A new ground acceleration based method of evaluating High Speed Rail (HSR) track bed integrity has been developed. The purpose of the implementation of the system is to provide an efficient means for monitoring HSR track to predict settlement and deformation conditions that would require maintenance. The method relies upon the use of an accelerometer array that can be installed in the substructure of the track, i.e., within the ballast, subballast and subgrade layers. The array can be installed on a permanent basis and monitored periodically to identify changes in the small strain elastic properties of the substructure layers. The methodology utilizes conventional downhole seismic shear wave testing. The aecelerometers are used in concert to simultaneously evaluate the arrival of seismic shear waves produced by surface initiated impact methods. The methodology was successful in measuring initial shear wave velocities. The shear wave velocities were used to calculate shear moduli and elastic moduli for the ballast, subballast and subgrade layers. Shear moduli were in the range of 14×10~3 kPa for the fouled ballast to 118× 10~3 kPa for the subgrade. Elastic moduli were in the range of 39×10~3 kPa for the fouled ballast to 320× 10~3 kPa for the subgrade. These values were compared with values that were measured separately at the site on similar soils and were found to be consistent. The monitoring can be done on a regular schedule requiring no interruption of track operations. The methodology has other applications including highway pavements, airport pavements and tunnels/underground facilities.
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