Impact of joint inclinations on the earth pressure against retaining structure in rock ground

The impact of different joint inclinations on the earth pressure was extensively carried out in this research, using Universal Distinct Element Code (UDEC) that is based on discrete element method. Numerical parametric investigations, which considered varying joint inclinations and rock types, were conducted after the numerical method had been verified through a physical model test. The joint inclinations considered ranged from 0° to 90° in the interval of 5° and the rock types are hard, slightly weathered and moderately weathered rocks. The results of the analyses were subjected to statistical analysis using analysis of variance (ANOVA) at 5% level of significance, and compared with empirical earth pressure envelope for sand ground as well as earth pressures measured from field observations in rock ground. The comparisons showed that earth pressures in rock ground are substantially varied from those in sand ground, while the earth pressures obtained from numerical analysis were consistent with those measured from field observations. The earth pressures obtained from numerical simulations increased with increasing joint inclinations and became highest around joint inclination angle of 60° as a result of joint sliding that occurred when the shear stress at the joints exceeded its strength. The impact of joint inclinations and joint sliding are more evident and significant in hard rock than slightly weathered and moderately weathered rock types. The result of ANOVA revealed that joint inclinations have statistically significant effect on the magnitude of the earth pressure, and practitioners should consider this factor while designing retaining structure in rock masses.