超载作用下软土盾构隧道横向变形机理及控制指标研究

隧道横向变形直接关系到结构安全，首先采用数值模拟方法研究了地面压载、土体侧向压力系数和土体抗力系数对隧道横向变形发展的影响，研究了隧道横向变形随压载的变化发展规律，建立了隧道直径变化和混凝土受力、螺栓受力以及接头张开量之间的关系，提出了以隧道直径变化作为隧道横向结构性态发展的判定指标；根据隧道横向变形发展规律，利用隧道结构变形发展过程中的结构几何特征，建立了隧道变形量发展的几何简易分析方法，利用该方法直接测量隧道直径变化就可以判定隧道变形状态，为隧道结构安全评价提供了十分简单有效的手段。

Mechanism of transverse deformation and assessment index for shield tunnels in soft clay under surface surcharge

The transverse deformation of shield tunnels may ultimately threaten the safety of tunnel structure. The surcharge above the tunnels is one of the leading factor to cause their transverse deformation. The evolution of transverse defromation of the tunnels under surchage is firstly studied using numerical simulation considering the effect of the elastic resistance of surrounding soil and lateral coefficient of earth pressure at rest. It is found that the development of joint opening and the stress states of both tunnel concrete and bolts are dependent on the variation of tunnel diameter. Thus, the variation of tunnel diameter can be taken as the assessment index to predict the performance of shield tunnels in soft soils. The criteria for tunnel assessment are determined in terms of diameter change. Then, a geometry-based simple method is proposed to study the relationship between joint opening and tunnel squating based on the tunnel crown settlement. The method is verified by the above- mentioned numerical simulation. This simple method provides a very convenient way to estimate the safety state of shield tunnels.