Shear behavior of single-joint bolted sandstone subjected to dry–wet cycles: Experimental and analytical approaches

Abstract

A series of direct shear tests under constant normal loading conditions were carried out on specimens of bolted sandstone single-joint treated with different numbers of dry–wet cycles. The experimental results show that the peak shear strength and shear stiffness of bolted sandstone joints were significantly reduced after 12 dry–wet cycles. The decrease in the shear strength of rough joints is more significant than that of flat joints. Due to the decrease in the strength of the surrounding rock, the deformation characteristics of the bolts are significantly affected by the number of dry–wet cycles performed. With an increase in the number of dry–wet cycles, the plastic hinge length of the bolt gradually increases, resulting in an increase in the corresponding shear displacement when the bolt breaks. Compared with the tensile–shear failure mode of the bolts in flat joints, the tensile–bending failure mode arises for bolts in rough joints. A shear curve model describing the whole process of bolted rock joints is established based on the deterioration of rock mechanical parameters caused by dry‒wet cycles. The model proposed considers the change in the friction angle of the joint surface with the shear displacement, which is applied to the derivation of the model by introducing the dynamic evolutionary friction angle parameter. The reasonably good agreement between a predicted curve and the corresponding experimental curve indicates that this method can effectively predict the shear strength of a bolted rock joint involving rough joint under dry–wet cycling conditions.

Keywords

• Reinforcement technique
• Interface behavior
• Bolted sandstone
• Cyclic drying–wetting
• Analytical model