Research On Evaluation Of Geological Environment Suitability Of Urban Underground Facilities

Problems such as overpopulation,land shortage and ecological pollution are becoming more and more serious with the development of cities in China,which aggravate the contradiction between man and land.It is an effective way to develop underground facilities and accelerate the three-dimensional urban construction.However,various safety problems caused by geological factors emerge in the process of underground facilities' development,which threaten the safety and stability of underground facilities.At present,most of the suitability evaluation is focused on a specific region,and there are few systematic and summative studies.Therefore,geological influencing factors and evaluation methods should be comprehensively analyzed to provide reference for the planning and construction of underground facilities and relevant decision-making.Through the comparison and statistical analysis of literature and cases,this paper starts with the urban geological environment factors and studies the suitability evaluation indicators and methods of underground facility development by combining qualitative and quantitative methods.According to the engineering geology types,grades and population sizes of cities,46 cases of 22 cities of 7 engineering geology subcategories were selected comprehensively.And the three theories of sustainable development,coordinated development and engineering geological environment stability evaluation were referred.They both laid a foundation for the research of indicators and methods.By means of expert consultation and summary,this paper sorted out 6 first-level indicators: landform,rock and soil conditions,hydrogeological conditions,geological disasters and geological tectonic activities,existing surface and underground space,ecological conditions.It also summarized the characteristics and specific influences of the indicators in detail.In this paper,the weight range of first-level&second-level indicators and the frequency of selecting indicators in cases of 7 geological cities are analyzed,and the importance and priority of firstlevel indicators in suitability evaluation are sorted.The results show that the geological disasters and geological tectonic activities,rock and soil conditions,hydrogeological conditions and existing surface and underground space have great influence on the development of underground facilities,while landform and ecological conditions have little influence.The selection of suitability evaluation indicators and its influence ranking should be based on the geological condition of the study area.In this paper,the application status of common evaluation methods in 46 cases is statistically analyzed.And the principles,characteristics and application steps of 9 conventional evaluation methods and 2 special evaluation methods are summarized respectively,meanwhile the applicability of various methods is analyzed.It is suggested to carry out the suitability evaluation based on the analytic hierarchy process.If the study area is simple,fuzzy comprehensive evaluation method(FCEM),comprehensive index method and extension evaluation method can be used;If the site is complex and the geological data is large,the neural network method and variable weight evaluation method are adopted.Three supplementary methods were used to eliminate geological hazards and other development restricted areas.Based on the summary and analysis of evaluation indexes and evaluation methods,taking a mobile phone production base in chongqing as an actual case,paper selected 5 first-level indicators and 14 second-level indicators,using AHP and expert investigation method to calculate the indicator weight.The suitability evaluation was carried out by FCEM and comprehensive index method respectively.Calculation results show that the two methods of suitability grades respectively ? level(good)and ? level(optimal).After analysis,the evaluation results of the FCEM are more in line with the situation of the site.Based on the calculation principle and application status,FCEM is recommended to be preferred in the suitability evaluation.