水平-竖向-扭转荷载下吸力沉箱基础承载特性数值研究

NUMERICAL ANALYSIS FOR BEARING CAPACITY OF SUCTION CAISSON FOUNDATION SUBJECT TO V-H-T LOADING

海上风机吸力沉箱基础承受结构自重及环境因素引起的竖向、水平、扭转荷载,处于复合加载状态。以位于饱和黏土地基上长径比为0.25～1.0的单桶沉箱基础为对象,ABAQUS为计算工具,研究沉箱基础的承载特性,并考虑沉箱与地基土的摩擦接触作用。首先分析沉箱基础在单一的竖向荷载、水平荷载及扭转荷载作用下的极限承载力,并给出沉箱基础在这些荷载组合下的破坏包络面,其中倾覆力矩通过施加偏心水平荷载实现。结果表明,沉箱基础的竖向承载力可用改进的经典承载力公式计算,而水平承载力系数在给定的接触条件下随沉箱长径比增加而减少,扭转承载力与理论预测结果非常吻合;扭转荷载对沉箱的竖向承载力影响较大,但对水平承载力影响较小;不同扭转荷载下的V-H包络面可用椭圆曲线拟合。

Suction caisson foundations for offshore wind turbines are subjected to vertical,horizontal and torsional loads,which are induced by self-weight of structures and offshore environment.This loading condition is referred to as combined loading mode.In this paper,the results of numerical study on the bearing capacity of suction caisson installed in homogeneous clayey soil to support wind turbine structures were presented,considering the frictional contact behavior of interface between skirt and subsoil.Suction caisson with aspect ratios of 0.25 ～ 1.0 and eccentricity ratios of horizontal loads varying in the range of 0.0 ～ 2.0 was considered.The bearing capacity behavior of the caisson under pure vertical,lateral,torsional loads was investigated through displacement controlled method first,followed by the interaction of these loads with each other by using load-displacement controlled analysis method.The interaction of various combinations of loading was presented in the form of failure locus.It is shown that the vertical capacity from FE analysis agrees well with that of modified conventional method,and horizontal capacity factor decreases with aspect ratio increasing.The torsional load has significant effect on the vertical capacity but has less effect on the horizontal capacity.The normalized failure loci for suction caisson with different eccentricity ratio can be fitted by elliptic curve.