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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。
In the Tianjin area, there are three subterranean metro stations and below. The shield tunneling mainly includes silt and silt, and confined water layer. High water pressure can easily lead to sandblasting, resulting in instability of excavation surface and land subsidence. To protect the ground building (structure) buildings, to ensure the safe shield to receive, the use of horizontal freezing method to reinforce the formation. As Tianjin has not yet carried out the permafrost test, in the frozen design, the strength index of frozen soil temporarily contrasts the value of Shanghai. Through the design and construction plan of the receiving horizontal freezing of the left shield in a certain section of Tianjin Metro Line 3 and the measured data of soil and brine temperature, the actual implementation effect of the freezing scheme is studied. The experimental results show that the freezing design meets the requirements of the thickness and average temperature of the frozen curtain and achieves the effect of strengthening the soil and stopping the water flow. However, due to the failure to effectively seal the sealing water during the shield construction, the water flow with sediment To the cutter position, by increasing the inner tube freezing, additional Myeongdong and other measures, the shield machine hole safe.