Study On Risk Analysis Method Of Goaf Collapse Considering Spatial Variability Of Parameters

Goaf collapse seriously restricts the safety of mine and has become an important factor affecting the economic development of mining area.How to comprehensively predict the risk of goaf collapse is a key problem in design and construction.The risk analysis method based on the reliability theory has certain advantages,which can quantitatively evaluate structural risk.The spatial variability of rock and soil parameters will directly affect the deformation and stability of surrounding rock in goaf.The risk analysis method of goaf collapse considering the spatial variability of parameters is established.It has theoretical and practical significance to study the influence of spatial variability of parameters on the risk of goaf collapse.At present,random field theory can describe the spatial variability of parameters.However,due to the lack of random field simulation tools,3D random field is not widely used in mine.Moreover,the random field can’t correspond to the actual project in the simulation and the boundary of strong and weak spatial variability is not clear.Therefore,the spatial variability of geotechnical parameters is analyzed by using 3D random field model.Based on the design and optimization of random field,the influence of the spatial variability of elastic modulus on the mechanical response of surrounding rock and the risk of goaf collapse is analyzed.Firstly,a simple and practical software for random field simulation and risk analysis is designed.On the basis of fully learning random field theory,the software of random field simulation and risk analysis is designed by using App Designer tool in MATLAB.A simple,convenient and practical random field simulation tool and a risk analysis tool based on reliability are provided to facilitate the application of random fields in engineering.Secondly,the ideas and methods of random field optimization simulation are proposed.Based on the background of actual engineering,a three-dimensional finite difference model is established.The parameters with large spatial variability and high sensitivity to mechanical response of surrounding rock are selected.The random field generated by K-L series expansion method is optimized by constraining the values of standard random variables in random field.The influence of the number of constraint points on the mechanical response of surrounding rock in goaf is discussed.In order to further express the effect of parameter random field optimization,the results of theoretical analysis and numerical simulation are compared.Thirdly,the influence of spatial variability of parameters on mechanical response of surrounding rock is studied.In the case of the same random variables in the 3D random field model,the influence of three directions(transverse,longitudinal and vertical)correlation distance on the deformation and failure of surrounding rock in goaf is studied.The calculation results of the model are compared with the deterministic results.Finally,the risk analysis method of goaf collapse considering the spatial variability of parameters is studied.The method of fuzzy probability density evolution is proposed to solve the reliability under the condition of parameter spatial variability.According to the analysis results of surrounding rock mechanical response,the influence of different correlation distance on the collapse risk of goaf is studied.By comparing the calculation results of random field model and random variable model,the boundary between the spatial variability of elastic modulus is found.The evaluation standard of the risk is established to judge the risk level of the project.