Influence Of Water Level Fluctuation On The Stability Of The Typical Landslides In Badong Formation In Three Gorges Reservoir Area

According to incomplete statistics,there are 1829 landslides in Hubei section of Three Gorges Reservoir Area,wherein 819 development in the Triassic Badong formation?T₂b?and gravel soil at least.Triassic Badong Formation belong to soft rock,which is based on marl and argillaceous weak group,resulting in that it become one of“slippery ground”in the Three Gorges reservoir area.With the normal operation of the Three Gorges Reservoir,the water level cyclical fluctuation between145-175m every year,such a huge water level amplitude will have a significant impact on the wading landslides in reservoir.Therefore,the study of water level fluctuations'influence on the Three Gorges Reservoir Badong typical landslide's stability has an important practical significance.This paper selected Lijiawan landslide and Hengliangzi landslide as Badong typical landslide,the former is gravel soil accumulation layer landslide,latter is cut landslide.Using GeoStudio software's SEEP/W module and SLOPE/W modules and Lizheng software to simulate and calculate the change of landslide's stability and seepage field variation in water level fluctuation conditions;Using FLAC3D software to simulation the way of slope failure may occur under conditions of water level fluctuations in Lijiawan landslide.The main conclusions as follows:?1?Despite massive collapse are developed in two landslides,overall did not have significant deform,the overall is in stable condition currently.Deformation monitoring data analysis shows that Lijiawan landslide's deformation having a front portion,the central and rear smallest features,suggesting that Lijiawan landslide has a retrogressive landslide characteristics;Hengliangzi landslide's deformation having a front portion,the central and rear largest features,suggesting that Hengliangzi landslide has a slumping landslide characteristics.?2?In steady state conditions,landslide's groundwater surface is relatively flat,landslide's stability is influenced by landslide shape,buoyancy and dynamic water pressure.Lijiawan landslide's stability coefficient are 1.102 and 1.116 in 145m and175m water level,Hengliangzi landslide's stability coefficient are 1.10 and 1.102 in145m and 175m water level.It suggests that the landslides's stability in 145m water level is lower than in 175m water level.?3?In water level rise condition?0.75-4.0m/d increase?,Lijiawan landslide's stability coefficient increase from 1.134 to 1.157,Hengliangzi landslide's stability coefficient increase from 1.14 to 1.175,landslide's stability coefficient has a positively correlation with water level rise rate;in water level decline condition?0.6-3.0m/d decrease?,Lijiawan landslide's stability coefficient decrease from 1.0 to1.083,Hengliangzi landslide's stability coefficient decrease from 1.08 to 1.065,landslide's stability coefficient has a negative correlation with water level decline rate.?4?Rainfall is not conducive to the stability of landslide,when a rainstorm added,the stability of Lijiawan landslide and Hengliangzi landslide are all reduced?approximately 0.001?,and the larger rainfall per unit time,the longer rainfall duration,the worse of stability of landslide.?5?In water level decline condition,there are partial collapse occurre in front of the landslides,with the increase of decline of water level,collapse range basically unchanged,but the stability codfficient decrease and collapse in speed.When extreme rainstorm added,collapsing speed further accelerate.Water level decline and rainfall are the main factors of collapse in landslide,which water level decline's influence is more important.?6?FLAC3D's simulation results show that Lijiawan landslide's displacement are mainly concentrated in the front of the landslide and which gradually decrease to the rear.The maximum displacement occurs at the surface of the landslide near fluctuating water level zone.The main impact of water level fluctuation to Lijiawan landslide is its surface deformation displacement.Since the slip zone is not completely through that Lijiawan landslide will not occur overall deformation.