Stochastic seepage stability analysis of the Pubugou clay core rockfill dam with potentially high permeability zone by integrating multi-source monitoring information

One of the most important causes of the failure of a clay core rockfill dam (CCRD) is seepage failure caused by defects inside the clay core (e.g. a high permeability zone, HPZ for short). This study conducted a seepage stability analysis of the Pubugou CCRD with an HPZ, considering the uncertainty of dam parameters, including hydraulic conductivities, water level, and height of the HPZ. The reliability analysis methodology, both with and without the monitoring information, was first introduced. By inputting multi-source monitoring data, the probabilities of both the seepage failure and the dam parameters can be updated. The results show that the large monitoring values on 1 December 2010 have incurred an increase in the failure probability from 3.28 × 10−5 to 8.47 × 10−5, which was mainly caused by the increase of the hydraulic conductivity of the clay core (k1). The failure probability then decreased from 8.47 × 10−5 to 7.46 × 10−6 when smaller monitoring values on 6 September 2011 were input. The maximum probability interval of the k1 decreased from greater than 1.48 × 10−7 to between 4.18 × 10−8 and 7.86 × 10−8 due to long-term consolidation. However, the hydraulic conductivity of HPZ (k2) slightly increased because of possible internal erosion caused by long-time seepage in HPZ.