地震加速度动态分布及对高土石坝坝坡抗震稳定的影响
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摘要
《水工建筑物抗震设计规范》(DL5073-1997)建议的土石坝地震加速度动态分布系数适合于150 m以下的土石坝,而前许多土石坝的设计高度已远大于150 m。与低坝相比,高坝受地基刚性的约束减弱,坝体的自振周期延长。在坝体地震反应中,高阶自振周期与地震卓越周期耦合的机率增大,高阶振型的振动易被激发放大,从而导致坝体地震加速度沿坝高的分布与低坝有所不同。据此,采用有限元法研究了高土石坝的加速度分布,提出了高于150 m土石坝的地震加速度动态分布系数图示。在此基础上,利用堆石材料的非线性强度准则,对高度超过150 m的土石坝坝坡抗震稳定性作了进一步的分析,得出随着坝体地震加速度动态分布系数的降低,坝坡临界破坏的安全系数有所提高。
The seismic coefficient suggested in the present Specifications for Seismic Design of Hydraulic Structures(DL5073-1997) is suitable for earth-rock dams lower than 150 meters.While at the present time,many earth-rock dams to be constructed are higher than 150 meters.Compared with low dams,high dams get less constraint from stiffness of foundation,and its natural vibrating period becomes prolonged.During the seismic response,high order naturalvibrating period gets more opportunities to coincide with the seismic predominant period,and the vibrations of high orders are easily to be activated and amplified,which result in the seismic acceleration distribution is somewhat different from low dams.With the finite element method,the seismic acceleration distribution of high earth-rock dams is analyzed.The figure of the seismic coefficient of earth-rock dams higher than 150 meters is put forward.Based on the above analysis,further research of the slope seismic stability of earth-rock dams higher than 150m is made.The conclusion is,with the decrease of the seismic coefficient in the dam body,the critical value of safety factor of the dam slope increases.
The seismic coefficient suggested in the present Specifications for Seismic Design of Hydraulic Structures(DL5073-1997) is suitable for earth-rock dams lower than 150 meters.While at the present time,many earth-rock dams to be constructed are higher than 150 meters.Compared with low dams,high dams get less constraint from stiffness of foundation,and its natural vibrating period becomes prolonged.During the seismic response,high order naturalvibrating period gets more opportunities to coincide with the seismic predominant period,and the vibrations of high orders are easily to be activated and amplified,which result in the seismic acceleration distribution is somewhat different from low dams.With the finite element method,the seismic acceleration distribution of high earth-rock dams is analyzed.The figure of the seismic coefficient of earth-rock dams higher than 150 meters is put forward.Based on the above analysis,further research of the slope seismic stability of earth-rock dams higher than 150m is made.The conclusion is,with the decrease of the seismic coefficient in the dam body,the critical value of safety factor of the dam slope increases.
引文
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[2]CRISTIANO M,SUNIL S.Seismic coefficients for pseudostatic slope analysis[C]//13th World Conference on Earthquake Engineering.VANCOUVER B C.Canada:[s.n.].2004:3 691-3 696.
[3]水利部水利水电规划设总院.DL5073-1997水工建筑物抗震设计规范[S].北京:中国水利水电出版社,1999.
[4]SEED H,GEOFFREY R,MARTIN.The seismic coefficient in earth dam design[J].Journal of the Soil Mechanics and Foundations Division,Proceedings of the American Society of Civil Engineering,1966,92(SM3):25-58.
[5]赵剑明.高土石坝地震反应的三维非线性有效应力分析[D].北京:中国水利水电科学研究院,1999.
[6]龚晓南.土塑性力学[M].杭州:浙江大学出版社,2001:71-76.
[7]迟世春.心墙堆石坝动力反应分析计算理论及抗震措施研究[R].大连:大连理工大学,2006.
[8]李亮.智能优化算法在土坡稳定分析中的应用[D].大连:大连理工大学,2005.
[9]吕擎峰,殷宗泽,王叔华,等.拟静力法边坡稳定分析的改进[J].岩土力学,2005,26(增刊):35-38.LV Qing-feng,YIN Zong-ze,WANG Shu-hua,et al.Improvement of pseudo-static method for slope stability analysis[J].Rock and Soil Mechanics,2005,26(Supp.):35-38.
[10]迟世春,顾淦臣.混凝土面板堆石坝的抗震稳定分析[J].东北水利水电,1995,11:3-5.CHI Shi-chun,GU Gan-chen.Seismic stability analysis of concrete faced rockfill dams[J].Water Resources and Hydropower of Northeast China,1995,11:3-5.
[11]吕擎峰,殷宗泽.高土石坝坝坡稳定非线性分析[J].岩土力学,2004,25(5):793-797.LV Qing-feng,YIN Zong-ze.Nonlinear analysis of slope stability for high earth-rock dams[J].Rock and Soil Mechanics,2004,25(5):793-797.
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