Constitutive testing of Red Wildmoor sandstone

The first objective of this research was to improve the experimental measurements for the constitutive behaviour of Red Wildmoor sandstone by optimizing the boundary conditions and specimen geometry, and improving the triaxial test instrumentation. The uniformity of deformation of the rock specimen was improved by minimizing specimen bulging due to specimen slenderness and end-surface frictional constraints. The improvements in the instrumentation were aimed at improving the monitoring of the applied forces, axial and radial deformations, and macroscopic rock failure through use of high precision LVDTs and cantilever gauges, acoustic emission measurements and acoustic pulse transmission velocities. The second objective was to obtain test data for the constitutive modelling and calibration of Red Wildmoor sandstone under various saturating conditions and saturation fluids. An additional task was an experi mental study for the improvement of the uniaxial compression test as an index text for rock mechanics applications. The performed modifications allowed the reliable collection of post-peak stress test data of material softening behaviour, and the identification of the point of macroscopic failure of the specimen beyond which the test data cannot be used directly for continuum modelling of material behaviour. © 2000 John Wiley & Sons, Ltd.