基坑区块施工对邻近地铁隧道变形影响

Impact from Foundation Pit Block Operation on Neighboring Subway Tunnel Deformation

城市中心基坑开挖对周围环境影响,特别是对地铁隧道的影响越来越引起人们的重视。杭州某基坑位于已运营的地铁1号线区间盾构北侧,基坑围护边线距离盾构隧道最近距离约20.0m。为了保护临近基坑地铁隧道的安全,基坑采用分区块的施工方法。施工时,先把基坑分为Ⅰ、Ⅱ两区块,Ⅰ区块再分成I-1区、I-2区,其中I-1区、I-2区采用钻孔灌注桩作挡土结构,I-1区、I-2区基坑北侧钻孔桩外围采用高压旋喷桩作止水帷幕,其余三侧钻孔桩外围采用TRD作止水帷幕,且支护桩间隙采用高压旋喷桩作止水帷幕。Ⅱ区采用TRD水泥土连续墙内插H型钢作挡土结构兼作止水帷幕。监测结果表明,分区块开挖的施工方法,具有变形量更小,隧道变形得到有效控制和保护,具有一定推广前景。

The impact from foundation pit excavation in central urban area on peripheral environment, especially more and more attention has been paid to subway tunnels. A foundation pit in Hangzhou is situated on the north side of operating subway Line 1 shield tunnel interval, the nearest distance from foundation pit enclosure line to the tunnel about 20.0m. To protect subway tunnel safety neighboring the foundation pit, the operation of the pit has been divided into blocks. During the operation, firstly has divided the pit into I and II blocks, then subdivided the block I into I-1 and I-2 two subareas then to use cast-in-place piles as retaining structure, their north side piles outer-ring has used high pressure rotating jet grouting piles as water check curtain, other three sides cast-in-place piles outer-ring used TRD as water check curtain, and interval between support piles used high pressure rotating jet grouting piles. While block II has used TRD cement-soil diaphragm wall inserted with H shaped steel as retaining structure doubled as water check curtain. The monitoring results have shown that to divide operation into blocks will has lesser deformation amount;tunnel deformation can get effective control and protect, thus has certain promotion prospect.