| The risk assessment and zoning of landslide is one of the hot spots in the research of landslide at home and abroad.And how to evaluate the risk of landslide accurately and reliably is also one of the difficulties in landslide research.Lanzhou is the capital of Gansu and one of the most important central cities in the west.The Yellow River valley and the surrounding high terrace loess plateau have become a densely populated area in Lanzhou because of the limitation of topography.Fulongping is one of the most densely populated and high terraced loess plateau,which is also one of the areas with serious landslide disasters.Therefore,study on the landslide risk zoning of Fulongping not only has important theoretical value,but also has obvious practical significance and potential application value.Based on the risk assessment framework of landslide,the stability,hazard and vulnerability of the slopes in different working conditions are evaluated,and then the landslide risk zoning in the research area is carried out.By means of engineering geological analogy,conditional analysis,evaluating grade method and risk matrix method,the stability,hazard,vulnerability and risk of the slopes are qualitatively and semi-quantitatively evaluated and regionalized.The Bishop method based on rigid equilibrium limit method and the Monte-Carlo method considering random variation of shear strength parameters of loess are adopted to calculate the stability and instability probabilities of slopes,and then the runout of landslides is estimated and the hazard of landslides is quantitatively evaluated.The model of vulnerability value is used,which combines the characteristics of property and population to obtain the vulnerability of risk elements and quantitative evaluation and zoning of landslide risk.The main conclusions as follows:(1)Results of semi-quantitative.Stability: Under natural condition,the qualitative method predicts potential unstable slopes are between No.12 and 17 west slopes.Under intense fall and earthquake conditions,these slopes may appear failure.Hazard: The high hazardous slopes are west No.13,15,16 under natural condition,east No.1,5 and west No.11,13~18 under intense fall,east No.1~5,17 and west No.10~20 under earthquake condition.Vulnerability: The high vulnerability slopes of property are east No.1~6 and west No.15,16 under natural and earthquake conditions,east No.1~5 under intense fall condition.The high vulnerability slopes of casualty are east No.1~7 and west No.15,16 under natural and earthquake conditions,east No.1~5,7 under intense fall condition.Risk: The high risk slopes of property are east No.1~6 and west No.15,16 under natural condition,east No.1~5 and west No.11,15~18 under intense fall condition,east No.1~6 and west No.10,11,15~19 under earthquake condition.The high risk slopes of casualty are east No.1~5 and west No.15,16 under natural condition,east No.1~5,7 and west No.11,15~18 under intense fall condition,east No.1~7 and west No.10~12,15~19 under earthquake condition.(2)Results of quantitative.Stability: The potential unstable slopes under natural condition,which stability coefficients between 1~1.05 are west No.13,15,16.The rest are in stable-basically stable state.A part of west No.11~16 slopes appeared to be unstable under intense fall and earthquake conditions,but there is no unstable slope in the east.Hazard: Slopes with a hazard above 50% are west No.13,15,16 under natural condition,east No.12,17 and west No.3,10~13,15,16,18,20 under intense fall condition,east No.1,5 and west No.11~18,20 under earthquake condition.Vulnerability: Except the east No.6 under intense fall condition,slopes with a vulnerability of property above 8 million yuan and a vulnerability of casualty above 100 people are east No.1~6 under three conditions.But the vulnerability of property and casualty on west slopes are under 5 million yuan and 100 people.Risk: Slopes with high risk of property are east No.1~3,5 and west No.15,16 under natural condition,which values are 4.86 million yuan,1.6 million yuan,1.09 million yuan,1.92 million yuan,1.14 million yuan and 2.91 million yuan respectively.East No.1~3,5 under intense fall condition,which values are 6.81 million yuan,1.58 million yuan,3.62 million yuan and 3.24 million yuan.East No.1~6 and west No.15~19 under earthquake condition,which values are 26.76 million yuan,10.77 million yuan,9.18 million yuan,1.05 million yuan,7.07 million yuan and 2.68 million yuan,1.86 million yuan,4.51 million yuan,1.85 million yuan,1.37 million yuan and 1.59 million yuan respectively.Slopes with high risk of casualty are east No.1~3,5 and west No.15,16 under natural condition,which values are 181 people,43 people,29 people,24 people,14 people and 14 people respectively.East No.1~3,5 and west No.16 under intense fall condition,which values are 254 people,42 people,36 people,41 people and 11 people respectively.East No.1~7 and west No.15,16,19 under earthquake condition,which values are 996 people,287 people,249 people,14 people,89 people,41 people,15 people,22 people,22 people and 39 people respectively.(3)Comparison of results: As a whole,semi-quantitative and quantitative stability,hazard and vulnerability are generally consistent except for individual differences.Under three conditions,the risks of semi-quantitative and quantitative landslides are high in the south and low in the north on the east side,but high in the middle and low in the north and south on the west side.However,the scope of semi-quantitative medium and high risk areas are greater than the scope of quantitative risks.Semi-quantitative property risks on both sides are higher than quantitative risks.The semi-quantitative casualty risk zoning in the east is more consistent with the quantitative zoning,while the difference is slightly larger in the west. |
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