5.极限强度破坏机理侧向受荷桩的破坏发生于:桩在土中整体转动(土破坏)或超过了桩截面的极限抵抗弯矩,即桩上出现一个或几个塑性铰(桩破坏)。顶端无约束桩及顶端约束桩的各种破坏机理如图5.1所示。顶端自由无约束长桩的破坏发生是当这个深度处弯矩达到最大值而发展成塑性铰所致,如图5.1a所示。顶端嵌固的约束短桩的破坏则是由于沿桩全长范围内超过了土的极限抵抗所致。在这种情况下,桩的作用象一个暗 5. Ultimate strength failure mechanism Laterally-loaded pile damage occurred in the soil: the overall rotation of the soil (soil damage) or more than the ultimate section of the pile to resist bending moment, that pile appears on one or several plastic hinge (pile damage ). The various failure mechanisms of the top unconstrained piles and the top restrained piles are shown in Figure 5.1. The failure of the top unconstrained long pile occurs when the bending moment reaches its maximum at this depth and develops into a plastic hinge, as shown in Figure 5.1a. The failure of the top-embedded constraint short piles is due to the extreme resistance of the soil beyond the full length of the pile. In this case, the pile acts like a dark one