Abstract: The dynamic characteristics of lime modified soil under freezing and thawing cycles were studied by dynamic tri-axial compression，and the effect of dynamic stress amplitude，freeze-thaw cycles，cooling temperature and confining pressure on the cumulative plastic deformation of the soil was analyzed.The prediction model of cumulative plastic deformation was established under dynamic stress and freezing-thawing cycles.Based on the analysis of cumulative plastic deformation，the effect of the ratio of cement and the number of freezing and thawing cycles on the critical dynamic stress was further analyzed.And then the conclusion that the critical dynamic stress of the clean soil was less than 80 kPa and the critical dynamic stress of lime modified soil was between 150 kPa and 250 kPa was drawn.On the basis of the standard value of dynamic resilient modulus of subgrade MR in standard condition，the subgrade soil modulus reduction coefficient Kηunder the freezing-thawing cycle and the humidity adjustment coefficient of resilient modulus of subgrade KS were introduced.Therefore，the dynamic resilient modulus of subgrade was obtained under the influence of freezing-thawing cycle and subgrade soil moisture.The resilient modulus of lime modified soil on the top and bottom surfaces of subgrade work area was 70.18 MPa and 58.48 MPa respectively，which can meet the requirements of resilient modulus of subgrade.

Key words: highway engineering, lime modified soil, subgrade filling, freezing and thawing cycle, dynamic tri-axial compression test, dynamic characteristics

摘要： 通过动三轴试验对冻融循环后的石灰改良土的动力特性进行了研究，分析了动应力幅值、冻融循环次数、冷却温度、围压对土体累计塑性变形的影 响，并建立了动应力和冻融循环作用共同影响下的累计塑性变形的预测模型；基于此进一步分析了掺灰比、冻融循环次数对临界动应力的影响，确定了素 土的临界动应力小于80 kPa、石灰改良土的临界动应力为150～250 kPa；在标准状态下的路基动回弹模量标准值MR的基础上引入冻融循环条件下路基土模 量折减系数Kη和路基回弹模量湿度调整系数Ks，得到了在冻融循环作用及路基土体湿度共同影响下的路基回弹模量，其石灰改良土在路基工作区顶面和 底面的回弹模量分别为70.18、58.48 MPa，能够满足路基回弹模量的要求。

关键词: 道路工程, 石灰改良土, 路基填料, 冻融循环, 动三轴试验, 动力特性