Reloading experimental research on the mechanical properties of limestone considering pre-peak unloading damage#br#
DENG Huafeng1，CHEN Tiannan1，LI Jianlin1，XIAO Yao1，ZHANG Hengbin1，LI Tao1，CHEN Xingzhou2
(1. Key Laboratory of Geological Hazards on Three Gorges Reservoir Area，Ministry of Education，China Three Gorges University，Yichang，Hubei 443002，China；2. College of Architecture and Civil Engineering，Xi'an University of Science and
Technology，Xi?an，Shaanxi 710054，China)
Abstract：The excavation unloading effect results in the unloading damage of rock，and the mechanical properties of unloading damage rock under load directly influence the stability and safety of engineering rock. Based on this，the unloading damage test of limestone and the reloading test of damaged rock samples are designed and carried out. The results show that：(1) The initial unloading damage has a significant impact on the deformation and bearing capacity of rock sample. When the unloading amount is greater than 80%，the compressive strength，deformation modulus and strain confining compliance show a nonlinear mutation trend. (2) On the basis of the characteristics of rock transformation from stable failure to unstable failure in the process of loading and unloading，the proportion of dissipated energy is proposed to determine the critical damage state of rock sample during unloading，the proportion of dissipated energy is about 0.33 as the limit. When the proportion of dissipated energy is less than 0.33，the initial unloading damage has little influence on its reloading performance. However，when the proportion of dissipated energy is greater than 0.33，the initial unloading damage has significant effect on its reloading performance. (3) During the unloading，there is a negative correlation between the proportion of elastic energy and the proportion of dissipated energy，therefore in accordance with the correlation between the growth of dissipated energy during unloading and the damage development of rock samples，the ratio of dissipated energy during unloading and dissipated energy in unloading failure is proposed to represent the visual damage variable. (4) With the increase of unloading amount，the failure mode of damaged rock sample under reloading is gradually transitioned from typical shear failure to shear-tensile failure and tensile-shear failure. (5) Applying a lateral stress to the unloading damage rock sample can control the development of tension cracks to a certain extent，and thus improve the bearing capacity of rock sample.
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2023, Vol. 42 
