Study On Deformation Mechanism And Simulation Method Of Full Deformation Process For Brittle Rock

As a typically brittle material,rock constitutive relation is an essential problem in the research of deformation mechanical properties,and it is also an important guarantee to ensure the safety of large-scale engineering construction.Based on the analysis of rock deformation mechanics characteristics and its mechanism,considering the effect of rock voids variation and confining pressure,continuous material mechanics theory,porous media theory and statistical mesoscopic damage theory have been integrated to reasonably rock damage constitutive model which could simulate the full process of rock deformation and failure and could explain the deformation mechanics for the shortage of existing constitutive relations of rock,and then it is applied in rock engineering.Firstly,deformation properties of rock under the influence of voids change is one of the important research contents of geotechnical engineering.Based on the depth analysis of rock with porous media characteristics,beginning from microscopic analysis of porous media rock,the relationships between micro-stress and macro-stress,micro-deformation and macro-deformation are established through discussing rock deformation affected by voids change,so as to reveal the deformation mechanics law of rock due to voids change.Based on this,a new rock damage model considering the effect of voids change is established by using Lemaitre strain equivalence theory.Then,the statistical damage theory is introduced to establish the statistical damage constitutive model of rock considering the influence of damage threshold and the methods of determining the model parameters are given.The model could reflect the nonlinear deformation characteristics of rock due to voids change,which indicates that voids are an important factor affecting the deformation properties of rock.Secondly,the whole deformation and failure process simulation of brittle rock is an important branch of rock mechanics research.As the macroscopic deformation mechanics properties of rock are closely related to the growth and development of its internal micro-cracks,rock under load is considered to be composed of voids part material and skeleton part material considering the limitations and shortcomings of existing rock damage model.The macroscopic deformation analysis model of rock is established by combining the macroscopic and microscopic analysis methods,and the statistical damage theory is introduced to study the whole deformation and failure process simulation of rock.Then,the statistical damage constitutive model of rock is established and the methods of determining model parameters are given.This model could complete deformation deformation stage characteristics of rock,and improve the research content of rock constitutive model.Thirdly,to further improve the research process of rock deformation simulation,based on the material mechanics theory and the statistical meso-damage theory,the deformation mechanics analysis methods of rock components,ie,the voids part material and skeleton part material,have been established considering the existing constitutive model of rock,which could not reflect the deformation rule of the rock compositions and the effect of confining pressure on the initial macroscopic nonlinear deformation.The analysis methods are combined with the rock macroscopic deformation analysis model to establish the statistical damage constitutive model of rock.It is shown that the model could reflect the deformation rule of rock compositions and the macro-micro deformation relationship of rock,and could explain the concave degree of the initial macroscopic deformation is decreasing with the increase of confining pressure through example analysis.Finally,micro-crack closure stress is one of the important thresholds for studying the deformation mechanics properties of rock.Aimed at the limitations and shortcomings of existing micro-crack closure stress determination method,considering the macroscopic deformation mechanics properties of rock are closely related to the micro-crack closure deformation,the end of micro-crack closure deformation means that the rock deformation is transferred from the initial compaction stage to the linear elastic deformation stage,and the axial stress corresponding to the turning point is the micro-crack closure stress.Based on this,a new method of determining the micro-crack closure stress is proposed by deeply analyzing the statistical damage constitutive model in this paper.This model could not avoid subjective interference,but also have the characteristics of theoretical significance and easy operation.It is shown that the method has strong rationality and superiority through engineering example analysis.