MECHANICS OF KINKING AND BUCKLING OF PLASTIC BOARD DRAINS

The deformational response of plastic board drains installed to accele rate consolidation of soft soils, is examined as a problem of downdrag . The drain is modelled as a beam-column in which the axial load incre ases nonlinearly with depth. The soil response is represented by the W inkler medium whose coefficient of subgrade modulus increases linearly with depth. The governing equations for the drain-soil system are der ived and solved as an eigenvalue problem. The critical buckling loads and the shape of the drain are obtained as functions of the normalized subgrade modulus of the soil at the top, the parameters signifying th e variation of axial load along the length of the drain and the increa se of subgrade modulus with depth. The derived deformed shapes of the drain are consistent with the observed ones.