Effect of Seepage Force on Stability of High Embankment with Coarse-Grained Soil during Rainfall

A new numerical calculation method for slope stability is proposed to analyze the effect of the seepage force of a coarse-grained soil embankment slope on the distribution of the plastic zone and the change in safety factor under rainfall condition. The framework of coarse-grained soil was analyzed, and the SEEP/W module of software Geo-studio was used to calculate the change in matrix suction, underground water table line, and seepage gradient. Then, the calculation result for seepage was imported into FLAC3D using FISH language, considering the change in underground water table line, matrix suction, and seepage force. The influence of seepage force on the stability of the slope was also analyzed. Results showed that rainfall affected the spatial distribution of the underground water table line, matrix suction, and seepage gradient. The underground water table line lifted gradually from the foot of the embankment slope and developed into a deep slope. After a rainfall, the underground water table line decreased rapidly and the height of the final line near the embankment center was higher than the initial state. The matrix suction dissipated gradually because of the change in the underground water table line but recovered slowly when the rainfall stopped. At the beginning of a rainfall, the positive values of X-direction seepage gradients turned to negative and the negative areas expanded gradually. The plastic zone of the slope extended gradually from the foot to the inside of the slope as the rainfall continued. After the rainfall, the plastic zone mainly occurred at the foot of the slope. The slope safety factor increased gradually at the beginning of the 24 h period. The safety factor decreased rapidly and reached the minimum after 72 h. Then, the rainfall safety factor was gradually restored, but the recovery of the safety factor was delayed and smaller than during the initial state.