Research On Risk Assessment Technology Of Urban Underground Diseases

With the rapid development of urbanization in China,more and more urban underground diseases are caused by human engineering activities and natural environmental factors.If allowed to develop,it will inevitably lead to pavement collapse,causing great losses to people's lives and property,and seriously affecting people's transportation.In order to avoid or reduce the damage caused by pavement collapse caused by underground diseases,it is particularly important to establish a scientific,rational and effective risk assessment system for urban underground diseases.In this paper,the urban underground disease body is taken as the research object.The main research contents and achievements are as follows:(1)The urban underground disease bodies are classified into four categories: void,empty,loose body and water-rich body.The risk level of urban underground disease body is divided into five levels,the risk consequence level of urban underground disease body is divided into five levels,and the risk level is divided into five levels according to the risk matrix method.(2)According to the index system method,the evaluation index system of the risk occurrence possibility of urban underground diseases was established.According to the analytic hierarchy process,the weight of each evaluation index is calculated.The weight calculation results of each index are as follows: the scale of the underground disease body is 0.122.In this index,the area of the underground disease body is 0.667,the height of the underground disease body is 0.333,and the adjacent facilities are 0.558.In this index,the road,underground pipeline,underground structure(non-pipeline)and ground facilities are all 0.250.In the road index,the coverage-span ratio is 0.800,the current situation of the road is 0.200,and the underground pipeline is 0.250.In the index,the relative position of disease body and pipeline is 0.570,pipeline vulnerability is 0.333,service life is 0.097,and environmental factor is 0.320.In this index,rock and soil condition is 0.364,construction interference is 0.364,surface load is 0.182,and water environment condition is 0.090.Using the same method,the risk consequence evaluation index system of urban underground disease bodies was established,and the weight of each evaluation index was calculated.The weight calculation results of each index were as follows: the scope of underground disease bodies was 0.389,the distribution of buildings was 0.293,the density of personnel was 0.152,the density of property was 0.083,and the social impact was 0.083.(3)The risk occurrence possibility evaluation index and risk consequence evaluation index of urban underground diseases were quantified by 0-100 assignment.The same method is used to quantify the risk occurrence possibility and risk consequence of urban underground diseases.Risk occurrence possibility grade: 0-30 is A,30-50 is B,50-70 is C,70-90 is D,90-100 is E;risk consequence grade: 0-20 is 1,20-40 is 2,40-60 is 3,60-80 is 4,80-100 is 5.According to the weight calculation results of each evaluation index and its quantification criteria,the total quantification score is calculated according to the ordered weighting method,and it is evaluated by comparing the quantification criteria of the risk occurrence possibility level and risk consequence level of underground disease bodies.According to the result of risk occurrence possibility grade and risk consequence grade evaluation,the risk grade of underground disease body is determined by risk matrix method,and the risk assessment model of underground disease body is established.(4)Nine different numerical models were established by using finite element software ABAQUS.Based on the results of numerical simulation,the sensitivity of typical evaluation indexes was analyzed by grey correlation method.Through analysis,the sensitivity of each evaluation index selected is as follows: the ratio of underground void cover to span > friction angle in soil > surface load > cohesion of soil > elastic modulus of soil > height of underground void > span of underground void.The result of sensitivity analysis is consistent with that of weight calculation,which shows that the weight of each evaluation index calculated by analytic hierarchy process is reasonable and credible.(5)Five typical underground cavern projects in Lanzhou City of Gansu Province are selected and evaluated according to the risk assessment model established in this paper.Through the evaluation and analysis,the risk level of the five selected underground caverns is V.The results of the assessment are consistent with the actual situation of the site,which proves that the risk assessment model of urban underground disease body established in this paper is scientific,reasonable and effective.