4.Study on the mechanical response and deterioration mechanism ofthe sandstone under loading after high-stress creep

Abstract:

To investigate the mechanical properties and deterioration mechanisms of surrounding rock under creep damage，thereby pro-viding theoretical support for the instability of repeatedly mined roadways caused by overlapping stress，uniaxial loading tests were con-ducted on sandstone after high-stress creep． Specimens were maintained at a constant stress of 40． 76 MPa for 3，6，and 9 hours re-spectively before failure loading． Ｒesults demonstrate: After 3，6，and 9 hours of sustained loading，peak strength decreased by8. 59% ，10． 13% ，and 11． 91% respectively，while elastic modulus declined by 22． 90% ，24． 20% ，and 27． 60% ，indicating pro-gressive deterioration of rock mechanical performance． The proportion of dissipated energy increased from 0． 235 to 0． 350，tensilecrack percentage rose from 60． 80% to 65． 80% ，and strength deterioration rate escalated from 8． 59% to 11． 91% ，collectively dem-onstrating that energy dissipation and tensile crack proportion effectively characterize damage accumulation． Field practice suggests thatreducing the interval between primary and secondary mining operations can effectively mitigate the risk of surrounding rock instability．

Keywords: high stress creep; creep damage; mechanical response; damage mechanism