Estimating the As-Placed Grout Volume of Auger Cast Piles

Augered Cast-in-Place (ACIP) piles are a geotechnical foundation element increasingly used to support large publicly funded structures as an alternative to drilled shafts or driven piles. ACIP piles are constructed by drilling an excavation to the full length of the designed pile with a continuous flight auger. Grout (cement, sand, and water mixture) is then pumped through the hollow auger stem to begin grouting the excavation. After establishing an initial head pressure, the auger is slowly extracted while the remainder of the pile is grouted. Once the auger is completely removed, the steel reinforcement cage is lowered into the grouted excavation while the grout is still fluid. To ensure the constructed pile meets design specifications, various integrity methods are used during and after construction. Careful monitoring of auger drilling/extraction parameters and grout volume during construction is an essential part in establishing pile integrity. Thermal wires, consisting of temperature transducers on one-foot intervals, are also installed along the length of the reinforcement cage. When curing, the grout undergoes an exothermic reaction, allowing the thermal wires to detect cooler or hotter regions that correspond to areas of less or more grout volume, respectively. These ACIP piles can reach depths of over one hundred feet and cannot be fully inspected making these verification methods vitally important. This thesis looks critically at field data from ACIP piles being constructed as part of the I-395 expansion project ongoing in Miami, Florida. Through this review, it has been determined that the current methods for monitoring and evaluating pile construction are often contradictory and result in substantial uncertainty regarding the as-built dimensions of ACIP piles. It is therefore the goal of this research to identify the current issues facing the construction of ACIP piles, the effects on pile integrity, and recommend future directions of research that will result in better ACIP pile construction and evaluation techniques