Experimental study on unloading damage and permeability of dolomite based on nuclear magnetic resonance technique
LI Kegang1，2，YANG Baowei1，QIN Qingci1
(1. Faculty of Land Resource Engineering，Kunming University of Science and Technology，Kunming，Yunnan 650093，China；
2. Yunnan Key Laboratory of Sino-German Blue Mining and Utilization of Special Underground Space，
Kunming，Yunnan 650093，China)
Abstract：Deep rock mass engineering is facing complex engineering geological problems such as increasing unloading effect of excavation，growing joints and fissures，and strong groundwater environment. In order to grasp the influence law of excavation unloading on mechanical properties and permeability characteristics of rock mass，take the Dolomite as the experiment object，the triaxial unloading tests under different unloading confining pressure ratio ??(100%，90%，60%，30%，0) and pore water pressure P(0，5，10 MPa) were conducted through GCTS rock mechanics test system，and the rock porosity before and after the test was measured by nuclear magnetic resonance(NMR) technology. The test results show that the unloading deformation laws of rock under different pore water pressures are basically the same，which all have four stages：smooth transition，uniform growth，fast growth and rapid expansion，and the strain limit of rock is almost equal. Correspondingly，the rock permeability during unloading process also has four stages：slow permeability，stable permeability，accelerated permeability and sudden-increase permeability. The existence of pore water pressure accelerates the generation and expansion of cracks in rocks. The larger the pore water pressure is，the larger the porosity is，and the larger the permeability is，there are a significant positive correlation among porosity，deformation and permeability. However，unloading confining pressure ratio has more influence on rock deformation than pore water pressure，when ??＞60%，the number and penetration of cracks in rock will increase sharply，it shows that strong excavation unloading can lead to the formation of macro-failure surface of rock mass and then increase the permeability，which is not conducive to the construction safety of underground engineering in rich groundwater areas.
李克钢1，2，杨宝威1，秦庆词1. 基于核磁共振技术的白云岩卸荷损伤与渗透特性试验研究[J]. 岩石力学与工程学报, 2019, 38(S2): 3493-3502.
LI Kegang1，2，YANG Baowei1，QIN Qingci1. Experimental study on unloading damage and permeability of dolomite based on nuclear magnetic resonance technique. , 2019, 38(S2): 3493-3502.
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2019, Vol. 38 
