长期竖向循环荷载作用下黄土中单桩沉降特性模型试验研究

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。

Model tests on settlement of single pile in loess under long-term axial cyclic loading

The settlement of a single pile under long-term axial cyclic loading is different from that under static loading. To study how the pile-top displacement s and displacement amplitude ρ_c change with the number of cycles and to analyze the development model of pile-top cumulative displacement under cyclic loading, a series of single-pile model tests on loess and saturated loess are performed. It is found that the static bearing capacity of the single pile in saturated loess is much lower than that in loess. The test s-N curve of pile head under cyclic loading in loess and saturated loess can be described by power function. With the same load size, the displacement of the single pile under cyclic loading is lower than that under static loading in loess. The cyclic displacement ratios (ratio of cyclic load displacement to static load displacement) are mostly in the range of 0.6 to 0.8. But the displacement of the single pile under cyclic loading is much higher than that under static loading in saturated loess, and the cyclic displacement ratios will grow with the cyclic loading ratio in a linear rule. The single-pile displacement amplitude under cyclic loading in loess is obviously higher than that in saturated loess, and it is mainly because of the cyclic loading amplitude and soil properties.