小半径曲线隧道盾构始发方式对轴线偏移的影响规律

Study on law of influence from small radius curve launching mode of tunneling shield on tunnel axis offset

曲线隧道需严格控制盾构施工轴线与设计曲线之间的偏移量。为此,推导了切线始发、割线始发以及内外侧预偏移始发时盾构机的轴线偏移量计算公式,提出了减少盾构始发偏移量的解决办法。在分析各种始发方式对直线段和姿态调整段的盾构轴线偏移的影响规律的基础上,探讨了盾体与连接桥之间转动受限时的解决办法。结果表明:小半径曲线段盾构施工宜采用割线始发或外侧预偏移始发,其中外侧预偏移始发的最大偏移量明显小于割线始发,且外侧预偏移始发比割线始发更易控制姿态调整段的偏移量;当线路转弯半径与盾构最小转弯半径相接近时,盾构始发后应提前调整盾构姿态,否则姿态调整段的最大偏移量很容易超过规范允许值;小半径曲线段盾构始发时,盾体与连接桥的转角容易超过盾构机的允许范围,应考虑将盾构设计轴线往曲线内侧适当平移。

The offset between the shield construction axis and the design curve is necessary to be controlled for curvilinear tunnel, thus the axis offset calculation formulas of shield machine for shield machine launching with the modes of tangent-line, secant-line and internal/external-offset are derived, and then a solution for reducing the shield launching offset is proposed herein. On the basis of analyzing the laws of the influences from all the launching modes on the shield axis offsets of the straight-line section and posture adjustment section, the solution to the rotation restriction between shield body and connecting bridge is discussed. The results show that secant-line launching or outboard pre-offset launching are suitable to be adopted for the shield construction of the small radius curved section, in which the maximum offset of the outboard pre-offset launching is obviously less than that of the secant-line launching, while the offset of the posture adjustment section is more easy to be controlled by the secant-line launching than the tangent-line launching. When the turning radius of the line is close to the minimum turning radius of the shield, the shield posture is necessary to be adjusted in advance after the shield launching, otherwise, the maximum offset of the posture adjustment section is easily to exceed the allowable value of the relevant specification. The turning angle between shield and connecting bridge is easy to exceed the allowable range of shield machine during the shield launching of the small radius curve section, thus the design axis of the shield must be considered to be properly shifted to the inside of the curve.