基于2.5维有限元基本原理,推导横观各向同性地基2.5维有限元控制方程,利用等代桩墙对CFG桩桩土复合路基进行简化,建立高铁荷载下横观各向同性CFG桩桩土复合路基2.5维有限元分析模型。考虑不同车速,分析横观各向同性地基土体刚度比n对高铁荷载下地面振动的影响,研究CFG桩桩土复合路基的减振机理,探讨桩径、桩间距、面积置换率m对其减振特性的影响。结果表明:高铁荷载下地面振动随横观各向同性地基土体刚度比n的提高而减小;CFG桩能更多地将高铁运行引起的动荷载沿深度方向传导至复合路基深处,从而显著减小地面振动,且减振效果随与轨道中心距离逐渐增强;CFG桩桩土复合路基的减振效果随桩径增大或桩间距减小而增强,当桩径≥0.5 m或桩间距≤4倍桩径时,进一步增大桩径或缩短桩间距难以显著提高减振效果;振动衰减系数FVR随CFG桩桩土复合路基面积置换率m的增大而减小增大面积置换率m对减振效果的影响较小。
Abstract
Deducing the 2.5D FEM governing equations for the transversely isotropic ground, and simplifying the CFG pile-supported subgrade by the equivalent pile walls, the 2.5D FEM model for CFG pile-supported transversely isotropic subgrade under high-speed train loading was established. Considering different train speeds, the effects of the stiffness ratio n of transversely isotropic ground on vibrations are analyzed. The vibration reduction mechanism of CFG pile composite subgrade is studied. Meanwhile, the influences of pile diameter, spacing, and area replacement ratio m on the vibration mitigation performance are discussed in detail. Results show that the ground vibrations induced by high-speed trains decrease with the increasing stiffness ratio n. Most of the dynamic load is undertaken by CFG pile composite subgrade, and transmitted along the depth into composite subgrade, which results in evidently reduction of ground vibrations. And the vibration mitigation effect enhances with the increasing diameter or the decreasing spacing. However, when the pile diameter or spacing exceeds one certain limit, further increasing diameter or shortening pile spacing cannot significantly improve the effect of vibration reduction. Additionally, with the increasing area replacement ratio m, the factor of vibration reduction FVR decreases gradually. When the area replacement ratio m is equal or greater than 0.06, further increasing area replacement ratio m has little effect on the vibration mitigation performance.
关键词
高速铁路 /
地面振动 /
横观各向同性地基 /
CFG桩桩土复合路基 /
减振特性 /
2.5维有限元
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Key words
high-speed railway /
ground vibrations /
transversely isotropic ground /
CFG pile composite subgrade /
vibration mitigation performance /
2.5D FEM
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