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长期竖向循环荷载作用下单桩的沉降特性与静载情况下明显不同,通过黄土及饱和黄土中单桩的竖向循环荷载试验,分析了循环荷载作用下单桩的累积位移发展模式,研究了桩顶位移s及循环位移幅值c?随循环次数N的变化规律。试验发现:黄土饱和后单桩的承载力明显下降;饱和前后单桩循环荷载试验的s–N曲线都可采用幂函数进行描述;相同荷载大小时,饱和前单桩的循环荷载位移小于静载位移,循环位移比(循环荷载位移与静载位移的比值)介于0.6与0.8之间,而饱和后单桩的循环荷载位移明显大于静载位移,且循环位移比随循环荷载比线性增长;饱和前单桩的循环位移幅值明显大于饱和后的位移幅值,主要受循环荷载幅值及桩周土性质的影响。
The settlement characteristics of single pile under long-term vertical cyclic loading are obviously different from those under static load. Through the vertical cyclic loading test of single pile in loess and saturated loess, the cumulative displacement development model of single pile under cyclic loading is analyzed. The displacement of pile top s and the cyclic displacement amplitude c? With the number of cycles N changes. The results show that the load-bearing capacity of single pile after loess saturation is obviously decreased. The s-N curve of single-pile cyclic loading test before and after saturation can be described by power function. At the same load, the cyclic load displacement of single pile before saturation is smaller than static load Displacement and cyclic displacement ratio (ratio of cyclic load to static load) is between 0.6 and 0.8. However, the cyclic loading displacement of single pile after saturated is obviously larger than static displacement, and the cyclic displacement ratio increases linearly with cyclic loading. The amplitude of cyclic displacement of single pile before saturation is obviously larger than the amplitude of displacement after saturation, which is mainly affected by cyclic loading amplitude and soil properties around pile.