Applied Sciences, Vol. 15, Pages 8905: Influence of Wetting and Drying Conditions on the Mechanical Behavior of Brittle Sandstone Containing Folded Cracks

Applied Sciences doi: 10.3390/app15168905

Authors:
Yan Ma
Jiangyuan Guo
Zelin Liu

Compressed air energy storage in aquifers (CAESA) offers advantages of wide availability and low cost, but natural cracks in aquifers may initiate, propagate, and coalesce under mechanical fields, posing potential security risks for CAESA projects. Most previous research has predominantly addressed straight cracks, while folded cracks, which are commonly encountered in geological formations, remain insufficiently studied. This gap in understanding the mechanical behavior of brittle rocks with folded cracks under wetting conditions presents a critical challenge to ensuring the stability of CAESA operations. In this study, uniaxial compression tests were carried out on sandstone specimens with different crack inclination angles (β) and crack folded numbers (n) under wetting and drying conditions using the MTS 815 testing system combined with an acoustic emission system and digital image correlation system. The deformation behavior, peak strength, crack initiation, and coalescence modes under wetting conditions were comprehensively investigated and compared with those under drying conditions. It can be found that the peak strength increases with β (with the maximum peak strength at 1.59–3.44 times the minimum for the same n), while the effect of n is relatively minor (only 1.09–1.21 times variation); the peak strength under wetting conditions is consistently lower than that under drying conditions (all wet/dry strength ratios < 1). Six distinct crack initiation modes and two coalescence patterns were identified. These findings provide valuable insights into the failure mechanisms of brittle rocks containing folded cracks under varying moisture conditions, offering practical references for anti-cracking design and risk assessment of CAESA cavern structures.

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