INSTABILITY MODELLING OF LOESS FILL SLOPE WITH INFLUENCE OF WEAK ZONE OF HIGH AND STEEP FILLING INTERFACE

In recent years,in order to expand the available land resources in the Loess Plateau area,people have carried out a wide range of engineering construction,such as gully filling and land building and city building. This paper aimed at the potential disaster hazard of the interface between high and steep original slope and filling slope and carried out the indoor physical model test. The results show that under continuous heavy rainfall,the loess slope would slip and lose stability along the high and steep filling interface. This paper further used finite element numerical simulation software and carried out a comparative analysis on working conditions including no weak zone,different weak zone thickness and weakening coefficient at the filling interface. It is found that the continuous development of soft zone reduces the stability coefficient of the filling slope and changes the position of the most dangerous sliding surface. The influence of the set weakening coefficient on the stability coefficient can be divided into three stages: no influence stage,equal speed steep descent control stage,equal speed slow descent control stage. This paper further defined the "key weakening factor". It is the critical weakening factor and has an initial impact on the stability of the slope. Measures in actual engineering should be taken to prevent the weakening factor of the weak zone from falling below its "key weakening factor". Under the influence of the weak zone of the high-steep intersection interface,the rainfall-induced instability mode of loess fill slopes can be summarized as: at first slope surface erosion and formation of gullies are developed,the multi-level local collapse of slope foot are present,then weak zone of cross-fill interface is gradually developed. The soil slips down along the interfill interface and the slope foot is sheared out shear cracks are penetrated and the fill slope is completely lost stable. The research results can provide theoretical support for the disaster prevention and mitigation work of loess-filled slopes built on steep slopes.