A Practical Method For Analyzing The Vertical Bearing Capacity And Settlement Of Pile Foundations With Defective Piles

The occurance of defective piles in practical prejects is highly frequent. Thedefective pile, though has some defects which would affect the development of itsside frictional resistance and tip resistance to some extent, it still has certain loadcapacity. Therefore, the defective pile should be fully investigated and utilized whenconsidering either cost aspect or project efficiency aspect. Howe ver, there’s no oneappropriate method until now to calculate the vertical load capacity and settlement ofpile groups containing defective piles.Therefore, based on the existing fundamental principles of vertical load capacityand settlement of pile group foundation, this paper introduced the Defect InfluenceFactor, used different values for differnet defective types, and discussed differnet trainof thought when calculating the vertical load capacity and settlement of pile groupwith stem enlargement, stem shrinkage, breakage, mud cake, dregs and concretesegregation piles. In order for easy numerical calculation, the author developed aFortran program——FPBS, which can numerically calculate the load capacity andsettlement of pile group foundation in layered soil with different pile lengths,diametres and defective types.With this program, the paper first analyzed and compared the pile top settlementsof experimental normal piles, experimental defective piles and FPBS results. Then aspecific calculating case was investigated by selecting a specific Defect InfluenceFactor, using three different calculating methods for load capacity and one method forsettlement based on Mindlin original superimposed stress function, integration,superposition and layer-wise summation, to calculate the vertical load capacity andsettlement of both regular pile group and pile group with broaching, gapping andbreak piles. The trend of how Defect Influence Factor influences the vertical loadcapacity and settlement of defective pile group was summarized by comparing theresults of regular ones with defective ones. This study has certain instructive meaningfor defective piles, especially in practical projects.