Projects: New Faster Approach to Density Testing Methods – Airport Runway

Geotechnical Engineering



Faced with placing 18,000,000 cubic yards of soil and rock mixture — enough to fill a football stadium six times — a grading contractor sought an efficient way to test for confirmation that material placed in the runway embankment met compaction requirements and minimized costs.



ATC’s alternative density testing method reduced the construction schedule by six months and convinced both the client and owner to adopt the program. The client was responsible for moving and placing fill material to raise the ground surface to proper elevations. To minimize costs, the owner selected a fill material composed of a soil and rock mixture from large rock quarries and adjoining properties. After reviewing the initial criteria with the contractor, ATC recognized that traditional density testing methods would not always work given rock content in portions of the fill. Further, we discovered that use of large-scale density tests, initially requested by the owner, would create unacceptable delays and render the project far too costly. ATC developed a faster approach – one based on tests ratified by the U.S. Army Corps of Engineers that reduced testing time and cost without compromising results. A series of seven test strips were employed for the rock and soil mixture. Rather than measuring density, the new method identified the number of equipment passes needed to minimize layer compression. Successful fill compaction was confirmed with a proof-roll test using a 50-ton pneumatic roller. Each day, ATC’s field team reviewed, organized, catalogued, and transmitted 40 to 60 pages of test reports to the owner. Upon completion, ATC will have conducted approximately 13,500 proof-roll and density tests.