Study On The Formation Mechanism And Stability Of The Wangjiadun Loess Landslide

Loess landslide is one of the most serious geological disasters in the loess area,and its formation condition and deformation mechanism are complicated due to the special material composition and engineering characteristics of loess.The loess landslide disasters in Qinan area are serious,which restrict the development of local economy,what is more,the WangJiadun loess landslide which locates at the northwest of Qinan county throws great threat to the operation safety of Baoji-Lanzhou High-speed Railway.This paper is devoted to study the mechanism of formation and deformation as well as stability of the Wangjiadun loess landslide by theoretical analysis and numerical simulation combining with the regional conditions of the study area,to provide practical guidance for loess landslide prevention engineering.The main conclusions are as follows:(1)The Wangjiadun loess landslide is a great old landslide,with 1650m rear elevation and 1290m front elevation.The topography is moderate at the middle and upper part with the slop angle of 15?20 degrees while is steep in front part with the slop angel of 30?40 degrees.The landslide was divided into three zones by the scarplets.There were plenty of gullies and scarplets in the slide mass as well as tensile cracks and springs in the front of the landslide.(2)The deformation of Wanfjiadun loess landslide is controlled by stratigraphic lithology,topography,earthquake and rainfall.After experienced the creep deformation,slip deformation and stabilization,the high-steep front of the landslide has reached at the first terrace of Hulu River,and the front stacked loess can resist the slide of the rear part of the landslide to some extent.(3)The stability of the zone I and II as well as the potential slip mass in zone I and II are calculated by transfer coefficient method after qualitatively evaluated,and the results show that the entire landslide is stable while the potential slip mass in zone I is unstable under rainstorm conditions.(4)The potential slip mass in zone I,which is evaluated to be unstable,was simulated by FLAC-3D,to analyze the rule of the stability under natural and rainstorm conditions,and the results are consistent to the theoretical calculation.(5)Considering the effect of the failure of the potential slip mass in zone I on the stability of the entire landslide,zone I and the potential slip mass in zone I were simulated by FLAC-3D.The deformation mechanism as well as the changes of stability after the failure of the potential slip mass in zone I were compared with that of before the failure under nature condition.And the results show that,the stress will re-contribute and the stability will significantly decrease after the failure of the potential slip mass in zone I.