基于相场法的沉管隧道结构损伤区识别

Identification of Damage Zone in Immersed Tunnel Structure Based on Phase Field Method

采用谱分解相场法对沉管隧道结构损伤区进行识别,建立了能量泛函数,利用断裂变分方法建立了相场和位移场控制方程组。采用有限元方法求解了相场模型,并通过基准算例验证了所用相场方法的求解实现手段。建立了二维相场分析模型,对襄阳市某沉管隧道的结构损伤断裂区进行了识别,研究了覆盖层厚度、水位和沉管结构能量释放率对损伤区的影响。结果表明:施工时沉管隧道损伤区主要出现在左右行车孔顶部内表面和中管廊顶部外表面,同时损伤最大值出现在中管廊顶部;覆盖层厚度和水位增加造成沉管损伤最大值逐渐增大,但E5管节仍具有充足的安全储备,沉管损伤值不超过0.04;当水位增加到沉管破坏时,中管廊顶部出现2条对称裂缝,左右2个行车孔中部出现从内表面向外表面扩展的竖向裂缝,左右两侧连接区域出现从外表面向内表面扩展的斜向裂缝;第40个荷载步时,最大损伤量随着能量释放率的增加逐渐减小且呈倒S型分布;沉管破坏水位与临界能量释放率呈线性关系,临界能量释放率增加时,沉管能够承受更高的水位;相场断裂方法能够对沉管隧道在施工及运营中的高度损伤或者断裂破坏区域进行直观的识别和精准刻画,为沉管隧道抗裂措施的施加提供参考。

The damage zone in an immersed tube tunnel structure is identified by using the phase field method for spectral decomposition. The energy functional is established, and the governing equations of phase field and displacement are established by using the fracture variational method. The phase field model is solved by using the finite element method, and the solving method obtained by the phase field method is verified by a benchmark example. A 2 D phase field analysis model is established. The structural damage and fracture areas of an immersed tunnel in Xiangyang City are identified. The influences of coverage thickness, water level and energy release rate of immersed tunnel are investigated. The result indicates that(1) the damages of immersed tunnel occur on the top inner surface of the left and right carriageways and the top outer surface of the middle pipe gallery, and the maximum damage occurs at the top of the middle pipe gallery;(2) the maximum damage value of the immersed tunnel increases gradually due to the increase of the coverage thickness and water level, but the E5 element of immersed tunnel still has sufficient safety reserve, and the damage value does not exceed 0.04;(3) when the water level increases to the failure point of the immersed tube, 2 symmetrical cracks appear at the top of the middle pipe gallery, vertical cracks extending from the inner surface to the outer surface appear in the middle of the left and right carriageways, and oblique cracks extending from the outer surface to the inner surface appear in the connecting areas on the left and right sides;(4) at the 40 th load step, the maximum damage decreases gradually with the increase of the energy release rate and shows an inverted S-shaped distribution;(5) the water level for tube failure has a liner relation to the energy release rate, and the tunnel can be subjected to a higher water level as the critical energy release rate increases;(6) the phase field fracture method can intuitively identify and accurately describe the highly damaged or fractured areas of immersed tunnels during construction and operation, and provide a reference for the application of anti-cracking measures to immersed tunnel.