软土浅埋超大直径盾构始发端头加固范围研究

为确定软土地层浅埋超大直径盾构始发端头加固的合理范围,以珠海杧州隧道为工程背景,采用有限元建模分析,研究了端头加固范围对素混凝土墙破除以及盾构始发掘进过程地层变形的影响。基于数值分析结果,以端头中心点水平位移为控制目标,得出横、竖向合理加固厚度约为0.28倍隧道开挖面直径,略大于理论计算值和工程经验值。盾构掘进模拟结果表明,当纵向加固长度超过盾构机长度后,横断面受剪区域未与地表形成“塑性贯通”,端头盾构掘进对地表扰动程度较低;如以地表最大沉降为控制值,软土地层合理加固长度为1.14倍盾构机长度,该结果与理论计算值接近,而略小于工程经验值。

Research on Reinforcement Range of Starting End of Shallow-Buried Super-Large Diameter Shield in Soft Soil

In order to determine the reasonable range of ground reinforcement of starting end for the shallow-buried super-large diameter shield in soft soil layer, this paper sets up the finite element modeling of the Mangzhou tunnel project in Zhuhai and investigates influence of the reinforcement range on the ground deformation during destruction of plain concrete walls and the initial excavation of shield tunnel. According to the results of numerical analyses, the reasonable horizontal and vertical reinforcement thickness is about 0.28 times the diameter of the tunnel when the horizontal displacement at the center point of starting end is taken as the control target. The value is slightly larger than the ones calculated by the theoretical formula and estimated based on the engineering experience. Numerical results show that the shear area of the cross section does not form a "plastic penetration" to the ground surface when the longitudinal reinforcement length exceeds the length of the shield machine. In this scenario, the end shield tunneling will impose low-degree disturbance to the ground surface. When the maximum surface settlement is taken as the control value, the reasonable reinforcement length obtained through numerical analyses is 1.14 times the length of the shield machine. The value is close to that derived from the theoretical formula, but slightly less than the value determined based on the engineering experience.