Study On Surface Subsidence Caused By Rail Transit Construction And Its Influence On Ancient Buildings

Because of its advantages of small land occupation,large capacity,high speed as well as punctuality,convenience and comfortableness,urban rail transit gradually becomes the major urban public transportation.When metro lines run across the city,ground surface settlement caused by the construction process is likely to affect the complicated surrounding environment,especially to those cultural relics and historic buildings on both sides of the track lines,which have long histories and declining structural durabilities and qualities.Suzhou is one of the first 24 national historical and cultural cities in China,and has a history of more than 2,500 years.The density of Suzhou's heritage sites ranks only after Beijing and Xi'an.There are 642 protected buildings in the urban area of Suzhou,including 33 under national-level protection and 59 under the provincial-level.At the age of the historical and cultural relics meeting the modern civilization,this paper studies the ground surface settlement caused by metro construction and its influence on the historic buildings along the lines,on the basis of the actual situation of Suzhou and the metro line 2,3,4.The main research contents and results are as follows:(1)Collect 48 cross-sectional surface settlement data of metro line 2,4 during shield construction process and 17 cross-sectional surface settlement data of metro line 2,3,4 during station foundation pit construction.Adopt the Peck formula and skewed distribution density function to fit the measured data of the cross-sectional surface settlement during shield construction and station foundation pit construction.Find the rules of the corresponding cross-sectional surface settlement,and give the impact area of shield construction and station foundation pit construction on the surrounding environment,under specific conditions of geological data and rail transit in Suzhou.(2)Take Le-Shi section of metro line 4 and Shishan Station of metro line 3 as the study objects,and establish the finite element calculation model of the cross-sectional surface settlement caused by shield construction and station foundation pit construction.Analyze the influence of the tunnel diameter and buried depth,underground continuous wall thickness and insert ration on surface settlement,and establish the relations between the surface settlement trough width parameter(i)with buried depth(z)and diameter(D)of tunnel.(3)Investigate the present situations and site geological data of the historic buildings such as Tianxiang Villas,Confucian Temple and North Temple Pagoda,etc.Establish the three-dimensional finite element calculation model of "tunnel-soil-historic buildings",and evaluate the influence of shield construction on the above-mentioned historic buildings.