基于土压平衡盾构施工的双层地铁隧道引起地面沉降分析

为了研究双线上下层盾构隧道施工时的短期地面沉降，以大连地铁二号西安路到交通大学区间盾构隧道施工为背景，使用Flac3D软件进行沉降的有限差分分析，模拟了地下隧道的掘进、支护和掌子面支护等。针对大连典型的地质特征进行预测，这些特征是决定地面沉降量的关键因素。研究区域的地质构造从地面向下分别为素填土、卵石、板岩。通过模拟上下双层非对称往返施工的盾构隧道施工过程，及掘进、支护和掌子面支护等详细步骤，得到了其单向和双向往返施工时的地面沉降，进而可分析其沉降规律。结果显示，上层隧道施工时，将降低岩层承载能力，同时改变下层隧道的土体平衡，加剧沉降，所以沉降量较大且两侧的测点沉降量不对称。通过模拟与分析为在市内建筑物密集区域修建地铁隧道提供安全可行的方法。

Study on surface settlement predictions for double-layer metro tunnels excavated by EPB-TBM

In order to study the short-term surface settlements caused by double-layer shield tunnels construction, the shield tunnel construction of No. 2 subway Dalian from xihn road to jiaotong university was taken as an engi- neering background. The settlement predictions were performed with finite element method by using FLAC3D. Ex- cavation, ground support and face support steps in analyses were simulated as applied in the field. Predictions were performed for a typical geological zone of Dalian, which was considered as critical in terms of surface settlement. Geology in the study area was composed of fill, pebble and slate, respectively, starting from the surface. Through the simulation of shield tunnel construction process, such as excavation, ground support and face support steps, in which the two tube were excavated with double-layer, roundtrip and asymmetric, the surface settlement of construc- tion of the unidirectional and two-way back and forth were obtained, and then the role of settlement was analyzed. The results showed that the rock bearing capacity was reduced during the upper tunnel construction, which changed the balance of soil on the lower tunnel at the same time and increased settlement, so the settlement of points on ei- ther side were asymmetric and settlement value change was bigger. The simulation and analysis provide a safe and feasible method for metro tunnel construction in the dense regions of the buildings.