Optimization Of Layout Schemes Of Horizontal Drainage Pipes For Typical Hydrodynamic Pressure Landslide In Three Gorges Reservoir Area

Due to poor permeability of hydrodynamic pressure landslides in the Three Gorges Reservoir area,water in the slope can’t be ruled out in time,and hydrodynamic pressure will exist in the landslides under the conditions of reservoir water level falling,which will bring adverse effect on the stability of the landslides.Decorating horizontal drain pipes within the sliding mass is an effective measure to reduce the hydrodynamic pressure and improve the stability of hydrodynamic pressure landslides.The effectiveness of the drainage pressure reduction is determined by the layout of the drainage pipe directly.In order to obtain efficient and reasonable layout scheme of horizontal drain pipes,a typical hydrodynamic pressure landslide — Woshaxi landslide was taken as a case to develop dynamic experimental study on soil-water characteristic curve and unsaturated permeability coefficient of slip soil during the drawdown of reservoir water level.Based on that,design and optimize the layout scheme of horizontal drainage pipe.The main research contents and results are summarized as follows:1)The hydraulic characteristics of hydrodynamic pressure landslide under the condition of drawdown of reservoir water level are analyzed.2)Using the self-developed permeability instrument,the infiltration process of representative points in the landslide is simulated through the experiment.The daily particle size distribution curve and the saturated permeability coefficient are obtained.Based on the results of penetration and size distribution testing,the soil water characteristic curve(SWCC)and the unsaturated seepage function of the sliding mass in the drawdown of reservoir water level are dynamically obtained by the Physical empirical model method and Fredlund&Xing function model.3)Uniform design method was used to design horizontal drainage schemes.Based on dynamically determined SWCCs,unsaturated permeability functions,other physical and mechanical parameters of landslide,the seepage field and stability of the landslide with or without drainage pipes are computed by means of the Geo-Studio software.The nonlinear mapping relationship between the parameters of drainage pipe layout,the drainage effects and stability of landslide after drainage is established using neural network,and the layout schemes of drainage pipe are optimized by genetic algorithm.