NUMERICAL ANALYSIS OF THE RESPONSE OF ADJACENT PIPELINES DURING STATIC PIPE BURSTING

摘要

The expansion of the soil around the pipe being replaced during static pipe bursting causes ground disturbance, and surrounding infrastructure like pipelines are potentially vulnerable. Three-dimensional finite element analyses are being used to investigate the mechanics of soil interacting with other pipes. The progression of a burst head (or expander) through an existing pipeline is simulated using ABAQUS, and the effect of the resulting ground movements on adjacent pipes is calculated. The analysis is evaluated against surface movements observed in a static pipe bursting experiment conducted in a 2 m long, 2 m wide, and 1.6 m deep test cell. Calculated deformations are within 10% of measured values. The analysis is then used to examine the effect of pipe bursting on both PVC and cast iron water pipes located in the vicinity of the gravity flow pipe being replaced. Firstly, a 122 mm OD (outside diameter) and 7 mm thick PVC pipe is studied, with orientation transverse to the bursting direction, and located 300 mm above the crown of the clay pipe being replaced. The three-dimensional deformations, strains, and stresses in the adjacent PVC pipe are calculated during the progression of the burst head through the clay pipe. Analysis is then conducted to examine the same PVC pipe oriented parallel to the existing clay pipe. Maximum longitudinal PVC pipe strain of about 0.2 % was calculated for both these cases. Next, the analysis is used to examine the impact of bursting on cast iron pipes located transverse and parallel to the pipe being replaced. Both thick (D/t = 11.2) and thin (D/t = 31.5) pipes are analyzed and the maximum incremental longitudinal strain calculated is 0.04%. This may be sufficient to cause fracture, since it is in addition to strains from thermal and fluid loads, and is more than half of the expected fracture strain (minimum of 0.07% for cast iron water mains examined in Toronto).