This is particularly the case in areas where deep coal mining has been followed by re-cultivation through the placement of stripped soil without compaction, creating made-up strata between 20m-40m thick – a practice which leads to long term settlement. Such geological conditions, especially involving clay soils, have considerable influence on the road bed design which required measures to accelerate creep of the underlying strata.
We were commissioned by the Road and Motorway Directorate to prepare a detailed design for this highly complex project. Our highway engineers developed a solution involving the application of high profile piles, designed to secure settlement of 150mm after 20 years, on the basis of 60-70% of ground movement occurring during the construction period. To accelerate the settlement process in sections with the highest thickness of made-up ground, the road bed area is being pre-consolidated using another layer of approximately 2m of material which will be excavated prior to construction.
As well as the 4.2km length of motorway and associated drainage system, our role involved designing one 470m long and three 50m long motorway bridges, with a grade separated junction at Úžín. The project also requires diversions of 3.3km of first and third class roads, 2.1km of water channels and 4km of field tracks, plus extensive diversions of gas mains and communications cables. Other elements we designed include an escape zone for heavy vehicles due to the gradient, traffic signage and markings, an emergency SOS system and an accident security system for a tunnel in the adjoining section of motorway towards the border with Germany.