The operating railway ballast bed and subgrade medium structure are relatively fixed. Establishing mechanical model can research the characteristics of vibration response of normal subgrade and diseased subgrade structure. Based on the staggered grid finite-difference algorithm, the numerical simulation of typical diseased subgrade indicates that the railway subgrade pseudo modal response or the characteristics of elastic waves frequency response is linked to the mechanical properties of the diseased medium. The railway subgrade within soft interlayer dominant frequency becomes low, while the railway subgrade structure dominant vibration frequency becomes high after reinforcement. The analysis results of transient state seismic imaging data of a heavy-haul railway are consistent with the theoretical conclusion. The method of railway subgrade structure response of pseudo modal analysis has practical value in operating railway subgrade assessment and rapid nondestructive testing.%基于波动方程的交错网格有限差分算法,建立力学模型对典型病害路基结构进行数值模拟,研究正常路基和病害路基结构的振动响应特征.研究结果表明:铁路路基结构模态响应或弹性波频响特征与病害介质力学性质密切相关,存在软弱层的铁路路基结构,其振动响应主频向低频方向偏移,加固后路基结构振动主频明显提高.某重载铁路瞬态地震映像实测数据分析结果与理论解析结论一致.铁路路基结构的拟模态响应分析方法对在营铁路路基快速无损检测和状态评估具有实用价值.
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