Subgrade Strengthening of Existing Airfield Runways

A number of subsurface treatment techniques are found to have definite potential for strengthening existing airfield pavements. Basic requirements for subgrade treatment beneath existing airfield pavements are examined. Changes in pavement structural behavior caused by subgrade strengthening are theoretically analyzed. It is shown that subgrade strengthening beneficially affects airfield pavement structural response. Techniques for treatment of the subgrade beneath existing pavements are reviewed. These techniques are evaluated relative to their potential for subgrade strengthening below existing airfield pavements. It is concluded that: (1) drilled-hole and pressure injection lime; (2) mixed-in-place pile; and (3) post hole pile procedures have definite potential for strengthening subgrades beneath existing airfield pavement systems.