Utrecht is the number one rail hub of the Netherlands. Each day, no fewer than 285,000 people use Utrecht Centraal station and, over the next 10 years, that number is expected to rise to 360,000 per day.
Since 2012, ProRail has therefore been working with the contracting consortium, U-centraal (a joint-venture of Volker Rail and BAM Rail), on the Utrecht Flow-Through Station (Door Stroom Station Utrecht [DSSU]) project, to improve the flow-through of rail traffic and increase capacity.
The rail renovation around Utrecht Centraal (DSS project) is part of the Ministry of Infrastructure and Environment's "High-Frequency Rail Transport Programme (Programma Hoogfrequent Spoorvervoer [PHS])".
The planning procedure decree for this project stipulates that vibration-reducing measures must be taken at a number of locations.
At the location of Adema van Scheltemabaan, in the area of Nicolaas Beetsstraat, it has been decided to install an Underground Vibration-Reducing Construction (UVRC) in the form of a jet grout wall.
In the preliminary phase, consultant Movares produced a preliminary design, after which VSF was approached to further detail and realise the UVRC.
The final design comprises a 150-metre-long jet grout wall, consisting of 362 jet grout columns with a length of 5 - 6 m and diameters of Ø1.000-Ø1.200 mm. The jet grout wall is fitted with a concrete cap, topped with fencing.
The jet grout columns for this project have specific quality requirements, as the jet grout wall has a vibration-reducing function, unlike many other projects where it fulfils a constructional or water-inhibiting function.
To keep the disruption of rail traffic to the minimum during the construction of the UVRC, the decision has been made to construct the UVRC starting from the Adema van Scheltemabaan.
Before the construction of the UVRC, the Adema van Scheltemabaan in Utrecht was a busy bus lane. In the summer of 2016, however, it was entirely closed to all traffic in order to, ultimately, build the Uithof Line. The period between the closing of the bus lane and the start of construction of the Uithof Line offered the opportunity to build the UVRC.
After a number of months of preparation to elaborate on the final design, investigate the subsoil for possible obstacles and produce a plan of execution, in July 2016 VSF began the actual execution of the project.
Work started with a nine-day closure of the line. During the closure, the critical columns around existing overhead line portals and other rail constructions were realized first, so that rail traffic could be resumed without any problems after the closure.
Due to the short time available between the closure of the bus lane and the start of construction of the Uithof Line, VSFcarried out the work with two jet grouting machines. A third, small jet grouting machine was used for a number hard-to-access locations.
Jet grouting causes a great deal of spoil. Due to limited space available at the worksite, it was decided to install a spoil basin at another location in Utrecht. The resulting spoil was extracted with vacuum trucks and transported to the basin, where it could settle and finally be disposed of from there.
Within a timeframe of roughly 7 weeks, all columns were finally installed. UC-Civiel (a combination of Van Hattum & Blankevoort and BAM Civiel, who are carrying out the concrete work for the main consortium, U-centraal) then started constructing the concrete beam.