饱和击实黄土的动力特性研究

Research on dynamic characteristics of saturated compacted loess

通过进行不同固结条件下饱和击实黄土的动三轴试验,研究了饱和击实黄土的动模量、阻尼比、动强度、动孔压及抗液化特性。研究结果表明:饱和击实黄土的动应力-应变关系符合双曲线模型,模型中参数起始动剪切模量和最大动应力与轴向固结应力间均有良好的幂函数关系,且可以对不同固结应力状态归一,固结围压和固结比对阻尼比的影响较小。动剪应力比随固结围压的增大而减小,随固结比的增大而增大。固结围压、固结比以及动应力皆对动孔压比(u/σm)与振次比关系有显著的影响,而动孔压与破坏时动孔压之比与振次比关系只受固结围压变化的影响,基本上不受固结比和动应力变化的影响,可以用幂函数关系来模拟;在均压固结条件下,当破坏振次小于等于30时,饱和击实黄土不会产生液化,而当破坏振次较大(动应力较小)时可以产生液化;在偏压固结条件下不会产生液化。

Some dynamic characteristics such as shear modulus, damping, strength, pore water pressure and liquefaction are studies by dynamic triaxial tests on saturated compacted loess under different consolidation stress conditions. It is indicated that from test results ,the relation between dynamic stress and strain can be fitted with hyperbola, power correlations between its two parameters containing the maximum dynamic shear modulus and the maximum dynamic shear stress and consolidation axial stress are obtained and normalized under different consolidation stress conditions. Damping ratio is almost independent of consolidation confining stress and consolidation ratio. Dynamic shear stress ratio increases with the increase of consolidation ratio, it decreases with the increase of consolidation confining stress. Relation between dynamic pore water pressure ratio u/σm and cyclic number ratio is dependent on consolidation confining pressure and consolidation ratio as well as dynamic stress. Relation between ratio of dynamic pore water pressure and cyclic number ratio at vibrating process and failure is only dependent on consolidation confining stress ,which is independent on consolidation confining stress and dynamic stress ,and can be fitted by power function. The saturated compacted loess can produce liquefaction when failure cyclic number is larger than 30 under isotropic consolidation stress condition and can not produce liquefaction under anisotropic consolidation stress condition.