Peak Shear Strength Of Joints Research Articles

Experimental study on the influence of height and dip angle of asperity on the mechanical properties of rock joints

Joint roughness significantly affects the damage areas and peak shear strength of the rock joint. In this study, theoretical analysis and numerical simulations were carried out, and the results indicated that the resistance angles and heights of asperities quantified the damage range and damage degree, respectively, during the shearing process. Direct shear tests and 3D scanning tests were conducted on sets of mortar joint replicas and sandstone joints. By analyzing the test data, several morphological parameters were proposed to quantify the damage zone of the joint surface. Based on these morphological parameters, a new peak shear strength model, involving the effects of the height and dip angle of the joint surface, was constructed. Finally, the new model and previous classical models were compared. Moreover, the new model was used to predict the shear strength of other joint samples as well. The comparison and prediction results revealed that the new model is suitable for effective prediction of the peak shear strength of joints.

Laboratory Investigation on Shear Behavior of Rock Joints and a New Peak Shear Strength Criterion

In this study, shear tests on artificial rock joints with different roughness were conducted under five normal stress levels. Test results showed that the shear strength of rock joints had a positive correlation with roughness and the applied normal stress. Observation of joint specimens after shear tests indicated that asperity damage was mainly located in the steep areas facing the shear direction. The damaged joint surfaces tend to be rough, which implies that tensile failure plays an important role in shear behavior. As a result of the anisotropic characteristic of joint roughness, two quantitative 2D roughness parameters, i.e., the revised root-mean-square of asperity angle tan−1(Z2r) and the maximum contact coefficient Cm, were proposed considering the shear direction. The proposed roughness parameters can capture the difference of roughness in forward and reverse directions along a single joint profile. The normalized tensile strength and the proposed roughness parameters were used to perform a rational derivation of peak dilatancy angle. A negative exponential-type function was found to be appropriate to model the peak dilatancy angle. Using the new model of peak dilatancy angle, we obtained a new criterion for peak shear strength of rock joints. The good agreement between test results and predicted results by the new criterion indicated that the proposed criterion is capable of estimating the peak shear strength of rock joints. Comparisons between the new criterion and published models from available literature revealed that the proposed criterion has a good accuracy for predicting the peak shear strength of joints investigated in this study.