改良土填筑过渡段基床底层的动力特性分析

Dynamic performance of bridge approach subgrade with improved soil as base course

通过动三轴试验及拟合参数法获得软岩改良土的动强度,以允许动强度为标准,评判软岩改良土可以作为基床底层以及路堤本体填料。同时,基于D’Alembert原理的能量弱变分和整体Lagrange格式,建立路桥过渡段半空间垂向耦合的动力计算模型,进一步分析不同列车速度下路桥过渡段的动态响应特征,并通过现场实测数据对比验证模型的正确性。研究结果表明:在列车荷载下,竖向动位移幅值波动范围为0.05～0.35mm,小于控制值;弹性应变幅值小于3×10-5,处于小变形阶段;竖向动应力幅值波动范围为15.5～19.5kPa,远小于改良土的动强度;采用刚性过渡较合理,掺入5%水泥的改良土可用于其基床底层及路基本体的填筑。

Dynamic strength was calculated by dynamic triaxial test and parameter-fitted method, and improved soft rock can fill the bridge approach embankment using permitted dynamic strength as a standard to judge. Based on weak variational form of the equilibrium equations for the transitional section in D＇Alembert method and whole Lagrangian form, an analysis model of semi-infinite tri-dimensional spatial finite elements was founded for the bridge approach embankment system, the longitudinal dynamic and time varying characteristics of the system at different train speeds were further analyzed, and this results were close to actual measure results, which approves the correctness of the model. The results show that under the train load, the fluctuant range of vertical vibrating displacement is from 0.05 mm to 0.35 mm and less than the controlling value. The fluctuant range of vertical vibrating elastic strain is less than 3 × 10^-5 and the embankment is in the state of small deformation. The fluctuant range of vertical vibrating stress is from 15.5 kPa to 19.5 kPa, and it is far below the dynamic strength of improved soft rock. Based on a comprehensive analysis, it is more rational to adopt rigid transition in this section, and improved soft rock with 5% cement can fill the bridge approach embankment.