Evaluation of Arching Action Generated in the Backfill between Outlet Conduit and Existing Embankment

Abstract

When improvement works for overage irrigation tanks are performed, existing embankment is first excavated, then a new outlet conduit is established and is buried with backfill material. In this case, the stress generated in the backfill between outlet conduit covered with reinforced concrete and the existing embankment may decrease. This phenomenon is called arching action and causes a large reduction of stress. Consequently, the backfill under the arch becomes a weak point in the structure and poses a risk of hydraulic fracturing. In this study, the arching action is evaluated quantitatively. Parametric studies on inclination angle of excavation, excavation width, stiffness of foundation and existing embankment and compaction stress are performed to reveal the influences on the stress condition. Moreover, the effect on the arching action of the stiffness of flexible conduit, which has recently become popularly used in the improvement of irrigation tank, are discussed.