A4 Junction Hofvliet
Year: 2017 - present
Client: Comol5
Location: Leiden
Fields of Expertise: Roads, flood defences and damage risk assessment
As part of the RijnlandRoute project, the Comol5 consortium is constructing a new road (N434) between the A44 and A4, which will be connected by two new traffic junctions: respectively Ommedijk (A44) and Hofvliet (A4).
Arthe Civil & Structure is responsible, besides the tunnel design, for the geotechnical design of the reconstruction and widening of the A44, the modifications to the A4 and the junction Hofvliet. During the tender, the geotechnical design had been drawn up by Arthe, and this design was subsequently elaborated into an economical, safe and optimized integral design at implementation level.
Hofvliet
The geotechnical design of junction Hofvliet (geological and organizationally the most complex part of the design) included:
- Widening of the A4 between The Hague and Leiden (including junction Hofvliet);
- Construction of N434 up to the tunnel entrance/exit ramp;
- Construction of tunnel logistics site, work sites and construction roads;
- Construction of a test embankment.
High embankments on soft soil
At the junction Hofvliet the subsurface predominately consists of layers of peat and organic clay, at some locations with a total thickness of 10 m. The combination of a 9 m high embankment at the west side of the junction, a challenging work schedule and a very weak subsoil subsurface has resulted in the application of a piled embankment. Part of the piled embankment was also used as a foundation for the Soil Treatment Plant, a temporary road and a storage area for the tunnel boring machine.
Summary of our activities
Our activities consisted of:
- Supervision and interpretation of the ground- and laboratory investigation
- Engineering of a test embankment and interpretation of the monitoring results in order to establishing the geotechnical boundary conditions
- Integral design of the pile mattresses
- Geotechnical design of reinforced earth structures
- Assessment of flood defenses
- Calculation of vertical and horizontal displacements
- Assessment of stability / squeezing
- Assessment of the influence of the embankments on nearby objects, such as (existing) infrastructure and cables & ducts
- Drafting of monitoring plans
- Site Engineering (embankments and pile mattresses)
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