某土石坝心墙料和坝基料动模量阻尼特性的试验研究
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摘要
土石坝震害将导致严重后果,目前国内外修筑于地震区的土石坝在抗震设计时都进行了动力分析。室内动力试验提供土石料可靠的动强度和动力参数是土石坝地震动力分析准确性的关键。水牛家心墙土石坝坝高100多米,大坝设防烈度9度,采用动三轴仪,对其坝基②层细砂砾料和心墙防渗土料进行大量的动力特性试验研究,分析两种土料的动模量阻尼特性,并简述其影响因素。分析试验结果有:使用一个试样完成三个不同的围压力σ3c或固结比Kc,与《土工试验规程》推荐方法相比,大大减小了试验和分析工作量,且有相当的规律性和准确程度;动模量阻尼比的主要影响因素是动应变幅、围压力、固结主应力比、孔隙比等。动应变水平影响动模量阻尼成倍增减,动模量随围压力σ3c增减而增减,阻尼比D随σ3c的升高而略有减小,动模量和阻尼比随固结比Kc增减而增减,Kc从1到2可使心墙土料的Edmax增加60%左右;土类不同,模量阻尼也不尽相同。水牛家心墙料的动模量较高,阻尼比较小,不易产生动力破坏。
Earthquake disaster of embankment dams will lead to serious results.At present embankment dams located at seismic area are all dynamically analyzed during aseismic design.Credible dynamic parameters of dam materials obtained from indoor tests are the key to the accuracy of dynamical analysis.Shuiniujia Core Embankment Dam is over 100 meters high and its earthquake fortify intensity is nine.Dynamic characteristics of core cohesive soil and damfoundation gravel are studied through the dynamic triaxial tests.And the dynamic modulus,damping ratio and their influencing factors are analyzed.The results show that the method of using one sample to finish the tests of three different confining pressures σ3c and three different consolidation ratios Kc is feasible,and has accuracy and regularity comparing with the method suggested by "Soil Mechanics Laboratory Regulations".There are many factors affecting dynamic modulus "Ed" and damping ratio "D",such as dynamic strain level,confining pressure,consolidated stress ratio and porosity ratio,etc.;"Ed" decreases and "D" increases very rapidly with strain level.And "Ed" increases while "D" decreases with confining pressure.Both "Ed" and "D" increases with consolidated stress ratio.Dynamic modulus and damping ratio are different due to different soils.And dynamic modulus of core cohesive soil of Shuiniujia Embankment Dam are high while its damping ratio is much lower;so it is not easy to suffer the dynamic destroy.
Earthquake disaster of embankment dams will lead to serious results.At present embankment dams located at seismic area are all dynamically analyzed during aseismic design.Credible dynamic parameters of dam materials obtained from indoor tests are the key to the accuracy of dynamical analysis.Shuiniujia Core Embankment Dam is over 100 meters high and its earthquake fortify intensity is nine.Dynamic characteristics of core cohesive soil and damfoundation gravel are studied through the dynamic triaxial tests.And the dynamic modulus,damping ratio and their influencing factors are analyzed.The results show that the method of using one sample to finish the tests of three different confining pressures σ3c and three different consolidation ratios Kc is feasible,and has accuracy and regularity comparing with the method suggested by "Soil Mechanics Laboratory Regulations".There are many factors affecting dynamic modulus "Ed" and damping ratio "D",such as dynamic strain level,confining pressure,consolidated stress ratio and porosity ratio,etc.;"Ed" decreases and "D" increases very rapidly with strain level.And "Ed" increases while "D" decreases with confining pressure.Both "Ed" and "D" increases with consolidated stress ratio.Dynamic modulus and damping ratio are different due to different soils.And dynamic modulus of core cohesive soil of Shuiniujia Embankment Dam are high while its damping ratio is much lower;so it is not easy to suffer the dynamic destroy.
引文
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[3]谢定义.土动力学[M].西安:西安交通大学出版社,1988.
[4]吴世明,徐攸在.土动力学现状与发展[J].岩土工程学报,1998,20(3):125-130.
[5]何昌荣,张利民.高应力水平下堆石料垫层料或过渡料的动变形特性研究[R].成都:四川大学水电学院,1994.
[6]吴世明等.土动力学[M].北京:中国建筑工业出版社会,2000.
[7]常亚屏.高土石坝抗震关键技术研究[J].水力发电,1998,(3):36-40.
[8]HARDIN B O,DRNEVICH V P.Shear modulus and damping in soils:measurement and parameter effects[J].Journal of the Soil Mechanics and Foundations Division,ASCE,1972,98(SM6):603-624.
[9]HARDIN B O,DRNEVICH V P.Shear modulus and damping in soils:design equation and curves[J].Journal of the Soil Mechanics and Foundations Division,ASCE,1972,98(SM7):667-692.
[10]何昌荣.动模量和阻尼的动三轴试验研究[J].岩土工程学报,1997,19(2):39-48.
[11]胡元芳.粉煤灰筑坝的工程性质与稳定性分析[D].成都:四川联合大学,1995.
[12]张茹,涂扬举,费文平,等.振动频率对饱和黏性土动力特性的影响.岩土力学,2006,27(5):18-23.
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