成都市城市地下空间开发中的环境工程地质问题

Problems of Environmental Engineering Geology for Exploitation of Urban Underground Space in Chengdu,China

成都市地质环境条件复杂,城市地下空间工程问题频发,给目前大规模城市地下空间开发利用,尤其是城市轨道交通、地下综合管廊和深地空间的开发利用带来了前所未有的地质挑战。本文在收集整理区域地质资料、地下空间开发资料的基础上,归纳总结了制约成都地下空间开发利用的主要环境工程地质问题和地质条件,包括活动断裂与地震、富水松散砂砾卵石土、膨胀性粘土、溶蚀性含膏盐(钙芒硝)泥岩、浅层天然气和含咸水地层;阐述并分析了各制约因素的分布特征、发育状况及危害类型。研究表明:活动断裂与地震对城市地下空间开发的主要危害表现为区域稳定性较差和破碎岩体的性质等;富水松散砂砾卵石土主要危害表现在地面沉降等;膨胀性粘土表现在基坑边坡破坏;溶蚀性含膏盐(钙芒硝)泥岩主要表现为膏盐溶蚀等;浅层天然气表现为气体易燃爆性;含咸水地层表现为水体腐蚀性。不同工程地质问题在不同深度地空开发中,对工程的影响各不相同,各工程地质问题之间既表现出独立性,又表现出相互关联性。通过研究,充分认识了成都地下空间开发面临的环境工程地质问题,对掌握其评价方法和预测防治手段、安全合理地开发成都市地下空间具有重要意义。

The complex geo-environment settings associated with frequent urban underground engineering incidents are unprecedentedly challenging large-scale exploitation of underground space in Chengdu City,China.The regular occurrence of geo-environment failures must be specifically concerned in urban rail transit,underground comprehensive pipe corridors and deep underground space.In this study,it collected and analyzed engineering geology data and the disasters in underground projects in Chengdu City for categorizing the main types of geo-environmental engineering problems and associated geo-backgrounds,following by inspecting the distributions,formation and types of the problems in the development and utilization of underground space.It found that the problems in underground constructions mainly consisted of 6 types,namely active faults and earthquakes,water-rich loose gravel soil,expansive clay,corrosive mudstone containing gypsum salt(glauberite),shallow natural gas and saline water stratum.To be specific,the main hazards inflicted by active faults and earthquakes to constructions in urban underground space were poor regional stability and broken rock mass;Water-rich loose gravel soil mostly resulted in subsidence in ground,house,etc.;Expansive clay occurred failures in foundation pit slopes;Corrosive mudstone containing gypsum salt generally led to gypsum-salt dissolution;Shallow natural gas was flammable and explosive;Saline water stratum was corrosive to water.Different engineering geological problems brought about different consequences to constructions in underground engineering in varied depths.Each consequence behaved with independence or interrelation.Since the process of excavation in underground is irreversible to urban environment,a scientific planning must be the top priority in the layout of urban underground space utilization.It is of great significance to properly recognize the geo-environmental engineering problems confronted in the exploitation of urban underground space in Chengdu,which would provide a solid foundation to deal with the evaluation,prediction and prevention of these problems for a safe and efficient urban underground space utilization in Chengdu City.