冻融循环作用对黄土微结构和强度的影响  

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

作　　者：倪万魁[1] 师华强[1] 

机构地区：[1]长安大学地质工程与测绘学院,陕西西安710054

出　　处：《冰川冻土》2014年第4期922-927,共6页Journal of Glaciology and Geocryology

基　　金：国家重点基础研究发展计划(973计划)项目(2012CB026101);国家自然科学基金创新群体项目(41121061);国家自然科学基金重点项目(41030741)资助;中国科学院西部行动计划项目(KZCX2-XB3-19)

摘　　要：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.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 in- creasing touch points of inter-particles. Shear strength of the undisturbed loess under repeated freezing-thawing cycles will be close to that of remolded loess.

关 键 词：黄土 冻融循环 微观结构 孔隙比 抗剪强度 

分 类 号：P642.131[天文地球—工程地质学]