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| Experimental research of the influence of different unloading stress paths on permeability evolution of sandstone |
| WANG Rubin1，2，XU Bo2，XU Weiya1，2，WANG Wei1，2，LIN Zhinan2，ZHANG Jiuchang3 |
(1. Institute of Geotechnical Engineering，Hohai University，Nanjing，Jiangsu 210098，China；2. Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering，Hohai University，Nanjing，Jiangsu 210098，China；
3. Department of Civil Engineering，Yunnan Minzu University，Kunming，Yunnan 650504，China) |
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Abstract In order to study the influence of the initial confining pressure and the unloading rate on permeability evolution of sandstone during unloading process，triaxial unloading seepage tests were carried out under different high initial confining pressures(10，20，30 MPa) and different unloading rates(0.1，0.5，1.0，1.5 MPa/min). The results show that the sandstone occurs brittle failure and that the lateral deformation and the volume expansion increase significantly with increasing the initial confining pressure or the unloading rate. The permeability evolution is closely related to the unloading stress and strain characteristics. The permeability increases slowly at the elastic deformation stage，rapidly at the yield deformation stage and sharply at the stress dropping stage，and eventually decreases to a stable value at the residual strength stage. The initial confining pressure and the unloading rate have a significant influence on the permeability evolution of sandstone. With increasing the initial confining pressure，the variation of the unloading pressure from the beginning of unloading to the moment of failure increases while the ratio between the final and initial confining pressures decreases. With ascending the unloading rate，the variation of the unloading pressure increases and the peak value of the permeability increases due to a lower confining pressure at failure. The results could provide a good reference for permeability and safety evaluation of surrounding rocks in deep underground rock engineering.
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2019, Vol. 38 
