中文摘要：

地铁建设中，盾构隧道下穿群桩时引起的地表沉降和桩身受力不可小觑。本文采用FLAC3D软件模拟了合肥地铁2号线下穿五里墩立交桥的工况，研究了下穿群桩引起的地表沉降和桩身受力规律。研究表明：地表最大沉降量偏向桥墩荷载较大的一侧，其值为-1.31mm；地表沉降曲线较明显的转折点均产生在桩与土的临界面处，且承台上方的地表沉降趋于直线；桩的水平位移和弯矩沿桩身分布曲线呈弓形，且上半部分变形较明显，两者的最大值均发生在桩基上部的1/3处，在以后工程实践中，可在此处加以钢套以提高桩基承载力。

英文摘要：

In the metro construction,surface settlement and stress distribution of piles can not be ignored during the process when the shield tunnel passes through the pile group.In this study,FLAC3D is used to simulate the under-crossing of Wulidun flyover of a part of Hefei metro line2and comes to some conclusions of the ground settlement and the stress distribution of the piles.The results show that the peak value of the surface settlement tends to the side with much pier loading,and the value is-1.31mm.All the sudden turning points of the surface settlement curve appear at the critical surface of piles and soil,the curve above pile caps tend to be a straight line.The horizontal displacement curves and bending moment curves of these piles like a bow,the deformation of its upper part is more obvious and their maximum values appear in a third place of its length,and we can st rengthen one pile wit h steel jacket at the key position in ot her projects.