Study On Landslide-Induced Wave Analysis And Hazard Mitigation Plan Of Wangjiashan Landslide In The Baihetan Reservoir Area

Since the impoundment of the Baihetan Reservoir in 2021,a large number of landslides have been induced or revived.After the instability and damage of the reservoir landslide,not only will it cause landslide disasters,but also the landslide enters the river water at high speed,which is prone to secondary surge disasters with a wider and more severe impact range.At present,the prevention and control measures for landslide surge disasters mainly focus on landslide prevention and control(stability coefficient as a measurement index)and emergency evacuation of personnel.The disaster body is locked for a long time to maintain a safe and stable state for a long time.However,there are a large number of newly formed landslides in the Baihetan Reservoir area,and the disaster mode of landslides along the river is caused by landslide waves and surging waves.The main target of harm is the residential areas along the river,and traditional landslide prevention and control methods are used,which have huge economic costs and are difficult to meet the needs of comprehensive disaster prevention and reduction.The main disaster causing form of landslides along the river in the outbound area should be accurately identified as secondary surge disasters,breaking through the engineering disposal theory of landslide surge disasters,preventing and controlling catastrophic surges,and researching new concepts for landslide surge risk prevention and control.This article takes the Wangjiashan landslide in the Baihetan Reservoir Area as the research object,and analyzes the deformation and failure mechanism of the Wangjiashan landslide before and after water storage based on the engineering geological characteristics of the landslide.And through the limit equilibrium method and Pan Jiazheng method,the stability and inflow velocity of the landslide under different unstable conditions are calculated.At the same time,a two-dimensional single width physical model flume test was established for the surge of the Wangjiashan landslide,and9 sets of tests were conducted to study the dynamic characteristics of the landslide surge under underwater terrain.Based on the characteristic parameters of the first wave in physical experiments,the propagation and climbing process of landslide surge were numerically simulated using water wave dynamics methods.The danger of Wangjiashan landslide surge was analyzed,and a set of analysis processes that can quickly and accurately evaluate the danger of specific landslide surge was constructed.Based on the scale and morphology of the Wangjiashan landslide,a cutting project was designed as a disaster reduction plan,and 14 sets of two-dimensional single width landslide surge physical model tests and numerical simulations were conducted under cutting conditions.Using the height of surge waves under different cutting volumes as a measurement indicator for landslide surge mitigation,optimize the landslide surge mitigation engineering plan and select a scientific and reasonable mitigation plan.The main research content and achievements of this article are as follows:(1)Through the analysis of the engineering geological overview,historical remote sensing images before water storage,and GNSS historical monitoring data of the Wangjiashan landslide after water storage,it was found that a large number of bulging cracks developed in the middle and front areas of the slope,and tensile cracks developed in the rear edge area,with a maximum deformation of up to 23 m.Before water storage,rainfall is the main cause of landslide deformation;After water storage,the rise in water level is the main reason for accelerating landslide deformation and damage.At present,the Wangjiashan landslide is in an unstable state.(2)Based on the Froude similarity criterion,a physical model similarity test was established for the single width surge of the Wangjiashan landslide,and the movement process and surge generation process of the landslide were obtained under different water level conditions and inflow velocities.It was found that under low Froude number conditions,the generated surge waves are mostly nonlinear transition waves,with a maximum wave steepness ratio of 0.03,which is much smaller than the limit value of wave steepness,resulting in extremely low fluctuation and high concealment of the surge waves.A prediction formula for the maximum wave height of swells under low Froude number conditions has been summarized.(3)Based on the characteristic parameters of the initial wave in the two-dimensional physical experiment of landslide surge,the propagation and climbing process of Wangjiashan landslide surge are simulated and calculated using water wave dynamics theory,further analyzing the danger level of landslide surge disasters.With the increasingly severe instability conditions of the landslide,the dangerous area of the surge generated by the Wangjiashan landslide continues to increase,which will strongly threaten the safety of the lives and property of residents along the line.(4)Based on 14 sets of physical model test results and numerical simulation results of landslide surge,the risk of landslide surge and the reduction of surge wave height under a series of disaster reduction plans were analyzed.Taking the control of surge size as a measure of landslide surge risk prevention and control,the most scientific and reasonable disaster reduction measure was selected to reduce the overall elevation of the landslide to 920 m,which can reduce excavation costs by about 37 million yuan.