An Experimental Method to Determine Rock Joint Stiffness under Constant Normal Load Conditions

Being physical mechanical parameters of joints, normal and shear stiffnesses are indispensable components the numerical simulation theoretical analysis behavior joints. The objective this work is to put forward an experimental method determine joint stiffness under constant load (CNL) conditions. For purpose, closure direct tests CNL conditions were conducted. Normal was determined by ratio stress increment corresponding displacement; calculated relative displacement. average instantaneous distinguished. Experimental results showed that time spatially varying during shearing. With increasing stress, stiffness, maximum increases. about 26–28 times higher than one level. Average little influenced velocity. Instantaneous shows velocity-dependent behavior. Maximum decreases rapidly with rate. At lower velocity, stiffness; minimum can be negative absolute value also faster These findings provide a reference for selecting appropriate evaluation response interface.