Tensile failure mechanism and a constitutive model of sandstone considering water-immersed softening and mechanical damage
Banquan Zeng , Jianhang Chen , Cun Zhang , Zhixiang Song , Shaokang Wu
Int J Min Sci Technol ›› 2026, Vol. 36 ›› Issue (8) : 1675 -1690.
To study the tensile failure mechanism of roof rock strata in deep water-rich mines, this paper conducts water immersion treatment and Brazilian splitting AE (acoustic emission) experiments on sandstone. Energy evolution characteristics, AE characteristics, and the constitutive relationship of sandstone are explored. During the loading process, the energy conversion of rock samples shows a stepwise evolution characteristic. In the initial loading stage, stable accumulation of elastic strain energy is accompanied by primary crack closure. It causes small fluctuations in dissipated strain energy. In the middle loading stage, stored energy keeps growing, and micro-crack adjustment makes the dissipated strain energy become stable. In the later loading stage, explosive expansion of new cracks leads to a sharp rise in dissipated energy in the stage, which is dominated by plastic deformation. When elastic strain energy approaches the storage limit, energy quickly releases through crack expansion and the kinetic energy of fragments. It causes overall instability of the samples. Water penetration remarkably changes the mechanical response mechanism of the samples. Mineral cementation weakening and particle interface loosening lead to a decrease in energy storage limit. Under water–rock interaction, expansion, and dissolution of clay materials lead to crack generation. Then, cracks make the rock’s energy storage capacity continuously decline with increasing immersion time. Besides, affected by water–rock interaction, the sample failure process shows a slower energy release rate. Meanwhile, their failure mode changes from brittle transgranular splitting to ductile intergranular splitting. This indicates that crack path adjustment, which is induced by water, effectively disperses local energy accumulation. It shows ductile failure features macroscopically. Dynamic evolution of AE signals and damage accumulation form a coupled response. In the initial stage, low-frequency signals are excited by particle friction and primary crack activities. Moreover, low-frequency signals become inactive as the energy-releasing rate slows down in the middle loading stage. Moreover, secondary crack penetration in the later loading stage triggers a sharp increase in high-frequency signals. For water-immersed samples, the crack expansion threshold decreases due to pore water pressure. Meanwhile, AE intensity weakens significantly. It reveals an internal mechanism that the water softening effect inhibits the generation of high-intensity pulses by reconstructing the energy release path. A constitutive model is proposed and verified by experiments. The proposed constitutive model can respond well to the mechanical behavior of water-immersed softening and the mechanical damage of the samples. Meanwhile, it can accurately predict the critical failure stress of samples. This study provides a theoretical basis for the stability evaluation of mine roof under complex hydrogeological conditions.
Rock strata / Water–rock interaction / Energy evolution characteristics / AE characteristics
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