单桩与群桩基础动力时程响应差异振动台试验

为探明强震作用下大直径深长单桩与群桩基础的动力时程响应差异，依托海文大桥实体工程，通过大型振动台试验，开展了4种不同类型地震波作用下单桩及群桩基础的桩顶加速度、桩顶相对位移、桩身弯矩时程响应变化规律及其差异性研究。研究结果表明：由于群桩效应的存在，桩顶加速度时程响应呈现双面性，群桩基础桩顶加速度峰值大于单桩基础，但峰值出现时刻滞后于单桩0.29～1.06 s；群桩基础的桩顶相对位移最大值显著小于单桩基础，且出现时刻明显滞后，Kobe波作用时滞后高达3.82 s；群桩基础的桩身弯矩最大值小于单桩基础7.54%～9.22%，且单桩基础受地震波影响较大，弯矩时程响应振幅明显大于群桩基础。桩基础抗震设计时，可充分发挥群桩基础动力时程响应滞后性特点，合理设计并选择最优桩型。

Shaking table test on the difference of dynamic time-history response between single pile and pile group foundation

In order to ascertain the difference of dynamic time-history response between large-diameter, deep-long single pile and pile group foundation under strong earthquake, a large shaking table test was carried out based on the physical project of Haiwen Bridge. The various rules and differences of pile top acceleration, pile top relative displacement, and pile bending moment between the single pile and pile group foundation under four types of seismic waves were studied. The results show that the time-history response of pile top acceleration is double-sided due to the pile group effect. The peak acceleration of pile group is larger than that of single pile, but the peak time lags behind that of single pile by 0.29–1.06 s. The pile top maximum relative displacement of the group pile is significantly smaller than that of the single pile, and there is an obvious lag in the time. Excited by the Kobe wave, the lag time is as long as 3.82 s. The maximum bending moment of the pile group is 7.54%–9.22% less than that of the single pile. Because the single pile is greatly affected by seismic waves, its amplitude of bending moment time-history response is obviously larger than that of the pile group. In the seismic design of pile foundation, the lag characteristic of dynamic time-history response of the pile group foundation can be fully used to design and select the optimal pile type reasonably.