C - Trackbed Evaluation Flashcards
What is measured using the New Measurement Train, and how does it record the data?
It uses a system of lasers to measure a continuous profile of the track under load Expressed as the standard deviation of the track level relative to a moving mean
What can a visual inspection find?
Rail breaks Dirty ballast Pumping
What are trial pits used for?
To investigate the condition of ballast and subgrade
What process is advantageous over ballast sampling and why?
Radar survey A continuous profile can be derived Rapid process
What are some issues with radar surveys?
Impossible to discriminate between similar layers Has to be calibrated against ballast sample data Radar can pick up moisture changes
What is used to measure the strength and stiffness of the trackbed?
Falling Weight Delfectometer
How does a falling weight deflectometer work?
The load applies a pulse like that from a train (5-20tonnes), sleeper deflection is measured by geophones By doing so it is possible to deduce the stiffness of the ballast and subgrade, taking multiple sites away from the loaded location.
