A study of the resonance characteristics of a staggered rock slope under the tri-dimension earthquake wave
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摘要:
地震引发的共振往往会对边坡造成严重的破坏,直接影响边坡的抗震性能。为研究错距岩质边坡的共振特性,通过有限元软件ANSYS建立三维边坡数值模型,分析错距对边坡固有频率的影响,并使用谐响应分析对坡面各点的共振响应规律及地震作用频率对边坡应力的影响进行探讨。结果表明:(1)在不同错距条件下均有可能出现共振现象,边坡错距越大,基频越小,坡面的水平共振位移大于竖向共振位移,前坡坡面位移峰值较大,发生共振的频率比后坡小;(2)低阶和高阶固有频率被激发都可引发共振,但高阶共振位移相对较小,前坡和后坡坡面水平位移峰值表现为:坡顶>坡中>坡脚,侧坡则是:坡中>坡顶>坡脚,在高频加载条件下,边坡会出现下部动力响应大于上部的现象;(3)坡体共振时发生的破坏主要以坡脚剪切破坏为主,最大剪切应力和最大拉应力出现的位置与加载频率范围有关,前坡更容易遭受破坏,低频地震动对前坡影响较大,而高频地震动则相反。所得结论可为错距边坡进行抗震设防时确定重点加固部位提供参考。
Abstract:The resonance induced by an earthquake often causes more serious damage to the slope and directly affects its seismic performance. To study the resonance characteristics of a staggered rock slope, a 3D numerical model of the slope is established by using the finite element software ANSYS, and the effect of staggered space on the natural frequency of the slope is analyzed. The resonance response laws of different locations on the slope surface and the effect of the earthquake frequency on the stress of the slope are discussed by the harmonic response analysis. The results show that (1) the larger the slope slip distance is, the smaller the fundamental frequency is, and the resonance phenomena may occur under different staggered distances. The horizontal resonance displacement of the slope surface is larger than the vertical one. The front slope has a larger peak displacement and lower resonant frequency compared with those of the back slope. (2) Both the low and high-order natural frequencies can be excited to cause resonance, but the displacement of the high-order resonance is relatively small. The horizontal displacement peak of the front slope and back slope is in the order: top > middle > foot, while that of the side slope is in the order: middle > top > foot. Under high-frequency loading, the dynamic response of the slope at the lower part may be greater than that at the upper part. (3) The shear failure of the slope toe is the main damage in slope resonance. The location of the maximum shear and tensile stress is related to the range of loading frequency. The front slope is more prone to damage. Ground motions with low frequency have a greater influence on the front slope, while high frequency ground motions have the opposite effect. The results can be used as reference to determine the key reinforcement position of a staggered slope in the seismic fortification.
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Key words:
- seismic action /
- staggered slope /
- slope failure /
- resonance characteristics /
- ANSYS /
- seismic fortification
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表 1 边坡岩体物理力学参数
Table 1. Physical and mechanical parameters of slope rock mass
参数 弹性模量/GPa 泊松比 密度/(kg·m−3) 取值 6.0 0.25 2200 表 2 计算模型
Table 2. Calculation models
模型编号 1 2 3 4 5 错距/m 0 20 40 60 100 -
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