Effect of Intermediate Principal Stress on the Strength, Deformation, and Permeability of Sandstone

Zhenlong Song, Minghui Li, Guangzhi Yin, Pathegama Gamage Ranjith, Dongming Zhang and Chao Liu
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Zhenlong Song: State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400030, China
Minghui Li: State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400030, China
Guangzhi Yin: State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400030, China
Pathegama Gamage Ranjith: Deep Earth Energy Research Laboratory, Department of Civil Engineering, Monash University, Melbourne, VIC 3800, Australia
Dongming Zhang: State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400030, China
Chao Liu: State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400030, China

Energies, 2018, vol. 11, issue 10, 1-11

Abstract: Although the mechanical behaviors and flow aspects of sandstone have been previously investigated, studies of the effect of the intermediate principal stress ( σ 2 ) on the strength, deformation, and permeability of sandstone are lacking. In this work, the mechanical behaviors and permeability of sandstone under true triaxial stress conditions were investigated using a newly developed true triaxial geophysical apparatus. The experimental results showed that with increasing σ 2 , the peak strength, octahedral effective normal stress, and octahedral effective shear stress of the sandstone increased, and the rate of increase decreased. This is because a larger intermediate principal stress coefficient b has an inhibitory effect on rock strength. In our study, as the ratio of σ 2 / σ 3 increased, the specimen entered compressive strain in the σ 2 direction during the first stress drop. The stress and strain path deviations occur during rock failure. The amount of deviation increased as the σ 2 increased before the peak stress. This phenomenon indicates that elastic mechanics are not suitable for understanding this sandstone rock during its failure. The permeability evolution of the sandstone under true triaxial stress conditions was measured and analyzed to investigate the effect of σ 2 . During the complete true triaxial stress-strain experiments, the variation we found in gas seepage velocity could be divided into two stages. Before the first pressure drop, the gas seepage velocity was mainly affected by volume strain. After the first pressure drop, the seepage velocity was affected by the deviator strain, which can change the seepage channels.

Keywords: intermediate principal stress; rock strength; deviator strain; permeability evolution (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2018
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