Study On Fracture Damage Mechanism And Creep Failure Law Of Rock Based On 3D Digital Core

As the shallow mineral resources tend to be exhausted,the acquisition of mineral resources will gradually enter the stage of deep mining.And into the deep mining of mineral resources,as a result of the "3 tall one disturbance" geological and construction environment lead to the organizational structure of the rock,the mechanical properties and engineering response change,leading to a deep geotechnical engineering disasters and there is a big difference with shallow geotechnical engineering disasters,in order to ensure the security of the mineral resources in the deep mining and reduce the cost of deep mining,It is urgent to study the fracture failure mechanism and creep failure law of deep rock.The deep rock in situ test experiment was carried out is still very difficult,and CT scan-digital core 3 d reconstruction,numerical simulation technology has become an emerging science research method in the field of geotechnical engineering,the technology is widely used in rock physics,micro-mesoscopic-macro mechanical properties and fracture mechanism of different scales,such as in the study.In this paper,the internal crack propagation and evolution of rock under load are taken as the main line,and the fracture damage mechanism of rock is deeply explored.Firstly,mechanical properties tests of sandstone under different loading conditions(triaxial compression test,Brazilian splitting test and triaxial rheological failure test)were carried out to explore the strength characteristics,deformation characteristics and failure law of rock.Secondly,through the real-time CT scanning test of rock compression failure process and SEM scanning test of rock failure fracture,the law of crack growth and evolution in rock was investigated.Then,based on the technology of CT scanning,digital core three-dimensional reconstruction and numerical simulation,the evolution law of crack growth,fracture damage mechanism and creep failure law of rock at the mesomacroscopic-engineering scales are deeply explored.The main research work can be summarized into the following five aspects:(1)The mechanical behavior and progressive failure law of rock were studied.Tests on uniaxial compression failure,Brazilian splitting failure,triaxial compression under different confining pressures and coupled percolation and stress triaxial compression were carried out.The progressive failure law of sandstone under different confining pressures is analyzed from the perspectives of mechanical behavior and energy evolution.The basic mechanical parameters of sandstone in ultra-deep mine are obtained to improve the understanding of sandstone damage medium and provide theoretical basis for numerical simulation.Based on the statistical damage theory,the sandstone damage constitutive model is established.Based on dissipative energy theory,the comprehensive evaluation index of rock brittleness is explored.(2)The law of internal crack propagation and fracture evolution of rock under external load is studied.Actis300-320/225 ct /DR high-resolution industrial CT real-time imaging system was used to scan the whole process of rock failure under uniaxial compression.MATLAB software was used to process the digital image of CT sections.MIMICS software was used to reconstruct the 3D digital core of CT sections.Based on the geometric characteristics of crack growth,a fractal model of crack growth was established.Fracture toughness is a key index to characterize the crack propagation ability.Based on the theory of energy dissipation and fracture mechanics,the equations of fracture initiation stress,stress intensity factor and fracture toughness were established considering the fractal characteristics.(3)The macroscopic mechanical properties and fracture characteristics of rock induced by the meso-pores inside the rock and the meso-damage mechanism of rock were studied.Two indexes,porosity and fractal dimension of pore spatial distribution,are used to quantitatively characterize pore structure.Based on the technology of micro CT scanning,digital core threedimensional reconstruction and numerical simulation,combined with the rock plastic damage constitutive model,numerical simulation research was carried out to explore the mesoscopic damage mechanism,macroscopic mechanical properties and fracture characteristics of rock under different pore structures.(4)The microscopic crack propagation and evolution mechanism of rock fracture was studied.SEM was used to scan the microscopic morphology characteristics of rock fracture samples under triaxial compression without confining pressure.Based on statistics and fracture mechanics theory,the microcrack propagation and evolution mechanism in rock was quantitatively characterized.(5)The GDSTAS type servo soft rock rheological test system is used to carry out the triaxial creep test on sandstone.The creep failure mechanism of rock is explored from the perspective of meso-crack growth,the relationship between meso-crack growth and long-term strength is determined,and the initiation and acceleration criterion of accelerated creep of rock under high stress state are determined.Finally,the creep constitutive model of rock considering meso-crack growth is established.There are 84 figures,24 tables and 183 references in this paper.