土体饱和度对移动荷载引起多层非饱和铁路地基振动的影响

Influences of soil saturation on the vibration of multi-layer unsaturated railway ground induced by moving load

采用半解析法研究了移动荷载作用下多层非饱和铁路地基的共振问题,分析了土体饱和度对非饱和地基振动的影响。采用分层非饱和多孔介质描述铁路地基;基于非饱和多孔介质的控制方程,采用多重傅里叶变换和土层界面位移、应力条件,推导了频率-波速域分层非饱和地基总体刚度矩阵。结合包括钢轨、轨垫、轨枕和道砟的轨道模型,建立耦合轨道-地基半解析模型。研究了移动简谐荷载作用在轨道上的多层非饱和地基的动力响应;考虑饱和度对土体剪切模量的影响,讨论了地基首层土和夹层土饱和度变化对地面振动的影响。采用频散曲线研究了地基共振模态。研究发现土体饱和度变化对振动位移的影响规律,与地基分层、荷载速度和频率有关。随饱和度减小,地基共振模态出现频率增大,地基关键速度增大。

Resonance of multi-layer unsaturated railway ground induced by moving surface load is studied using a proposed semi-analytical approach. Influences of the soil saturation on ground vibrations are studied. The half space of railway ground is modelled as a layered unsaturated poroviscoelastic medium, the multiple Fourier transform method, the interface stress and displacement conditions for each soil layer are used to derive the global dynamic stiffness matrix of multi-layer unsaturated ground in the frequency-velocity domain based on the governing equations of unsaturated porous medium. A semi-analytical model for coupled track-ground is established by assembling a track model including a rail, rail pads, sleeper and ballast. The dynamic response of the multi-layer unsaturated ground caused by a moving harmonic load on the track is analysed. Considering the influences of the soil saturation on the soil shear modulus, the different dynamic response of the ground with various degrees of soil saturation for the surface layer and interlayer are discussed. The shading representation dispersion curves are used to study resonant modes for the unsaturated ground in the spectral domain. This research found that the influences of the soil saturation on ground displacements depend on soil layer properties, load speeds and frequencies. Besides, the ground saturation reduction can increase the appearance frequency of the ground resonant mode as well as the ground critical speed.