某海上大直径灌注桩完整性缺陷成因及预防措施  

Causes of defects in integrity of a large diameter cast-in-place pile at sea and preventive measures

作　　者：王新刚[1,2] 司维 WANG Xin-gang;SI Wei(Tianjin Port Engineering Institute,Co.,Ltd.of CCCC First Harbor Engineering Co.,Ltd.,Tianjin 300222,China;CCCC First Harbor Engineering Co.,Ltd.,Tianjin 300461,China)

机构地区：[1]中交天津港湾工程研究院有限公司,天津300222 [2]中交第一航务工程局有限公司,天津300461

出　　处：《中国港湾建设》2023年第5期35-39,共5页China Harbour Engineering

摘　　要：某海上大直径混凝土灌注桩海水水面以上桩身出现了较为严重的完整性缺陷,而海水水面以下桩身基本没有缺陷。为了弄清缺陷产生原因并研究制定预防措施,首先对灌注桩缺陷位置进行取芯验证,确定了缺陷类型为混凝土竖向开裂,然后建立了灌注桩有限元模型,在考虑现场边界条件的基础上,对灌注桩混凝土温度应力进行仿真计算。温度应力计算结果显示,由于空气的导热系数较小,水面以上桩身混凝土内部温度明显高于水面以下桩身混凝土温度,在温度下降过程中,混凝土收缩受到护筒约束作用下产生较大拉应力从而导致混凝土开裂。最后据此研究制定了缺陷控制技术措施。实践结果表明,桩身完整性缺陷控制效果良好,后续施工灌注桩未出现类似缺陷。A large diameter concrete cast-in-place pile has serious defects in its integrity in the pile shaft above the sea water surface,but there is no defect below the sea water surface.In order to find out the causes of the defects and develop preventive measures,coring was made first at the location of the defects of the cast-in-place pile and tested to verify that the type of defects was determined as vertical cracking of concrete.Then,a finite element model of the cast-in-place pile was established and was used to simulate and calculate the temperature stress of the cast-in-place pile on the basis of considering the field boundary conditions.The calculation results of temperature stress show that,due to the low thermal conductivity of air,the internal temperature of pile concrete above the water surface is significantly higher than that below the water surface.In the process of temperature decline,concrete shrinkage is constrained by the protective casing and the tensile stress is greater,resulting in concrete cracking.Finally,technical measures for defect control are studied and formulated accordingly.The results of practice show that the effect of pile integrity defect control is good,and no similar defects are found in the subsequent construction of cast-in-place piles.

关 键 词：灌注桩 完整性缺陷 大体积混凝土 裂缝控制 温度应力 

分 类 号：U655.544[交通运输工程—港口、海岸及近海工程] TU473.14[交通运输工程—船舶与海洋工程]