Track behaviour: the importance of the sleeper to ballast interface

The aim of this research is to develop a fuller understanding of the mechanical behaviour of the<br/>sleeper/ballast interface, related in particular, to the forces applied by high speed tilting trains on<br/>low radius curves. The research has used literature review, field measurements, and laboratory<br/>experiments on a single sleeper bay of track. Theoretical calculations are also presented.<br/><br/>Field measurements are carried out using geophones to record time/deflection for sleepers<br/>during passage of Pendolino trains on the West Coast Main Line. Calculations are presented to<br/>quantify normal and extreme magnitudes of vertical, horizontal and moment (VHM) loads on<br/>individual sleepers.<br/><br/>Results from laboratory experiments, on the pre-failure behaviour of the sleeper to ballast base<br/>contact area, show that lateral load/deflection behaviour is load path dependent and relations are<br/>determined for improved computer modelling of the sleeper/ballast interface. Further test results<br/>are used to establish the failure envelopes for combined VHM loading of the sleeper/ballast base<br/>contact area. Tests show that the sleeper/ballast base resistance at failure occurs at a load ratio<br/>(H/V) of about 0.45 (24°) at 2 mm of displacement tending to 0.57 (30°) at greater<br/>displacements. In addition, measurements from pressure plates within the testing apparatus are<br/>used to describe the development of confining stress within the ballast during 100 cycles of<br/>vertical load. The development of confining stress is assessed with reference to a finite element<br/>model of the laboratory apparatus and it is shown that the earth pressure ratio moves towards the<br/>active condition for peak load and the passive condition at minimum load per cycle.<br/><br/>The contribution to lateral resistance of the crib ballast and varying sizes of shoulder ballast is<br/>also established and it is found that the shoulder and crib resistance can best be characterised by<br/>taking the mean resistance over a range of deflection from 2 mm to 20 mm. Calculations are<br/>presented, supported by the experimental data, to quantify the resistance from different sizes of<br/>shoulder ballast and a chart is presented which can be used as the basis for shoulder<br/>specification in practice.

Name dc:type.qualificationname

Ph.D.

Level dc:type.qualificationlevel

doctoral

Grantor dc:publisher.institution

University of Southampton

Year dc:date.issued

2008

Author dc:creator

• Le Pen, Louis

Advisor dc:contributor.advisor

• Powrie, William