Case Study: Jacking Force of Curved Pipejack (Prediction VS Actual)

Abstract

Jacking force is a critical element of a pipejacking operation. It influences the length of the tunnel drive, pipe integrity, and location of the shafts and utilisation of Intermediate Jacking Stations. Thus, it has strong impact on the constructability and end use of the pipejacking operation. Therefore, it is important that jacking forces are accurately predicted to enable the operation to be planned, designed and executed appropriately. This case study analyses a curved 1.5m ID pipejacking drive employing a steel reinforced concrete jacking pipe. The drive being analysed is 574m in length and it incorporates a horizontal curve with a radius of 700m. The complexity of a curved pipejack is greater than a straight drive, and the predictive jacking force is also more difficult to calculate. This paper focuses on the predictive calculation of jacking force for the curved drive taking into account the ground conditions, jacking pipe capacity, cutting head resistance, frictional ground resistance and the use of Intermediate Jacking Stations. This predictive assessment of the jacking load is then compared to the actual loads recorded in the field to determine the level of accuracy of the current industry jacking load equations and it suggests refinement.