基于纵向沉降曲线的黄土地层盾构土舱压力分析

为分析黄土地层盾构土舱压力设置问题,根据西安地铁4 号线区间盾构隧道施工过程建立盾构施工数值模型,基于对模型不同位置处地表沉降量的监测,通过将不同监测点的地表沉降曲线转换到同一坐标下进行对比,分析土舱压力对掌子面前方未开挖地层的影响,进而提出盾构土舱压力合理取值方法。研究结果表明: 1)盾构掘进对掌子面前方地层的扰动具有累积性,地层的变形具有滞后性,即盾构对掌子面前方地层挤压或支护不足时对掌子面前方地层的扰动会不断累积,表现为各监测断面的沉降曲线量值和分布规律不一致; 2)当土舱压力与地层土压力相平衡时,各监测断面的监测曲线基本相似,针对设置工况,土舱压力为0. 1 MPa 时,地表沉降曲线落在同一狭长区域内,即表明该值为与该地层相匹配的土舱压力值。

Study on Chamber Earth Pressure of Shield Tunneling Based on Longitudinal Settlement Curve in Loess Stratum

In order to analyze the chamber earth pressure of shield tunneling in loess stratum, a numerical model of shield construction is established according to the construction of interval shield tunnel in Xi′an Metro Line 4. Based on the monitoring of the surface settlement at different locations of the model, the surface settlement curves of different monitoring points are converted to the same coordinates for comparison, and the influence of the soil pressure on the unexcavated strata in front of the face is analyzed, and then the method of determining the value of chamber earth pressure is proposed. The results shows that: (1) When the formation in front of the tunnel face is squeezed or insufficiently supported by the shield, the disturbance of the unexcavated stratum will continuously accumulate, and the heave or settlement deformation of the formation in front of the tunnel face will appear with the shield tunneling, which represents that the magnitude and distribution of the settlement curves of each monitoring section are inconsistent. (2) When the chamber earth pressure balances with the water and earth pressure from stratum, the settlement curves of each monitoring section are analogous. For the setting working condition, when the chamber earth pressure is 0. 1 MPa, the ground settlement curves locate in a narrow area, which represents that the pressure value matches the formation.