Using a seismic survey to measure the shear modulus of clean and fouled ballast

Abstract

In this paper a first time attempt has been made to measure the low strain shear modulus of clean and fouled ballast using a seismic survey of Multi-channel Analysis of Surface Wave (MASW). A model rail track was built with nine sub-sections, each having different fouling characteristics. MASW survey was performed in the top of each section of ballast and shear wave velocity was measured. The shear modulus of ballast fouled by pulverized rock, clayey sand and coal was calculated by using shear wave velocities and densities of each section and presented. The optimum and critical fouling points are defined considering the shear stiffness and drainage criteria for ballast fouled by clayey sand and coal. In both cases the shear stiffness increased to a maximum and then decreased as the percentage of fouling increased. The degree of fouling corresponding to the maximum shear wave velocity is defined as the optimum fouling point. After a particular degree of fouling the shear stiffness decreased less than clean ballast and the corresponding drainage condition become unacceptable. This point is defined as the critical fouling point. The results obtained from the model track were compared with the field data.

Keywords:

• Ballast
• fouling
• MASW
• shear stiffness
• optimum fouling
• critical fouling

Acknowledgement

The first author thanks the Endeavor and Australian Government for being invited to be an Endeavor Research Fellow.