饱和原状Q_3黄土液化应变发展试验研究

Experimental study on strain development of liquefaction of saturated undisturbed Q_3 loess

基于室内动三轴试验,以宁夏固原石碑塬原状Q3黄土为对象,研究了其液化过程中轴向应变的发展趋势,分析了饱和Q3黄土在轻微、中等、完全液化等三个阶段动应力-动应变滞回曲线随等效振动次数(烈度)的变化规律及轴向应变与黄土的应力路径、孔隙水压力变化等的关系。研究表明:随着振动次数的增加饱和Q3黄土进入特殊的应力状态,其结构发生变化,滞回曲线在不同液化等级时呈现不同的特征;其应变发展与应力路径紧密相关,当进入状态转换面后,应变、孔隙水压力出现大的发展;黄土的残余孔隙水压力与残余应变发展不同,残余孔隙水压力最终有限值,而残余应变不断发展;孔压幅值与轴向应变幅值有着单调的函数关系,即随着振动次数的增加呈递增趋势。

Based on the dynamic triaxial tests,taking undisturbed Q3loess in Guyuan Stele-tableland of Ningxia for an example,the trend of the development of axial strain in the liquefaction process is studied.The change rules of dynamic stress and dynamic strain hysteresis curve depending on the vibration frequency(intensity) and the relationship among axial strain,stress path and pore pressure of the saturated Q3loess at mild,moderate,complete liquefaction stages are analyzed.The results show that,with the increase of vibration frequency,saturated Q3 loess gets into a special stress state.Its structure changes,hysteresis curve presents different characteristics in different liquid levels.The strain development closely relates with the stress path.When the loess gets into the state transition stage,the strain and pore pressure exhibit a big development.However the residual pore pressure and residual strain development of the loess are different.The residual pore pressure has a finite value,but the residual strain keeps on developing.The amplitudes of pore pressure and axial strain both increase with the vibration frequency in a monotonic function.