A study of macro mechanical response and microstructure characteristics of loess under irrigation mechanism
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摘要: 从黄土特有的水敏性和微结构角度出发，开展灌溉作用下，水体入渗过程中黄土宏观力学响应与微观结构特性之间变化规律的研究。设定了不同含水量下的黄土宏观力学与微观结构试验，旨在得到水对黄土的应力应变响应规律及试验前后剪裂面上黄土微观结构的变化特征。结果表明：研究区Q3黄土的应力-应变曲线随着围压的增大呈现出由应变软化型向应变硬化型转变，随着含水量的增大呈现出由应变硬化型向应变软化型转变的规律；并以此确定了研究区黄土结构屈服应力σk所对应的应变值一般小于2%；结合饱和Q3黄土三轴固结不排水剪切试验获得了研究区黄土的稳态线参数及状态边界面参数，并在假设不同围压条件下稳定状态收敛的前提下，得到近似状态临界面公式；分析了Q3黄土在不同围压和含水量下的破坏模式，其特征表现在黄土试样剪切前后的微观结构变化主要表现在微结构类型的转变、孔隙含量减小及微裂隙的发育程度上。Abstract: Based on the properties of water sensitivity and microstructure of loess, the present study investigates the variation laws of macro mechanical response and microstructure of loess during the process of water infiltration. Tests of the macro mechanics and microstructure of loess with different amount of water content are conducted to explore the stress & strain response laws of the loess affected by water as well as the microstructure change of loess on the shearing surface. The results indicate that the stress-strain curve of the loess Q3 in the study area transforms from strain softening to strain hardening with the increase in confining pressure but it transforms from strain hardening to strain softening with the increase in water content. As a result, this study concludes that the corresponding strain value of the studied loess structure yield Sigma K(σk) is generally less than 2%. Additionally, steady state parameters and boundary surface parameters are obtained from the tri-axial undrained consolidation shear test of the saturated loess Q3. Meanwhile, the approximate pro interface formula is obtained with the hypothesis of stable convergence state under different confining pressures. Failure modes of the loess Q3 under different degree of confining pressures and different amount of moisture content are analyzed and it is found that the change in the microstructure of loess samples before and after being sheared is characterized by transformation of microstructure, pore content decrease and micro fracture development.
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Key words:
- loess /
- irrigation /
- mechanical testing /
- microstructure
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