Obstructed and Damaged Piles–Some Case Histories of Pile Repairs

Five piled foundation case histories from construction projects in Greater Vancouver, British Columbia are presented. Driven steel pipe piles and drilled shafts had to be repaired to address damage or concerns regarding insufficient ultimate capacity in compression, uplift and/or lateral loading. For many of the piles, lateral loading requirements under extreme seismic events controlled the design, which in turn required minimum embedment depths. These case histories demonstrate that piles which drive short are more difficult to deal with than piles which drive long. In two of the case histories, the presence of confined water pressures resulted in disturbance of the material at the drilled shaft base elevation. Driven pile obstructions occurred because of large glacial erratics that are often present in till-like deposits. In some cases, obstructions were caused by tree trunks entrained within ancient slide debris. Repair methods had to be used when drilling out and replacing obstructed piles was not possible. The repair methods included: driving stinger H-piles inside damaged pipe piles to increase vertical capacity, installing anchors inside and outside driven pipe piles to increase uplift resistance, base-grouting drilled shafts to harden loose zones at the base, and construction of a composite foundation with a shaft carrying lateral loads and a near-surface footing carrying compression loads. Identifying pile installation risks early in the project and providing guidance and potential remediation techniques for the piling contractor was useful for developing repair solutions under tight schedule constraints.