长期循环荷载作用下海洋饱和粉砂的弱化特性

Degradation Characteristics of Saturated Marine Silty Sand Under Longterm Cyclic Loading

摘要:

为了研究海洋饱和粉砂在长期循环荷载作用下的弱化特性,对原状饱和粉砂进行了一系列不同固结条件下不排水单调和循环加载三轴试验,并在循环加载过程中通过弯曲元测试土体剪切波速.主要分析固结方式、动应力比以及循环次数对饱和砂土循环弱化特性的影响.试验结果表明,在相同的固结条件下,随循环次数的增加和动应力比的提高,土体的强度和刚度衰减显著,在相同的动应力比作用下,偏压固结相对于等压固结减缓了土体的循环弱化.利用动偏应力水平对海洋饱和粉砂循环荷载作用下强度和刚度的弱化特性进行了描述.

Abstract:

In order to study the long term cyclic degradation characteristics of saturated marine silty sand,a series of monotonic and cyclic undrained triaxial tests were conducted on isotropically and anisotropically consolidated natural undisturbed saturated silty sand with the shear wave measured by bender element system during cyclic loading.The influences of consolidation mode,cyclic stress ratio and cyclic number on the reduction of stiffness and strength of saturated sand were mainly analyzed.The experimental results show that under the same consolidated condition the undrained strength and stiffness of saturated sand markedly reduce with the increase of the cyclic stress ratio and the progressive number of cycles.On the other hand,anisotropic consolidation decelerates the degradation of stiffness under the same cyclic stress ratio.The dynamic deviatoric stress level is used to describe the reduction of stiffness and strength of saturated marine silty sand under cyclic loading.