摘要
现浇X形混凝土桩是高速公路软土地基处理新技术。依托南京长江四桥北接线现浇X形桩复合地基试验段,采用低应变反射波法、静载荷试验法和桩头开挖法对现浇X形桩的质量进行了现场检测。试验结果表明:现浇X形桩低应变检测波形受到高频波干扰,当激振力周期较短时,检测曲线的高频波干扰明显。低应变测试平均波速在3 600 m/s左右,均为I类桩,桩身质量完整。桩长14 m时单桩极限承载力达到600 kN,桩长20 m时的单桩复合地基承载力特征值达到160 kPa,均满足设计要求。在靠近地面的桩头存在往外扩大的趋势,而深度越深,X形桩的成形效果越好。现浇X形桩混凝土的充盈在凹弧处更为明显,而在凸起段不甚显著。现浇X形桩成桩截面与设计截面相比面积增加而周长减小,混凝土充盈系数为1.16～1.32,截面周长比设计截面减小5.1～6.7%。
Cast-in-place concrete X-section pile is a new technology for improvement of highway soft ground.Based on the highway engineering of the fourth Nanjing Yangtze river bridge,field tests of cast-in-place concrete Xsection pile composite foundation are conducted. The methods of low strain testing,static load testing and excavation of pile head are adopted to detect the quality of cast-in-place concrete X-section pile. The results indicate that the low strain integrity test waveform is disturbed by high frequency waves. This phenomenon is obvious when the period of the excitation force is short. The average wave velocity is about 3 600 m / s in the low strain integrity testing,as a result,all the piles are intact. The ultimate bearing capacity of the single pile reaches 600 kN when the pile length is14 m. The ultimate bearing capacity characteristic value of the pile composite foundation reaches 160 kPa when the pile length is 20 m,both of which satisfy the design requirements. The pile head which is close to the ground has a widening trend,and X-section pile has better forms as the depth is deeper. Concrete filling of Cast-in-place concrete X-section pile at the concave arc is more apparent than that at the convex section. The constructed cast-in-place concrete X-section pile section has a larger area and a smaller perimeter than the design section,concrete filling coefficient is 1. 16 ～ 1. 32,the perimeter is smaller than the design section by 5. 1 ～ 6. 7%.
出处
《地下空间与工程学报》
CSCD
北大核心
2013年第S2期1989-1995,共7页
Chinese Journal of Underground Space and Engineering
关键词
现浇X形桩
低应变检测
静载荷试验
桩头开挖
现场试验
cast-in-place X-section pile
low strain integrity testing
static loading test
excavation of pile head
field test
