盾构隧道穿越上软下硬地层施工力学特性分析

上软下硬复合地层在盾构施工中常常造成盾构掘进姿态不佳及地表塌陷,严重时还可能导致管片局部出现破损。结合深圳地铁7号线穿越上软下硬地层的工程实例,采用数值模拟方法研究盾构隧道穿越上软下硬地层段("由软入硬"与"由硬入软")的施工力学特性,对地表及管片拱顶沉降、管片应力的变化规律进行分析,研究结果表明:盾构在穿越上软下硬交界地层过程中,地表沉降出现显著增大(增量最大可达1 cm),拱顶不均匀沉降的现象较为严重;对较软侧地层进行适当加固,可以有效减小上软下硬地层交界处的地表及管片拱顶沉降,同时能够降低"由软入硬"段管片的应力水平。

Construction Mechanical Property Analysis of Shield Tunnel through Upper-soft and Lower-hard Stratum

The poor shield tunneling posture and ground surface collapsing are usually caused by theupper-soft and lower-hard composite stratum in the shield construction, which may lead to partial damageof the segment in some serious cases. Based on the shield tunnel engineering through upper-soft andlower-hard stratum in Shenzhen Metro Line7 Project, a numerical simulation method is used to study themechanical characteristics of shield construction of the tunnel through upper-soft and lower-hard stratum(including the section "from soft into hard" and the section "from hard into soft"). The analysis of thechange rule of the ground surface settlement, and the segments vault settlement and stress concludes thatthe surface subsidence increases significantly(maximum increment up to 1 cm), and the uneven segmentvault settlement is getting more serious during the construction of shield tunneling through upper-soft andlower-hard composite stratum. The results also show that suitable reinforcement in the softer side stratumcan effectively reduce surface subsidence and segment vault settlement in the section of upper-soft andlower-hard stratum, and lower the stress level of the segment in the section "from soft into hard".