Study On Improvement And Application Of Landslide Hazard Assessment Model In Active Fault Zone

China is a country with frequent earthquakes.Active fault zones and tectonic zones are widely distributed in China,especially in the weak parts of active fault zones or tectonic zones,which are more prone to destructive earthquakes,seriously threatening the lives and property of local residents.In recent years,scholars at home and abroad have carried out a series of studies on earthquake landslide hazard assessment and achieved a lot of achievements.However,the existing research results have not established a landslide hazard assessment model suitable for fault zones systematically.Therefore,it is of great theoretical and practical significance to find out the distribution characteristics of landslide along the active fault zone and actively explore the landslide hazard assessment methods along the fault zone for disaster prevention and reduction in the region.In this paper,the Lixian-Luojiabu fault zone in Gansu province is taken as the research area.Based on the analysis of landslide types along the fault zone,the distribution characteristics of landslide along the fault zone are systematically summarized.The improved landslide hazard assessment model suitable for the fault zone is constructed on the regional scale and the monomer scale respectively,and the application research is carried out with the improved model.The effectiveness of the improved model is verified by comparing with the evaluation results of the traditional model,which provides a scientific basis for geological disaster prevention and control and territorial space planning along the fault zone.The main knowledge and achievements of this paper are as follows:(1)The distribution characteristics of landslide along the Lixian-Luojiabu fault zone in Gansu province are summarized.There are 588 landslides in the area.Historically,landslides in this area mainly occurred at the same time of Luojiabu 8.0 earthquake in 1654.The closer to the fault zone,the greater the number and density of landslides.The density of landslides in hanging wall of active fault is greater than that in footwall.The dominant main sliding direction of the earthquake landslides is approximately perpendicular to the strike of the earthquake fault.There is a positive correlation between point density and area density of landslides and earthquake intensity,and the positive correlation of area density is more significant.(2)The concept of fault effect correction coefficient is put forward exploringly.This coefficient is a comprehensive correction coefficient value obtained after considering factors such as landslides distribution and fault zone distance,and the relative position of the upper and lower plates,which can effectively improve the accuracy of landslide hazard assessment of fault zone.Based on the analysis of the relationship between landslides distribution and fault zone distance and the relationship between upper and footwall along the Lixian-Luojiabu fault zone in Gansu province,the value table of fault effect correction coefficient suitable for the fault zone along the fault zone is established,and the corresponding distribution diagram of fault effect correction coefficient is compiled.(3)A method for evaluating the hazard of regional landslides in fault zone based on fractal theory model and considering fault effects is proposed.From the perspective of statistical analysis,based on fractal theory and combined with the characteristics of fault effect,fractal theory model and fractal theory-information coupling model considering the effect of fault effect are constructed.The landslide hazard assessment is carried out by using the constructed fractal theory model,fractal theory-information coupling model and traditional models(information quantity model,analytic hierarchy model,logistic regression model,analytic hierarchy-information coupling model and logistic regression-information coupling model).Finally,ROC curve method and Kappa coefficient method are used to test the accuracy.The results show that the evaluation results of fractal theory-information coupling model are more accurate and reasonable.The model is easy to understand,convenient to operate and has strong applicability,and can be widely used in the assessment of regional landslide hazard along the fault zone.(4)A method for evaluating the hazard of regional landslides in fault zone considering the coupling effect of matrix suction and fault effect is proposed.From the perspective of mechanical analysis,while considering the fault effect,Newmark model is extended to the field of unsaturated soil mechanics,and Newmark improved model considering the coupling effect of matrix suction and fault effect is constructed.The improved model and the traditional model are used to evaluate the landslide hazard,and finally the accuracy test is completed by ROC curve method and Kappa coefficient method.The results show that the evaluation results calculated by Newmark improved model considering the coupling effect of matrix suction and fault effect are more reasonable and reliable.The model has clear physical and mechanical significance,simple operation and rapid evaluation,and is more suitable for rapid prediction and evaluation of the distribution and hazard of landslides along the fault zone in the loess coverage area as soon as possible after the occurrence of an earthquake.(5)A method for evaluating the hazard of single landslides in fault zone considering the coupling effect of topographic effect and fault effect is proposed.Taking the landslide in Haitou Village,a typical earthquake landslide,as the research object,based on the reliability theory,the Monte Carlo improved model considering the coupling effect of topographic effect and fault effect is constructed.The improved model and the traditional model are used to evaluate the landslide hazard,and the calculation results are compared and analyzed.The results show that the hazard assessment results obtained by Monte Carlo improved model considering the coupling effect of topographic effect and fault effect are more scientific and reasonable.This model has refined correction of ground acceleration and can be widely used in the hazard assessment of single landslides along the fault zone.