水平循环荷载引起的砂土沉陷-致密作用对刚性桩承载力的影响分析

Influence analysis of sand subsidence and densification caused by lateral cyclic loading on bearing capacity of rigid piles

为研究砂土中刚性桩基础在循环荷载作用下的承载力演化规律,提出了一种循环后单桩承载力的评估方法.首先,基于沉陷坑与致密区域土体的质量守恒原理,量化了由沉陷引起的土体参数变化;然后,根据API规范中的砂土水平土抗力位移模型计算循环前后的单桩承载力;最后,提出了循环后单桩承载力的评估模型,并对沉陷坑尺寸、土体初始相对密实度和致密区域模式等因素进行对比分析.结果表明:单桩承载力随沉陷坑的发展不断增大;对于松砂、中密砂和密砂,循环后的单桩承载力可分别提高约3.0、1.5、1.2倍,提高幅值随相对密实度的增大而降低;2种土体变形模式中,单锥模式相比于双锥模式更符合真实的致密区域形态.

To study the evolution law of the bearing capacity of rigid piles in sand under cyclic loading,an evaluation method for the monopile bearing capacity after cycling was proposed.Firstly,based on the mass conservation principle of subsidence pits and densified regions,the change of the soil parameters caused by subsidence was quantified.Then,according to the sand lateral soil resistance-displacement model in API(American Petroleum Institute),the monopile bearing capacities before and after cycling were calculated.Finally,an evaluation model for the monopile bearing capacity after cycling was proposed,and the multi-factors such as the subsidence size,the initial relative density and the densified region mode were compared and analyzed.The results show that the monopile bearing capacity increases with the development of the subsidence pit.As for loose sand,medium dense sand and dense sand,the monopile bearing capacity after cycling can be increased by 3.0,1.5 and 1.2 times,respectively,revealing that the improvement ratio of the monopile bearing capacity decreases with the increase of the relative density.As for two soil deformation modes,the single-cone mode is more in line with the real densified region morphology than the double-cone mode.