Study On Evaluation Model Of Rockfalls And Landslides Induced By Earthquake Based On The Quantification Theory Ⅰ

The rockfalls and landslides induced by earthquake have such characteristics as outburst and simultaneous occurrence. The Wenchuan earthquake occurred in 2008 is the most serious earthquake-hazard charactered by the maximum strength, the most serious destructive damage, the maximum damage area and the most serious casualty loss. Because the earthquake occurred in the middle and high mountains with weak geological environment, it induced a mass of rockfalls and landslides. These disasters brought significant threat to after-disaster reconstruction and major projects construction. Based on the analysis of distribution rules and influence factors, taken the rockfalls and landslides in Jushui river basin as examples, this paper ulitlized the quantification theoryⅠestablished the evaluation model of rockfalls and landslides induced by earthquake and verificated the applicability of the model by the seismic stability of monomer slope and regional slopes respectively. This paper gained some research achievements in the distribution rules, influence factors and evaluation model of the rockfalls and landslides induced by earthquake, all as follows:(1) Mass field datas statistics show that the disasters are dominated by small and medium scale in quantity, but in causing threaten, the disasters are dominated by large scale.(2) By analysising the correlativity between developing characteristics and distribution characteristics of secondary rockfalls and landslides and geological influence factors, this paper selected gradient, distance to basal slope, slope structure, rock integrity, distance to causative faults, upper or lower walls of the fault seven factors as evaluation indexes. Then combined with the quantification theory, this paper classified indexes to detailing the system. (4) Based on the analysis of influence factors and estimating index system, taken the disasters in Juishui river basin, this paper ulitlized the quantification theoryⅠestablished the evaluation model of rockfalls and landslides induced by earthquake. By the fitting degree and residuals analysis, the rationality of the model was verified and obtained better effect.(5) This paper identified the weight order of influence factors and grading factors of rockfalls and landslides disasters induced by earthquake. According to the partial correlation coefficient, range and variance ratio, this paper analysed the weight order of factors influenced that whether the slople will produce rockfalls or landslides is gradient, height of slope, distance to causative fault, rock integrality, slope structures, upper or lower walls of fault and lithology. By the covariance matrix, this paper judged the contribution to disasters of all categories. The results showed that the most high score categories are the height of slope between 100 to 300 meters, distance less than 5 kilometers to causative fault, gradient between40 to 50 degree and bad rock integrality. The existence of the four categories has significant impact to the seismic stability of slopes.(6) To verify the applicability of the evaluation and prediction model, this paper applied the model to the monomer slopes in Mianyuan river basin, whose geological conditions are similar to the Jushui river basin, and in regional slopes that signed the seismic stability of monomer slopes and regional slopes respectively. The results showed that the evaluation and prediction model's accuracy rate is about 80% and gained better effect of prediction.