我国水能资源丰富的西部地区，河床覆盖层深厚、靠近发震断裂带等问题难以避免，软弱土层受震液化是土石坝地震安全评价主要内容之一。本文针对建在含有易液化夹层的深厚覆盖层上的高沥青混凝土心墙土石坝，提出了可同时考虑动孔压和永久变形累积发展过程的改进孔压-变形耦合有效应力分析方法（IES法），开展了近断层脉冲和非脉冲地震动作用下，软弱土层液化特性及对其上沥青混凝土心墙土石坝响应影响研究，揭示了近断层地震动的脉冲特性对土层液化的触发影响机制，论证了忽略孔压的总应力法相对于考虑孔压的有效应力法在计算液化和坝体加速度响应的误差，分析了地震动的脉冲特性、孔压对坝体竖向永久变形累积发展过程的影响。结果表明：总应力法所得液化区和有效应力法相比虽然位置相同，但分布面积却远大于有效应力法；脉冲特性使得软弱土层多数特征点的孔压在短时间急剧上升，触发液化迅速； 动孔压使得坝顶和坝底加速度相对于不考虑孔压情况有20%~30%的减小；脉冲型地震动作用下，动孔压使得坝顶沉降量最大增大35%，竖向沉降发展过程在脉冲期有明显的激增，对坝体抗震安全稳定性构成了严重的威胁。
Abstract
In the western region of China, which is rich in hydropower resources, problems such as deep riverbed cover and proximity to seismogenic fault zone are unavoidable. The liquefaction of weak soil layer is one of the main contents of safety evaluation of earth-rock dams. In this paper, aiming at the high asphalt concrete core dam built on the deep overburden layer with easily liquefied interlayer, an improved pore water pressure-deformation coupling effective stress analysis method (IES method) is proposed. The liquefaction characteristics of weak soil layer and its influence on the dynamic response under near-fault ground motions are studied. The results show that the liquefaction zone obtained by the total stress method is much larger than that by the effective stress method. Pulse characteristics make the pore pressure of most characteristic points in soft soil layer rise sharply in a short time, triggering liquefaction quickly; Dynamic pore pressure makes the acceleration of dam top and bottom decrease by 20%~30%. Under the action of pulsed ground motion, the dynamic pore pressure makes the maximum settlement of the dam crest increase by 35%, and the development process of vertical settlement increases significantly in the pulse period, which poses a serious threat to the seismic safety and stability of the dam body.
关键词
深厚覆盖层 /
近断层地震动 /
液化 /
土石坝响应 /
永久变形
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Key words
Deep overburden /
Near fault ground motion /
liquefaction /
Dynamic response /
permanent deformation
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