In a bog area in Jutland soft subsoil had been causing settlements on a crossing road for some time. The problem was solved by using Leca® lightweight aggregate as load compensation underneath the road.
The crossing road, Korupskovvej, which is located in Djursland near Kolind runs through a 450-metre stretch of bog area with very soft subsoil causing settlements. Through the years, the road has subsided by up to 1.5 metres and during wet periods, it has been flooded to such an extent that closure has been necessary.
In 2017, Syddjurs Municipality decided to repair the stretch through the bog area and therefore joined forces with the engineering company Viggo Madsen A/S as specifier and the contracting company Gert Moller ApS as contractor.
Viggo Madsen A/S initially suggested installing load compensation under the entire road as the problem with settlements was not merely centred locally in the bog area. This solution, however, turned out to be too expensive, so to start with only a 100-metre stretch in the bog area has been repaired. At the same time, a new bicycle track has been constructed, also with load compensation, on the 450-metre long particularly challenging stretch.
Leca lightweight aggregate for load compensation
Leca lightweight aggregate was the product chosen for load compensation under the road as well as the
bicycle track because gravel proved too heavy and thus liable to cause settlements.ettleme
Morten Lynghus from Viggo Madsen A/S explains the choice of material: – This is not our first experience with Leca LWA.12-15 years ago we applied the principle for some vehicle inspection facilities in Lystrup, and they are still fine. That project is the basis for choosing Leca lightweight aggregate for this task as well.
Geotechnical studies under the stretch of road have shown that over time, without the load compensation the road would have subsided by 35-50 cm on the 100-metre stretch and by 25-30 cm on the remaining stretch.
Two different solutions
When incorporating the Leca LWA under the road they excavated part of the softest stretch, installed geotextile and then applied 1,075 m3 of Leca 10-20, which was distributed in a layer of up to 80 cm. Finally, the geotextile was wrapped around the lightweight aggregate and the road was built on top.
With this solution the maximum settlements has been limited to approximately 25 cm for the entire stretch of road through the bog area.