基于CPT的振动沉桩贯入分析理论模型

针对振动沉桩贯入预测问题,推导了基于一维波动方程的理论模型,建立了基于静力触探试验(Cone Penetration Test,CPT)结果的预测方法,编写了对应的计算程序,并通过实际工程案例进行了验证.在此基础上,探讨了桩锤工作频率、偏心力矩和配重对沉桩速度的影响.研究结果表明,该模型可较好地模拟桩的振动贯入过程;在桩的贯入过程中,桩身各位置最大拉应力一般小于最大压应力,桩身最大拉应力出现在沉桩结束时.此外,参数分析表明增加桩锤工作频率和偏心力矩均可有效提升桩锤沉桩能力和加快桩的贯入速率,如工作频率由30 Hz提高67％时,平均贯入速率可提高约170％;桩锤偏心力矩提高50％时,平均贯入速率可提高240％;相比于前两种方式,增加配重的方式起到的效果较为有限.

CPT-based Model for Pile Penetration Analysis with Vibratory Hammer

To simulate the process of pile installation with a vibratory hammer, this paper presents a theoretical model based on the one-dimensional wave equation and develops a prediction method of the results of the in-situ cone penetration tests (CPT). Computer program is also compiled and verified against an industrial project. Furthermore, the effect of hammer''s working frequency, eccentric moment and additional weight are investigated. It shows that, the presented model in this paper simulates the penetration process well for a vibrator driven pile; during installation, the maximum tensile stress in pile shaft is generally smaller than that in compression; the maximum tension stress happens at the end of pile driving. In addition, parameter studies show that increasing the hammer''s frequency and eccentric moment improves the hammer''s drivability and makes a quicker penetration, e.g. 67% increase in hammer frequency from 30Hz leads to a 170% increase in pile penetration rate, and 50% increase in eccentric moment makes a 240% increase in pile penetration rate; compared with the aforementioned two approaches, a limit positive effect is shown by increasing the additional weight.