| With the increasing of coal mining depth,the influences of high stress and strong disturbance on the roadway surrounding rock within deep soft rock result in its serious deformation and increase the difficulty of engineering support.Both the high development of primary joints and secondary fractures in deep soft rock and the different arrangement of mineral particles will cause the changes of rock mechanical characteristics and its parameters,which makes it difficult to accurately evaluate the mechanical parameters of rock mass.Reasonably and accurately inverting the mechanical parameters of deep soft rock,mastering its damage characteristics and clarifying the deformation and instability mechanism and the evolution law of roadway surrounding rock caused by the mining under high stress will provide a theoretical basis for putting forward a safe,reliable,economical and reasonable support program.Taking 11503 working face of coal No.11 mining area 5 in Zhujixi mine as the engineering background,this paper applies Rocscience series numerical simulation program and proposes a numerical modeling method of heterogeneous material based on triangulation joint network.And combined with the research methods of theoretical analysis and field monitoring and so on,this paper also reveals the heterogeneous characteristics of deep soft rock,expounds the deformation mechanism and characteristics of the roadway surrounding rock,and analyzes its characteristics of plastic zone and the degree of failure and deformation under high ground stress.The research results provide a certain reference value for the effective control of roadway support on the stability of surrounding rock under similar geological conditions.The research results are as follows:(1)The influences of triangulation joint density and the heterogeneity of materials on the macro mechanical properties of the uniaxial compression model are explored.By using the MATLAB programming,the triangulation mesh in RS2(Rock and Soil 2-dimensional analysis program)program is transformed into triangulation joint network readily.And the establishment of triangulation joint network in RS2 provides a method of parameter setting for adding other joint network types to the joint library and enriches the selection of joint network in RS2.It is found that the triangulation joint density is inversely proportional to the elastic modulus,while the uniaxial compressive strength tends to remain unchanged when the triangulation joint density reaches up to 900.The mechanical properties and failure characteristics of the heterogeneous uniaxial compression model are probed.According to the Weibull distribution model,the uniaxial compression model of heterogeneous material in RS2 is compiled based on MATLAB platform.And the effects of different material quantities and homogeneities on the uniaxial compression model are studied.It is found that the increase of the number of materials has little effect on the strength characteristics of the model,while the proportion of the main material has a great effect on it.(2)The accuracy of the uniaxial compression model of heterogeneous material with triangulation joint network for the simulation of soft rock samples is verified.Through the investigation of 11503 working face conditions of coal No.11 mining area 5 in Zhujixi mine,the roadway control condition under the original support is monitored on site.Based on RS2 finite element numerical simulation program,MATLAB program and the Weibull distribution,the uniaxial compression model of heterogeneous material with triangulation joint network is established and the mechanical properties of roadway surrounding rock are calibrated.The errors between the calibration results of roof silt,side coal rock and floor mudstone in the uniaxial compression model and the laboratory test results are 5.8%,13.1% and 2.2%respectively.The distribution of plastic zone and the joint failure characteristics of siltstone and that of coal rock in uniaxial compression numerical simulation are compared with those of laboratory rock samples,which verifies the reliability of the inversion experiment.The heterogeneous model with the triangulation joint network can well characterize the growth of fractures of rock samples and can provide a more accurate numerical simulation method for studying the mechanical properties of sedimentary rock.(3)The deformation mechanism of the roadway surrounding rock and its the failure range in deep soft rock are revealed.Based on the calculation theory of plastic zone radius in elasticplastic model and the field geological conditions,the height of plastic zone of roadway roof is obtained,that is 1.29 m.And it is found that the radius of plastic zone of roadway surrounding rock is inversely proportional to the support resistance and is directly proportional to the mechanical parameters of surrounding rock.Among them,the radius of plastic zone is highly sensitive to the cohesion force.The slip-line model of roadway floor is established,and the stress of each area is analyzed according to the “three zone" theory and slip-line theory to obtain the law of ultimate bearing capacity of roadway floor.Based on the elastic-plastic theory and slip-line theory,the amount of roadway floor heave is obtained.(4)The influences of mining-induced stress on the stress distribution of roadway surrounding rock and its deformation law under high stress environment are expounded.The in-situ stress measurement result shows that the 11503 working face of Zhujixi mine is a high vertical stress field.And the RS3(rock and soil 3-dimensional analysis program)finite element numerical model program is used to study the stress distribution and deformation law of roadway surrounding rock caused by the mining under the condition of high ground stress.The result shows that the roadway is subjected to the lead abutment pressure of the working face within 10 m away from it.When the distance is within 15 m before and after the working face,the stability of the roadway surrounding rock is affected by the mining-induced stress.(5)The failure types and distribution characteristics of roadway surrounding rock and its deformation law under high stress are clarified.According to the stratum conditions and support design of 11503 haulage gate in Zhujixi mine,the roadway model of heterogeneous material with triangulation joint network is established based on RS2 finite element numerical simulation program.And the deformation of roadway surrounding rock obtained through adjusting the joint density and the material homogeneity is in accordance with the field measurement result.Then,the reasonable improved support scheme is proposed to effectively control its deformation and the growth of plastic zone based on the deformation characteristics of roadway surrounding rock.The roof subsidence and its maximum depth of plastic zone are reduced by 26.9% and 59.1% respectively,the floor heave and its maximum depth of plastic zone are reduced by 28.6% and 27.3% respectively,and the convergence of two sides and its maximum depth of plastic zone are reduced by 25.4% and 43.3% respectively. |
PDF Full Text Request