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Bridging of Sinkholes

Project information

Project name

Motorway A1


Pyrzowice – Piekary Slaskie - Maciejow, PL


Budimex S.A. and Dragados S.A.

Construction time


Project details

Project description and challenge

The motorway A1 in Poland will be the main highway running from North to South all the way through central Poland. It stretches from Gdansk on the Baltic Sea through Łódź and the ‘Silesian Industry’ area around Gliwice to the Polish-Czech border in Gorzyczki, where it will connect with the Czech motorway D1. The total length of the motorway is planned to be 565 km. The first section from Gdansk to Grudziądz has been constructed between 2005 and 2008 and the last sections are planned to be upgraded by 2015. The majority of the A1, however, is to be finished by the spring of 2012, in time for Euro 2012 football championships. Parts of the Motorway A1 are running through the Upper Silesian Industry area which is characterized by extensive underground mining activities dating back from the early 19th century up to today. The recent mining activities have led to a number of severe deformations on the ground surface as can be clearly seen on the existing infrastructure in the region.


The project-owner decided to use a combination of discrete interlinked concrete slabs and high strength geogrids for securing the motorway together with a sophisticated monitoring system. A multilayer overbridging system is selected for the protection of the motorway against sinkholes and faults or steps in the base of embankment. The first monitoring level is installed at the embankment base in the form of diagonally placed measurement wires to detect, locate and measure deformations forming under the embankment. This layer is followed by a 6 cm sand levelling layer and 20 cm crushed stone layer (0/63 mm), which both act on the first monitoring system as a ballast layer. Above this sandwich a 14 cm thick continuous mattress of discrete reinforced concrete slabs (130 x 130 cm) which are interlinked together. The mattress of concrete slabs is then followed by two soil layers: 20 cm crushed stone layer (0/63 mm) and 20 cm round shaped gravel layer. Especially, the upper layer should act as self-levelling layer due to its round shaped grains. On the levelling layer a high strength geogrid system is then installed in four layers, two layers cross-wise and two layers longitudinal to the road axis. The ultimate tensile strength of each geogrid layer was equal to 1.200 kN/m by the elongation at rupture of 2,5 %. The allowable tensile load of each layer was equal to 404 kN/m at allowable elongation 2,25 %. Up to elongation of 1,4 % system is able to overtake the traffic without reduction of speed or weight of vehicles. The road can be used for traffic at elongation in the range 1,4 % and 2,25 % but the safety level should be continuously examined by the staff of owner. In order to control the tension forces in geosynthetic reinforcement 13.030 elongation sensor GEOKON 4420 were installed on the first layer cross-wise to the longitudinal road axis. The readout frequency of monitoring system was defined with 5 minutes but can be changed depending on the rate of deformation or tension in reinforcements.


The overbridging system which combines geotextile reinforcements and two level electronic monitoring presents a mile stone project in this category. The first deeper monitoring system informs about the state of deformations, which will be caused by movement of destroyed deep underground. The second upper monitoring system gives information about the elongation and tension in reinforcements. The main advantage of the system is the possibility of controlling the deformation level and safety level of trafficked highway pavements, without stopping the traffic for measurements or control inspections. This system enables the owner to regulate the traffic depending on the actual safety level or to close the highway in case of emergency.

The coupling of high tensile strength geosynthetics with the modern monitoring systems opens the new possibilities for the use of intelligent systems in earth reinforced structures such as bridge abutments or high reinforced walls and embankments.