The Nottingham railway test facility, UK

A major new full-scale laboratory test facility for railway trackbeds is described. The equipment was designed and developed by the research team at the University of Nottingham, and has been used initially for two projects concerned with the performance of railway ballast. One dealt with the application of geogrid reinforcement to reduce the rate of settlement under repeated vehicle loading, and the other was concerned with ballast degradation both under loading and tamping. The facility allows application of cyclic loads of up to 94 kN directly to the sleepers using a loading system constructed in a laboratory test pit. Three sleepers are involved, and loads are applied by servo-controlled hydraulic actuators with their inputs phased to simulate a moving wheel. A tamping bank can be attached to the loading frame to perform the normal maintenance operation. Instrumentation is used to measure the permanent track settlement and the transient deflection of the central sleeper. Earth pressure cells can be installed in the subgrade to monitor transient stresses. Facilities are incorporated to determine the degree of particle degradation and to control the subgrade water table level. The design and performance of the equipment are described, together with some typical results from early experiments.