Oil sand deformation under cyclic loading of ultra-class mobile mining equipment

Abstract

The strain softening of oil sand in the underfoot, due to the loading action of large mobile mining equipment such as trucks and shovels, yields a highly unstable condition for the operation of this ultra-class equipment. High maintenance costs as a result of truck and shovel frame failures are a frequent result of this instability. With the advent of ever larger units as mining operations move towards in-pit extractive technologies, some of these units are now approaching 2800 tons GVW. The ultra class units are able to operate year round, the interactions with the ground conditions have become an integral concern in selection of these units. The scaling approach and multi cycle convergent value approximation allows operations personnel to predict the degree of ground deformation for large mobile mining equipment. Thus enabling the decision of whether to operate equipment in a given soft ground location to be made. A full-scale field test was performed to study the ground stiffness behaviour during ground loading by ultra-class mobile mining equipment. The test involved a P&H 4100 BOSS ultra class shovel, which was tested with respect to its loading and ground response on high-grade oil sand. The field test mimicked real conditions while operating a shovel. This test was the first attempt to measure the stiffness of the oil sand environment by using in-place pressure cells and displacement-measurement tools. The model’s average error for deformation prediction for the shovel underfoot test was approximately 5%. The mining-induced confinement during the plate load test and equipment activities using the elastic model using Boussinesq’s approach was estimated. The Boussinesq’s approach provides a reasonable match between the field shovel test and the model’s outcome.