Soil nail walls are an excellent solution when vibration-free foundation installations are required such as construction next to existing structures, reconstruction projects and reinforcement of existing embankments. Soil nail walls are installed in a continuous excavation method whereby shallow 3′ – 6′ vertical cuts are made in the soil, holes are drilled for the nails, soil nail tendons are installed and grouted, a shotcrete layer is applied and bearing plates and nuts are attached. This process is repeated until the final grade is reached. The grouted nails increase the shear strength of the overall soil mass and limit displacement during and after excavation.
Featured Project
University of Michigan East Quad
Ann Arbor, Michigan
Project Details
The renovations to University of Michigan East Quad residence hall presented quite a few challenges for the project team. East Quad required Chemical Grouting, H-Pile and Lagging, Low Head Auger cast Piles, Tangential Auger cast Pile Walls, Soil Nails, Drilled Low-Head Micropiles, Push Piles, and Underpinning.
Walbridge was the construction manager for the 90 million-dollar renovations and SOLID BRIDGE CONSTRUCTION Inc (HCI) was hired for all the above-mentioned aspects of the project. This project was particularly difficult due to the schedule that needed to be met. On similar scope projects it would have typically taken seven months, however Walbridge required for the contract to be executed within three months.
All together there were 21 separate areas that required some form of work from HCI. The basement provided some of the most challenging work. The work that was done in the basement had to be done within seven to eight feet of headroom. Most of the work in the basement was needed for all of the new underground utilities that needed to be installed; HVAC, Plumbing, Sanitary, and Electrical would all be run underground. This would allow the university extra space in the basement. The underground utilities were 4 to 10 feet below the bottom of the column footings. With over 200 column footings no more than 20’ apart, they needed a solution on how to excavate for the utilities without compromising the buildings structural integrity. The soils below the footings needed to be chemically grouted. HCI facilitated the injection of over 60,000 gallons of micro fine silica cement into the basement. There were some locations that required excavation to be 10’ below the bottom of footing right next to the footing. Some of the footings were also supported with Micro or push piles. The basement area also presented HCI with the opportunity to install low-head Tangential Auger cast ERS (Earth Retention System). Elevator pits were required in the basement for this to happen and HCI had to install an ERS system that would allow the concrete contractor to form the walls. The piles that were installed were 15’ long and 24” diameter with a full-length cage. HCI also installed soil nails and underpinned in the basement.
As with any construction project unknown issues and problems arise, East Quad was no different. SOLID BRIDGE CONSTRUCTION worked closely with Walbridge and Soils & Materials Engineers to solve unexpected and emergency issues all while keeping the project on time. This project was a tough job that required a company with a wide array of skills and the ability to solve tough problems. HCI completed the job successfully and satisfied the needs of the construction manager as well as the needs of the owner.