New construction of Strengelbacherstrasse underpass in Zofingen

Initial situation

The ground level railway underpass in Strengelbacherstrasse had to be expanded to create a new underpass to considerably improve traffic movement and road safety. As a result of the heavy use of the access tracks to the Zofingen station, a construction method had to be found which would reduce the closure period to an absolute minimum. The requirement from SBB was to limit the disruption to traffic to two weekends of closure.

Solution and assessment

The concept developed by the engineers envisaged a cut-and-cover construction method in combination with the rapid-hardening concrete Concretum^® Q-FLASH 2/20. First, large foundation piles were created for the cover. Then, with a closure on just two weekends, each of 48 hours,
the existing track structure was dismantled, the excavation was completed, the cover was formed, reinforced, concreted, and sealed, and the track structure was re-instated.
Then the underpass was opened to traffic. The residual moisture of below 4 CM-% was reached after approximately just 4 hours, according to the checks performed. Depending on the weather conditions, conventional concrete takes approx 4 weeks to reach this.
By using the rapid-hardening concrete, Concretum^® Q-FLASH 2/20, it was possible to adhere to the scheduled specified by SBB without problems. The additional work steps, such as earthworks and completion of the railway underpass, could be performed without disrupting rail traffic.
Intelligent planning, a detailed works scheduling and excellent interaction between the several disciplines, resulted in the success of this extremely ambitious construction project. This project exemplifies how the combination of cut-and-cover construction and rapid-hardening concrete can be used effectively and efficiently to achieve reliable results within strict time management constraints.