Stability analysis of abutment slopes based on long-term monitoring and numerical simulation

• We analyze the stability of abutments controlled by faults and intercalations.
• Multiple stabilizing measures are proved to be effective by long-term monitoring data.
• Increasing the FOS of upstream part or downstream part will increase the FOS of the entire right abutment.
• FOS relationship between the entire abutment and the downstream and upstream parts is established.
• Stabilizing the downstream and upstream parts according to different FOSs is a cost effective method.

The Shimenzi Roller-Compacted Concrete (RCC) arch dam is built in a soft rock region where faults and intercalations have developed. The abutments are divided by major faults and intercalations into several potential sliding wedges, which bring difficulties and threats to the construction of the dam and the operation of the reservoir. Several types of large-scale reinforced concrete structures, such as shear keys, shear wells and shear tunnels, are constructed in the faults and intercalations in order to increase the stability of the abutments. Long-term monitoring data, which reveal the deformation of the faults and intercalations, are used to investigate the stability of the stabilized abutments. A three-dimensional finite difference numerical model, in which the faults and intercalations of the dam and reinforced concrete structures are considered, is established to improve understanding of the abutment behavior and to calculate the factor of safety for every major sliding wedge. The rationality of a controversial design method, in which the upstream and the downstream parts of the right abutment are stabilized according to different standards, is also discussed. Based on the analysis of the monitoring data and the results of the numerical simulation, it is concluded that the FOSs of the stabilized sliding wedges have reached their design values. The abutments have been in a stable condition since 2000, when the dam construction was completed. It would be a cost-effective method if the downstream part and the upstream part of large-scale unstable abutment were stabilized according to different FOSs.