非对称交通荷载作用下拓宽路堤动力特性分析

针对山西省境内长期承受非对称交通荷载的公路拓宽路堤,采用FLAC~(3D)建立数值模型,土工格栅采用FLAC~(3D)内置土工格栅单元(geogrid)模拟,其余部分均采用实体单元,屈服准则采用Mohr-Coulomb准则。将交通荷载简化为半正弦波荷载,分析非对称交通荷载作用下不加筋和加筋两种工况下拓宽路堤的变形特性及稳定性,进而改变拓宽路堤部分填土参数、交通荷载幅值、频率和行车间隔等参数,分析其对加筋工况下拓宽路堤变形的影响。结果表明:非对称交通荷载作用下,设置土工格栅加筋对新、旧路堤变形的约束作用有限,但能提高路堤的整体稳定性;增大拓宽路堤填土的压缩模量和黏聚力,可减小新、旧路堤沉降差;增大交通荷载一侧幅值会引起新、旧路堤过大差异沉降;增大交通荷载频率和时间间隔,路堤沉降均逐渐减小,但沉降差保持不变。上述结论对受非对称交通荷载拓宽路堤的施工提供了一定的理论依据。

Dynamic Characteristics Analysis of Widening Embankmentsunder Asymmetric Traffic Loading

A numerical model was established for the widening of a road embankment subjected to long-term asymmetric traffic loading in Shanxi Province, China. The model was created using FLAC^3D software, with traffic load simplified to half-sine wave. The geogrid was simulated by FLAC^3D structural element, and the soil was modeled by solid element. Mohr-Coulomb criterion was used to estimate the failure of geogrid and soil. The deformation and stability of both unreinforced and reinforced embankment widening under asymmetric traffic load were analyzed. Furthermore, parametric study was conducted to investigate the deformation of reinforced widening embankment under different parameters including:fill properties of the widening embankment, amplitude and frequency of traffic load, and running interval. The results show that the deformation of the widened embankment is only partially restricted by the geogrid, while the global stability of the embankment under asymmetric traffic load is effectively improved. Differential settlement decreases as the fill properties of the widening embankment increases. Through comparative analysis, it was found that the effect of cohesion on the differential settlement is more obvious than that of the compression modulus. Smaller differential settlement can be obtained when the soil properties of the new and old embankments are similar. In practical engineering use, by ensuring the properties of new embankment fill are the same as those of the old embankment fill, differential settlement can be effectively controlled under dynamic load situations, and will not affect the comfort and safety of the vehicle. The increase in amplitude of traffic load only on one side of the embankment will lead to excessive differential settlement and the pavement smoothness will be seriously affected. As the frequency of asymmetric traffic load and running interval increases, embankment settlements gradually decrease, while the differential settlement will remain constant. The findings in this investigation can provide a theoretical basis for the construction of the widening embankment under asymmetric traffic load.