Abstract: More buildings are facing difficulties in pile foundation design and construction under karst geological conditions. The case history of a project in Hangzhou is presented in this paper. A systematic study was conducted on the design and construction methods of pile foundations in well-developed areas. Based on the specific situation of the project, the design parameters were optimized, and the pile foundation design scheme was compared and analyzed. The plan of using cast-in-place piles to pass through karst sections was selected, and the distribution of rock cavity was explored at each pile location. After comparison, the rotary pile driver was selected for the construction. After comparing and analyzing multiple pile foundation construction schemes, the principle of schedule and cost optimization was adopted to implement the pile concrete over pouring scheme. Targeted technical measures were taken to address specific issues such slurry borehole protection, construction safety of rotary pile drivers, concrete pouring, and steel reinforcement cage jamming during the pile foundation construction process. On the basis of ensuring project quality and safety, project schedule was accelerated, and the project cost was effectively reduced. The pile foundation QA testing results all met the design and specification requirements, which can provide guidance for similar projects.

Key words: Karst Geology, Pile Foundation, Cast-in-Place Piles, Design Optimization, Construction Methods