混凝土重力拱坝整体安全度评价方法探究
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摘要
针对混凝土重力拱坝的特点,基于混凝土弥散裂缝模型,采用三维非线性有限元法,以坝体位移响应突变、坝基塑性区贯通、坝体开裂破坏以及计算收敛性作为重力拱坝体系整体失稳的判断准则,探讨了重力拱坝整体安全度评价的方法。以国内某重力拱坝为例,从上游水压超载、坝基强储、地震灾变等方面对其整体安全度做出评价,揭示重力拱坝的薄弱部位,为其优化设计及抗震安全评价提供依据。研究表明:不同破坏模式下,该重力拱坝因水压力超载引起系统失效的整体安全度为5.0;坝基岩体抗剪强度降低使系统失效的整体安全度为3.5;地震灾变引起系统失效的整体安全度为1.7;重力拱坝的破坏模式区别于拱坝,水压力超载破坏主要表现为坝肩中下部开裂破坏和坝基岩体屈服破坏导致整体失稳;基岩强度折减破坏主要表现为坝体沿坝基面的滑动失稳破坏;地震灾变破坏主要表现为坝踵、溢流道闸墩底部的开裂破坏,其中,溢流道闸墩是坝体相对薄弱的高地震响应区。
According to the structural characteristics of gravity arch dams,a 3D nonlinear finite element method based on smeared-crack model is used in this paper to evaluate the global safety degree(GSD) of a gravity arch dam.The displacement mutation,plastic zone connectivity,dam failure modes and calculation convergence are suggested as criteria to estimate the safety of the concrete gravity arch dam system.Taking a domestic concrete gravity arch dam as an example,its global safety degree is evaluated by the overload of upstream water pressure method,shear strength reduction of rock method and overload of seismic intensity method.Based on the results of comprehensive evaluation we point out the weak part of the dam,and provide a theoretical basis for optimization design.The results indicate that GSD under upstream overloading water pressure is about 5.0;GSD under shear strength reduction of rock in dam foundation is about 3.5;GSD under earthquake is about 1.7.The failure modes of concrete gravity arch dam are different from the general arch dam.It may fail because of the lower dam abutment damage and the base rock yield caused by upstream overloading water pressure.With the reducing of the shear strength of rock,sliding may occur because of the base rock failure.Cracking damage,causes the failure of the dam-rock system under earthquake.It is mainly located at the dam heel and the base of the spillway pier which are considered to be the relatively weak parts under earthquake.
According to the structural characteristics of gravity arch dams,a 3D nonlinear finite element method based on smeared-crack model is used in this paper to evaluate the global safety degree(GSD) of a gravity arch dam.The displacement mutation,plastic zone connectivity,dam failure modes and calculation convergence are suggested as criteria to estimate the safety of the concrete gravity arch dam system.Taking a domestic concrete gravity arch dam as an example,its global safety degree is evaluated by the overload of upstream water pressure method,shear strength reduction of rock method and overload of seismic intensity method.Based on the results of comprehensive evaluation we point out the weak part of the dam,and provide a theoretical basis for optimization design.The results indicate that GSD under upstream overloading water pressure is about 5.0;GSD under shear strength reduction of rock in dam foundation is about 3.5;GSD under earthquake is about 1.7.The failure modes of concrete gravity arch dam are different from the general arch dam.It may fail because of the lower dam abutment damage and the base rock yield caused by upstream overloading water pressure.With the reducing of the shear strength of rock,sliding may occur because of the base rock failure.Cracking damage,causes the failure of the dam-rock system under earthquake.It is mainly located at the dam heel and the base of the spillway pier which are considered to be the relatively weak parts under earthquake.
引文
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[16]李德玉,侯顺载,张艳红,等.龙羊峡重力拱坝动力特性和抗震安全评价[J].土木工程学报,2003,36(10):41-45,59.LI Deyu,HOU Shunzai,ZHANG Yanhong,et al.Dynamic behavior and seismic safety evaluation of Longyangxia gravity arch dam[J].China Civil Engineering Journal,2003,36(10):41-45,59.(in Chinese)
[2]段庆伟,耿克勤,吴永平,等.小湾拱坝变形承载力及整体安全度评价与分析[J].岩土力学,2008,11:15-20.DUAN Qingwei,GENG Keqing,WU Yongping,et al.Evaluation of global safety degree of Xiaowan arch dam[J].Rock and Soil Mechanics,2008,11:15-20.(in Chinese)
[3]周伟,常晓林,唐忠敏.溪洛渡高拱坝渐进破坏过程仿真分析与稳定安全度研究[J].四川大学学报:工程科学版,2002,34(4):46-50.ZHOU Wei,CHANG Xiaolin,TANG Zhongmin.Research of gradually destruction process simulation analysis and stabilization safety on Xiluodu high arch dam[J].Journal of Sichuan University:Engineering Science Edition,2002,34(4):46-50.(in Chinese)
[4]余天堂,任青文.锦屏高拱坝整体安全度评估[J].岩石力学与工程学报,2007,4(4):787-798.YU Tiantang,REN Qingwen.Evaluation of global safety degree of Jinping high arch dam[J].Chinese Journal of Rock Mechanics and Engineering,2007,4(4):787-798.(in Chinese)
[5]Yu X,Zhou Y F,Peng S Z.Stability analyses of dam abutment by 3D elastic-plastic finite-element method:a case study of Houhe gravity-arch dam in China[J].International Journal of Rock Mechanics&Mining Sciences,2005,42:415-430.
[6]Ahmadi M T,Izadinia M,Bachmamn H.A discrete crack joint model for nonlinear dynamic analysis of concrete arch dam[J].Computers and Structures,2001,79:403-420.
[7]张社荣,王高辉,王超.混凝土重力拱坝极限抗震能力评价方法初探[J].四川大学学报:工程科学版,2012,44(1):7-12.ZHANG Sherong,WANG Gaohui,WANG Chao.Preliminary Study on the Ultimate Seismic Capacity Evaluation of Concrete Gravity Arch Dam[J].Journal of Sichuan University:Engineering Science Edition,2012,44(1):7-12.(in Chinese)
[8]Griffiths D V,Lane P A.Slope stability analysis by finite elements[J].Geotechnique,1999,49(3):387-403.
[9]Bhattacharjee S S,Léger P.Application of NLFM models to predict cracking in concrete gravity dams[J].Journal of Structural Engineering ASCE,1994,120:1255-1271.
[10]Calayir Y,Karaton M.Seismic fracture analysis of concrete gravity dams including dam-reservoir interaction[J].Computers and Structures,2005,83:1595-1606.
[11]Drucker D C,Prager W.Soil mechanics and plastic analysis or limit design[M].Quart Appl Math,1952,10:157–165.
[12]李子昌.特高拱坝应力与整体安全度控制指标研究[D].北京:清华大学,2010.LI Zichang.Study on control criteria of stress and integrity safety of super-high arch dams[J].Beijing:Tsinghua University,2010.(in Chinese)
[13]何建涛,陈厚群,马怀发.拱坝非线性地震反应分析[J].地震工程与工程振动,2012,32(2):68-73.HE Jiantao,CHEN Houqun,MA Huaifa.The nonlinear seismic response analysis of arch dam[J].Journal of Earthquake Engineering and Engineering Vibration,2012,32(2):68-73.(in Chinese)
[14]杜荣强,林昊,陈士海,等.强地震作用下高拱坝的破坏分析[J].水利学报,2012,44(5):567-574.DU Rongqiang,LIN Hao,CHEN Shihai,et al.Failure analysis of high arch dam subjected to strong earthquake[J].Journal of Hydraulic Engineering,2012,44(5):567-574.
[15]江守燕,杜成斌,陈灯红.Name Ngum5水电站分缝重力拱坝地震响应分析[J].河海大学学报:自然科学版,2010,38(3):308-312.JIANG Shouyan,DU Chengbin,CHEN Denghong.Seismic response analysis gravity jointed arch dam of Nam Ngum5 hydropower station[J].Journal of Hohai University:Natural Sciences,2010,38(3):308-312.(in Chinese)
[16]李德玉,侯顺载,张艳红,等.龙羊峡重力拱坝动力特性和抗震安全评价[J].土木工程学报,2003,36(10):41-45,59.LI Deyu,HOU Shunzai,ZHANG Yanhong,et al.Dynamic behavior and seismic safety evaluation of Longyangxia gravity arch dam[J].China Civil Engineering Journal,2003,36(10):41-45,59.(in Chinese)
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