中文摘要：

北京地铁6号线平安里—北海北站区间下穿既有4号线区间隧道工程为北京地区首例暗挖隧道下穿盾构隧道工程。依托该工程,通过12个地表沉降监测断面及既有盾构隧道变形实测数据的统计,分析新建隧道与既有结构的相互影响,对地层及既有结构的变形特性取得以下认识：（1）非下穿段暗挖隧道地表最大沉降值随其埋深增大而减小;双线隧道间距小于2.0D（D为单线隧道宽度）时,地表沉降模式为＂单凹槽状＂,间距大于2.0D时,则为＂双凹槽状＂;下穿段既有结构呈＂双凹槽状＂变形,地表沉降模式为＂单凹槽状＂。（2）盾构隧道结构呈柔性变形,纵向柔性更为明显,下穿段既有结构的最大沉降值分别为7.32,6.69 mm,结构变形损失率分别为0.36%,0.45%,结构纵向沉降变形宽度系数为0.41-2.43。（3）下穿段地表最大沉降值为非下穿段的24%-27%,地表沉降槽宽度系数是非下穿段的1.2-2.3倍。既有结构的存在及地层的深孔注浆加固显著减小了暗挖隧道引起的地表沉降值,增大了地表沉降槽宽度。该研究成果可为今后类似工程提供参考。

英文摘要：

Using shallow tunneling method,tunnels between Pinganli and Beihaibei of Beijing Metro Line 6 traverse adjacently under Line 4 which is a shield tunnel. To obtain the deformation law of existing structures and ground surface settlement,the measured displacement of ground surface settlement and existing structures were analyzed. The research shows that：（1） For the stratum in non-crossing part,the maximum values of settlement decrease with the increase of buried depth of tunnel. If center distance between two tunnels is less than 2D,the surface subsidence is ＂single groove＂ shaped,otherwise the surface subsidence is ＂double grooves＂ shaped. In the crossing part,deformation of existing structures is ＂double groove＂shaped,the surface subsidence is ＂single groove＂shaped.（2） The maximum ground surface settlement of existing structures are 7.32 mm and 6.69 mm. The values of V are 0.36%,0.45%,the values of K range from 0.41 to 2.43.（3） The maximum ground surface settlement in crossing part is about 24%–27% of that in-non crossing part and the value of K is about 1.2–2.3 times. The research result can provide reference to the similar engineering.