Urban Geological Environment & Corresponding Engineering Significance Of Beijing City

Beijing is the capital of the People's Republic of China, it is the world-famoushistorical ancient city, well-known city of culture. It is politics , traffic and culturalcenter of the whole country. In the past 20 years, the development of construction ofBeijing are very fast. This kind of development is not only shown as the constantexpansion of the level range but also reflect to the development of ground andunderground space. Especially underground space has already been up to more than20 meters with the depth, and is still strengthening constantly.The geologicalenvironment of some projects is comparatively complicated .These projects havebeen done in detail by relevant surveying units before constructing, but they still havenot studied deep enoughly for some bad geological condition ,such as fault on side orin depth,underground river,earthquake taken place in history in this area .Thus theproject hidden danger, even the serious project accident was produced ,which causedgreat losses to national and people's life , property , security. So it seems particularlyurgent and important to summarizes in detail and further investigates to the geologicalenvironment in Beijing.The paper based on the above reason studied the characteristics of urbangeological environment in Beijing City, including buried fault structure, Quaternarysediments, paleochannels, seismic characteristics and ground collapse, distribution ofcrevices, based on which the paper also studied its corresponding engineeringsignificance of Beijing City. Thus offers the geological basis for selecting site,drafting the scheme to improve and prevent the bad geological environment.According geological condition and existing problem of the site that have beenselected, we put forward suggestions about the style,scale,frame and constructionmethod of the building .They are shown as following:(1) The engineering geological characteristics of sedimentary soil vary from asedimentary face to another.Generaly speaking,from riverbed face to floodplain faceand then to flooding sedimentary face,and from upstream riverbed to downstreamone,the engineering geological characteristics of sedimentary soil are graduallybecoming bad.In the western part of this area, riverbed face should be as subgrade,andfloodplain face should be as subgrade in the eastern part.(2)The northern section of Miyun-Liangxiang fault(Qianmen-Miyun reservoirsection) obviously moved in horizon and also flutuated with little range fromQuaternary. Eight degree earthquake once happened in insidious Dachang Basincontrolled by Xinxiadian fault. Therefore, we should notice especially the two faultsin selecting sites.(3)It is the best that when foundation pits are mined in western suberb of Beijing,north area to Sunyi,Dashi River in Fangsan and southern area to Nankou , low flowperiods should be selected or stronger precipitation methods should be used;there areseveral waterbearing stratums in vast plain,Yangqing Basin and southeastern areas. Soevery waterbearing stratum come down to a project should be found out and confinedaquifer buoyancy to the superstructure should be noticed. Light-well precipitation isoften used in the area.(4)Inside Beijing ,Tong county,yanqing and Huairou of Beijing are comparativelmultiple earthquake areas;outside Beijing, multiple earthquake areas areLangfang,Bohai,Jingning,Qulu and Huailai. Therefore,we should select carefully sitesin these areas,and increase one degree when designing earthquake-resistance.(5)There are two methods in treating the ground sink of Xisan: â‘ ganguebackfilling, â‘¡ blasting;cracks in Sunyi should be mainly prevented;we shouldaggregate analysis and evaluate deep insidious karst sink with GIS and then adoptrelevant measures when building projects.