多级框架锚索和抗滑桩联合作用下边坡抗震性能的振动台试验研究

Shaking table test of seismic response of slope reinforced by combination of anti-slide piles and multi-frame foundation beam with anchor cable

基于原型边坡设计了大型振动台模型试验,通过监测锚索轴力、桩身土压力、坡体加速度和坡面位移时程,研究多级锚索框架梁与双排抗滑桩组合结构加固含软弱夹层岩质边坡的地震动力特性。试验结果表明:在0.15g El Centro地震波激振时锚索预应力产生损失,最大损失比为23%,建议对变形等级要求较高的边坡在锚索抗震设计时适当提高预应力初始值1.2~1.3倍;沿边坡不同高度布置的锚索其轴力响应峰值几乎同一时刻到达,而峰值增加比例呈现出空间非一致性,在锚索抗震设计时应以坡体中部抗滑桩为界将边坡分为上、下区分别考虑;坡脚抗滑桩受荷段、锚固段土压力均随着输入地震波峰值加速度的增加而增大,主动土压力分布规律将由"上小下大"转变成"上大下小"的形状,被动土压力Ⅰ、Ⅱ区的分界点将向桩体下部发展;锚索与抗滑桩在地震时表现为协同工作机制,工程设计中要充分考虑地震效应对桩锚下滑力分担比的影响。该研究成果可为更加合理地考虑地震区锚索框架梁与抗滑桩组合支护结构的设计提供指导。

A large-scale shaking table model test is designed to study the dynamic behaviors of slope reinforced by multi-frame foundation beam with anchor cable and double-row anti-slide piles under seismic loading. Several critical parameters are monitored during the test, including axial force of pre-stressed anchor cable, earth pressure on piles, acceleration of slope body and displacement-time relationship of slope surface. Experimental results show that the pre-stressing of anchor cable varies with input seismic wave, and its maximum value of pre-stress loss reaches 23% when input wave is El Centro seismic wave with an amplitude of 0.15 g. The test results suggest that the applied pre-stress value should be risen up to 1.2 to 1.3 times of the designed value for reinforced slope with strict deflection limit. The axial forces of anchor cables installed at different altitudes reach the maximum almost simultaneously, but the increase proportion of peak axial force demonstrates non-uniformity in space, so the aseismic design of anchor cable should be divided into upper and lower sections with anti-slide piles installed in the middle section of the slope. The earth pressure increases with the amplitude of input seismic waves. As the amplitude increases, the distribution of active earth pressure changes from ‘upper small-lower big shape＇ to ‘upper big-lower small shape＇. The demarcation line between the passive earth pressure zones I and II shifts to the bottom of pile. Anchor cables and anti-slide piles should perform as a collaborative structure under earthquake, so the effect of earthquake on the sliding force sharing ratio between pile and anchor cable should be carefully considered. The results can provide references for the design of anchor cable frame beam and anti-slide pile supporting structure in earthquake zone.