The structural failure of round and egg-shaped sewer pipes is investigated by means of laboratory experiments and finite element method analyses. Two different round pipes are considered, which have an inner diameter of 400 mm and 500 mm, and are respectively referred to as R400 and R500 sewer pipes. The egg-shaped pipe considered in this study has a horizontal inner diameter of 400 mm and a vertical inner diameter of 600 mm, and is labeled as the E400/600 sewer pipe. Sewer pipes with these dimensions are most commonly used in the Netherlands. In full-scale experimental tests the sewer pipe specimens are subjected to biaxial loading, whereby the horizontal pressure loading is set equal to 1/3 times the vertical pressure loading. This loading condition is representative of a sewer pipe embedded in a well-graded sandy gravel and subjected to neutral horizontal earth pressure. Apart from the global load–displacement behaviour, the local strain response is measured at various locations, which indicates how the applied load is distributed across the sewer pipe. The fracture pattern at catastrophic failure is recorded by means of cameras placed at the front side of the pipe specimen. The round pipes fail under the development of 4 distinctive failure cracks, which are located at the top and bottom of the sewer pipe, and halfway the left and right sides. The egg-shaped sewer pipes also fail under the development of 4 failure cracks, which emerge at the top and bottom of the pipe, and at the top-left and top-right sides. The round R500 pipe fails at the lowest ultimate failure load, which is, respectively, a factor of 1.16 and 2.25 smaller than the ultimate failure loads of the round R400 pipe and the egg-shaped E400/600 pipe. The FEM models of the round and egg-shaped pipes accurately predict both the failure response and the fracture pattern measured in the experiments. Accordingly, the FEM model of the round R400 sewer pipe is used to analyse the sensitivity of the overall failure response of the sewer pipe to various parameters, which are the load contact area, the ratio between the applied horizontal and vertical loads, the wall thickness of the sewer pipe, and the tensile strength, mode I toughness and Young’s modulus of the concrete. The variation of these parameters mimics how the load bearing capacity of a sewer pipe decreases under the effects of soil erosion, changes in lateral earth pressure, biochemical degradation, and ageing. The knowledge obtained from the experimental–numerical study may support the decision making process on maintenance and replacement of sewer systems.

通过实验室试验和有限元方法分析，研究了圆形和蛋形下水道管道的结构失效。考虑了两种不同的圆管，它们的内径分别为 400 mm 和 500 mm，分别称为 R400 和 R500 污水管。本研究中考虑的蛋形管道的水平内径为 400 毫米，垂直内径为 600 毫米，标记为 E400/600 下水道。这些尺寸的下水道管道在荷兰最常用。在全尺寸实验测试中，污水管试样受到双轴载荷，其中水平压力载荷设置为等于垂直压力载荷的 1/3。这种加载条件代表下水道管道嵌入分级良好的砂砾石中并承受中性水平土压力。除了整体载荷-位移行为外，还会在不同位置测量局部应变响应，这表明施加的载荷如何分布在下水道管道上。灾难性故障时的断裂模式通过放置在管道试样前侧的摄像机记录下来。圆管在下水管上下、左右中途出现4条明显的破坏裂纹。蛋形下水管在管道顶部和底部以及左上角和右上角出现 4 条失效裂缝的情况下也失效。圆形 R500 管在最低极限破坏载荷下失效，分别比圆形 R400 管和蛋形 E400/600 管的极限破坏载荷小 1.16 和 2.25 倍。圆形和蛋形管道的 FEM 模型准确预测了实验中测量的失效响应和断裂模式。相应地，利用圆形 R400 下水道管的有限元模型来分析下水道管整体失效响应对各种参数的敏感性，这些参数是载荷接触面积、施加的水平和垂直载荷之间的比率、壁厚下水管道的抗拉强度、I 型韧性和混凝土的杨氏模量。这些参数的变化模拟了下水道管道的承载能力如何在土壤侵蚀、侧向土压力变化、生化降解和老化的影响下降低。从实验-数值研究中获得的知识可以支持下水道系统维护和更换的决策过程。