粗粒料的切线模量表达式与参数确定方法
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摘要
运用两座250 m级高土石坝的实测沉降资料与有限元计算结果,分析了高土石坝的应变量级与应力水平,在此基础上分析了双曲线应力应变模型及其参数确定方法的合理性。研究表明,250 m级高土石坝竖直向应变量级可以达到5%,故常规三轴试验可以适应变形预测对应变范围的要求,但坝内应力水平普遍较低,与确定参数所用的高应力水平段试验数据不协调,从而给土石坝应力变形计算带来不确定性。为更充分地运用低应力水平时的试验结果,建议了应力应变数据的多项式拟合方法,提出一个新的切线模量表达式。对比研究表明,双曲线模型及其参数确定方法高估了等向压缩应力状态下粗粒料的初始切线模量;低估了剪切应力状态下粗粒料的切线模量。文中所提出的表达式可以更好地与应力应变试验结果相吻合,且参数的不确定性大为降低,为提高土石坝应力变形计算的可靠性奠定了基础。
The strain magnitude and the stress level in high earth and rockfill dams were studied based on the field settlement data and the corresponding finite element simulation results of two typical dams with heights of about250 m. The reasonability of the widely used hyperbolic model and its parameter identification method were analyzed. It is found that the shear strain in 250 m-high earth and rockfill dams can achieve a magnitude of 5%,and triaxial experiments can be satisfactorily used in deformation prediction. However,the stress level in dams is generally lower than those segments of experimental data used for parameter determination,which adds considerable uncertainty to stress and deformation analysis. To use the experimental data at low stress level fully,a polynomial method is suggested to fit the stress stain data and a new tangential modulus model is proposed. It is found that the initial loading modulus under an isotropic stress state is overestimated by the hyperbolic model,while the tangential modulus under a shear stress state is underestimated. The newly proposed model can fit the experimental data better and the degree of uncertainty in the calibrated parameters is considerably reduced,which lays a foundation for improving the reliability of stress and deformation analysis for high earth and rockfill dams.
The strain magnitude and the stress level in high earth and rockfill dams were studied based on the field settlement data and the corresponding finite element simulation results of two typical dams with heights of about250 m. The reasonability of the widely used hyperbolic model and its parameter identification method were analyzed. It is found that the shear strain in 250 m-high earth and rockfill dams can achieve a magnitude of 5%,and triaxial experiments can be satisfactorily used in deformation prediction. However,the stress level in dams is generally lower than those segments of experimental data used for parameter determination,which adds considerable uncertainty to stress and deformation analysis. To use the experimental data at low stress level fully,a polynomial method is suggested to fit the stress stain data and a new tangential modulus model is proposed. It is found that the initial loading modulus under an isotropic stress state is overestimated by the hyperbolic model,while the tangential modulus under a shear stress state is underestimated. The newly proposed model can fit the experimental data better and the degree of uncertainty in the calibrated parameters is considerably reduced,which lays a foundation for improving the reliability of stress and deformation analysis for high earth and rockfill dams.
引文
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[3]刘大康,刘京茂,孔宪京,等.筑坝堆石料邓肯-张模型参数确定方法的改进[J].水利与建筑工程学报,2016,14(3):91-95.(LIU Dakang,LIU Jingmao,KONG Xianjing,et al.An improved method to determine Duncan-Chang model parameters of rockfill material[J].Journal of Water Resources and Architectural Engineering,2016,14(3):91-95.(in Chinese))
[4]KUMAR J,CLAYTON C R I.Effect of sample torsional stiffness on resonant column test results[J].Canadian Geotechnical Journal,2007,41(2):221-230.
[5]LINGS M L,GREENING P D.A novel bender/extender element for soil testing[J].Géotechnique,2001,51(8):713-717.
[6]CLAYTON C R I,THERON M,BEST A I.The measurement of vertical shear-wave velocity using side-mounted bender elements in the triaxial apparatus[J].Géotechnique,2004,54(7):495-498.
[7]SCHOLEY G K,FROST J D,PRESTI D C F,et al.A review of instrumentation for measuring small strains during triaxial testing of soil specimens[J].Geotechnical Testing Journal,1995,18(2):137-156.
[8]CLAYTON C R I.Stiffness at small strain:research and practice[J].Géotechnique,2011,61(1):5-37.
[9]ENOMOTO T,QURESHI O H,SATO T,et al.Strength and deformation characteristics and small strain properties of undisturbed gravelly soils[J].Soils and Foundations,2013,53(6):951-965.
[10]杨启贵,刘宁,孙役,等.水布垭面板堆石坝筑坝技术[M].北京:中国水利水电出版社,2010.(YANG Qigui,LIUNing,SUN Yi,et al.Construction technologies in the Shuibuya concrete face rockfill dam[M].Beijing:China Water and Power Press,2010.(in Chinese))
[11]张宗亮,冯业林,相彪,等.糯扎渡心墙堆石坝防渗土料的设计、研究与实践[J].岩土工程学报,2013,35(7):1323-1327.(ZHANG Zongliang,FENG Yelin,XIANG Biao,et al.Design,researches and practices of impervious materials for core wall of Nuozhadu hydropower station[J].Chinese Journal of Geotechnical Engineering,2013,35(7):1323-1327.(in Chinese))
[12]WU Y K,ZHANG B Y,YU Y Z,et al.Consolidation analysis of Nuozhadu high earth-rockfill dam based on the coupling of seepage and stress-deformation-physical state[J].International Journal of Geomechanics,2016,16(3):04015085.
[13]谭志伟,邹青,刘伟.糯扎渡水电站高心墙堆石坝监测设计创新与实践[J].水力发电,2012,38(9):90-99.(TANZhiwei,ZOU Qing,LIU Wei.Innovation and practice on monitoring design of Nuozhadu high core rockfill dam[J].Water Power,2012,38(9):90-99.(in Chinese))
[14]BEEN K,JEFFERIES M.Stress-dilatancy in very loose sand[J].Canadian Geotechnical Journal,2004,41(5):972-989.
[15]PRADHAN T B S,TATSUOKA F,SATO Y.Experimental stress-dilatancy relations of sand subjected to cyclic loading[J].Soils and Foundations,1989,29(1):45-64.
[16]王庭博,陈生水,傅中志.“南水”双屈服面模型的两点修正[J].同济大学学报(自然科学版),2016,44(3):362-368.(WANG Tingbo,CHEN Shengshui,FU Zhongzhi.Two modifications to Shen Zhujiang’s double yield surfaces model[J].Journal of Tongji University(Natural Science),2016,44(3):362-368.(in Chinese))