冻融循环作用对黄土微结构和强度的影响

通过对洛川黄土在反复冻融作用下的电镜扫描观测、单轴压缩试验和三轴剪切试验，研究了冻融循环作用对黄土微结构和强度的影响. 结果表明：随着冻融循环次数的增加，黄土的原始胶结结构逐渐被破坏，颗粒重新排列，土的结构越来越疏松，同级压力下土体的孔隙比不断增大；冻融循环50次后土样的原始胶结已完全破坏，当压力超过自重应力时会产生很大的附加变形. 反复冻融作用使黄土颗粒之间原始固有胶结逐渐减弱，造成黏聚力不断降低. 同时，较大的团粒破碎，颗粒均一化，颗粒与颗粒之间的接触点增多，表现为内摩擦角不断增大. 多次冻融循环后，原状黄土的抗剪强度与重塑黄土的强度接近.

Influence of freezing-thawing cycles on micro-structure and shear strength of loess

By taking the loess from Luochuan in Shaanxi Province to prepare specimens, a series of compression tests and tri-axial shear tests were conducted to explore the characteristics of micro-structure and shear strength of undisturbed loess with freezing-thawing cycles. The experimental results indicate that the initial cementation structure of loess is gradually broken to become more and more loose with increasing of freezing-thawing cycles, and the void ratio of loess continuously increases in the same press. The initial structure of loess is completely disrupted after 50 freezing-thawing cycles, and a great deal of deformation probably produce when the additional press is more than geostatic stress. Because of shortening the initial cementation structure of loess with repeated freezing-thawing cycles, cohesive force of loess constantly decreases, and internal friction angle increases by increasing touch points of inter-particles. Shear strength of the undisturbed loess under repeated freezing-thawing cycles will be close to that of remolded loess.