Proposition for in Situ Evaluation of Geotechnical and Structural Aspects of a Heavy Haul Track

Abstract

Over time railroad tracks have their structural quality varying in function of traffic accumulation and maintenance. These changes can provoke different track responses in terms of unexpected stresses and deformations that, in turn, can bring on some loss of geometric quality and cause impact to the trafficability. Track condition monitoring can indicate the variation of geotechnical and structural characteristics in terms of traffic accumulation, maintenance, drainage, etc. The knowledge about these variations can provide information about the major factors that affect track behaviour and so support the maintenance planning of a railroad management operator. The aim of this paper is to propose a procedure for in situ evaluation by monitoring geotechnical and structural responses of typical sections of a heavy haul track (314 kN/axle) in the north region of Brazil. The implemented instrumentation was conceived using strain gauges for deformation measurements, vertical pressure cells for stresses monitoring and linear variable displacement transducer (LVDT) coupled to displacement measurement device (DMD) and tactile sensors. In addition, suction sensors were installed for measuring negative pore-pressure in the subgrade. From the deformations in the web rail and considering an analytical model, it was possible to determine the wheel dynamic loads. It was observed the load factor values varying according to train speed and track quality, as well as the influence of the dynamic load in the stresses over the profile. Concerning the subgrade, the suction pressure presented slight variation (condition near saturation) during the period of analysis, so it could influence the track structural responses to the loads.