初始剪应力对汶川震区饱和砂土动力特性影响分析
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摘要
文章以汶川震区中密饱和砂土为研究对象,利用DDS-70动力试验系统,进行振动频率f=1Hz时,固结比分别为K_c=1.0、K_c=1.5和K'_c=2.0条件下的固结不排水动三轴试验,分析了初始剪应力对汶川震区中密饱和砂土动力特性的影响,得出了如下结论:随着初始剪应力的增大,饱和砂土动孔压极值随之降低;在相同的围压和动应力作用下,随着初始剪应力的增大,饱和砂土动应变达到转折点所需的振次增大。在循环振次一定时,初始剪应力越大,其动强度越高;试样动强度均随着循环振次增加而降低的趋势,初始剪应力越大,降低的趋势越明显。
Taking the saturated medium dense sand in Wenchuan earthquake area as the research object, the undrained dynamic triaxial tests were conducted on the sand with K_c=1.0, 1.5 and 2.0 using DDS-70 Dynamic Experiment System when the vibration frequency was 1 Hz. The effects of initial shear stress on the dynamic properties of the saturated medium dense sand in the Wenchuan earthquake area were analyzed. The results are as follows: the critical dynamic pore pressure of the saturated sand decreases with the increase of the initial shear stress. Under the same confining pressure and dynamic stress, it will need more vibration times for saturated sand to reach the turning point of the dynamic strain if the initial shear stress grows. The initial shear stress has a positive effect on the dynamic strength if the cyclic vibration times keep constant. The dynamic strength decreases with the increase of cyclic time, and this trend is more obvious when the initial shear strength is higher.
Taking the saturated medium dense sand in Wenchuan earthquake area as the research object, the undrained dynamic triaxial tests were conducted on the sand with K_c=1.0, 1.5 and 2.0 using DDS-70 Dynamic Experiment System when the vibration frequency was 1 Hz. The effects of initial shear stress on the dynamic properties of the saturated medium dense sand in the Wenchuan earthquake area were analyzed. The results are as follows: the critical dynamic pore pressure of the saturated sand decreases with the increase of the initial shear stress. Under the same confining pressure and dynamic stress, it will need more vibration times for saturated sand to reach the turning point of the dynamic strain if the initial shear stress grows. The initial shear stress has a positive effect on the dynamic strength if the cyclic vibration times keep constant. The dynamic strength decreases with the increase of cyclic time, and this trend is more obvious when the initial shear strength is higher.
引文
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[2]Tan K,Vucetic M.Behavior of medium and low plasticity clays under cyclic simple shear conditions[C]//K.Atakan.Proceedings of the4th International Conference on Soil Dynamics and Earthquake Engineering.Mexico City:[sn].1989.
[3]郭中华.路基软粘土动力反应及震陷变形研究[J].建筑结构,2004,34(12):31-33.GUO Z H.Soft clay subgrade dynamic response and settlement deformation research[J].journal of building structures,2004,34(12):31-33.
[4]刘闻欣,王德咏,敖谦,等.坝基粉土液化的影响因素及防治对策[J].水电能源科学,2010,28(11):81-83.LIU W X,WANG D Y,AO Q,et al.The influence factors of dam foundation silt liquefaction and prevention countermeasures[J].Water Resources and Power.2010,28(11):81-83
[5]马梅英.初始固结剪应力对饱和砂土动强度的影响[J].水利水运科学研究.1988(1):63-65.MA M Y.The initial consolidation shear stress effects on saturated sand dynamic strength[J].Waterway transportation scientific research,1988(1):63-65.
[6]张茹,何昌荣,费文平,等.固结应力比对土样动强度和动孔压发展规律的影响[J].岩土工程学报,2006,28(1):101-105.ZHANG R,HE C R,FEI W P,et al.Effect of consolidation stress ratio on dynamic strength and dynamic pore water pressure of soil[J].Chinese Journal of Geotechnical Engineering,2006,28(1):101-105.
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