在进行高边坡抗震设计分析时,采用动力有限元数值模拟法较为普遍。但当地震作用致使边坡岩体部分已进入塑性状态且变形加大时,若仍然采用线弹性方法来分析,则存在较大误差。为此,采用弹塑性动力方法计算静力与地震动全平衡状态的弹塑性边坡地震响应,对岩质边坡弹塑性动力状态进行了尝试性探讨,分别输入2条等峰值加速度、不同特征周期和持续时间的地震波,结合边坡的固有频率特性,着重分析常用于抗震设计的地震动参数峰值加速度及累积塑性应变的地震响应规律。结果表明,输入相同峰值、不同特征周期和持续时间的地震波,地震响应累积塑性应变有明显差异;对地震波来说,尽管峰值相同,但持续时间与频谱特性不一样,地震效应存在较大差异。因此,在进行边坡抗震设计计算时,地震波选取一定要慎重,应具体问题具体分析,否则有可能得到不真实的抗震安全评价结果。
Abstract
Dynamic finite element numerical simulation is commonly used in the seismic design for high slopes. However,linear-elastic methods will cause big errors when the slope rock displays plastic behavior and the deformation develops under earthquake action. In view of this,elastoplastic method is adopted to calculate the seismic response of elastoplastic slope in the full equilibrium of both static and seismic motion,trying to explore the dynamic state of rock slope elastoplasticity. Two seismic waves with the same peak acceleration but different periods and durations were input. The peak accelerations of seismic motion parameters and the mechanism of seismic response for accumulative plastic strain,both widely used in seismic design,were analyzed in consideration of the natural frequency of slope. Result shows that the seismic accumulative plastic strains are distinct when inputting seismic waves with the same peaks but different periods and durations; although the peaks are the same,the seismic effect varies given different durations and spectral characteristics. As a result,in the calculation for slope seismic design,the seismic wave should be chosen discreetly,varying from one case to another,otherwise it would cause unreal seismic safety evaluation result.
关键词
岩质边坡 /
地震响应 /
地震波持续时间 /
累积塑性应变
Key words
rock slope /
seismic response /
duration of seismic wave /
accumulative plastic strain
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参考文献
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基金
国家重点基础研究发展计划(973)项目(2011CB710603)
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