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Development of an Innovative Ground Penetrating Radar System for Fast and Efficient Monitoring of Rail Track Substructure Conditions (SAFERAIL)

Final Report Summary - SAFE-RAIL (Development of an Innovative Ground Penetrating Radar System for Fast and Efficient Monitoring of Rail Track Substructure Conditions)

The purpose of the project SAFE-RAIL was the development of an innovative Ground penetrating radar (GPR) system for efficient, cost-effective, fast and safe rail track substructure conditions monitoring. SAFE-RAIL was designed and proposed for developing efficient technological tools for achieving continuous assessment of the hidden and hard-to-monitor substructure conditions in fast and accurate way. The identification of the dielectric and geometric properties of the ballast layer was the main objective on which SAFE-RAIL project was focused; availability of such information concretely allows qualitative and quantitative evaluation of the conditions of the rail-track substructure. The SAFE-RAIL processing tools are designed to allow increasing risk management and accident prevention capabilities while optimising planning of construction, reconstruction and maintenance operations along the rail network with the minimum possible degradation of rail network capacity.

According to the EC White Paper 'European Transport Policy for 2010: time to decide' (2001), the statement of improving capability and exploitability opportunities of European transport network represents the key strategic action for the sustainable development. In particular, the improvement of the capacity and safety of the railway infrastructure represents the main objective to be achieved in the midterm at both national and trans-national level. The accurate, fast and continuous assessment of rail-track conditions is today widely recognised as the primary need of railways owners and users towards the minimisation of the traffic slow-down and the optimisation of the network capacity and safety: as a matter of fact, extensive human resources are currently applied to the problem of evaluating railroad health, and important factors, such as the condition of the ballast, sub-ballast and sub-grade, critical in the maintenance and integrity of rail track systems, require subsurface measurements to be made.

The hidden and hard-to-monitor substructure conditions are extremely important to railway track performance. GPR is today the most promising technology for non-destructive subsurface investigation and buried object detection, localisation and classification. A wide set of dedicated studies and relevant scientific literature is currently contributing to promoting GPR based solutions and technologies in several fields of application. Several railway companies have started to use GPR data for monitoring the condition of ballast and sub-ballast layers; GPR systems have been mounted on trains, lightweight inspection carts and also hand carried to measure ballast and substructure condition and to identify fouled ballast and trapped water on railroad. GPR technology based sensors are used to detect the geologic structure under the railway and to map the subsurface conditions giving the GPR images a good indication of the subsurface layer configuration.

Based on an evolutionary approach specifically intended to overcome the identified limitation of conventional radar instrumentation, the SAFE-RAIL project seeks to develop an innovative rail-track substructure conditions monitoring system. The successful completion of the SAFE-RAIL project, thanks to this revolutionary approach, led to the following major achievements:
- to demonstrate the capabilities of quickly and accurately referenced detection, localisation and classification of rail track condition deterioration in the rail-track ballast, sub ballast and sub-grade;
- to provide a prototypic processor for user-friendly on-board diagnostic data interpretation and early warning against the probability of critical failures of the line.

In the four-year project the SAFE-RAIL consortium followed a coherent, engineering approach for the achievement of the stated objectives. The key implemented steps are the following:
- identification of user main needs via engagement of end-users (rail track owners, rail track maintenance engineers);
- system requirements specification and system design, including the identified HW and SW sub-systems;
- sub-systems development and testing (prototyping, assembling, coding, etc.);
- sub-system validation, including the collection of validation sources (e.g. commercial GPR data);
- system integration;
- system testing via data acquisition campaigns in real scenarios with the collaboration of end-users;
- assessment of system performances on the basis of the collected datasets.

The SAFE-RAIL system is composed by the following major components:
- the Fast substructure array radar (FSAR), based on:
- Innovative antennas array (ANTS), allowing precise estimation of subsurface layers while maximising penetration depth under any terrain conditions in real track scenarios and optimising high speed platform operations;
- High performances radar control unit (HPRCU), allowing real time control of position channels and recording of raw collected data supporting train speeds higher than 300 Km/h;
- an innovative Rail-track positioning unit (RTPU), allowing fast and accurate measurement of the platform position and radar triggering;
- an innovative On-board processor (OBP) based on expert systems and neural networks algorithms for real-time GPR data interpretation, acquisition strategy supervision and control, and user-friendly presentation;
- a Networked data interpretation and processing software (NDIPS), supporting long-term monitoring of rail substructure conditions through the networking of different sensors operating along multiple segments of the railway infrastructure.

The main result of SAFE-RAIL project is represented by the operational, fully validated system prototype. The successful integration of the components and their subsequent validation represents an important goal due to the innovative technologies involved and to the development of components via a distributed strategy. The SAFE-RAIL system in final configuration completed its first run on real rail track scenarios in December 2007.

The following key results followed from the demonstration phase:
- SAFE-RAIL data acquisition: The acquisition campaigns by means of the integrated system prototype have been performed on different diagnostic vehicles involving up to three antenna arrays with a maximum of 15 simultaneous receiving channels. During data acquisition different along track resolutions have been used as a function of train speed. The resolution has been varied between 2 cm to 1 metre while the vehicle speed has been raised up to 200 Km/h. The prototype has shown the capability of transmitting the radar signal at the commanded repetition rates with continuity and to correctly acquire and store the collected data from the subsurface. Test campaigns have been performed on different railways tracks with acquisition distances up to 30 km;
- SAFE-RAIL data interpretation: The extraction of the information regarding the subsurface layers (ballast, sub-ballast, sub-grade) from raw collected data has been performed by the OBP during data acquisition tests in both on-line mode - showing the real time instrument processing capability - and in off-line mode for algorithms parameters tuning.
- SAFE-RAIL data inversion: The dielectric constant estimation of the ballast layer by means of the neural network processing applied to the data acquired during test campaigns has been tested in on-line and off-line mode to ensure real time requirements and algorithms best tuning.

The SAFE-RAIL project fully succeeded in the development of an 'innovative ground penetrating radar system for efficient, cost-effective, fast and safe rail-track substructure conditions monitoring'. The main innovation issues in radar and ICT technology were addressed by the SAFE-RAIL consortium through the effective design, implementation, testing and overall engineering of a rail-track monitoring system based on three antenna arrays in multi-channel configuration and on an innovative data interpretation and analysis tool based on expert systems and neural networks. The outstanding result of the project, consisting in an operational, fully validated system prototype, paved the way to the integration of the SAFE-RAIL subsurface monitoring system on high-speed diagnostic trains for:
(i) the real-time subsurface assessment and the delivery of 'diagnostic' information to the on-board operator, and
(ii) the storage of the collected information for off-line multi-temporal multi-instrument analyses.

More information on the project can be found at the project website: http://www.saferail-project.eu.
126459731-6_en.pdf