Predicting Loess Landslide Sliding Distance Based On Energy Dissipation And Mass Point Kinematics

Landslide is one of the main types of geological disasters in mountain areas.Landslide is also an extremely complex geological and geomorphic phenomenon.Its developmental characteristics are affected by the conditions of its own area such as the topographic and geological conditions,internal and external dynamic conditions,climatic conditions and human engineering activities,which have great uncertainty.Due to the importance of disaster prevention and mitigation,forecasting landslide sliding distance is always the hot and difficult problem in landslide research.When landslide danger occurs,landslide sliding distance forecast is one of the most difficult problems in the process of emergency disposal,which is directly related to the accuracy of the formulation and people's life and property security,and is also the first concern of the government management department.Misunderstanding of landslide sliding distance,overestimate or underestimate of sliding distance,cannot effectively reduce disaster losses.At present,scholars in China and abroad,have proposed many landslide sliding distance prediction models,and have obtained many research results.Each model is based on different methods and conditional assumptions,and has certain advantages and limitations.It is still difficult to establish a universally applicable landslide sliding distance forecast model.Therefore,it is still a practical and feasible way to carry out the study of sliding distance prediction for a certain type of landslide in a certain area,which can solve some difficult problems in the prevention and control of landslide disasters.To solve the problems mentioned above,this study used a mixed method of the theory of classical physics,statistical analyses,and the particle kinematics and energy subtraction to establish a landslide sliding distance prediction model.The performance of the model was verified by applying to existing landslide events.The main results are as follows:(1)Based on a large number of analyses of landslide sliding distance models and method on the basis of using classical physics of movement and the law of conservation of energy,to be landslide movement into particle motion,the acceleration and deceleration sliding surface are as two sliding section analysis of landslide sliding distance,and considering the energy consumption in the process of landslide movement and the change in length,introduced an energy reduction factor(?)and the concept of "L ratio"(?),landslide sliding distance prediction model is established.The difference between prediction model and other models is mainly in the process of building model,combining theoretical model and empirical model,the landslide movement process is simplified to the expression of physics,sliding distance prediction formula is deduced.(2)The way of energy conversion during landslide movement can be divided into the conversion of potential energy and kinetic energy inside mechanical energy,and the conversion of mechanical energy and thermal energy.The potential energy of the landslide will eventually be converted into thermal energy dissipated(slip friction,block collision),while kinetic energy is only a process quantity.When the conversion rate of kinetic energy is high,the thermal energy consumption is small,the landslide speed is fast and time is long,and the landslide slip distance is large;on the contrary,when the kinetic energy conversion rate is low,the thermal energy consumption is large,the landslide speed is slow and time is short,and the landslide slip distance is small.(3)This study proposes the concept of “sliding strength” to characterize the shear strength of slip zone soil during the sliding process of landslide sliding.Sliding strength is a state strength,which is different from peak strength,starting strength,full softening strength,and residual strength.In the case where the existing test means cannot be obtained,the residual strength can be used instead of the sliding strength to predict the landslide distance.(4)In the theoretical model of landslide distance prediction established in this study,the sliding friction coefficient(tan?)and the energy reduction coefficient(?)are important parameters,which affect and couple the landslide distance.If the sliding friction coefficient(tan?)is taken as the peak strength index of the slip zone soil,the energy consumed by the friction portion will increase,and the thermal energy dissipation between the blocks such as the collision will decrease,and the corresponding energy reduction coefficient(?)will increase;conversely,if the sliding friction coefficient(tan?)is taken as the residual strength index of the slip zone soil,the energy consumed by the friction portion will decrease,and the thermal energy dissipation between the blocks such as the collision will increase.The corresponding energy reduction factor(?)will decrease.(5)Research on prediction models of landslide sliding distance for specific research areas at the regional scale based on the physical processes.Loess landslides are widely development in Lanzhou district and as the study area,screened out with detailed and reliable landslide characteristics data samples of 12 typical loess landslide disasters.Based on the known landslide characteristic parameters,analysis to determine the sliding distance prediction theory values of various parameters in the formula,build up the statistical regression equation of the ? and ?,and then puts forward the loess landslide sliding distance model in Lanzhou.(6)Based on the methods of simulation and prediction,we used the numerical simulation software,such as Slide and CDEM to analyze two typical loess landslides in Lanzhou to verify the reliability of the established loess landslide sliding distance prediction model in Lanzhou.Results show that the model is better to simulate the loess landslide sliding distance in Lanzhou.(7)A typical loess dig-fill construction site in Lanzhou is selected.The prediction of landslide sliding distance for unstable slope areas was conducted,which would provide technical support for the construction site.This study complemented and perfected the theory and practice of landslide spatial prediction and risk assessment,for geological disaster prevention and management decision-making departments,and has high theoretical significance and practical application value.The proposed prediction model of loess landslide sliding distance will provide necessary scientific and technological support for disaster prevention and mitigation of loess landslide disasters in Lanzhou,and will promote the prevention and control of landslide disasters in Lanzhou and even the Loess Plateau region.