沉管海底隧道强度折减法分析探讨

将强度折减法用于静荷载作用下海底钢筋混凝土沉管隧道安全稳定性分析。首先,基于应变协调原理并按照沉管钢筋的分布形式和受力特征,推导出钢筋混凝土沉管等效模型抗剪强度指标、抗拉强度的计算公式；其次,利用FLAC^3D软件建立了沉管-土体-海水相互作用强度折减法非线性数值分析模型,探讨钢筋混凝土沉管的破坏分析方法。研究结果表明：不能用位移突变作为沉管破坏分析判据；通过综合分析沉管顶板下沉位移与折减系数的关系、塑性状态以及剪应变增量的分布规律,得到了沉管隧道的安全系数；强度折减法能直观地揭示沉管破坏机理,沉管段的破坏模式主要表现为沉管顶板中部及其与两侧墙壁交汇处的拉伸、剪切破坏。

Strength reduction method for submarine immersed tunnels

The strength reduction method is proposed to study the safety and stability of a submarine immersed tunnel made of reinforced concrete under static loading. Firstly, based on the strain compatibility principle considering the distribution and mechanical characteristics of reinforcing bars, formulas for calculating the shear strength and the tensile strength of the equivalent model of reinforced concrete structures are derived. Secondly, a non-linear numerical model for the strength reduction method considering structure-soil-seawater interaction is established by means of FLAC^3D software to simulate the failure of the immersed tunnel. The simulated results show that a sudden change of displacement can not be used as one of failure criterions for the immersed tunnel. The safety factor of the immersed tunnel is obtained considering the plastic state, shear strain increment and relationship between the tunnel roof displacements and the reduction factors. By using the strength reduction method, the failure mechanism of the immersed tunnel is revealed. Failure modes of the immersed tunnel section are mainly the shear failure and the tensile failure distributed near the center of the tunnel roof slab and the intersection between the roof slab and the two lateral walls.