利用扫描电子显微镜，对饱水冻结兰州砂土在－５℃和围压（０－２２ＭＰａ）下进行结构观测，结合围压对强度影响的宏观特征分析发现：当０≤σ３＜８ＭＰａ时，结构以压密为主，强化作用占优势，强度随围压的增大而增大；当８≤σ３＜１６ＭＰａ时，颗粒出现破碎现象，某些颗粒接触点处的冰发生融化，粒间摩擦减少，致使强度随围压的增大而缓慢降低；当σ３≥１６ＭＰａ时，颗粒破碎程度加剧，某些团粒中出现大的裂隙，结构联结破坏，导致冻土强度急剧下降。 Using scanning electron microscopy, the structure of Lanzhou sandy soil saturated with freezing water at -5 ℃ and confining pressure (0-22MPa) was observed. The macroscopical analysis of the effects of confining pressure on the strength shows that when 0≤σ3 <8MPa, The main effect is compaction, the strengthening effect is dominant and the strength increases with the increase of confining pressure. When 8≤σ3 <16MPa, the particles are broken, the ice at the contact point of some particles melts and the interfacial friction decreases , The strength decreases slowly with the increase of confining pressure. When σ3≥16MPa, the degree of particle crushing is aggravated. In some of the crumbs, large fissures appear and the structural connection is destroyed, resulting in the sharp decrease of the strength of frozen soil.