Stability assessment of tunnel slopes along the Dujiangyan City to Siguniang Mountain Railway, China

This work focuses on integrated stability assessment of rocky tunnel slopes along a planned railway, namely, the Dujiangyan City to Siguniang Mountain Railway (DS Railway), which is an important transportation corridor in Southwest China. Investigating the stability of slopes at the entrances and exits of tunnels represents the first step of railway construction. Based on detailed geological engineering studies, the stability of 32 tunnel slopes was measured and evaluated by means of the slope mass rating (SMR), Chinese slope mass rating (CSMR) and Chinese continuous slope mass rating (CCSMR) systems. Moreover, a kinematic analysis technique was also employed to identify the potential failure modes of the jointed rock masses in tunnel slopes. The results reveal that the CSMR, by considering the slope height and discontinuity condition coefficient, can more robustly assess the slope stability than the SMR. Similarly, the CCSMR, which is based on continuous functions and can identify potentially dangerous slopes that should be reinforced, can reduce subjectivity. Many slopes deemed unstable and completely unstable by the CSMR and CCSMR are located on the banks of the river from Longchi to Longtan and from Xindianzi to Siguniang Mountain. The potential failure modes of the 32 slopes determined by kinematic analysis are basically consistent with the results obtained by the slope mass classification systems. These research results pave the way for stability assessment and intervention decision-making during the construction of the DS Railway.