海上风电大直径超长钢管桩竖向承载特性现场试验研究

Field tests on vertical bearing characteristics of large-diameter extra-long steel pipe piles in offshore wind power projects

钢管桩是海上风电工程最主要的基础型式,但针对海上大直径超长钢管桩竖向承载力问题的研究却相对较少。结合广东汕头海上风电工程,进行了海上大直径超长钢管桩竖向承载力特性的现场试验研究,对比了桩底沉降和桩顶沉降随上部荷载的变化特点,分析了桩身侧摩阻力和桩端阻力随上部荷载的变化规律,并依据试验结果对大直径超长钢管桩极限承载力判定方法进行了探讨。试验结果表明:大直径超长钢管桩桩身变形较大,利用桩底沉降随荷载的变化曲线更容易对现场加载量进行控制和调整,也更容易对承载力的极限状态进行判断;大直径超长钢管桩端阻力随桩顶荷载的变化曲线呈“S”形;现行规范中采用Q/Qmax-s/d曲线斜率开始转变为0.2的点所对应的荷载作为极限承载力,将过高的估计大直径超长钢管桩的竖向抗压极限承载力。

The steel pipe piles are the main foundation type for offshore wind power projects,but there are relatively few researches on the vertical bearing capacity of large-diameter ultra-long steel pipe piles in the sea.The field tests are conducted on the vertical bearing capacity characteristics of the large-diameter ultra-long steel pipe piles based on their application in an offshore wind power project in Shantou City of China.The variation rules of side shaft friction and tip resistance with pile load are analyzed,and the variation characteristics of tip settlement and top settlement of the pipe piles are compared.Additionally,based on the on-site test results,the method for determining the bearing capacity of the large-diameter ultra-long steel pipe piles is explored.The tests results indicate that there is a significant pile deformation.It was easier to control and adjust the on-site loading amount by using the curve of tip settlement versus load,and it is also easier to judge the ultimate state of bearing capacity.The curve of tip resistance versus pile load shows an"S"shape.In the current code,the load corresponding to the point at which the slope of Q/Qmax~s/d curve begins to change to 0.2 is used as the ultimate bearing capacity to overestimate the vertical compressive ultimate bearing capacity of the large-diameter ultra-long steel pipe piles.