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Installation of Aggregate Piers at New Carolina NeuroSurgery & Spine Associates Building


Tyler 2 is currently constructing a new 16,000 sf two-story building for long-time client Carolina NeuroSurgery & Spine Associates (CNSA).

The facility will house CNSA’s business functions including accounting, administration, pre-certification, research offices, conference rooms, and support areas.

The site work at CNSA Lillington requires aggregate piers to support the building structure’s column foundations and perimeter wall foundations.  The aggregate piers will limit the total settlement of the structure to less than 1.0”. 

Tyler 2 selected subcontractor Hayward Baker based on their use of the Vibro System which has alleviated a wide range of static, dynamic, and seismic foundation problems for the last 70 years.  The vibrators are designed to densify and reinforce soils in situ through the use of horizontal vibrations.  The motor and eccentric weights are located near the vibrator nose cone or vibrator tip which insures maximum vibratory energy is focused through the entire length of the aggregate pier column as the vibrator is penetrated and withdrawn in 1 to 2 foot increments.  The vibratory energy and ramming action of the vibrator cause the dense aggregate to interlock and form a stiff pier that engages the surrounding soil, providing reinforcement and increased shear resistance.

Aggregate piers are typically installed to depth of 5 to 30 feet for the support of new loads.  Tyler 2 installed a total of 83 piers (ranging from 8 to 15 feet in depth) including the 5 piers required for modulus testing.  The holes dug on site for testing were 30” in diameter and approximately 12 feet deep.  The procedure used on the site was to place aggregate in the hole, vibrate to height, place concrete in the hole and vibrate to height and finish off the top of the hole with aggregate.  The aggregate on the top is sacrificial for removal when footers are dug and placed.

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