大型地下洞室群地震响应分析的动力子模型法
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摘要
水电站地下洞室群埋深大,在动力分析时若将模型建至地表将使网格规模庞大,不利于分析效率的提高。提出适合于大型地下洞室群地震响应分析的动力子模型法。该方法将大范围、粗网格的地下地震波动场计算与小范围、细网格结构动力计算分开,分别建立粗网格和细网格模型进行分析。首先,根据深部基岩的地震波传播特性,采用幅值线性折减的方法对地表加速度时程向基岩深处推算,得到在模型底边界的加速度时程,再输入模型可算得大范围的地震波动场。其次,把结构计算模型边界节点放入波动场计算模型中插值,可获得计算模型边界条件,最后,完成地震荷载的输入。算例表明,推算所得模型底部加速度时程考虑工程具体条件,比规范规定的单一折减系数更能反映实际工程的地下地震动特性。同时,在地下洞室的地震响应分析中,地震波过早被地表反射或不考虑地震波的反射,都会对计算结果造成误差,动力子模型方法能够在保证计算结果精确性的同时,使细网格的计算模型不建至地表自由面,可显著缩减网格规模,提升动力计算效率。
The overburden depth of underground caverns in hydropower plants is always huge.When earth surface is considered in mesh discretization,the computation cost is considerable and the computation lowers analysis efficiency.To solve this issue,the dynamic sub-model method is proposed for earthquake response analysis of large-scale underground caverns.This method separates large-scale,coarse-grained calculation of underground seismic motion and small-scale,fine-grained calculation of structural dynamic analysis by performing calculation on seismic field wave model and structural analysis model,respectively.Firstly,based on the transmitting characteristics of seismic wave in deep bedrock,the acceleration data in deep rock mass are estimated by linearly reducing the time-history of ground acceleration data.By inputting the estimated acceleration data along bottom boundary,seismic wave field covering wide range is derived.Afterwards,boundary points of structural analysis model are interpolated in seismic wave field model.The boundary conditions of structural model are then obtained and the earthquake input of structural model is realized.The numerical example indicates that the estimated acceleration data at the bottom boundary take specific engineering conditions into consideration.Therefore the estimated results are more efficient in reflecting actual underground seismic motion than the fixed reduction coefficient in design codes.Meanwhile,the simulation of earth surface reflection of seismic wave has considerable influences on the accuracy of calculation results.The proposed dynamic sub-model method not only guarantees the accuracy of calculation results but also ensures that the earth surface needs not to be modelled.The computation cost is therefore lowered considerably and the computation efficiency is greatly enhanced.
The overburden depth of underground caverns in hydropower plants is always huge.When earth surface is considered in mesh discretization,the computation cost is considerable and the computation lowers analysis efficiency.To solve this issue,the dynamic sub-model method is proposed for earthquake response analysis of large-scale underground caverns.This method separates large-scale,coarse-grained calculation of underground seismic motion and small-scale,fine-grained calculation of structural dynamic analysis by performing calculation on seismic field wave model and structural analysis model,respectively.Firstly,based on the transmitting characteristics of seismic wave in deep bedrock,the acceleration data in deep rock mass are estimated by linearly reducing the time-history of ground acceleration data.By inputting the estimated acceleration data along bottom boundary,seismic wave field covering wide range is derived.Afterwards,boundary points of structural analysis model are interpolated in seismic wave field model.The boundary conditions of structural model are then obtained and the earthquake input of structural model is realized.The numerical example indicates that the estimated acceleration data at the bottom boundary take specific engineering conditions into consideration.Therefore the estimated results are more efficient in reflecting actual underground seismic motion than the fixed reduction coefficient in design codes.Meanwhile,the simulation of earth surface reflection of seismic wave has considerable influences on the accuracy of calculation results.The proposed dynamic sub-model method not only guarantees the accuracy of calculation results but also ensures that the earth surface needs not to be modelled.The computation cost is therefore lowered considerably and the computation efficiency is greatly enhanced.
引文
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[13]张雨霆,肖明,刘嫦娥.三维有限元任意截面的插值和剖分计算方法[J].武汉大学学报:工学版,2008,41(2):37–41.(ZHANG Yuting,XIAO Ming,LIU Chang′e.Calculation method for meshing and interpolation on arbitrary cross-section of 3D finite elements[J].Engineering Journal of Wuhan University,2008,41(2):37–41.(in Chinese))
[14]赵建锋,杜修力,韩强,等.外源波动问题数值模拟的一种实现方式[J].工程力学,2007,24(4):52–58.(ZHAO Jianfeng,DU Xiuli,HAN Qiang,et al.An approach to numerical simulation for external source wave motion[J].Engineering Mechanics,2007,24(4):52–58.(in Chinese))
[15]中华人民共和国国家标准编写组.GB 17741—2005工程场地地震安全性评价技术规范[S].北京:中国标准出版社,2005.(The National Standards Compilation Group of People′s Republic of China.GB 17741—2005 Evaluation of seismic safety for engineering sites[S].Beijing:Standards Press of China,2005.(in Chinese))
[16]中华人民共和国行业标准编写组.DL 5073—2000水工建筑物抗震设计规范[S].北京:中国电力出版社,2001.(The Professional Standards Compilation Group of People′s Republic of China.DL 5073—2000 Specifications for seismic design of hydraulic structures[S].Beijing:China Electric Power Press,2001.(in Chinese))
[2]王如宾,徐卫亚,石崇,等.高地震烈度区岩体地下洞室动力响应分析[J].岩石力学与工程学报,2009,28(3):568–575.(WANG Rubin,XU Weiya,SHI Chong,et al.Dynamic response analysis of rock underground caverns in highly seismic region[J].Chinese Journal of Rock Mechanics and Engineering,2009,28(3):568–575.(in Chinese))
[3]隋斌,朱维申,李晓静.地震荷载作用下大型地下洞室群的动态响应模拟[J].岩土工程学报,2008,30(12):1 877–1 882.(SUI Bin,ZHU Weishen,LI Xiaojing.Simulation on dynamic response of large underground opening complex under seismic loads[J].Chinese Journal of Geotechnical Engineering,2008,30(12):1 877–1 882.(in Chinese))
[4]博弈创作室.ANSYS 9.0经典产品高级分析技术与实例详解[M].北京:中国水利水电出版社,2005:395–402.(Game Studio.Advanced analysis technique and detailed examples of classical products using ANSYS 9.0[M].Beijing:China Water Power Press,2005:395–402.(in Chinese))
[5]郑永兰,肖明.复杂地下洞室群三维有限元网格剖分在CAD中的实现[J].岩石力学与工程学报,2004,23(增2):4 988–4 992.(ZHENG Yonglan,XIAO Ming.Realization of 3D FEM mesh subdivision for complicated underground cavity group in CAD[J].Chinese Journal of Rock Mechanics and Engineering,2004,23(Supp.2):4 988–4 992.(in Chinese))
[6]张志国,肖明,张雨霆,等.大型地下洞室三维弹塑性损伤动力有限元分析[J].岩石力学与工程学报,2010,29(5):982–989.(ZHANG Zhiguo,XIAO Ming,ZHANG Yuting,et al.Dynamic finite element analysis of large-scale complex underground caverns with three-dimensional elasto-plastic damage model[J].Chinese Journal of Rock Mechanics and Engineering,2010,29(5):982–989.(in Chinese))
[7]廖振鹏.工程波动理论导论[M].北京:科学出版社,2002:49–59.(LIAO Zhenpeng.Introduction to wave motion theories for engineering[M].Beijing:Science Press,2002:49–59.(in Chinese))
[8]解振涛,张俊发,田勇,等.地面地震动时程向地层深处反演研究[J].西安理工大学学报,2007,23(4):418–421.(XIE Zhentao,ZHANG Junfa,TIAN Yong,et al.Research on inversion of earthquake acceleration time-period from ground to interior stratum[J].Journal of Xi′an University of Technology,2007,23(4):418–421.(in Chinese))
[9]胡进军,谢礼立.地下地震动频谱特点研究[J].地震工程与工程振动,2004,24(6):1–8.(HU Jinjun,XIE Lili.Spectral characteristics of earthquake sub-ground motions[J].Earthquake Engineering and Engineering Vibration,2004,24(6):1–8.(in Chinese))
[10]徐龙军,谢礼立,胡进军.地下地震动工程特性分析[J].岩土工程学报,2006,28(9):1 106–1 111.(XU Longjun,XIE Lili,HU Jinjun.Analysis on engineering characteristics of sub-ground motions[J].Chinese Journal of Geotechnical Engineering,2006,28(9):1 106–1 111.(in Chinese))
[11]谷音,刘晶波,杜义欣.三维一致黏弹性人工边界及等效黏弹性边界单元[J].工程力学,2007,24(12):31–38.(GU Yin,LIU Jingbo,DU Yixin.3D consistent viscous-spring artificial boundary and viscous-spring boundary element[J].Engineering Mechanics,2007,24(12):31–38.(in Chinese))
[12]杜修力,赵密.基于黏弹性边界的拱坝地震反应分析方法[J].水利学报,2006,37(9):1 063–1 069.(DU Xiuli,ZHAO Mi.Analysis method for seismic response of arch dams in time domain based on viscous-spring artificial boundary condition[J].Journal of Hydraulic Engineering,2006,37(9):1 063–1 069.(in Chinese))
[13]张雨霆,肖明,刘嫦娥.三维有限元任意截面的插值和剖分计算方法[J].武汉大学学报:工学版,2008,41(2):37–41.(ZHANG Yuting,XIAO Ming,LIU Chang′e.Calculation method for meshing and interpolation on arbitrary cross-section of 3D finite elements[J].Engineering Journal of Wuhan University,2008,41(2):37–41.(in Chinese))
[14]赵建锋,杜修力,韩强,等.外源波动问题数值模拟的一种实现方式[J].工程力学,2007,24(4):52–58.(ZHAO Jianfeng,DU Xiuli,HAN Qiang,et al.An approach to numerical simulation for external source wave motion[J].Engineering Mechanics,2007,24(4):52–58.(in Chinese))
[15]中华人民共和国国家标准编写组.GB 17741—2005工程场地地震安全性评价技术规范[S].北京:中国标准出版社,2005.(The National Standards Compilation Group of People′s Republic of China.GB 17741—2005 Evaluation of seismic safety for engineering sites[S].Beijing:Standards Press of China,2005.(in Chinese))
[16]中华人民共和国行业标准编写组.DL 5073—2000水工建筑物抗震设计规范[S].北京:中国电力出版社,2001.(The Professional Standards Compilation Group of People′s Republic of China.DL 5073—2000 Specifications for seismic design of hydraulic structures[S].Beijing:China Electric Power Press,2001.(in Chinese))
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