Detection of Voids under a Concrete Airfield Parking Apron using a Heavy Weight Deflectometer (HWD)

A series of incidents involving aircraft punching through pavements prompted the Navy to develop procedures for detecting voids on airfields. Initially, a successful void detection survey was completed at a Naval Air Station (NAS) where several voids were generated by leakage of large underground drainpipes. To determine the location of the voids, a procedure was developed which used a combination of methods such as internal videotaping of the pipes, heavy weight deflectometer (HWD) testing, ground penetrating radar (GPR), and dynamic cone penetrometer (DCP) testing. This procedure is now routinely applied at all 70 major Navy and Marine Corps airfields. This paper summarizes the methodology and presents a recent field case where a waterline ruptured under a concrete airfield parking apron. After evaluating an area of interest with a HWD possible voids were detected under a number of slabs which were then drilled to be able to take DCP measurements. Grout was used to fill in the voids and Pavement-Transportation Computer Assisted Structural Engineering (PCASE) analysis showed that the pavement should be able to support the estimated traffic levels of that airfield for the next 10 years.