Location: Ann Arbor, MI
Contract Value: $5 million
The new $50 million dollar 5th Ave. Parking Structure required the installation of a temporary Earth Retention System walls consisting of Temporary Soldier Piles & Lagging as well as Augercast Tangential Wall Systems. The ERS system was a tangential auger cast pile wall – TACPW & Soldier Pile & Lagging System. Augercast Tangential Walls were selected over secant walls for the tangential pile areas, and the Soldier Pile & Lagging Systems was per the original scope of services. The primary reason for the augercast wall was the economics and schedule constraints that the secant wall presented. The project was set up as a secant wall design, however when the final bids were received, the project team decided to use the TACPW as it was a substantial saving to the project. The scope of services was the construction of the new parking garage adjacent to the existing downtown buildings. The site was extremely congested and deliveries had to be scheduled days in advance of actual deliveries. The existing buildings were still in service and our work could not affect these operations. The project required an ERS system to support the existing residential, & commercial building that are present (6) on site, numerous utilities that serviced the existing buildings, and tower cranes. The ERS system had to be vibration free, due to the sensitive nature of the existing operations, which were directly adjacent to our work. Due to the site conditions, weekly meeting with project managers were held throughout the project, daily activity meeting with the site superintendent and look ahead schedules were required. The settlement of the existing structures was monitored by settlement points. These points were checked throughout the project’s duration and to date there has been no settlement of any adjacent structures or utilities. The project included 1,510 lineal foot of TACPW (855’) & Soldier Piles & Lagging (656’). The excavation depths were up to 71’ deep. There was over 40,000 lineal foot of augercast pile drilling installed, 1,130,000 lbs. of reinforcing steel installed, and over 6,000 cubic yards of grout used for the project. To our knowledge, this is one of the deepest excavation depths which utilized TACPW. The TACPW utilized earth anchors which was installed using duplex drilling and self-drilling/grouted anchors. Over 700 earth anchors were installed. All of the anchors were tested and locked o at their required loads. The duplex drilled earth anchors were tested to maximum of 235 Kips and the self-drilling anchors were tested to 144 Kip. The duplex-drilled anchors were installed usingwater/grout and air as the drilling mediums.