A thick, compressible, high plasticity, alluvial silt deposit along the Delaware River in Philadelphia, required surcharging to facilitate a shallow foundation system. A 10-ft high embankment was constructed across the building pad after installing prefabricated strip drains to expedite the consolidation process. A new mechanical room, which was added after completion of the strip drains, required 20 ft of fill to complete the consolidation at the same time as the rest of the building area. The preloading program was monitored using vibrating wire settlement sensors and drive point piezometers for 6 months and post-surcharge verification tests were also carried out for added assurances ahead of starting construction. The verification tests included standard penetration tests (SPT), cone penetration tests (CPT), flat dilatometer tests (DMT) as well as collecting undisturbed Shelby tube samples for laboratory consolidation testing. The post-surcharge laboratory tests demonstrated a significant increase in preconsolidation pressure or maximum past stress (p'_c). Of the in situ verification tests, however, only the dilatometer test captured the increase inp'c consistent with the laboratory consolidation test, and none showed an increase in the undrained shear strength due to surcharging.
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