高频免共振法沉桩对周围土体影响的现场测试与分析

为研究高频免共振法沉桩对周围土体振动和变形的影响，以国家会展中心(上海)双层改造工程为例进行了现场测试。该改造工程中桩基施工环境敏感，沉桩在室内进行且邻近地铁和燃气管道。试桩采用开口钢管桩(桩径700mm，桩长60m)，测试了沉桩过程中激振力、地面振动以及土体的竖向和水平变形等。结果表明：每根试桩沉桩用时23~37min(不包括现场接桩时间)，沉桩速度较快；三节桩沉桩用时和所需激振力幅值随着沉桩深度增加而逐渐增大；地面最大振动速度在水平距离约1.5倍桩径处为13.32mm/s，3.5倍桩径处为8.51mm/s，随水平距离增加呈指数衰减；在水平距离约1.5倍桩径处，竖向和水平变形明显，分别产生最大沉降35.0mm和最大挤压变形14.96mm，其他水平距离处则影响较小。实测数据与工程实践表明，高频免共振法沉桩对周围土体振动和变形的影响程度低、衰减快、范围小。本研究可为敏感环境桩基施工提供新的方法。

Field test and analysis on effects of pile driving with high-frequency and resonance-free technology on surrounding soil

To study the effect of pile driving with high-frequency and resonance-free (HFRF) technology on ground vibration and soil deformation, a field test, based on a renovation project of the National Exhibition and Convention Center (Shanghai), was carried out. The pile driving was confronted with sensitive construction environment, including indoor construction and being adjacent to metro and gas pipeline. Open-ended steel pipe piles (diameter 700mm, length 60m) were used, and centrifugal force, ground vibration, as well as vertical and horizontal deformation of soil were measured. The results show that the pile driving is rapid and takes 23 to 37 minutes for each pile (leaving out welding time). The time and centrifugal force amplitude for each pile segment are increasing gradually with depth. Meanwhile, the maximum ground vibration velocity is 13.32mm/s at around 1.5 times diameter, and 8.51mm/s at around 3.5 times diameter, which appears to attenuate exponentially. At about 1.5 times diameter, the vertical and horizontal deformation is evident, and the maximum settlement is 35.0mm and the maximum squeeze is 14.96mm, respectively. While the deformation of other points is little. The field test and project practice show that the effect of HRFR technology on ground vibration and soil deformation is low, and the ground vibration and soil deformation attenuate quickly and present at limited area, providing a new construction method for piling driving in sensitive environment.