Risk Assessment Of Geological Hazards Of Typical Slopes In Hangzhou Luniao Town

Slopes are very common in engineering construction.Because of their special properties,they are prone to instability and damage to various geological disasters such as collapse and landslides under the influence of various internal and external geological camps.Luniao Town,Hangzhou is a mountain town located in northwestern Zhejiang.It has a large population density and a relatively developed economy.But nearly 80% of geological disasters in the region are related to slope instability after rainfall and artificial excavation.In order to effectively reduce the risk of disasters,reduce casualties and property losses,this paper takes the Starling Town as the research area,analyzes the geological disaster characteristics within the area,generalizes the slope model,and uses the finite element limit equilibrium method to simulate the slope stability;Based on the stability analysis,the typical slope is selected and the Monte Carlo simulation method is used to analyze the slope instability probability under different conditions,that is,the danger.And then the empirical formula method is used to estimate the impact range after slope instability,the probability of the disaster is used to analyze the vulnerability of the affected body based on the danger and the impact range.Finally,the risk and vulnerability analysis results are combined to calculate the disaster risk.Through the above research and analysis,this article has obtained the following results and conclusions,which can provide reference and reference for similar studies in relevant regions.(1)The numerical simulation results of the stability show that the slope is basically stable in the natural state,and it is in a potential instability state near the foot of the slope after the excavation.The analysis shows that the factors that affect the stability of the slopes are slope and excavation footage,and the slope has a greater degree of influence on stability;The critical value of the excavation footage when the slope is unstable is calculated by fitting the functional relationship between the excavation footage of the slope and the safety factor after excavation.The results show that the slope estimation error of slopes less than 20 ° is large,and that of slope slopes greater than 20 ° is small,about 10%.And this conclusion is of guiding significance for slope excavation related projects.(2)Combined with the finite element limit equilibrium principle,the Monte Carlo method was used to simulate and analyze the typical slope danger under different excavation and rainfall conditions.It was concluded that the unexcavated slope was in a safe state in its natural state,and the annual slope damage under the Meiyu climate the probability is 0.012%,which is basically stable.The probability of annual slope damage during typhoon is 0.125%,which is in a low-risk state;After the slope is excavated for 10 m,the probability of instability and failure in the natural state is 10.9%,which is in a low-risk state.Under Meiyu climate,the annual slope destruction probability is 8.190%,which is in a middle-dangerous state.At the same time,the probability of annual slope damage during typhoon is 1.436%,which is a high-risk state.(3)Using the Scheidegger formula,the maximum slip distance of the slope is calculated.The calculation results show that the maximum slip distance is 14 m under Meiyu conditions and 4.9m under typhoon rain conditions.Then,according to the maximum slip distance after instability,the vulnerability analysis of the disaster bearing body is carried out.(4)Using the risk calculation method proposed by Morgan et al.,Calculated the interannual total casualty rate of slopes under the Meiyu climate condition is 0.026,and the interannual total casualty rate of slopes under the typhoon rain type rain conditions is 3.2 × 10-3;The risk value of total economic property loss of slopes under Meiyu type and typhoon rain type is 215,300 and 31,600 yuan respectively.Its disaster risk is unacceptable.