Experiment-based estimation of the settlement potential due to dynamic loads from heavy vehicle traffic on the A 44n motorway built on the dump of the Garzweiler opencast mine

Abstract

The A44 motorway was rebuilt on the dump of the Garzweiler opencast mine over a length of 7 km. The maximum thickness of the dump beneath the motorway is 185 m. Mostly sands showing a loose relative density were dumped. This leads to time-delayed settlements of the dump. In order to reduce these settlements of the dumped subsoil, which could jeopardise the serviceability limit state of the motorway, a top layer consisting of gravel and sand, with a minimum thickness of 10 m, was dumped using opencast mining equipment. This layer was compacted in the upper part using earth-moving machinery. To what extent vibrations from traffic loads can lead to grain rearrangements and thus settlements of the freshly dumped and compacted subgrade is the question of the investigation presented herein. Based on results of a customized exploration of the subsoil and dynamic field tests, in which loaded trucks drove over a measuring cross-section, it could be demonstrated that shear strain amplitudes induced by road traffic loads in the underlying compacted and loose granular soils do not exceed the strain threshold required for the accumulation of plastic deformations. Therefore, admissible settlements should not be exceeded even at very high numbers of traffic load cycles.