An oil sand pseudo-elastic model for determining ground deformation under large mobile mining equipment

Abstract

Strain softening of oil sand under dynamic loading from large mining equipment inhibits the ability of the equipment to function at optimal design performance. This paper looks at the findings of dynamic plate load tests, which effectively mimick the loading and unloading action of a shovel track pad. A pseudo-elastic model was proposed based on the results of the dynamic plate load testing to predict the deformation of oil sand under cyclic loading. Both field and laboratory cyclic plate load tests were performed on oil sand materials. The field tests were performed with different plate sizes, or footprints. The load was normalized based on the pressure stiffness concept in units of pressure per unit deformation. FLAC was used to model the field plate load test deformation with the elastic concept. The laboratory tests were performed at room temperature with more control on the load, loading rate, and cycles than possible during the field testing. Tests were conducted using a circular plate of 14.9 cm diameter, at stress magnitudes of 200, 400, 500 and 600 kPa. The plate load tests were conducted for varying loads, holding, and relaxation times of 0, 2, 5 and 10 min respectively for each magnitude of stress. The outcome of laboratory plate load tests show that after frequent cycles, the pressure stiffness (ratio of stress to deformation) converges on a plateau value of 8 kPa/mm. The proposed approach can be used to evaluate oil sands ground performance, enhancing the prediction process for ground deformation under the operation of ultra-class mining equipment.