By providing reliable geotechnical data for rail formation and ballast condition assessment, our innovative testing methods enable rail asset managers / infrastructure managers to optimise the track maintenance and track renewal strategy by prioritising and allocating rehabilitation efforts and funding only to the sections that require priority attention whilst minimising track downtime. Their objectives maybe:
- Maintain the current usage requirements
- Accommodate increases in safety, train frequency, speed and load
Our innovative testing methods provide both mechanical and physical properties of the existing ballast and formation (subgrade and sub ballast layers) – both very important for future planning and track design. They enable you to assess:
- Performance under loading (modulus) – using tools including the Light Weight Deflectometer and Plate Load Test, we are able to simulate insitu how the track will perform under the dynamic loadings applied on passenger, freight or heavy haul rail networks. This can be informative for both planning track maintenance and rehabilitation works and during new construction, maintenance and rehabilitation works. There is also the possibility to assess California Bearing Capacity (CBR) insitu, using Dynamic CBR.
- Ballast and formation condition assessment – a versatile diagnostic approach for pseudo-continuous condition assessment of subgrade, rail formation, sub-ballast capping and ballast layers using GPR and PANDOSCOPE®. In simple terms, the GPR helps us pinpoint where to look in more detail and the PANDOSCOPE® provides the additional detail vital for track design purposes:
- Ground Penetrating Radar (GPR) – a non-intrusive geophysical method that uses radar pulses to create a continuous profiling image of the subsurface. It is a method of surveying that provides continuous input data for track profile studies, in particular the depth of the various railway base layers.
- PANDOSCOPE® – a geotechnical tool that couples the cone resistance vs depth profile with down hole imagery and is used for non-destructive rail track ballast assessment (ballast fouling) and condition monitoring of the formation (rail track substructure layers). It also calibrates the GPR data. To be more specific, the PANDOSCOPE® allows layer characterisation for ballast and formation (identification, thickness, water content (qualitative), estimation of the ballast Particle Size Distribution (PSD) and ballast condition (ballast fouling) assessment. Cone resistance values can be correlated with CBR or other geotechnical parameters.
GRIZZLY Dynamic Probing DPSH and push tube sampling are also used to calibrate Ground Penetrating Radar (GPR) data and to provide more information in problem areas.
Numerous studies have shown that around 75% of track problems stem from geometric defects mainly related to supporting layers with poor mechanical characteristics or drainage problems.
The main functions of railway ballast are:
- to provide high load bearing capacity which reduces pressure from the sleeper bearing area to acceptable levels at the surface of the subgrade soil
- to provide rapid drainage
Rail ballast usually contains uniformly graded large, angular particles of typical size ranging between 25 and 50 mm, creating a sufficiently large pore structure to facilitate rapid (free) drainage. When ballast is aged and degraded, fine particles accumulate within the voids (fouling) thus impeding drainage. The process of ballast fouling, when it becomes extreme, can also generate excess pore water pressure under fast moving trains (i.e., high cyclic loading), thereby reducing the track resiliency and stability (undrained).
To find out more, Contact Us.
