The behaviour of under-sleeper pads at switches and crossings (S&C) - field measurements

Abstract

Major growth in rail traffic in many parts of the world in recent years has brought railway networksclose to capacity and restricted the time available for track access to carry out maintenance workwithout costly temporary route closures. There are, therefore, significant benefits in designing ormodifying ballasted track systems to reduce maintenance and associated access requirements.Under sleeper pads (USPs) offer the potential to extend ballasted track system life and to extend theintervals between routine maintenance. This paper presents and evaluates field measurements,made using geophones and high speed filming with digital image correlation (DIC), of theperformance of a renewed section of track incorporating two switches and crossings (S&C) over aperiod of two years. One S&C was fitted with two types of USP (categorised as medium and soft),while the other had no USPs and acted as a control. Measurements demonstrate that the bearerswith USPs fitted showed less variability in movement than bearers without USPs fitted. The provisionof soft USPs caused large increases (>40%) in vertical bearer movements relative to bearers withoutUSPs, although the medium USPs showed little difference. Increased movements of elongatedbearers supporting both tracks fitted with soft USPs led to increased bearer rotations towards theloaded track. This effect was aided by the rigid steel collar fixing in the middle of the bearer used inthis design of S&C, and raises questions concerning the desirability of this feature. DICmeasurements showed that the at rest position of the elongated bearers rotated towards the trackon which a train had most recently passed.

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Identifiers

ORCID for Louis Le Pen: orcid.org/0000-0002-4362-3895

ORCID for Geoffrey Watson: orcid.org/0000-0003-3074-5196

ORCID for William Powrie: orcid.org/0000-0002-2271-0826

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