A hollow cylinder apparatus to study the cyclic loading behaviour of dry granular material

The Nottingham Hollow Cylinder Apparatus was developed with the particular aim of studying the stress-strain behaviour of dry granular material in the context of wheel loading in pavements and rail track, where shear stress reversal is a critical issue. The equipment design was influenced by earlier developments at Imperial College but needed to accommodate cyclic loading involving large numbers of repetitions as well as monotonic testing. It featured independent control of torsion and axial load using servo-hydraulic closed loop systems with digital controls and data acquisition. Confining stress was statically applied equally on the inside and the outside of the cylinder. Careful attention was given to the measurement of applied loads, pressures and deformations. These latter were measured directly on the specimen using a combination of LVDT's and strain gauged cast epoxy rings so that all strain components could be determined with appropriate accuracy. Details of the equipment are presented, together with data illustrating its capabilities to apply a variety of stress paths defined in terms of the direction of the major principal stress (alpha) and the shear to normal stress ratio (eta). Some typical results from tests on Leighton Buzzard sand showing the accumulation of plastic strain over 10,000 cycles are given. For the covering abstract see ITRD E128041.