Study On Starting Mechanism And Early Warning Theory Of Diluted Debris Flow In Northeast China

Debris flow is one of the three major geological disasters,is a complex natural geographical process.Northeast region is vast,mountainous hilly landform,geological disasters,especially diluted debris flow disasters.When the rainy season is concentrated,the probability of diluted debris flow is high and the destructive force is huge.In 1981,the diluted debris flow disaster in Laomaoshan area of Dalian City,caused 664 deaths,resulting in huge economic losses,has been highly valued by the national government.Previous studies on diluted debris flow in Northeast China focused on the evaluation of the damage degree of such disasters and the post-disaster management,and there were few research results on the starting mechanism.Since the starting mechanism of debris flow directly affects the effectiveness of prevention and control measures,it is of great significance to explore its starting mechanism for prevention and early warning.Therefore,this paper relies on the project “ Investigation and Evaluation of Debris Flow in Laomaoshan District of Dalian City ”(Project number: HYCG16-15),and takes Laomaoshan Debris Flow in Dalian City as an example to conduct in-depth research on its starting mechanism according to the characteristics of diluted debris flow in Northeast China,so as to guide the prevention and early warning of diluted debris flow in Northeast China.Based on indoor physical model experiment,numerical simulation and theoretical analysis,this paper studies the relationship between rainfall conditions,material source conditions and debris flow rainfall threshold.Based on field investigation,local rainfall data and laboratory experiments,a physical model is built based on similarity theory to monitor the changes of rainfall intensity,rainfall duration and internal parameters of soil under different working conditions.Combined with discrete element numerical analysis method,the starting mechanism of diluted debris flow is explored from macroscopic and microscopic aspects.Based on the above experimental analysis,the rainfall threshold prediction results of the critical condition model under special conditions and the IPD,IPM new multi-parameter debris flow start warning model under conventional conditions are compared with the actual rainfall in the existing data,and the early warning and prediction scheme is formulated.The main conclusions of this paper are divided into the following four parts:1.Through field investigation and a large amount of data collection,taking the Laomaoshan debris flow as an example,the classification distribution,disaster characteristics and disaster conditions of the dilute debris flow in the study area are analyzed in detail,and it is concluded that the Laomaoshan debris flow is located in the large-scale disaster area of the study area,which is a typical rainfall-dilute debris flow and has the typical characteristics of the dilute debris flow in Northeast China.2.Taking Laomaoshan debris flow as an example,the starting mechanism of diluted debris flow in Northeast China is studied by equal scale physical model experiment.The experiment shows that the starting of diluted debris flow is mainly affected by rainfall intensity and soil gradation under similar terrain conditions.3.The particle flow method is used to simulate the starting of diluted debris flow in northeast China,and the meso-scale analysis of the starting process is carried out.The meso-scale characteristics of the simulation results are basically consistent with the macro-scale characteristics of the indoor model experiment.The reliability of the results is verified by the macro-scale and meso-scale analysis,and the starting mechanism of diluted debris flow in northeast China is obtained.4.Taking Laomaoshan debris flow as an example,the key problem of debris flow forewarning of diluted debris flow in Northeast China,rainfall threshold forecasting,is studied,and the critical condition model of debris flow starting under this condition is put forward according to the special situation that material source is destroyed in unsaturated state.A modified multi-parameter early warning model(IPM,IPD)is proposed.The prediction results of the two models have certain accuracy and reliability,which provides a new idea for the study of early warning theory of diluted debris flow in Northeast China.