Experimental Study on the Mechanical Behavior of Layered Sandstone under Horizontal Squeezing Action

Squeezing-induced buckling or flexural deformation of rock layers always occurs on consequent rock slopes and laminated roof of tunnels or underground openings. To reveal the mechanical mechanism and inducing factors of this instability, tests on cuboid rock samples comprised of bedding sandstone under horizontal squeezing stress were conducted. In addition, numerical modeling based on cohesive-element-model was conducted to further reveal the influence of inter-layer bonding strength on the mechanical behavior of laminated rock. According to the results, remarkable size effects exist on the buckling-fracture characteristics of tested samples. Subjected to the same horizontal stress, tested samples with different dimensions have quite different failure patterns, including upper buckling-lower shearing, integral buckling and end squashing. It is recommended that the length-thickness ratio of tested samples for buckling failure research should be less than 150/8. Moreover, numerical simulations indicate that failure characteristics of the samples are greatly influenced by the bedding structure such as bedding thickness and inter-bedded bonding strength. Buckling deformation at one end becomes quite obvious when inter-bedded bonding strength decreases to a smaller value. The research results will not only contribute to understanding the buckling mechanism of stratified rock mass subjected to horizontal stress, but also provide a guidance for similar experimental design in terms of sample preparation, loading and monitoring.