Model experimental study on the failure mechanisms of a loess-bedrock fill slope induced by rainfall: Fid-Bau Portal

Model experimental study on the failure mechanisms of a loess-bedrock fill slope induced by rainfall

Guo, Zhiyu / Huang, Qiangbing / Liu, Yue / Wang, Qianqian / Chen, Yiping

Abstract Large-scale gully land consolidation projects have been implemented on the Loess Plateau of western China. These projects have formed a large number of fill slopes, which are prone to failure induced by rainfall. However, the failure mechanisms of the loess-bedrock fill slope, especially the influence of the weak interlayer between the loess fill and bedrock on slope failure, are not clear. In this study, a laboratory flume model experiment was carried out to investigate rainfall infiltration processes and failure mechanisms of a loess-bedrock fill slope induced by rainfall. The volumetric water content, pore water pressure, wetting front migration, and deformation characteristics of the slope were analyzed to reveal the effects of the weak interlayer on slope failure. The results show that rainfall-induced failure of loess-bedrock fill slope exhibited characteristics of mode transformation, initiated by the local failure of the slope toe and gradually transforming into a multi-stage rotational slide-earthflow and gully erosion with continued rainfall. The maximum migration rate of the wetting front in the weak interlayer is about 3 times that in loess fill, occurring in the weak interlayer within a depth of 0.64 m (about 16 m in the prototype). The preferential flow formed in the weak interlayer accelerated the saturation of the fill slope and generated seepage force towards the outside of the slope, which makes the upper fill slope more prone to shear failure along the weak interlayer. These results provide a theoretical basis for preventing or mitigating related risks associated with gully land consolidation projects on the Loess Plateau.

Highlights • A model test is used to study infiltration process and failure mechanisms of loess-bedrock fill slope induced by rainfall. • The effect of weak interlayer between bedrock and loess fill on the failure of loess-bedrock fill slope is analyzed. • Moisture migration of the loess-bedrock fill slope during rainfall is revealed. • The failure mode of loess-bedrock fill slope induced by rainfall is identified.