Tests on steel reinforced rubber bearings were carried out by TWI for R T James & Partners Ltd, consultants to the London Underground Ltd Jubilee Line Extension team for the design of floating track slab sections for the new railway.
As part of the work to extend the Jubilee Line it was proposed that floating slab tracks be used in some places. This means that the rails are supported by concrete slabs on special rubber bearings to provide noise damping and prevent vibration transmission into the ground around tunnels.
Tests at TWI were carried out up to six million cycles using one of TWI's universal fatigue testing rigs equipped with a 250kN axial and a 6kN horizontal hydraulic actuator to allow biaxial loading.
Compressive and shear loads and their corresponding displacements were computer logged and recorded throughout the test. In addition, manual checks were made and recorded at regular intervals.
The approximate temperature variation of the rubber bearing was also measured at regular intervals using a thermocouple.
Results of tests helped R T James & Partners Ltd, in association with the rubber bearing manufacturer, to improve bearing design and to provide assurance of their mechanical durability within six million cycles.