I-85 Widening

S&ME completed a preliminary geotechnical exploration during the design build prep phase.  Our team’s services included 28 soil test borings along the I-85 median, 10 borings (with rock coring) for proposed replacement bridges over I-85 at five interchanges, and 66 borings for proposed retaining walls, culverts, and associated ramps/roadways.

We conducted shear wave velocity measurements (by geophysical MASW/MAM analysis methods) at the five bridge replacements. We performed index testing on over 260 soil samples, Proctor and CBR testing on 16 bulk samples, CU/UU Triaxial Shear testing and Consolidation testing on 10 undisturbed samples, corrosion series testing on 5 bulk samples from the bridge sites, and unconfined compressive strength testing on 18 rock core specimens.

Following the SCDOT GDM guidelines, we prepared a Geotechnical Base Line Report to present the exploration results and our preliminary engineering recommendations for design and construction considerations. These included: feasible foundation types for the replacement bridges, settlement potential for MSE walls (and feasible ground improvement options), areas of likely difficult excavation conditions (due to rock/PWR), foundation support for culvert extensions, and pavement subgrade support recommendations based on the CBR test values.