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- 2018
粉煤灰改良饱和黄土的抗液化特性
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Abstract:
为了经济、环保地达到改良处理减轻饱和黄土地基液化震害的目的，通过配备不同粉煤灰掺量的改良黄土进行动三轴试验，研究饱和粉煤灰改良黄土的动应力、动应变和动孔隙水压力变化特征，分析粉煤灰掺量对饱和改良黄土液化应力比、动残余变形和动孔隙水压力的影响规律，并结合微结构试验结果，探讨饱和粉煤灰改良黄土抗液化的物理化学机制。结果表明：粉煤灰掺量对饱和改良黄土的液化应力比、动应变和动孔隙水压力比均具有较为显著的影响。随着粉煤灰掺量的增加，饱和改良黄土的液化应力比持续增加，且当掺量达到15%后，继续增加粉煤灰掺量时改良黄土的液化应力比增加显著。饱和改良黄土的动应变和动孔隙水压力比均随着粉煤灰掺量的增加而减小；掺量达到25%后，饱和改良黄土不液化。饱和粉煤灰改良黄土的SEM细观结构试验照片中呈现大量的圆球状、粒状粉煤灰颗粒和絮凝状胶结物，表明其抗液化的物理化学机制主要包括粉煤灰的水化作用、胶体生成物和颗粒的填隙作用和粉煤灰对游离水的吸附作用。
To economically reduce seismic liquefaction damage to saturated loess foundations, variations in the characteristics of dynamic stress, dynamic strain, and dynamic pore water pressure are analyzed using dynamic triaxial tests on improved saturated loess with different dosages of fly ash. The law of influence of this dosage on the liquefaction stress ratio, dynamic residual deformation, and dynamic pore water pressure of the improved loess is then studied. Combined with microscopic test results, the physical-chemical anti-liquefaction mechanism of saturated loess improved by fly ash is also discussed. Results show that the dosage of fly ash has a significant influence on the liquefaction stress ratio, dynamic strain, and dynamic pore water pressure of the improved loess. With an increase in the dosage, there is a respective increase in the liquefaction stress ratio of the improved loess:after the dosage reaches 15%, there is an evident increase in the liquefaction stress ratio with a continued increase in the dosage. In addition, the dynamic strain and dynamic pore water pressure of the improved loess increase with a decrease in the fly ash dosage:after the dosage reaches 25%, the saturated improved loess cannot be liquefied. Scanning electron microscope (SEM) results indicate that the physical-chemical anti-liquefaction mechanism of saturated loess improved by fly ash is mainly related to the hydration process of the fly ash with respect to the filling effect of the colloid product and particles and adsorption of free water by fly ash.
