North South Line
Customer
SGS INTRON worked for several companies working on the Amsterdam Metro line called the North South Line. At first for the consulting company called the “Adviesbureau Noord Zuid Line”. This company was especially established to study and quantify the risks involved in this project.
At later stages during construction SGS INTRON worked for the main contractor being Max Bögl GmbH.
Case
One of the major risks in this project is the unstable soil in Amsterdam. Often referred to as thick water. The metro line runs through the center of Amsterdam. An open pit construction would have caused major logistical problems and traffic jams. Therefore for the tunnel a bored tunnel was chosen. Given the fact that Amsterdam is built on old wooden piles any underground construction but especially a bored tunnel introduces major risks of damages to the buildings. Especially a bored tunnel because the TBM (tunnel boring machine) had to pass the piles within a few meters. Any movement of the pile will immediately cause damage to the building. Another major risk was for the underground stations being potential leakages in the outer walls, the slabs and the grout body below the slabs.
Solution
SGS INTRON is involved in this project for 10 years now and provided several services ranging from standard testing of materials to highly complex finite element calculations. Three services however characterize the range of services best.
SGS INTRON developed special tests to measure in the laboratory the expected static and dynamic friction between the boring machine, soil and injection grout. These data were used for finite element calculations.
As a result of these SGS INTRON organized and conducted a large pilot scale test in which the movement of the TBM through the soil was simulated. In a series of 60 experiments different types of grouts, boring speeds and calamities were simulated in the pilot. The pilots were equipped with over 70 sensors measuring soil pressures, water pressures, grout pressured displacements and so on.
Finally INTRON developed construction procedures for all underground parts (like the underground stations) that limit the risk of cracking due to early age thermal stresses to such an extent that leaking cracks can be prevented. This involves highly specialized finite element calculations in which the casting of concrete is simulated. SGS INTRON calculated the temperatures and stresses that evolve during the hardening of the concrete with this technique and simulate the procedures that limit the stresses. An example of this is the use of active cooling by cooling pipes in the concrete.