免共振沉桩原位试验研究

In-situ Test on Resonance-free Pile

为解决传统桩基施工过程中存在的环境污染、挤土效应、效率低及能耗高等突出问题,以某高架桩基工程为例,基于免共振液压振动锤系统沉桩施工工艺,通过原位沉桩试验测试、现场振动测试,研究钢管桩沉桩过程中桩周土体、地铁运行期间桥墩变形特征及其振动变化规律。研究结果表明:钢管桩沉桩过程中桩周土体水平位移集中分布在近地表0~2/3 L(L表示桩长)范围内,地表以下0~1/4 L范围水平位移较大,土体水平和竖向位移最大值分别为2.37 mm和3.13 mm,桥墩倾斜0.4‰~0.7‰,分析发现沉桩过程中挤土效应不明显;现场振动测试结果显示,当无地铁经过时桥墩振动速度最大峰值为0.823 mm/s,有地铁经过时为1.90 mm/s,充分表明沉桩过程对周边环境影响程度弱;实现了对环境“低影响”的效果,为沉桩施工新技术的研发提供理论和实践指导。

The construction of traditional pile foundation is featured by environmental pollution,soil squeezing effect,low efficiency and high energy consumption.In an attempt to tackle these problems,the deformation characteristics and vibration of pile’s surrounding soil during pile sinking and those of a high-rise bridge pier during adjacent subway running were investigated via in-situ pile sinking test and field vibration test.The resonance-free hydraulic vibratory hammer system was adopted for pile sinking test.Results demonstrated that the horizontal displacement of soil around the pile during pile sinking concentrated in the range of 0-2/3 L(L represents pile length)near the ground surface,and in particular,the horizontal displacement in the range of 0-1/4 L below the surface was very large.The maximum horizontal and vertical displacement of surrounding soil was 2.37 mm and 3.13 mm,respectively,and the inclination of the pier was 0.4‰-0.7‰.The soil squeezing effect was not obvious during the pile sinking.Field vibration test results showed that the maximum peak velocity was 0.823 mm/s in the absence of subway running,while in the presence of subway running,the peak velocity was 1.90 mm/s,which indicates that the impact on the surrounding environment is weak during pile sinking.