列车荷载下的桩网结构低路基土拱效应  

Soil arching effect of low subgrade with pile-net structure under train load

作　　者：魏静[1,2] 魏平[1,2,3] 杨松林[1,2] 张栋[1,2] 

机构地区：[1]北京交通大学土木建筑工程学院,北京100044 [2]北京交通大学轨道工程北京市重点实验室,北京100044 [3]北京工业职业技术学院建筑与测绘工程学院,北京100042

出　　处：《交通运输工程学报》2015年第6期35-44,共10页Journal of Traffic and Transportation Engineering

基　　金：北京市教育委员会科技计划项目(KM201410853004);中央高校基本科研业务费专项资金项目(2013JBM065)

摘　　要：运用ABAQUS软件建立了桩网结构低路基动力有限元模型,通过计算结果与实测结果的对比验证了模型的可靠性,并分析了列车荷载下路基中动应力分布、桩土应力比与等沉面高度变化特征。分析结果表明:采用模型计算的路基不同深度处动应力与实测结果最大差值为0.56kPa,动位移的最大差值为7μm,计算和实测的平均动应力和动位移沿路基深度的传递趋势相同,因此,有限元模型可靠;在动荷载作用下,路基中存在土拱效应,土拱高度约为1.6m,与静荷载作用下土拱高度近似,路基表面的应力变化率比路基基底大;路基中动应力的分布受到土拱效应的影响,表现为传递到桩间土上方土体的动应力部分转移至桩顶上方,且在路基垫层附近动应力转移现象最明显;在动荷载作用后,路基中心处桩顶与两桩间的桩土应力比减小,而桩顶与四桩间的桩土应力比增大,桩顶与两桩间的桩土应力比始终大于桩顶与四桩间的桩土应力比;距离路基中心1m处纵断面等沉面高度为1.55m,布置桩体的纵断面等沉面高度大于未布置桩体的纵断面等沉面高度,且沿路基中心到路肩,同类纵断面的等沉面高度逐渐降低,动荷载作用后,路基中心处等沉面高度增大。The dynamic finite element model of low subgrade with pile-net structure was built by using ABAQUS software.The reliability of the model was verified by the comparison of calculated and measured results.The distribution of dynamic stress,the vibration characteristics of pile-soil stress ratio and the height of equal settlement plane under train load were analyzed.Analysis result indicates that the maximum differences of calculated and measured values for dynamic stress and dynamic displacement at different depths of subgrade are 0.56 kPa and 7μm respectively,the transmission trends of average dynamic stress and dynamic displacement of calculated result are similar to the measured result along the subgrade depth,so the proposed dynamic finite element model is reliable.There exists soil aching effect in subgrade under dynamic load,and the height of soil arching effect is about 1.6 mthat is approximately the same with the value under static load.The stress variation ratio under dynamic load in subgrade surfaceis larger than the value in subgrade base,and the stress variation rate in subgrade base is extremely diminutive.The distribution of dynamic stress in subgrade under dynamic load is effected by soil arching effect,and the dynamic stress is partly transferred from soil among piles to pile top,and the phenomenon is most obvious in the cushion of subgrade.After dynamic load,in the center of subgrade,the pile-soil stress ratio of pile top to soil between two piles decreases,and the ratio among four piles increases.The pile-soil stress ratio between two piles is always larger than the value among four piles.The height of equal settlement plane of vertical section with the distance of 1mto the center of subgrade is about 1.55 m.The height of equal settlement plane in vertical section with piles is larger than the value without piles.From subgrade center to subgrade shoulder,the height of equal settlement plane in the same vertical section decreases gradually.After dynamic loading,the height of equal settlement plane

关 键 词：铁路路基 桩网结构 列车荷载 数值分析 土拱效应 等沉面 

分 类 号：U213.11[交通运输工程—道路与铁道工程]