| The construction of underground engineering is more and more extended to the deep,and the dynamic disasters represented by rock burst and rock burst are gradually emerging and becoming more and more serious.The combined reinforcement of anchor and grouting is a common support method for the prevention and control of dynamic disasters of fractured surrounding rock in deep underground engineering.However,the design of anchor and grouting anti-shock support is mainly based on experience construction,and the basic research of dynamic and static characteristics of fractured surrounding rock reinforced by anchor and grouting needs to be further improved.In this paper,physical test,numerical calculation and theoretical analysis are used to study the dynamic and static properties of the fractured rock mass reinforced by bolt-grouting.The main achievements of this paper are as follows:(1)The red sandstone with good homogeneity was selected,and the fractured rock mass with different dip angles,openings and lengths was artificially prepared.The bolt and grouting material were used to reinforce the fractured rock mass,and the uniaxial static load compression test was carried out.The test results show that the stress-strain curve and acoustic emission evolution curve of the sample can be divided into four stages.When the dip angle of the fracture increases,the uniaxial compressive strength and elastic modulus show fluctuating changes,and the direction and range of crack propagation on the failure surface change.When the fracture opening increases,the stress-strain curves are different in each stage,and the main mechanical parameters show a nonlinear trend.The number of cracks and the initiation mode on the failure surface are affected.(2)The triaxial compression test of fractured rock mass reinforced by anchor injection was carried out.The test results show that the peak strain decreases and the elastic modulus increases with the increase of fracture inclination angle.The crack initiation mode,extension range and number of cracks on the failure surface change under the influence of confining pressure and inclination angle.When the crack length and opening increase,the strength parameters of the specimen are weakened,but the deformation capacity increases.The number,distribution and expansion of cracks change under the influence of crack length and confining pressure.(3)One-dimensional dynamic test was carried out on the fractured rock mass reinforced by anchor and grouting.The test results show that the dynamic stress-strain curve is composed of four stages.The dynamic strength parameters have a good quantitative relationship with the inclination,opening and length,and the energy is greatly affected by the changes of various factors.When the grouting material changes,the main mechanical parameters of the fractured rock mass reinforced by anchor and grouting have obvious fluctuation changes.The dynamic failure degree,failure mode and crack initiation and propagation mode of the specimen are greatly affected by the inclination angle,opening degree and length.Under one-dimensional stress state,the variation laws of dynamic and static mechanical parameters are different,and the differences are large.(4)The three-dimensional dynamic test of fractured rock mass reinforced by anchor injection was carried out.The experimental results show that the dynamic stressstrain curves under different confining pressures and impact velocities are basically similar.The dynamic strength characteristics increase with the increase of confining pressure and impact velocity.The dynamic deformation characteristics decrease with the increase of confining pressure and increase with the increase of impact velocity.The main energy parameters decrease with the increase of confining pressure and increase with the increase of impact velocity.The failure mode and degree of fractured rock samples reinforced by anchor-grouting change with confining pressure and impact velocity.The difference between the mechanical parameters of three-dimensional dynamic and static load is obvious,and the stress state has an obvious influence on the impact characteristics of the sample.(5)Combined with the physical test results,the parameters of HJC dynamic constitutive model in LS-DYNA numerical software are modified,and the numerical calculation model consistent with the real anchor grouting reinforcement of prefabricated fractured red sandstone is established,and the numerical simulation research is carried out.The results show that the damage evolution process of prefabricated fractured red sandstone samples reinforced by anchor injection can be divided into four stages.Under one-dimensional and three-dimensional stress conditions,the overall impact resistance of fractured rock mass reinforced by anchor injection increases.The change of rock strength and bolt preload has a certain influence on the DIF value and energy absorption efficiency of rock samples.(6)Based on the results of physical test and numerical calculation,the dynamic Mohr-Coulomb and Hoek-Brown strength criteria of the bolt-grouting reinforced fractured rock mass were established on the basis of the modification of static MohrCoulomb and Hoek-Brown strength criteria.The results showed that the dynamic MohrCoulomb strength criterion was more suitable for the variation of triaxial strength at different strain rates,while the dynamic Hoek-Brown strength criterion was more suitable for the variation of triaxial strength at low strain rates,and the deviation was larger at high strain rates.The unified model of damage evolution is introduced,and the damage evolution under various load modes is described by this model.The changes of elastic modulus,brittleness index,brittle-ductile turning point and residual strength with different factors are obtained.This paper has 102 pictures,20 tables and 163 references. |
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