Bethlehem, Northampton County, PA –
Development of a new health center in Bethlehem, PA required soil pre-treatment and the need to stabilize the soil pre-construction. Test boring logs proved subsurface erosion and karst activity. The logs also verified the need to improve the subsurface soils to support the proposed three-story office building. Sinkhole activity was revealed by 5 of the 31 test soil borings. The tests also showed soils consisting of moisture-sensitive silts and clays varying 6 to 47 feet below the ground’s surface. Compaction grouting was the method chosen to improve the soils for foundation support and reduce the risk of sinkhole activity.
CGS worked with the engineer and contractor to design the most efficient and appropriate grouting program. Compaction grouting was performed in locations within the building and at continuous perimeter footings. Grout injection locations were pre-drilled into approximately five feet of rock and injected in controlled one-foot stages from the bottom of the drilled hole to the bottom of the proposed footing. Low mobility grout was pumped in a controlled bottom-up process to displace and densify the surrounding soils. Once grout refusal criteria was reached at each location, CGS continued on to the next stage.
CGS injected approximately 687 cubic yards of grout in 345 grout injection points. Over 14,243 linear feet were drilled for an average depth of 17.3 feet per location. The project was completed on time, in 36 days using three grout crews.