Sensitive neighborhood range of red sandstone under rheological disturbance condition

WANG Bo; TIAN Zhiyin; MA Shiji; REN Yongzheng; GAO Xiangyu; SUN Hongxu; HUANG Wanpeng; WANG Jun

doi:10.13225/j.cnki.jccs.2023.1609

Abstract：Under the action of disturbance load,the rheological rock mass in the"sensitive neighborhood"is prone to de-formation and failure.In order to study the influence of confining pressure on the range of disturbance"sensitive neighbor-hood",the red sandstone is taken as the research object,and the RRTS-Ⅳ rock rheological disturbance effect test system is used to carry out the disturbance impact test on the rheological rock mass under different confining pressures and axial pressures.The change rule of axial disturbance strain with axial pressure is observed,and the change of"sensitive neigh-borhood"under different confining pressure conditions is analyzed.The nuclear magnetic resonance analysis system is used to compare and analyze the rheological rock mass under different confining pressure conditions.The variation of porosity,T2 spectrum curve,spectral peak area and pore size distribution of rheological rock mass in sensitive and non-sensitive areas before and after disturbance.The results show that:When the confining pressure remains constant,the axi-al disturbance strain value shows a nonlinear trend of decreasing first and then increasing with the increase of axial pres-sure,and when the axial pressure applied to the rheological rock mass is closer to the long-term strength under the confin-ing pressure condition,the axial disturbance strain value generated by the dynamic disturbance is larger.There is a sensit-ive transition point(σm)in rheological rock mass under different confining pressure conditions,which determines the sens-itivity of rheological rock mass to dynamic disturbance.When σ1＜σm,the sensitivity of rheological rock mass decreases with the increase of axial pressure.When σ1 ≥ σm,the sensitivity of rheological rock mass increases with the increase of axial pressure.According to the sensitivity of rheological rock mass,three sensitive areas are divided:R1 non-sensitive area,R2 sensitive area and R3 creep failure area.It is determined that the range of sensitive neighborhood(Δσ)should be between long-term strength(σp)and sensitive transition point strength(σm).By calculating the change of"sensitive do-main ratio"under different confining pressure conditions,it is found that the inhibition of confining pressure on crack propagation in rock mass and the increase of damage threshold do not increase nonlinearly,but show a trend of decelera-tion growth.When the rheological rock mass is in the sensitive area,the external disturbance impact will lead to the gener-ation of new micro-pores inside the rock mass,and under the action of disturbance impact,the micro-pores inside the rock mass will gradually penetrate and expand into new large-aperture pores,which makes the number of pores inside the rock mass increase.At the same time,the influence of external disturbance impact on the development of pores inside the rock mass will gradually decrease with the increase of confining pressure.When the rheological rock mass is in the non-sensit-ive area,the external disturbance impact will make the large pores in the rock mass close,resulting in a decrease in the total number of pores in the rock mass.At the same time,the formation rate of new micro pores and the closure rate of large pores in the rock mass will gradually decrease with the increase of confining pressure.The research results have im-portant practical significance for enriching the theory of rheological disturbance effect of triaxial rock.