中文摘要：

利用FSY30型应变控制式非饱和土三轴仪采用常含水率试验,研究陕西泾阳县某边坡原状黄土在不同含水率（无偏应力条件下增湿）、不同固结围压下的强度和变形特性,求得Fredlund双应力状态变量抗剪强度公式中b？值并利用含水率建立了工程中实用的抗剪强度公式;再将天然原状土在不同偏应力水平下增湿饱和后继续剪切,观察其力学特性。两种增湿条件下试验结果表明：该地区黄土应力应变曲线关系呈剪切硬化型;含水率与初始基质吸力呈双曲线关系,剪切过程中基质吸力无明显变化,抗剪强度指标黏聚力随着含水率的增大显著降低而内摩擦角所受影响较小;有偏应力条件下试样浸水饱和后破坏强度显著降低,但对应力应变关系影响较小,增湿时偏应力水平越低,土样饱和后的稳定偏应力值越小。

英文摘要：

In order to study the mechanical properties of undisturbed loess slope under different circumstances in Jingyang county of Shaanxi Province, two humidification experiments are conducted. The constant water content tests are operated to observe the strength and deformation characteristics under different water contents （humidify with no stress conditions） and confining pressures by obtaining the value ofb？ in the shear strength formula of Fredlund’s double stress state variables, and a practical shear strength formula for the water content is derived by using FSY30 type strain controlled triaxial apparatus for unsaturated soils. The other tests are the experiments under different confining pressures and partial stresses in which cuts of the undisturbed loess are operated twice before and after the flooding to saturation. The two experiments reveal： （1） The stress-strain curves of loess in this region takes a hardening type according to the data analysis from the two tests; （2） Based on the constant water content tests, the water content and initial matric suction are hyperbolically related, and the matric suction shows no significant changes in the process of shearing. And the increase of water content has larger influence on the decrease of cohesion of shear strength index than the impact on internal friction angle; （3） On the basis of the second experiment, the strength of specimens decreases significantly after flooding which has little effect on the stress-strain curves. The lower the partial stress when humidification takes place, the lower the stable partial stress values.