| The unique geological conditions of the Three Gorges Reservoir Area(TGRA)area have bred a large number of accumulation landslides.The accumulation landslide structure is loose and broken.Under the influence of strong external factors such as rainfall,the shear strength of the slope rock and soil is weakened and prone to instability.This study takes the Piansongshu landslide as the research object.The transfer coefficient method and GEO-STUDIO numerical simulation software are employed to evaluate the stability of the landslide.The changes in the seepage field,displacement field,and stability of slope under different rainfall conditions are discussed.The following conclusions are drawn:(1)The development of landslides is closely related to the regional geological background,such as geological structure,topography,and water system distribution.The landslides in the TGR area are mainly accumulation landslides,which are controlled by the geological background such as the development of multi-level terraces,tectonic movement,and river incision.(2)Based on the field geological survey of the Piansongshu landslide,the macroscopic deformation signs and deformation mechanism of the landslide are analyzed.Rainstorm is the main inducing factor of landslide disaster in the study area.The deformation rate of the landslide slope changes periodically with the rainy season.The average displacement growth rate is subtle or insignificant during the stage of scarce rainfall.The deformation rate fluctuates greatly during the stage of increasing rainfall.Rainfall and displacement deformation has a good response relationship.(3)According to the stability calculation results under the transfer coefficient method,the stability state of the potential secondary shear surface of the three longitudinal sections of the Piansongshu landslide varies greatly.The Piansongshu landslide is stable under natural conditions,but unstable under rainstorm conditions.The stability coefficient of the secondary shear of the landslide 2-2’ section and the overall calculation of the landslide is smaller than that of the 1-1’ section and the 3-3’ section.The corresponding landslide stability state is also weaker in the middle than on both sides,indicating that the landslide deformation is strong in the middle and gradually weakens on both sides.The stability calculation results are consistent with the field investigation of landslide deformation signs.(4)Multi-field coupling analysis based on GEO-STUDIO shows that as the rainfall continues,the transient saturation zone appears on the surface of the slope and continues to expand downward.The saturation line at the front edge of the landslide deposit is flat and linear and protrudes to the surface at the larger deformation site.The maximum displacement of the landslide occurs at the steeper terrain in the middle and upper parts of the landslide.The shear strain zone is located on the contact surface between the slip zone and the bedrock.The location with the strongest shear strain is consistent with the main sliding position,which is prone to landslide.(5)The stability coefficient of the secondary shear surface of the landslide is larger than that of the overall sliding surface.The greater the rainfall intensity,the longer the rainfall duration,and the greater the decrease in the stability coefficient.The influence of different rainfall types on stability in general,with the rainfall infiltration,the safety factor of the slope gradually decreases with time,and the stability factor will continue to decrease after the rain stops.As the rain stops,the slope stability factor rises again until it reaches a stable state. |
