液压夯实机补强台背路基影响因素分析

Analysis on Influencing Factors of Reinforcing Subgrade on Back of Abutment Using Hydraulic Compactor

为研究液压夯实机补强台背路基过程中对桥台的动力影响,依托某高速公路桥隧过渡段台背路基填筑工程,采用有限元软件ABAQUS建立了"夯锤-路基-桥台"相互作用模型,模型的准确性采用足尺夯击试验进行验证,仿真过程中以桥台最大动位移和最大动应变值作为评价指标,分析了夯锤落距、夯点与桥台距离、路基初始压实度、桥台混凝土强度等级和桥台顶部支撑条件等因素对桥台变形的影响。结果表明:夯击产生的土压力实测数值与仿真数值的误差均在10%以内,并且桥台动位移和动应变沿桥台高度方向的变化趋势符合常规,仿真模型可靠;桥台在夯击作用下的最大动位移及最大动应变随夯锤落距的增加呈线性增大,随夯点与桥台间距离的减小呈指数型增大;路基初始压实度由75%增加至95%过程中,桥台最大动位移和最大动应变基本一致,路基初始压实度对桥台变形影响较小;桥台混凝土强度等级的提高对减小桥台变形有显著影响;桥台顶部无伸缩缝时的最大动位移和最大动应变相比于有伸缩缝时分别减小了75%和24%,补强过程中可采用临时阻塞桥梁伸缩缝的方法改变桥台的受力形式。

To study the dynamic influence of hydraulic compactor on abutment in the process of reinforcing subgrade on back of abutment,based on the subgrade filling project of the abutment back in the bridge and tunnel transition section on an expressway,the interaction model of rammer,subgrade and abutment is established by FE software ABAQUS.The accuracy of the model is verified by full-scale compaction test.In the process of simulation,taking the maximum dynamic displacement and maximum dynamic strain of abutment as the evaluation indicators,the influence of factors such as dropping distance,distance between compacting point and abutment,initial compactness of subgrade,strength grade of abutment concrete and top support conditions of abutment are analysed.The result shows that(1)the error between the measured and simulated values of soil pressure caused by ramming is within 10%,and the variation trend of dynamic displacement and dynamic strain of abutment along the abutment height is in line with the convention,the simulation model is reliable;(2)under the action of compaction,the maximum dynamic displacement and maximum dynamic strain of abutment increase linearly with the increase of dropping distance and increase exponentially with the decrease of distance between compacting point and abutment;(3)when the initial compactness of subgrade increases from 75%to 95%,the maximum dynamic displacement and the maximum dynamic strain of abutment are basically the same,and the influence of initial compaction degree of subgrade on abutment deformation is little;(4)the improvement of concrete strength grade of abutment has significant influence on reducing abutment deformation;(5)when there is no expansion joint at the top of abutment,the maximum dynamic displacement and the maximum dynamic strain are reduced by 75%and 24%compared with those with expansion joint,the method of temporary blocking of bridge expansion joint can be used to change the stress form of abutment in the process of reinforcement.