天津地铁盾构接收水平冻结实测与分析

Field monitoring and analysis of horizontal freezing method for shield received in Tianjin metro tunnels

天津地区地下3层及以下地铁车站,盾构掘进范围内主要为粉砂和粉土,并包含承压水层,水压高容易造成喷沙现象,引起开挖面失稳和地面沉降。为保护地面建(构)筑物,保证盾构安全接收,采用水平冻结方法加固地层。由于天津尚未开展冻土试验,在冻结设计中,冻土强度指标暂比照上海地区取值。通过对天津地铁3号线某区间左线盾构接收水平冻结设计与施工方案,以及土体和盐水温度实测数据进行分析,研究冻结方案的实际实施效果。实测结果表明,冻结设计满足冻结帷幕厚度和平均温度的要求,达到了加固土体和止水的效果,但由于盾构施工中未能有效地注浆封闭止水,造成带有泥沙的水流到刀盘位置,通过采取增加内排管冻结、增设明洞等措施后,盾构机安全进洞。

For three layers and more of underground subway station in Tianjin area, the range of shield driving mainly includes silt and silty soil, as well as artesian aquifer. High water pressure will easily cause sandblasting, instability of excavation face and surface subsidence. In order to protect the buildings and ensure safe shield received, horizontal freezing method is taken to strengthen the stratum. Because frozen ground experiments have not been taken in Tianjin, design of freezing method uses parameters of Shanghai. By analyzing horizontal freezing design and construction method of left line shield received in Tianjin No. 3 subway project, as well as temperature of ground and saline water, implementation effect was studied. The measured results show that freezing design satisfies the requirements of freezing curtain wall thickness and average temperature, reaches the effect of soil strengthened and water sealed. However, the gap between shield and segment has not been effectively sealed, water with silt flows into shield cutter head. By taking, the measures of increasing inner freezing pipes and open tunnel, shield machine safely enters into the station.