Semiprepared Airfield Characteristics at Higher Elevations

During combat in April 2004, the Defense Department airdropped $\mathrm{45,000}\mathrm{t}$ of engineering equipment to build a semiprepared airfield in eastern Afghanistan. Engineers encountered two types of challenges as they shaped the natural material into a runway. First, significant quantities of aggregate in the soil highlighted the limitations of determining bearing properties by dynamic cone penetrometer indexing alone. When field expediency is required in these conditions, both the penetrometer and a complementary mechanism—such as the Unified Soil Classification System—should be used to determine the material’s bearing capacity. Wear layer confinement in semiarid climates is also addressed, and meteorological observations complemented data development. Second, weather phenomena corresponding to airfields at higher elevations generally decrease aircraft performance. The engineering result is reduced tolerance for runway unevenness when aircraft are traveling at high speeds. When building airfields located at higher elevations, design criteria must account for this diminished tolerance and its relationship to aviation safety. This paper presents data derived from military activities and suggests a mechanism for measuring the degree of runway unevenness.