FACTORS ACOUNTING FOR ACTIVITY-TIME AND PROJECT-TIME UNCERTAINITIES IN BORED PILES CONSTRUCTION PLANNING: CASE STUDY ON A BUIDLING PROJECT IN HONG KONG

Planning the construction for a system of bored piles in building foundation engineering is (1) to predict the time duration required to complete all the bored piles with due consideration of relevant engineering factors and site constraints; then (2) to predict the total project time generally by aggregating the predicted working duration for construction of each bored pile. The duration for construction of an individual bored pile results from analyzing various working sequences and different activity duration (such as predrilling, excavation, steelfixing, air-lifting, and concreting, etc.), which is informed by experiences and site records of previous projects. However, determining the project duration for constructing many bored piles on one site is much more complicated than adding up the time duration for individual piles. In practice, project schedules are often found to be unrealistic and incorrect during the construction stage. This is because construction planning is not based on a exhaustive and comprehensive evaluation of site factors, such as site layout plan, site constraints, quality control, environmental control, safety control and logical relationships between different trades. In this paper, we identify those factors based on a foundation engineering site in Hong Kong with ninety-seven bored piles and address their effects on uncertainties in activity time and project time.