The main reason is the effect of weld toe and weld crack on the fatigue limit .

疲劳断口分析认为，焊缝的焊 趾 和 裂纹是影响高强钢疲劳强度的主要原因。

The floodgate may be regarded as a series system with four main failures modes including slip along the foundation compression failure of the floodgate toe in the downstream line tension crack of the floodgate heel in the upper stream and non-uniform stress distributions .

软基上的水闸可看成由4种主要失效模式（沿闸基面的滑动、下游闸 趾压坏、上游闸踵 拉裂和上下游应力不均匀）所组成的串联体系。

Based on the analysis and stochastic model for surface crack growth at weld toe the limit state of the surface crack growth was discussed . A probabilistic method of assessing the fatigue life and safety of welded joints containing surface cracks is presented .

本研究以对接接头焊 趾表面裂纹疲劳扩展随机模型与统计分析为基础，分析了 焊 趾表面 裂纹 疲劳扩展的极限状态，探讨了带表面裂纹焊接构件疲劳扩展寿命与安全性的概率评定方法。

The initial model the deformation mainly concentrated in the front of the toe of slope Department followed by posterior slope showed the foot of rock crack a small tensile cracks appeared after the edge .

模型计算初始，变形主要集中在边坡前缘的 坡脚处，其次为边坡的后缘，表现为坡脚岩体 开裂，后缘出现小拉裂缝。

The weld toe leads to high nonlinear stress distributed across plate thickness which affects the stress field around surface crack tip .

由于焊接结构的焊 趾位置存在很高的非线性分布应力，焊趾 处表面 裂纹尖端附近的应力场必然受到影响。

The notch effect at the welded toe reduces very much the initiation life of crack ( 0 ~ 10 μ m or 20 μ m in depth ) .

焊 趾的缺口效应使 裂纹的萌生（0～10μm或20μm深）寿命极短。

The working method and process of constructing bored cast - in-place piles are very complicated and variety so there occurred many phenomena such as small resistance of pile toe expansive and shrinkage of hole diameters pile break and crack .

灌注桩施工工艺环节多，边界条件复杂，因此，桩 尖阻力偏小，浅部发生扩径、缩径和 断桩等现象较多。