PANDOSCOPE® for Rail Ballast & Formation Condition Assessment
- Non-destructive rail track ballast assessment (ballast fouling) and condition monitoring of the formation (rail track substructure layers)
- PANDOSCOPE® is a coupling of tip resistance vs depth profile with very high quality down the hole imagery
- Used for planning rail track maintenance and renewal programs
- PANDOSCOPE® testing is used to calibrate Ground Penetrating Radar (GPR) data and to provide more information in problem areas.
Applications
In rail applications, the PANDOSCOPE® measures geotechnical aspects of the track bed and can provide the following outcomes:
- Layer characterisation for ballast and formation (identification, thickness, water content (qualitative), estimation of the soil grain size distribution (Granulometry) and ballast condition (ballast fouling) assessment
- Mechanical information: cone resistance (direct measurement) or CBR or other parameters with correlations
- Sometimes, PANDOSCOPE® testing is combined with network Ground Penetrating Radar (GPR) data to provide more information in problem areas.
The PANDOSCOPE® data helps rail asset managers / infrastructure managers 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 minimizing track downtime. Their objectives maybe:
- Maintain the current usage requirements
- Accommodate increases in safety, train frequency, speed and load
The PANDOSCOPE® provides engineering services with reliable geotechnical data for track design purposes. The knowledge of mechanical and physical properties of existing formation (subgrade and sub ballast layers) is very important for the future track design.
The maintenance costs of ballasted tracks can be significantly reduced if an accurate estimation of the different types and degree of fouling materials can be related to track drainage.
Here are some of the research papers on the PANDOSCOPE® technology rail applications.
Advantages
The PANDOSCOPE® overcomes the limitations of the majority of classical geotechnical tests (drilling rigs, pot holing). Benefits include:
- Proven approach
- Tried and tested investigation strategy for track maintenance and renewal (localised or cross network)
- Stand alone PANDOSCOPY or the coupled use of PANDOSCOPY and GPR
- Several thousand kilometres of investigations over 50,000 tests
- Passenger and heavy haul freight networks
- Several countries including France (SNCF), UK, Netherlands, Belgium, USA, Canada, Singapore and Australia
- No destabilisation / disturbance of the track
- Important if renewal works are delayed or do not proceed
- Granulometry using PANDOSCOPE® imagery avoids the need for ballast sampling (non-traumatic control) and eliminates the subjectivity of sampling
- Better informed decision making
- Speed and versatility
- Limited track possession time required (e.g. can test between trains working under lookout protection)
- Light weight portable equipment enables track access onto embankments and into cuttings
- Testing not limited by the height of equipment e.g. due to overhead electrification
- Cost effective methodology
- Reduced cost per hole compared to conventional approaches like potholing
- Reduced head count on site
- Less flights/accommodation required for remote site working
The PANDA® Instrumented Dyamic Cone Penetrometer (DCP) involves driving a variable energy cone penetration device into the rail track substructure to collect the strength (and modulus by correlation) profile with depth.
Condition monitoring of the rail track substructure layers is accomplished through insertion of a camera into the same hole, also called Geoendoscopy. The combined system is referred to as the PANDOSCOPE®. The PANDA®, PANDOSCOPE® and Geoendoscopy are all systems developed by Sol Solution.
Once the PANDOSCOPE® data has been processed, the results can be presented.
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 material 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).
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A is the cross-sectional area of the cone
