strategic selection of core sample locations throughout the production area. The team performed coring of the soil mix columns at any location where construction anomalies occurred. These locations were remixed if analysis of the core samples deemed it necessary. The coring program helped to ensure the bottom seal plug met the design requirements. A permanent onsite surveying team helped to confirm the proper locations of the augercast piles. In addition, all piles were constructed under direct supervision of an onsite third- party inspector. Testing of cube samples verified grout strength. Data Acquisition The team used proprietary data acquisition (DAQ) hardware and software systems to record all parameters of soil mix column construction. The DAQ systems also incorporated GPS to triple check the surveyed layout of all soil mix columns. An in-cabin graphical user interface displayed all construction parameters to the rig operators during column construction. The soil mixing operator monitored rotation speed, penetration rate, depth, withdrawal rate, binder content, grout slurry density and injection pressure during penetration and withdrawal of the soil mixing tool. This allowed the operator to adjust the parameters during the construction processes to keep the columns within project specifications. DAQ systems on the augercast drill rigs recorded all stages of augercast pile construction. The augercast pile operator monitored drilling operations (auger tip depth, torque, rotation speed, withdrawal rate, start and stop times, and leads inclination) and grouting operations (grout volume pumped vs depth, and grout line pressure). The operator used this data to make adjustments during construction, ensuring a high-quality deep foundation. All data were available remotely via Internet to the owner and their engineer for review. Production The aggressive construction schedule, which began in December 2013, required the concurrent performance of all aspects of the turnkey scope of work, from layout to excavation, including wet soil mixing, augercast pi les, pi le cutoff , water management, spoil and excavation handling, and removal and disposal. This resulted in a peak average jobsite traffic pattern of a truck entering and leaving the site every 3 minutes. The team maintained constant communication and coordination internally and with the general contractor. Daily on-site coordination meetings minimized conflicts and made sure the work matched the fast paced schedule. The soil mixing operations generated 75 to 100 cu ft (2.1 to 2.8 cu m) of spoil per day. This spoil was removed from the site, allowing for an efficient and safe work zone. Rain water storage posed a logistical challenge in addition to the spoils, as the soil mixing operations decreased the soil permeability, preventing rain water absorption into the ground. A system of storage ponds, pumps, and recharge wells were used to clear the site of standing water. The careful planning and monitoring of all activities allowed the successful completion of the work. In December 2014, the areas for the waterproofing and concrete shell trades were released, and the major excavation was completed in March of 2015. Keller completed the program with pile cutoff and placement of a layer of graded stone on top of the soilcrete plug. The stone provided a smooth, dry surface for final waterproofing and allowed easy pumping of rain water from the basement during subgrade construction. Upon completion, inspections observed minimal water infiltration for the 107,000 sq ft (9,940 sq m) excavation, at less than 15% of the agreed upon allowed value. Safety, Quality, and Production The team performed the complete project with no lost time accidents, reflective of its dedication for safe and productive work. The team held daily safety meetings. Prior to high-risk activities the team would conduct thorough task analyses to identify and address potential safety hazards. While managing up to six simultaneous oper- ations the team completed over 80,000 man hours without a recordable incident. The challenging excavation and foundation program combined the need for a dry, deep excavation in a permeable rock formation with a tight schedule, difficult spoils management requirement and challenging site logistics. The team provided the owner with a single source, turnkey, design-build excavation and foundation package. The innovative design, state-of-the-art quality control program, deep-rooted safety culture, careful planning and coordination, and an efficient execution allowed successful completion of the program. The authors wish to acknowledge Coastal Construction, NV5 Engineering, Desimone Consulting Engineering, Arquitectonica, Consultatio, for their expertise, comradery and guidance. Final pile cap and initial building construction 78 • DEEP FOUNDATIONS • NOV/DEC 2015
