水泥改良风积砂负温动力性能与流变特征研究

为研究水泥掺量对风积砂改良效果影响及不同负温、频率下的改良风积砂动力特征，开展了单轴、动力循环加载和蠕变试验。通过单轴试验获得了不同水泥掺量的改良风积砂7、28 d单轴抗压强度，并结合冻胀量随时间变化规律确定了最优水泥掺量；通过动力循环试验测定了不同次数的滞回曲线，确定了改良风积砂动弹性模量衰减、动损伤和阻尼比的演化规律；通过流变试验确定了能够描述滞回曲线流变特征的西原模型参数，建立了屈服前后滞回曲线的演化方程，并给出了每个循环内的时间划分标准。研究发现：（1）电镜观测显示水泥在风积砂颗粒间形成絮状连接结构，增加颗粒间的黏结强度，有效抑制动力损伤发展；（2）负指数模型可以描述改良风积砂动弹性模量衰减特征，阻尼比随加载次数增加逐渐变大，最终趋于某一定值，掺入水泥可以有效控制阻尼比发展；（3）提出了考虑围压影响的改进西原模型，根据实际加载特征建立了滞回曲线的加载方程，最小二乘原理可以对流变参数进行识别。

Study of dynamic performance under negative temperature and rheology characteristic for cement improved aeolian sand

To study the effect of cement content on the improvement of aeolian sand and its dynamic characteristics under different negative temperatures and frequencies, uniaxial, dynamic cyclic loading and creep tests were carried out. 7 days and 28 days uniaxial compressive strengths of improved aeolian sand with different cement contents were obtained to determine the optimal amount of cement by combining with frost heave variation with time. Hysteretic curve of different times was measured through the dynamic cycle test. Dynamic modulus attenuation, dynamic evolution damage and damping ratio evolution law of improved aeolian sand were determined. Parameters in the Nishihara model describing the rheological characteristics of hysteretic curves were determined by rheological experiments. Evolution equation before and after yielding hysteresis curve was established and time division standard was given for each loop. The electron microscope observation showed that the flocculent connection structure between the sand particles increased the bond strength between the particles and effectively inhibited the development of dynamic damage. The negative exponential model can be used to describe the dynamic modulus attenuation characteristics of the improved aeolian sand, and the damping ratio increased with the loading times, and finally tended to a certain value. Nishihara model considering the influence of was derived. The loading equation of the hysteresis curve was established based on the actual loading characteristics. The least squares principle can be used to identify rheological parameters.