均质黏性土坝漫顶溃决机理及溃坝过程模拟
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摘要
水库大坝的溃决对下游人民生命及财产带来巨大威胁,而中国已溃大坝中有85%以上为均质黏性土坝,且50%以上为漫顶溃决,因此有必要深入研究均质黏性土坝的漫顶溃决机理,提高溃坝洪水流量过程的预测精度,为溃坝应急抢险提供理论与技术支撑。基于均质黏性土坝大尺度漫顶溃决模型试验,揭示了漫顶水流作用下溃口在3维空间的发展机理,在此基础上提出了一个模拟均质黏性土坝漫顶溃决过程的数学模型。该模型基于坝体形状和漫顶水流特征确定"陡坎"的形成位置,采用宽顶堰公式计算溃口流量;选择可考虑坝料物理力学特性的溯源冲刷公式模拟"陡坎"的移动,并通过力学分析判断"陡坎"上游坝体的坍塌;引入坝料冲蚀系数,通过分析水流剪应力与坝料临界剪应力建立坝料的冲蚀率方程,模拟坝顶与下游坡溃口的发展;采用极限平衡法模拟溃口边坡的失稳,并假设滑动面为平面。模型考虑了不完全溃坝与坝基冲蚀,以及坝体的单侧与两侧冲蚀。选择国内外3组具有实测资料的大尺度均质黏性土坝漫顶溃坝模型试验对模型进行验证,实测值与计算结果的比较表明,溃口峰值流量、溃口最终平均宽度及溃口峰值流量出现时间的相对误差均在±25%以内,并且计算获得的溃口流量过程线与实测结果基本吻合,验证了模型的合理性。
Breaching of the reservoir dams would pose great threats to the lives and property of people downstream. In China, more than 85% of failed dams are homogeneous cohesive earthen dams, meanwhile, over 50% of the failure caused by overtopping-induced breach. Therefore, it has great significance to deeply study the overtopping breach mechanism of the homogeneous cohesive earthen dam, so as to improve the prediction accuracy of the breach hydrograph, and to provide theoretical and technical support to the emergency rescue following dam breach. The mechanism of the breach evolution in the three-dimensional space for homogeneous cohesive dam due to overtopping failure was studied according to the large scale model tests, after which a numerical model for overtopping-induced dam breach is developed. The forming position of the headcut is determined by the dam configuration and characteristics of the overtopping flow, and the breach flow discharge is calculated using the broad-crested weir formula. Then a backward erosion formula which considers the physical and mechanical properties of the dam materials is adopted to simulate the migration of headcut, while the mechanical analysis is utilized to judge the collapse of the dam body upstream of the headcut. The erosion coefficient of dam material is introduced, and the erosion rate equation of dam material is established by analyzing the flow shear stress and the critical shear stress of dam material. The erosion rate equation is then used to simulate the breach development of dam crest and downstream slope. In addition, the limited equilibrium method is adopted to model the instability of the side slope of breach, and the sliding surface is assumed to be a plane. Moreover, the model can consider incomplete and base erosion, as well as one-and two-sided breach. Three large scale model tests for homogeneous cohesive dam due to overtopping failure with detailed measured data are chosen to validate the proposed model. The comparison of measured and calculated data indicated that the relative errors of peak breach flow, final breach average width, and time to peak are all within ±25%. In addition, the calculated breach hydrograph is in accordance with the measured one. In summary, the case studies verify the rationality of the proposed model.
Breaching of the reservoir dams would pose great threats to the lives and property of people downstream. In China, more than 85% of failed dams are homogeneous cohesive earthen dams, meanwhile, over 50% of the failure caused by overtopping-induced breach. Therefore, it has great significance to deeply study the overtopping breach mechanism of the homogeneous cohesive earthen dam, so as to improve the prediction accuracy of the breach hydrograph, and to provide theoretical and technical support to the emergency rescue following dam breach. The mechanism of the breach evolution in the three-dimensional space for homogeneous cohesive dam due to overtopping failure was studied according to the large scale model tests, after which a numerical model for overtopping-induced dam breach is developed. The forming position of the headcut is determined by the dam configuration and characteristics of the overtopping flow, and the breach flow discharge is calculated using the broad-crested weir formula. Then a backward erosion formula which considers the physical and mechanical properties of the dam materials is adopted to simulate the migration of headcut, while the mechanical analysis is utilized to judge the collapse of the dam body upstream of the headcut. The erosion coefficient of dam material is introduced, and the erosion rate equation of dam material is established by analyzing the flow shear stress and the critical shear stress of dam material. The erosion rate equation is then used to simulate the breach development of dam crest and downstream slope. In addition, the limited equilibrium method is adopted to model the instability of the side slope of breach, and the sliding surface is assumed to be a plane. Moreover, the model can consider incomplete and base erosion, as well as one-and two-sided breach. Three large scale model tests for homogeneous cohesive dam due to overtopping failure with detailed measured data are chosen to validate the proposed model. The comparison of measured and calculated data indicated that the relative errors of peak breach flow, final breach average width, and time to peak are all within ±25%. In addition, the calculated breach hydrograph is in accordance with the measured one. In summary, the case studies verify the rationality of the proposed model.
引文
[1]中华人民共和国水利部,中华人民共和国国家统计局.第一次全国水利普查公报[M].北京:中国水利水电出版社,2013.
[2] Zhang Jianyun,Yang Zhenghua,Jiang Jinping.An analysis on laws of reservoir dam defects and breaches in China[J].Science China(Technological Sciences),2017,47(12):1313–1320.[张建云,杨正华,蒋金平.我国水库大坝病险及溃决规律分析[J].中国科学(技术科学),2017,47(12):1313–1320.]
[3]水利部大坝安全管理中心.全国水库垮坝登记册[R].南京:水利部大坝安全管理中心,2018.
[4]Wu W M.Earthen embankment breaching[J].Journal of Hydraulic Engineering,2011,137(12):1549–1564.
[5]陈生水.土石坝溃决机理与溃决过程模拟[M].北京:中国水利水电出版社,2012.
[6]Kakinuma T,Shimizu Y.Large-scale experiment and numerical modeling of a riverine levee breach[J].Journal of Hydraulic Engineering,2014,140(9):04014039.
[7]Schmocker L,Frank P J,Hager W H.Overtopping dikebreach:Effect of grain size distribution[J].Journal of Hydraulic Research,2014,52(4):559–564.
[8]Tabrizi A A,Elafly E,Elkholy M,et al.Effect of compaction on embankment breach due to overtopping[J].Journal of Hydraulic Research,2017,55(2):236–247.
[9]Zhong Q M,Chen S S,Deng Z.Numerical model for homogeneous cohesive dam breaching due to overtopping failure[J].Journal of Mountain Science,2017,14(3):571–580.
[10]Morris M W,Hassan M A A M,Vaskinn K A.Breach formation:Field test and laboratory experiments[J].Journal of Hydraulic Research,2007,45(S1):9–17.
[11]Hanson G J,Cook K R,Hunt S L.Physical modeling of overtopping erosion and breach formation of cohesive embankments[J].Transactions of ASAE,2005,48(5):1783–1794.
[12]Zhang J Y,Li Y,Xuan G X,et al.Overtopping breaching of cohesive homogeneous earth dam with different cohesive strength[J].Science in China Series E(Technological Sciences),2009,52(10):3024–3029.
[13]Chen Shengshui,Xu Guangming,Zhong Qiming,et al.Development and application of centrifugal model test system for break of earth-rock dams[J].Journal of Hydraulic Engineering,2012,43(2):241–245.[陈生水,徐光明,钟启明,等.土石坝溃坝离心模型试验系统研制及应用[J].水利学报,2012,43(2):241–245.]
[14]Ralston D C.Mechanics of embankment erosion during overflow[C]//Proceedings of 1987 National Conference on Hydraulic Engineering.Reston:ASCE,1987.
[15]Ploey D J.A model for headcut retreat in rills and gullies[R].Cremlingen:CATENA Supplement 14,1989.
[16]Robinson K M,Hanson G J.Headcut erosion research[C]//Proceedings of 7th Federal Interagency Sedimentation Conference.Reno:USGS,2001.
[17]Hahn W,Hanson G J,Cook K R.Breach morphology observations of embankment overtopping tests[C]//Proceedings of 2000 Joint Conference on Water Resources Engineering and Water Resources Planning and Management.Minneapolis:ASCE,2000.
[18]李云,宣国祥,王晓刚,等.土石坝漫顶溃决模拟与抢护[M].北京:中国水利水电出版社,2015.
[19]Singh V P.Dam breach modeling technology[M].Dordrecht:Kluwer Academic Publishes,1996.
[20]Mohamed A A A,Samuels P G,Morris M W,et al.Improving the accuracy of prediction of breach formation through embankment dams and flood embankments[C]//Proceedings of International Conference on Fluvial Hydraulics.Rotterdam:A.A.Balkema Publishers,2002.
[21]Fread D L.Breach:An erosion model for earthen dam failure[R].Silver Spring:National Weather Service,1988.
[22]Temple D M,Hanson G J,Neilsen M L.WINDAM-Analysis of overtopped earth embankment dams[C]//Proceedings of ASABE Annual International Meeting.Portland:American Society of Agricultural and Biological Engineers,2006.
[23]Fread D L.Dambreak:The NWS dam break flood forecasting model[R].Silver Spring:National Weather Service,1984.
[24]Visser P J.Breach growth in sand-dikes[M].Delft:Delft University of Technology,1998.
[25]Zhong Qiming,Chen Shengshui,Deng Zhao.Research on mathematical model for homogeneous earthen dam breach process due to overtopping failure and its application[J].Journal of Hydraulic Engineering,2016,47(12):1519–1527.[钟启明,陈生水,邓曌.均质土坝漫顶溃坝过程数学模型研究及应用[J].水利学报,2016,47(12):1519–1527.]
[26]Temple D M.Estimating flood damage to vegetated deep soil spillways[J].Applied Engineering in Agriculture,1992(8):237–242.
[27]Mei Shiang,Huo Jiaping,Zhong Qiming.Determination of headcut migration parameters for homogeneous earth dam due to overtopping failure[J].Hydro-science and Engineering,2016(2):24–31.[梅世昂,霍家平,钟启明.均质土坝漫顶溃决“陡坎”移动参数确定[J].水利水运工程学报,2016(2):24–31.]
[28]Hutchinson D L.Physics of erosion of cohesive soils[D].Auckland:University of Auckland,1972.
[29]Temple D M,Hanson G J.Headcut development in vegetated earth spillways[J].Applied Engineering in Agriculture,1994,10(5):677–682.
[30]Wu W M.Computational river dynamics[M].London:Taylor&Francis,2007.
[31]Morris M W,Hassan M,Vaskinn K A.Breach formation technical report(WP2)[R].Oxfordshire:HR Wallingford,2005.
[32]Morris M W.IMPACT project field tests data analysis[R].Oxfordshire:HR Wallingford,2008.
[33]Hanson G J,Temple D M,Hunt S L,et al.Development and characterization of soil material parameters for embankment breach[J].Applied Engineering in Agriculture,2011,27(4):587–595.
[2] Zhang Jianyun,Yang Zhenghua,Jiang Jinping.An analysis on laws of reservoir dam defects and breaches in China[J].Science China(Technological Sciences),2017,47(12):1313–1320.[张建云,杨正华,蒋金平.我国水库大坝病险及溃决规律分析[J].中国科学(技术科学),2017,47(12):1313–1320.]
[3]水利部大坝安全管理中心.全国水库垮坝登记册[R].南京:水利部大坝安全管理中心,2018.
[4]Wu W M.Earthen embankment breaching[J].Journal of Hydraulic Engineering,2011,137(12):1549–1564.
[5]陈生水.土石坝溃决机理与溃决过程模拟[M].北京:中国水利水电出版社,2012.
[6]Kakinuma T,Shimizu Y.Large-scale experiment and numerical modeling of a riverine levee breach[J].Journal of Hydraulic Engineering,2014,140(9):04014039.
[7]Schmocker L,Frank P J,Hager W H.Overtopping dikebreach:Effect of grain size distribution[J].Journal of Hydraulic Research,2014,52(4):559–564.
[8]Tabrizi A A,Elafly E,Elkholy M,et al.Effect of compaction on embankment breach due to overtopping[J].Journal of Hydraulic Research,2017,55(2):236–247.
[9]Zhong Q M,Chen S S,Deng Z.Numerical model for homogeneous cohesive dam breaching due to overtopping failure[J].Journal of Mountain Science,2017,14(3):571–580.
[10]Morris M W,Hassan M A A M,Vaskinn K A.Breach formation:Field test and laboratory experiments[J].Journal of Hydraulic Research,2007,45(S1):9–17.
[11]Hanson G J,Cook K R,Hunt S L.Physical modeling of overtopping erosion and breach formation of cohesive embankments[J].Transactions of ASAE,2005,48(5):1783–1794.
[12]Zhang J Y,Li Y,Xuan G X,et al.Overtopping breaching of cohesive homogeneous earth dam with different cohesive strength[J].Science in China Series E(Technological Sciences),2009,52(10):3024–3029.
[13]Chen Shengshui,Xu Guangming,Zhong Qiming,et al.Development and application of centrifugal model test system for break of earth-rock dams[J].Journal of Hydraulic Engineering,2012,43(2):241–245.[陈生水,徐光明,钟启明,等.土石坝溃坝离心模型试验系统研制及应用[J].水利学报,2012,43(2):241–245.]
[14]Ralston D C.Mechanics of embankment erosion during overflow[C]//Proceedings of 1987 National Conference on Hydraulic Engineering.Reston:ASCE,1987.
[15]Ploey D J.A model for headcut retreat in rills and gullies[R].Cremlingen:CATENA Supplement 14,1989.
[16]Robinson K M,Hanson G J.Headcut erosion research[C]//Proceedings of 7th Federal Interagency Sedimentation Conference.Reno:USGS,2001.
[17]Hahn W,Hanson G J,Cook K R.Breach morphology observations of embankment overtopping tests[C]//Proceedings of 2000 Joint Conference on Water Resources Engineering and Water Resources Planning and Management.Minneapolis:ASCE,2000.
[18]李云,宣国祥,王晓刚,等.土石坝漫顶溃决模拟与抢护[M].北京:中国水利水电出版社,2015.
[19]Singh V P.Dam breach modeling technology[M].Dordrecht:Kluwer Academic Publishes,1996.
[20]Mohamed A A A,Samuels P G,Morris M W,et al.Improving the accuracy of prediction of breach formation through embankment dams and flood embankments[C]//Proceedings of International Conference on Fluvial Hydraulics.Rotterdam:A.A.Balkema Publishers,2002.
[21]Fread D L.Breach:An erosion model for earthen dam failure[R].Silver Spring:National Weather Service,1988.
[22]Temple D M,Hanson G J,Neilsen M L.WINDAM-Analysis of overtopped earth embankment dams[C]//Proceedings of ASABE Annual International Meeting.Portland:American Society of Agricultural and Biological Engineers,2006.
[23]Fread D L.Dambreak:The NWS dam break flood forecasting model[R].Silver Spring:National Weather Service,1984.
[24]Visser P J.Breach growth in sand-dikes[M].Delft:Delft University of Technology,1998.
[25]Zhong Qiming,Chen Shengshui,Deng Zhao.Research on mathematical model for homogeneous earthen dam breach process due to overtopping failure and its application[J].Journal of Hydraulic Engineering,2016,47(12):1519–1527.[钟启明,陈生水,邓曌.均质土坝漫顶溃坝过程数学模型研究及应用[J].水利学报,2016,47(12):1519–1527.]
[26]Temple D M.Estimating flood damage to vegetated deep soil spillways[J].Applied Engineering in Agriculture,1992(8):237–242.
[27]Mei Shiang,Huo Jiaping,Zhong Qiming.Determination of headcut migration parameters for homogeneous earth dam due to overtopping failure[J].Hydro-science and Engineering,2016(2):24–31.[梅世昂,霍家平,钟启明.均质土坝漫顶溃决“陡坎”移动参数确定[J].水利水运工程学报,2016(2):24–31.]
[28]Hutchinson D L.Physics of erosion of cohesive soils[D].Auckland:University of Auckland,1972.
[29]Temple D M,Hanson G J.Headcut development in vegetated earth spillways[J].Applied Engineering in Agriculture,1994,10(5):677–682.
[30]Wu W M.Computational river dynamics[M].London:Taylor&Francis,2007.
[31]Morris M W,Hassan M,Vaskinn K A.Breach formation technical report(WP2)[R].Oxfordshire:HR Wallingford,2005.
[32]Morris M W.IMPACT project field tests data analysis[R].Oxfordshire:HR Wallingford,2008.
[33]Hanson G J,Temple D M,Hunt S L,et al.Development and characterization of soil material parameters for embankment breach[J].Applied Engineering in Agriculture,2011,27(4):587–595.
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