LATERAL DISPLACEMENTS OF LOW EMBANKMENTS ON ALLUVIUM CONTAINING THIN PEAT LAYERS

The paper describes the events leading to the development of wide longitudinal cracks in the lean-mix concrete road-bases of motorway pavements, together with the subsequent investigations to establish the probable cause of the problem. The motorway embankments were only 2-3 M high and were founded on the flat alluvial plain of the river Trent. The embankments were formed by the excavation of local surface deposits of sand, relatively rapid deposition of the granular fill material, and compaction by heavy vibratory rollers. Thin layers of essentially fibrous peat were discovered at shallow depths within the alluvium. New drainage channels were formed parallel to and near the toes of the side-slopes of the low embankments. The paper examines mechanisms which could have contributed to the mode of pavement failure and makes general recommendations to obviate the problem in similar circumstances. (Author/TRRL)