摘要
为探讨铁路既有线粉土路基的工作性状及病害机理,通过室内动三轴试验,研究不同密实度、不同含水率粉土路基土在不同动应力水平下的循环累积塑性变形规律。结果表明:循环荷载下粉土路基土的累积塑性变形随动应力的增加而增大,随试样含水率的降低而降低,随压实系数的增大而减小,且动应力水平越高、含水率越大、压实系数越小,变化趋势越明显;在既有线路基动应力水平范围内及路基土处于饱和含水率状态下,可用粉土路基土的压实系数0.93作为路基土破坏形态的分界点;粉土路基土的临界动应力约为静强度的50%。基于试验结果,以Monismith指数模型为基础,引入路基动应力与静极限抗剪强度的应力比系数,建立了能同时考虑动应力和土体物理状态条件的路基土循环累积塑性变形预测模型。模型计算值与试验值吻合较好,说明该模型能较好地预测粉土路基土的循环累积塑性变形。
In order to discuss the working performance and disease mechanism of silt subgrade of the existing railroad, a series of indoor dynamic triaxial tests were conducted to investigate the cumulative plastic deformation behaviors of the silt subgrade soil at different degree of compaction, water content, and dynamic stress levels. Results show that the cumulative plastic deformation of the silt subgrade soil grows with increasing the dynamic stress and reduces with decreasing the water content or increasing the compaction coefficient, especially at a higher dynamic stress, higher water content or smaller compaction coeffi- cient. In the scope of the dynamic stress level of the existing railroad subgrade and the saturated state of subgrade soil, the degree of compaction coefficient 0.93 of the silt suhgrade soil can be regarded as a boundary point of different failure modes of subgrade soil. Moreover, it is also obtained that the critical dynamic stress of silt subgrade soil is about 50 percents of its static strength. Based on the tests results and Monismith＇s power exponential model, and by introducing the stress ratio coefficient of the dynamic stress of the subgrade to its ultimate static shear strength, a new model for predicting the cumulative plastic deformation of silt subgrade soil is established, which can take both the factors of the dynamic stress and soil＇s physical states into consideration. The calculated value agrees well with the test value, which indicates that the model can better predict the cumulative plastic deformation of silt subgrade soil under repeat- ed loading.
出处
《中国铁道科学》
EI
CAS
CSCD
北大核心
2010年第1期1-8,共8页
China Railway Science
基金
国家自然科学基金资助项目(50678020)
铁道部科技研究开发计划项目(2005G012)
中国博士后科学基金(20090460660)
关键词
路基
粉土
循环荷载
累积变形
临界动应力
Subgrade
Silt
Cyclic loading
Accumulative deformation
Critical dynamic stress
