Abstract: The leakage of slurry during cast-in-place pile construction in karst area often results in poor quality and insufficient bearing capacity of pile. In view of the wide distribution of connected channels in the karst area, we propose a new type of cast-in-place pile in dendritic shape with bags socketed into the karst caves. We probed into the feasibility of such bag-pile by designing bedrock model for pile-forming test, and on this basis, we further investigated the bearing characteristics and influencing factors of bag-pile via eight groups of static load model tests. Results demonstrated good quality of cast-in-place bag-pile. The ultimate bearing capacity of the proposed bag-pile is about 1.5 times that of ordinary pile of equal diameter, and the settlement of bag-pile is much smaller than that of ordinary pile of equal diameter under the same load conditions. Besides, the axial force of bag-pile body obviously reduced at the upper and lower interfaces of the dendritic structure which enhanced the side friction performance of the pile. Load transfer is of obvious time effect. The bearing capacity of bag-pile is positively correlated with the length, number, and buried depth of the dendritic structure.

Key words: bored pile, bag pile, bearing capacity, pile-forming test, deformation performance, influencing factors, karst area