experimental studies on the shear behavior of natural rock joints

Rock joints significantly decrease the strength of rock masses and considerably influence their instability because the sliding can easily occur along joints. this phenomenon is more important at shallow depths. the aim of this study is to investigate the shear behavior of natural, unfilled rock joints that were obtained from core drilling. for this purpose, direct shear tests were conducted on 37 natural rock joints in constant normal loading condition. all the specimens were obtained from core drilling of a geotechnical project. the morphological characteristics of joints were captured by photogrammetry before the test. based on barton and other classical theories, laboratory test data, and using the quantitative three-dimensional morphological parameters, a new peak shear strength criterion has been proposed for natural, unfilled rock joints. the predicted peak strengths using the new model match well with the observed values. in addition, a comparison of the new criterion with the grasselli’s model (2003), xia’s model (2014), and yang’s model (2015) shows that compared to other criteria, the predicted value based on the new criterion is more consistent with the test data. it was observed that the estimation accuracy of the new criterion is appropriate for natural, unfilled joints.