Anisotropic Failure Strength of Shale with Increasing Confinement: Behaviors, Factors and Mechanism
Key Laboratory of Shale Gas and Geoengineering, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China
Institutions of Earth Science, Chinese Academy of Sciences, Beijing 100029, China
College of Earth Sciences, University of Chinese Academy of Sciences, Beijing 100049, China
Institute of Crustal Dynamics, China Earthquake Administration, Beijing 100085, China
Author to whom correspondence should be addressed.
Received: 25 October 2017 / Revised: 13 November 2017 / Accepted: 13 November 2017 / Published: 15 November 2017
Some studies reported that the anisotropic failure strength of shale will be weakened by increasing confinement. In this paper, it is found that there are various types of anisotropic strength behaviors. Four types of anisotropic strength ratio (
) behaviors and three types of anisotropic strength difference (
) behaviors have been classified based on laboratory experiments on nine groups of different shale samples. The cohesion
and friction angle
of the weak planes are proven to be two dominant factors according to a series of bonded-particle discrete element modelling analyses. It is observed that shale is more prone to a slight increase of
and significant increase of
with increasing confinement for higher cohesion
and lower to medium friction angle
. This study also investigated the mechanism of the anisotropic strength behaviors with increasing confinement. Owing to different contributions of
under different confinements, different combinations of
may have various types of influences on the minimum failure strength with the increasing confinement; therefore, different types of anisotropic behaviors occur for different shale specimens as the confinement increases. These findings are very important to understand the stability of wellbore and underground tunneling in the shale rock mass, and should be helpful for further studies on hydraulic fracture propagations in the shale reservoir.
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Cheng, C.; Li, X.; Qian, H. Anisotropic Failure Strength of Shale with Increasing Confinement: Behaviors, Factors and Mechanism. Materials 2017, 10, 1310.
Cheng C, Li X, Qian H. Anisotropic Failure Strength of Shale with Increasing Confinement: Behaviors, Factors and Mechanism. Materials. 2017; 10(11):1310.
Cheng, Cheng; Li, Xiao; Qian, Haitao. 2017. "Anisotropic Failure Strength of Shale with Increasing Confinement: Behaviors, Factors and Mechanism." Materials 10, no. 11: 1310.
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