Cyclic performance of soft ground

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. Increasing our knowledge about the behaviour of oil sand due to its dynamic interactions with equipment would enhance the long-term equipment design strategy for OEM's (Original Equipment Manufacturers) and provide mine operators with improved operational guidelines for planning and maintaining this equipment.

This thesis will focus on evaluating the oil sand's behaviour under cyclic loading of large mobile mining equipment. I propose a cyclic plate load test for evaluating ground performance established and performed in both field and laboratory tests and a pseudo-elastic model is proposed that increases the ability to predict, within a reasonable error, ground deformation under ultra-class mining equipment. I will explain the empirical relationships for the pseudo-elastic model build to predict deformation under cyclic and static loading conditions. 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.

In the laboratory tests, the cyclic and static unconsolidated undrained triaxial test under low confining pressure was performed. Also, the cyclic plate load tests were performed in big box of oil sand (large scale). The large scale laboratory tests were used to build a relationship between the load level, number of cycles and deformation. The numerical modeling was carried out to predict and compare the field cyclic plate load test results.

The underfoot shovel test (P&H shovel 4100 BOSS) was performed to understand the equipment and ground interaction. Also, ground deformation results during underfoot shovel test was predicted and compared by pseudo-elastic model.