Research On Dynamic Characteristics And Risk Quantitative Assessment Of The Gully-Type Debris Flow In Strong Earthquake Area

In the southwest earthquake-prone mountains areas of our country,the people’s lives and property safety was being seriously threatened by the frequent debris flow,which restricts regional economic development.The debris flow disaster is significantly affected by the"post-effect"of the earthquake,and its evolution law and development trend had changed greatly,which seriously affects the design work and governance effect of disaster prevention engineering.At present,it is urgent to study the dynamic characteristics and risk degree of debris flow in strong earthquake area.This research was supported by the National Key R&D Program"Comprehensive prevention and Control technology and Demonstration application of Super-Large debris flows in strong earthquake area—The dynamic characteristics of debris flow with wide and slow and narrow steep channel in strong earthquake area".The main work and research results of the dynamic characteristic parameters and risk assessment are as follows:(1)Based on the case of debris flow in Wenchuan earthquake area,the factor regression analysis was used to study the intrinsic relationship between the basin characteristic parameters and the peak discharge in this paper,and a multivariate prediction model for peak discharge of debris flow was established.The problem of information superposition caused by the collinearity of the original variables was solved,and the prediction accuracy was improved remarkably;At last,the prediction model was used to draw the peak discharge threshold zoning map in the study area.Based on this,a new index parameter system was proposed for the classification of"super-large-scale high-level long-distance debris flow"in the earthquake area.(2)Based on the fluid continuity equation,the principle of momentum conservation and the jet theory,the Reynolds number turbulence model of hydrodynamics was used to simulate the problem of debris flow jet scouring behind dam,and the numerical calculation model for the scour depth behind dam was constructed.Then,the scour equilibrium curves under different working conditions were analyzed by dimensional principles,and the dimensionless formula was established for calculating the maximum scour depth behind dam.Finally,comparing the prediction results with the previous empirical formula,the feasibility of the model was verified.(3)Based on the risk of hazard and the vulnerability of disaster-bearing bodies,quantitative assessment of debris flow in strong earthquake area was realized.Firstly,according to the characteristics of the debris flow disaster-causing model,three quantitative dynamic parameter indexes(I_F、I_M、I_V)were defined.And the vulnerability curves of disaster-bearing body based on three kinds of risk indexes were established respectively.Secondly,the Sidoroff damage model,the Aas-Jakobsen fatigue cumulative damage model and the entropy method were introduced to determine the weight value of the risk index.Then,the quantitative risk expression of debris flow was constructed,which was a relatively complete quantitative risk assessment system.Finally,some typical cases were used to verify the risk quantification model,and the results showed that the model is scientific.The above research results can partly reveal the dynamic evolution law and disaster-forming characteristics of gully-type debris flow in strong earthquake area,so as to provide theoretical support for the design and construction of debris flow disaster prevention and mitigation engineering,predicting the risk level of debris flow scientifically.This thesis contains 41 figures,23 tables and 161 references.