固结应力比对土样动强度和动孔压发展规律的影响

回顾了初始剪应力对土样动强度和和动孔压发展规律的影响,使用动三轴对某土石坝坝基饱和砂砾石料进行动强度试验,研究固结应力比Kc对土样动力特性的影响。分析试验结果如下:所有土料都存在一个转折点Kc′:KcKc′时动强度随Kc的增大而降低,动变形和动孔隙水压力随Kc的增大有稍许加大趋势。转折点Kc′的具体数值与土料性质及所受应力状态有关。本次试验Kc=0.5～3.0,转折点Kc′为2.8左右。Kc过大后,初始剪应力较高、剩余强度较低而导致动强度降低。偏压固结Kc=0.7～1.3时,试验土料最终孔压值均可达到围压;偏压固结Kc≥1.5后,试样最终孔压值是否可达到围压取决于动应力σd是否大于主应力差(σ1c-σ3c),即σd是否形成拉应力使试件伸长。但当Kc很大后,σ1c和σ3c相差太大,需施加非常大的动应力σd才能使其应力应变反向,试样不可能达到初始液化。

Effect of consolidation stress ratio on dynamic strength and dynamic pore water pressure of soil

To study the effect of consolidation stress ratio on soil dynamic strength and dynamic pore water pressure,firstly the related previous research results were reviewed,then the dynamic triaxial tests with saturated gravel samples from the foundation of a rockfill dam were performed.The results of dynamic strength tests showed that there was a turning point of consolidated stress ratio Kc′.When KcKc′,dynamic strength decreased while dynamic deformation and dynamic pore water pressure increased with the increase of Kc.The value of turning point Kc′ depended on the soil properties and stress condition.The approximate value of Kc′ was equal to 2.8 in this test when Kc=0.5～3.0.When Kc=0.7～1.3,final pore water pressure could be equal to confining pressure,and when Kc exceeded or equaled 1.5,the possibility of liquefaction of samples depended on whether the dynamic stress σd could stretch samples or not.