循环荷载下阶梯形变截面桩与等截面桩复合地基承载性状研究

Experimental Research on Bearing Behaviors of Composite Foundations with Stepped Cross-Section Pile and Uniform Section Pile under Cyclic Loading

为探究循环荷载作用下,阶梯形变截面桩与等截面桩复合地基工作性状的差异,对阶梯形变截面桩与等截面桩的9桩复合地基进行室内模型试验,分析循环加载次数对阶梯形变截面桩与等截面桩复合地基永久沉降、桩-土应力比的影响规律,以及循环荷载作用下桩身应变的分布规律。研究结果表明:阶梯形变截面桩和等截面桩的沉降速率起初较大,随着加载次数的增加,沉降速率逐渐减小,并趋于稳定;在相同加载条件下,阶梯形变截面桩的沉降明显小于等截面桩,并且前者先趋于稳定。桩-土应力比随加载次数的增加而降低,降低的幅度开始较大,然后慢慢减小,并趋于稳定;在相同条件下,阶梯形变截面桩的桩-土应力比大于等截面桩的桩-土应力比,并且前者先趋于稳定。对于阶梯形变截面桩,在上下段各出现一个应变峰值,上段的应变峰值明显大于下段的峰值;而对于等截面桩,只出现一个应变峰值。

To study the work behavior differences of the composite foundations with stepped cross-section piles and uniform piles under cyclic load, conducted indoor contrast model tests on the composite foundations with 9 stepped cross- section piles and uniform section piles, analyzed the influence law of cyclic loading numbers on the permanent settlement and the pile-soil stress ratio of the composite foundations with stepped cross-section piles and uniform piles, and studied the strain distribution law along the piles under cyclic loading. The results show that the settlement rates of stepped crosssection piles and uniform piles are comparatively large at first, with the increment of loading times, the settlement rates decrease gradually and tend to be stable. Under the same loading conditions, the settlement of stepped cross-section piles is significantly less than that of the uniform piles, and the former tends to be stable firstly. The pile-soil stress ratio decreases with the increment of the number of loading, and the reduction magnitude is very large at first, then decreases slowly and tends to be stable. Under the same conditions, the pile-soil stress ratio of stepped cross-section piles is greater than that of uniform section piles, and the former tends to be stable firstly. For the stepped cross-section pile, the upper and lower section respectively emerge a strain peak value, and the upper pile strain peak is greater than that of the lower pile. And the uniform pile only emerges a strain peak.