From the earliest installation of cast-in-place piles, the question of, “How do you know what you have here?” has asked been asked. The issues of whether or not the piles being formed were sound, continuous and of the proper diameter were of high concern, as installation was very operator-sensitive. Early basic inspection guides included monitoring the drill depths and the grout volume and reinforcing steel placement. The drill leads were marked to indicate drill depths and the grout pumps were calibrated for their output. From this, a pumping procedure in terms of the number of strokes-per-foot could be established for given diameters in varying soil conditions. Early installation of ACIP piles The project included 16 in (0.4 m) diameter piles with a design compressive load of 150 tons (1,335 kN), requir- ing a grout compressive strength of 6,000 psi (41.4 MPa). This, in contrast with the struggle to produce 3,000 psi (20.7 MPa) grout 30 years earlier is an example of how one component of the ACIP system has advanced, and all aspects of the process have advanced similarly. Clearly, the major thrust in the use of ACIP piles has been in development of equipment, materials and processes to go “bigger and deeper,” and the increase in design loads reflects that emphasis. Certainly, increases in capacity of conventional ACIP piles will occur with development of more powerful equipment; however, new processes seem to be the likely source of significant changes in the cast-in-place pile industry. Clearly, the major thrust in the use of ACIP piles has been in development of equipment, materials and processes to go “bigger and deeper,” and the increase in design loads reflects the emphasis. Approximately 400 ACIP piles were placed for the Maui Hyatt Timeshare Tower in 2012 This same basic process is used today, but the methods of gathering information have changed radically. There are numerous monitoring systems on the market to electronically measure tool depth, torque, grout placement and a variety of other parameters during ACIP pile construction. The first modern automated monitoring system in North America was the Pile Installation Recorder (PIR), developed by Pile Dynamics, Inc. working with Berkel & Company on its development and implementation in 1995. Since that time numerous other automated monitoring systems have become available. An example of the market penetration of ACIP piles in the 1990s was the preparation for the 1996 Olympic Games in Atlanta, where the system was selected for the majority of construction where deep foundations were needed. The most visible symbol of the Olympics, the Olympic Stadium (later to be transformed into Turner Field, home of the Atlanta Braves), saw the installation of more than 123,000 ft (37,490 m) of piling that ranged from 35 ft to 85 ft (10.7 m to 25.9 m) in length. 14 • DEEP FOUNDATIONS • NOV/DEC 2013
