Study On The Improvement Of Newmark Model And Seismic Landslide Risk Prediction Based On Rainfall Infiltration/excess Pore Water Pressure

Earthquake and rainfall are two important factors leading to landslide.Landslide has become one of the most important geological disasters in China and even the world because of its high frequency,strong destructiveness,wide area and its loss is often greater than that caused by earthquake or heavy rainfall.However,most of the factors considered in the application of simple mechanical model to landslide research at home and abroad are relatively single.Many researchers only consider rainfall or earthquake.A large number of facts have proved that the coupling effect of earthquake and rainfall will greatly increase the probability of landslide.Therefore,this paper mainly starts from the earthquake during rainfall,considers the loss of rainwater in saturated soil along the slope direction in the process of rainfall infiltration,improves the traditional green Ampt rainfall infiltration model,and then improves the traditional Newmark cumulative displacement model by combining the pore water pressure with the excess pore water pressure caused by earthquake,In order to make it more suitable for landslide risk prediction under the joint action of earthquake and rainfall.Based on the collected ground motion data,the correlation analysis between landslide cumulative displacement DN and critical acceleration ratio(AC / PGA)and arias intensity IA(Arias)is carried out.Through analysis and comparison,Newmark cumulative displacement model with critical acceleration ratio as parameter is selected and fitted in combination with the collected seismic data,Then,taking Xiaozhai town of Ludian earthquake event as the study area,the fitting formula is verified.Based on the regional geological characteristics and average annual rainfall of Zhaotong City,Yunnan Province,a small area of Zhaotong City is selected as the study area,and the newly fitted displacement formula is selected to carry out the seismic landslide risk prediction and analysis under the condition of no rainfall.Then,the seismic landslide risk prediction and analysis under the condition of rainfall in the study area is carried out based on the improved Newmark model,Finally,the landslide risk zoning and the distribution characteristics of landslide high risk areas obtained in the two cases are studied and compared.The results show that:(1)the correlation coefficient R2 of Newmark cumulative displacement formula with the critical acceleration ratio as the parameter newly fitted according to the ground motion data is 0.761,and it performs well in the application of xiaozhaizhen research area of Ludian earthquake event.(2)From the results of landslide probability analysis map of Zhaotong study area,it can be seen that the area of high-risk landslide area in the study area accounts for 1% under the condition of no rainfall.With the rainfall lasting for 12 hours and 24 hours,it reaches 3% and 5% respectively,and the area proportion of high-risk area increases by 200% and 400% respectively,indicating that the seismic landslide risk is greatly improved under the coupling effect of earthquake and rainfall.The improved model and research method proposed in this paper can provide a new idea and method for landslide risk assessment and analysis under the coupling effect of earthquake and rainfall in China,and provide a certain scientific reference for landslide risk prediction,important traffic routes,dam and reservoir site selection and disaster prevention and reduction projects in the future.