The Development and Use of a Test Facility for Large Diameter Pipes
This thesis examines the performance of a new deep burial facility through numerical modelling and physical experiments. A numerical investigation was conducted to investigate the influence of the loading scheme and boundary conditions on the pipe behaviour in this new facility using both two – dimensional and three – dimensional analyses. The numerical analyses suggested that two independent grillages on the surface produced a more uniformly distributed ‘overburden’ pressure and friction treatment must be used in this facility to minimize the impact of sidewall friction on the pipe response. Two large diameter culverts, a 3.05 m diameter composite pipe and a 2 m steel pipe, were tested to study their strength limit states while evaluating the facility. The 3.05 m diameter composite pipe supported a maximum overburden pressure of 224 kPa and reached its ultimate limit state at a total overburden pressure of 258 kPa. The pipe failed as a result of local buckling of the steel ribs in the vicinity of both springlines. The 2 m diameter corrugated steel pipe did not reach its ultimate limit state at a total applied pressure of 358 kPa, but plastic hinges were seen to have occurred in the vicinity of both haunches. The plastic hinges observed in this experiment could lead to a failure mechanism that is not considered in the existing design models for structures of this type. A series of model erosion void experiments were conducted to investigate the potential for using the new facility to investigate the development of erosion voids. The results indicated that an erosion void stabilized in the vicinity of the pipe shoulder when erosion occurred through holes in the pipe haunch due to groundwater infiltration. The erosion extended to the ground surface when it was driven by simulated rain water flow through the holes in the pipe haunch. The final geometry, width and height, of the erosion void also depended on the elevation of the groundwater table, initial condition of the backfill, and the backfill material.