Creative within the frameworks

The new N206 ir. G. Tjalmaweg is sandwiched between Valkenburg airport on one side and a new residential area to be built on the other. So the land take was definitely the limiting factor in the design. Geonius' specialists know how to deal with that. It has resulted in a creative road design that is still within the lines.

Geonius was commissioned by Boskalis to design the road infrastructure in the final situation, phasing and geotechnical measures for the new Tjalmaweg. "We were also involved in the first section of the RijnlandRoute, commissioned by Comol5 at the time. The knowledge we gained there, as well as the experience and cooperation with all stakeholders and the province, made it relatively easy for us to move on to the next subproject, the Tjalmaweg," says Suzan van Venrooij, Manager of Infrastructure at Geonius. "Admittedly commissioned by a different main contractor, but we have also successfully taken on several projects together with Boskalis in the past."

Colleagues hooking up

In early 2019, Geonius started with a small design team at Boskalis in Rotterdam. "Later we 'moved' to Leiden and finally we ended at the project site in Valkenburg," says Thomas van Tongeren, chief GWW designer at Geonius. "This involved focusing on the design of the sunken location and modeling the reinforced soil structures. The design team was increasingly expanded to include Geonius colleagues and we were also able to be extremely creative with that, in the middle of corona time. Because everyone worked from home and Teams was pretty much the standard means of communication, we could also very easily get colleagues from the south to join the project."

Interface alignment

The biggest design challenge, according to Van Tongeren, was the limited space. "From the reference design, the boundary of the sunken location was fixed, everything had to be done within it," he says. "That meant we had to design in great detail to fit everything in, more than we are normally used to. For that, we made grateful use of BIM for, for example, the interface coordination, so that we could tackle most of it in advance." Van Venrooij adds: "This is precisely where the strength of Geonius lies, the combination of design and execution knowledge. We know how the contractor works. In doing so, we push the limits as much as possible to come up with an optimal design that can also be executed efficiently."

Specific solutions

The limited space in combination with the sunken location and reinforced soil construction required creativity, according to Van Tongeren. "We had to come up with a specific solution for many aspects, such as the foundation of portals on the reinforced soil or roadside protection that 'clashes' with the same reinforced soil construction. Matters that are extremely important in this project in particular and that in many cases are not reflected in the final situation. That is where most of the time went. At peak times, the design team consisted of ten people, six of whom were Geonius colleagues. A lot of attention was also paid to the landscape aspect of the design with the vegetated slat walls and the park zone."

While the design of Tjalma Road is largely complete, the design team has not yet been "disbanded. "On the south side of Tjalmaweg, an HOV lane will be constructed in the future. During the course of the design process, we came to understand that it would be better to include parts of it within the design development," says Van Venrooij. "That means that the design has to be adjusted at points." Three colleagues from Geonius are involved in this to get that properly incorporated. Van Tongeren: "Through our years of experience with the contracting industry, we are able like no other to think along with the contractor in a very flexible way, even in unexpected situations. Again, that proves to be of great added value."