原状黄土的平面应变剪切、屈服性状的试验研究

黄土工程中有许多平面应变问题。模拟黄土原位沉积方向，通过开展均压固结竖向加载和侧向卸载的平面应变试验，揭示剪切变形特性和屈服、破坏强度变化规律。表明黄土竖向柱状结构抵抗压缩作用，结构屈服前侧胀变形很小，结构屈服后侧胀变形发展明显，存在明显的屈服特征，剪切过程呈剪缩硬化性，屈服强度不同于破坏强度；侧向卸载条件下侧胀变形发展明显，结构屈服前竖向压缩变形增长较小，结构屈服后竖向压缩变形增长较大，也存在明显的屈服特征，剪切过程呈剪胀理想塑性，屈服强度与破坏强度近似一致；黄土的竖向加载强度线和侧向卸载强度线服从同一变化规律。不同含水率黄土竖向加载与侧向卸载的剪切变形特性和强度变化规律相似，同一含水率黄土的平面应变强度线近似呈同一线性变化规律。随着含水率的增大，黄土的屈服强度线和破坏强度线依次降低。

Experimental study on plane-strain shear and yield characteristics of intact loess

A lot of plane-strain problems have been witnessed in loess engineering. In this work, the loess was simulated in the in-situ deposit direction, and the plane-strain tests were carried out for intact loess in the isotropic consolidation condition with vertical loading and lateral unloading. Based on the tests, the shear deformation characteristics, the variation laws of yield strength and failure strength can be revealed. It is disclosed that the vertical columnar structure of loess may resist the compression action, the lateral swelling deformation is insignificant before yielding of the structure, but its development is obvious after yielding of the structure and the yielding characteristics are remarkable. During shearing, loess exhibits the shear shrinkage and hardening behavior, and the yield strength is different from the failure strength. In the lateral unloading condition, the lateral swelling deformation is obvious, and it is found that before yielding of the structure, the increase of vertical compression deformation is small, but after yielding of the structure the increase of vertical compression deformation is significant accompanied with obvious yielding characteristics. During shearing, loess exhibits shear dilatancy with perfect plasticity and the yield strength is consistent with the failure strength. Moreover, strength curves of loess with vertical loading follows the same variation law as that of loess with lateral unloading. Shear deformation characteristics and strength variation law of loess with different water contents under the vertical loading and lateral unloading conditions are basically similar. Plane-strain strength curves of loess with the same water content appear to follow the same linear variation law. With the increase of water content, the yield strength curve and failure strength curve drop accordingly.