Research On Relationship Between Reservoir Water Level Fluctuation And Reactivation Of Typical Accumulation Landslides In Three Gorges Reservoir Area

The reservoir water level fluctuations have induced some old landslides in theThree Gorges Reservoir Area where the accumulation landslides are most sensitive toreservoir water level changes due to the loose structure and good permeability. TakingLijiapo Landslide and Tangjiao1#landslide as examples, which both are accumulationlandslides of different structures and morphology in the Three Gorges Reservoir Area,this thesis was completed based on the deformation and pore water pressuremonitoring data, the response characteristics of which were analyzed. Landslidestabilities were predicted under different reservoir water level fluctuation rates bynumerical simulation means, from which results, the critical reservoir water levelfluctuation rates were determined. The main research results include:Reservoir water level rising affects more than the falling on the deformation ofLijiapo Landslide and Tangjiao1#landslide, where the deformation in the front issignificantly larger than the one in the back indicating Lijiapo Landslide is anretrogressive landslide and Tangjiao1#landslide is an retrogressive landslides ofthree-level sliding as a whole with the characteristic of thrust load caused landslidelocally. Reservoir water lever fluctuations have greater impact on the landslidedeformation than the precipitation, demonstrating that the former is the leadinginducement.Lijiapo Landslide deforms in the early and middle decreasing periods and laterincreasing period of pore water pressure, especially in the decreasing period,indicating that Lijiap Landslide is a hydrodynamic pressure type landslide which isco-existed with the falling of reservoir water level. Pore water pressure is in almostsimultaneously on the trend, but it lags in changing magnitude as a result of reservoirwater infiltration.Tangjiao1#Landslide deforms in the later decreasing and early increasing periodof pore water pressure, especially in the former one. Pore water pressure lagsobviously behind reservoir water level both in trends and magnitude due to the poorpermeablility.Lijiap Landslide and Tangjiao1#Landslide deform differently under reservoir water level fluctuating conditions as a result of combination effects of differentpermeability, slip surface angle and the process of reservoir water level fluctuations.For Lijiapo Landslide, there is still some room for upward adjustment in reservoirwater level fluctuation rates, while there is only some room for upward adjustment inreservoir water level rising rate for Tangjiao1#Landslide with a critical reservoirwater level falling rate of0.1m/d. Though, taking rainfall, earthquick and other factorsinto account, if a safety reserve coefficient is given, the critical reservoir water levelfalling rate should be determined depend on it.