creep numerical model according to the rock creep curve to obtain the reasonable block creep parameter value;
the reasonable block creep parameter degradation equation determining module is used for constructing a second single-axis creep numerical model of which a block unit is an improved Cvisc creep model by using UDEC discrete element simulation software according to the reasonable contact surface parameter value and the reasonable block creep parameter value and inverting the block creep parameter degradation equation of the second single-axis creep numerical model according to the rock creep curve to obtain a reasonable block creep parameter degradation equation; the block unit of the second uniaxial creep numerical model is an improved Cvisc creep model; the improved Cvisc creep model is a Cvisc creep model of which the degradation equation is a block creep parameter degradation equation;
the roadway discrete element numerical simulation model determining module is used for constructing a roadway discrete element numerical simulation model according to a curve of deformation of the roadway surrounding rock to be simulated along with time, the occurrence condition and the reasonable block creep parameter degradation equation and performing grid division on the roadway discrete element numerical simulation model by adopting a discrete method to obtain a discrete grid-processed roadway discrete element numerical simulation model;
the fracture length determining module is used for performing simulated excavation on the discrete element numerical simulation model of the roadway subjected to the discrete gridding treatment according to occurrence conditions of the surrounding rock of the roadway to be simulated, physical and mechanical parameters of rock strata in a set range of the roadway to be simulated and a curve of deformation of the surrounding rock of the roadway to be simulated along with time to obtain the accumulated length of the tensioned fracture and the accumulated length of the sheared fracture of each grid; the accumulated length of the tensioned fracture is the sum of the lengths of all the tensioned fractures in the grid; the accumulated shear fracture length is the sum of all shear fracture lengths in the grid;
and the instability range determining module is used for determining the range of the creep instability of the surrounding rock of the roadway to be simulated according to the accumulated length of the tension fracture, the accumulated length of the shear fracture and the critical creep damage value of each grid.
9. The discrete element system for simulating roadway surrounding rock creep instability according to claim 8, wherein the module for determining the reasonable contact surface parameter value and the reasonable block parameter value specifically comprises:
the single-axis compression numerical model and Brazilian splitting numerical model building unit is used for building a single-axis compression numerical model and a Brazilian splitting numerical model by using UDEC discrete element simulation software;
and the reasonable contact surface parameter value and reasonable block parameter value determining unit is used for inverting the block parameters and the contact surface parameters of the single-axis compression numerical model according to the single-axis pressure test stress-strain curve by using an iterative trial and error method so as to enable the single-axis compression numerical model to be matched with the single-axis pressure test stress-strain curve, and inverting the block parameters and the contact surface parameters of the Brazilian splitting numerical model according to the Brazilian splitting experiment stress-strain curve so as to enable the Brazilian splitting numerical model to be matched with the Brazilian splitting experiment stress-strain curve, so that reasonable contact surface parameter values and reasonable block parameter values are obtained.
10. The discrete element system for simulating roadway surrounding rock creep instability according to claim 8, wherein the reasonable block creep parameter value determination module specifically comprises:
the first uniaxial creep numerical model building unit is used for building a first uniaxial creep numerical model with a block unit being a Cvisc creep model, a block parameter being the reasonable block parameter value and a contact surface parameter being the reasonable contact surface parameter value by using UDEC discrete element simulation software;
and the reasonable block creep parameter value determining unit is used for inverting the block creep parameters of the first uniaxial creep numerical model according to the rock creep curve by using an iterative trial and error method so as to enable the first uniaxial creep numerical model to be matched with the rock creep curve to obtain the reasonable block creep parameter values.
CN202210179692.5A 2022-02-25 2022-02-25 Discrete element method and system for simulating creep instability of roadway surrounding rock Pending CN114547746A (en)

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CN115906525A (en) * 2022-12-29 2023-04-04 重庆大学 Method for determining mapping relation of mechanical parameters in process of numerically simulating rock stratum movement

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN115906525A (en) * 2022-12-29 2023-04-04 重庆大学 Method for determining mapping relation of mechanical parameters in process of numerically simulating rock stratum movement
CN115906525B (en) * 2022-12-29 2023-07-25 重庆大学 Method for determining mechanical parameter mapping relation in numerical simulation rock stratum movement process

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