OPENING PLENARY: Georgia Geology and Deep Foundation History-PPT Presentation

PPT Presentation

Pdf Summary

The presentation reviews Georgia’s geology and the evolution of deep foundations over roughly 50 years. North Georgia’s Piedmont is underlain by igneous and metamorphic rocks, including granite, schist, and gneiss. Weathering creates layers of residuum and saprolite above partially weathered rock (PWR) and competent bedrock. South of the Fall Line, the Coastal Plain contains a complex sequence of marine and freshwater sediments deposited during repeated sea-level changes over about 100 million years. Conditions vary considerably, so local investigation is essential.<br /><br />Atlanta’s early deep foundations included drilled shafts, Raymond Step-Taper piles, and pipe piles. Auger-cast-in-place (ACIP) piles gained acceptance gradually, supported by stronger installation equipment, improved grout mixes, and growing industry experience. By the 1990s and 2000s, ACIP piles were widely used for major projects, including the Georgia Dome, Olympic Stadium/Turner Field, and Phillips Arena. Modern practice includes larger, higher-capacity piles, automated installation data, and displacement piles. Other approaches also developed: rammed aggregate piers provided an intermediate foundation and ground-improvement option, while micropiles became an important solution where conventional systems were impractical.<br /><br />A bridge project near Mercedes-Benz Stadium illustrates the need to adapt designs to site-specific conditions: PWR depth varied substantially between bridge bents, and competent rock was present at only one. Testing considered both refusal on rock and termination in PWR. At the Hyundai Mega Site in the Coastal Plain, different systems—ground-improvement elements, rigid inclusions, and ACIP piles—were selected for slab support, settlement control, and structural loads.<br /><br />The presentation’s broader message is that soils and rocks are variable, but their behavior follows natural physical and chemical principles. Successful foundation design depends on understanding local geology, gathering reliable site data, testing assumptions, and selecting systems suited to actual ground conditions.

Keywords

Georgia geology

deep foundations

Piedmont bedrock

Coastal Plain sediments

partially weathered rock

saprolite

augur-cast-in-place piles

micropiles

ground improvement

foundation design