摘要
The high-frequency interference exists obviously in low strain integrity testing of large-diameter pipe pile when a transientpoint load is applied. An analytical solution of vertical vibratory response of large-diameter pipe piles in low strain testing isdeduced in this paper. The analytical solution is verified by both numerical simulation and model test results. The time-domainvelocity responses on pile top are analyzed. The calculation results indicate that the time-domain responses at various pointssuffer different high-frequency interferences, thus the peak values and phases of different points are different. The influence ofvibratory modes on high-frequency interference is analyzed. It is found that the high-frequency interference at 90° point main-ly derives from the second flexural mode, but for other points it mainly originates from the first flexural mode. The factors af-fecting the frequency and peak value of interference waves have been investigated in this study. The results indicate that thelarger radius angle between the receiving and 90° points leads to greater peak value of high frequency wave crest. The leasthigh-frequency interference is detected at the angle of 90°. The frequency of interference waves is decreased with the increaseof pile radius, while the peak value is almost constant. The frequency is also related to pile modulus, i.e. the larger pile modu-lus results in greater frequency. The peak value varies with impulse width and soil resistance, i.e., the wider impulse width andlarger soil resistance cause smaller peak value. In conclusion, the frequency of interference waves is dependent on the geomet-rical and mechanics characteristics of the piles such as pile radius and modulus, but independent of the external conditionssuch as impulse width and soil resistance. On the other hand, the peak value of interference waves is mainly dependent on theexternal conditions but independent of the geometrical and mechanics characteristics of the piles. In practice, some externalmeasures should be adopted to weaken high-frequency interference such as using soft hammer, hammer cushion and adoptingsuitable receiving point.
The high-frequency interference exists obviously in low strain integrity testing of large-diameter pipe pile when a transient point load is applied. An analytical solution of vertical vibratory response of large-diameter pipe piles in low strain testing is deduced in this paper. The analytical solution is verified by both numerical simulation and model test results. The time-domain velocity responses on pile top are analyzed. The calculation results indicate that the time-domain responses at various points suffer different high-frequency interferences, thus the peak values and phases of different points are different. The influence of vibratory modes on high-frequency interference is analyzed. It is found that the high-frequency interference at 90° point mainly derives from the second flexural mode, but for other points it mainly originates from the first flexural mode. The factors affecting the frequency and peak value of interference waves have been investigated in this study. The results indicate that the larger radius angle between the receiving and 90° points leads to greater peak value of high frequency wave crest. The least high-frequency interference is detected at the angle of 90°. The frequency of interference waves is decreased with the increase of pile radius, while the peak value is almost constant. The frequency is also related to pile modulus, i.e. the larger pile modulus results in greater frequency. The peak value varies with impulse width and soil resistance, i.e., the wider impulse width and larger soil resistance cause smaller peak value. In conclusion, the frequency of interference waves is dependent on the geometrical and mechanics characteristics of the piles such as pile radius and modulus, but independent of the external conditions such as impulse width and soil resistance. On the other hand, the peak value of interference waves is mainly dependent on the external conditions but independent of the geometrical and mechanics characteristics of the piles. In practice, some external measures should be adopted to weaken high-frequency interference such as using soft hammer, hammer cushion and adopting suitable receiving point.
基金
supported by the National Natural Science Foundation of China(Grant No.51008115)
the Provincial Science Foundation of Jiangsu(Grant No.BK2008040)
