曲线盾构隧道开挖面极限支护力研究

Research on the Limit Supporting Force of the Shield Tunnel Excavation Face

研究目的:曲线盾构隧道掘进施工存在巨大安全隐患,受盾构刀盘超挖、盾壳挤压内壁土体和千斤顶不对称推力等因素的影响,致使开挖面前方变形复杂,开挖面稳定性难以控制。基于筒仓理论,本文提出曲面梯度楔形棱柱体开挖面极限平衡模型,推导曲线盾构隧道开挖面极限支护力理论计算公式;进而以济南地铁R1线王府庄至大杨庄区间段曲线盾构隧道为工程背景,探究不同曲率半径下开挖面的变形分布特征,以期为曲线盾构隧道掘进开挖面稳定性提供科学的理论指导。研究结论:(1)曲线盾构隧道开挖面破坏呈现不对称分布,受开挖面偏心支护压力的影响,开挖面前方土体形成曲面梯度楔形棱柱体平衡模型;(2)随着曲率半径的减小,开挖面位移和极限支护压力先增大后减小,且支护压力非常规的按中心支护力进行计算,而是偏向于曲线外侧,其值大于直线盾构隧道;(3)极限支护压力随开挖面土体黏聚力、内摩擦角增大而增大,随两侧破裂角的差值增大先呈现增大趋势,当β1>32.3°后减小,最后趋于平缓;(4)本研究成果可为曲线盾构隧道施工开挖面稳定性及其支护提供理论指导和科学依据。

Research purposes： There are great potential safety problems in the construction of shield tunnelling, under the influence of the over excavation of the shield cutter, the inner wall of the shield shell and the asymmetric thrust of jack, resulting in front of the excavation face deformation is complex, difficult to control the stability of the excavation face. Based on the theory of the curved surface of silo, the limit equilibrium model of the surface of the curved wedge prism was proposed, and the theoretical calculation formula of the limit supporting force was deduced; then in the engineering background of the shield tunnel of Jinan rail transit line R1 Wangfuzhuang to Dayangzhuang section, the deformation distribution characteristics of excavation face with different curvature radius were studied, to provide scientific theoretical guidance for the stability of curved tunnel excavation face. Research conclusions： （ 1 ） The damage of curved shield tunnel excavation face presented asymmetric distribution, by the influence of eccentric support pressure of excavation face, the surface gradient wedge prism balance model was formed. （2） With the decrease of the radius of curvature, the excavation surface displacement and the limit support pressure first increased then decreased, and the supporting pressure was calculated not according to the central supporting force, but rather according to the lateral side of the curve, and its value was greater than the straight line of shield tunnel. （3） Limit support pressure increased with the increase of cohesion, internal friction angle of the soil excavation surface, first showed a trend of increase with the increase of the difference in value on both sides of the rupture angle, decreases when the β1 〉 32.3°, and eventually flatten out. （4） The research results can provide theoretical guidance and scientific basis for the stability of the excavation face and its support in the construction of the shield tunnel.