高性能混凝土桩的应力波波速试验研究

Experimental Research on Stress Wave Velocities of High Performance Concrete Pile

本文根据弹性理论推导了高性能混凝土声波与低应变波速的简化计算公式,并对其波速比进行分析探讨,根据铁路工程常用的基桩高性能混凝土配合比,制作了C25~C50六种强度等级的模型桩进行了波速与强度试验研究。结果表明：波速与强度均随龄期的增长而增长,且存在较好的相关性,波速在10 d前迅速增长,28 d以后趋于定值,而强度在28 d以后仍继续增长;声波波速与低应变波速的比值随龄期的增长而增长,本次试验波速比介于1.049~1.109,平均值1.075,与工程调研结果吻合。当龄期大于7 d时,桩身材料阻尼的影响较小,适合工程基桩完整性检测。

Based on the elasticity theory,the simplified calculation formulas of ultrasonic wave velocity and low-strain reflected wave velocity were inferred about high-performance concrete pile,their wave velocity ratio was analyzed and discussed.The experimental research about wave velocities and compression strength were performed on the concrete model piles of C25~C50,which fabricated according to the high-performance concrete mix on railway engineering.The results indicate that there are good correlation between wave velocities and compression strength,which increase with increasing of concrete age.The wave velocities increase rapidly before 10d and become steady after 28d.In contrast,the compression strength increase slowly with increasing of the concrete age,and continue to increase after 28d.The ratio of ultrasonic wave velocity to low-strain reflected wave velocity ranged from 1.049 to 1.109 in this test,the average ratio is 1.075,which increased with concrete age.It is satisfied with the investigation results of engineering piles.Waveform analysis of model piles shows that the influence of material damping on stress wave become smaller after 7d,which adapt to detect pile structural integrity.