Reinforced soil walls designed on the cutting edge

The substructure of the wildlife bridge and part of the flyover for HOV in 't Gooi are quite deliberately
performed in reinforced soil construction. Building with such products has its tolerances. Reason enough for BAM Infra Nederland to engage Voets Gewapende Grondconstructies. Thanks to their many years of experience, they were able to engineer and realize the structures right down to the last detail.

"The natural bridge and fly-over are a stone's throw from each other and located in a beautiful nature reserve just outside Hilversum," begins Gino Jongmans, business manager at Voets Gewapende Grondconstructies. "Because of the location, requirements and budget, the obvious choice was to execute the substructure of the natural bridge and part of the fly-over in a reinforced soil construction. However, this project was so special that we were invited by BAM Infra as early as the tender to help think about the best possible solution. In doing so, we very consciously chose the active system of Terre Armee."

Point of contact for Terre Armee

The Terre Armee system, in which the Terra Plus concrete elements are anchored in the body of the ground, is a very reliable system, according to Jongmans. "Terre Armee is a strategic partner for us. Together we can come up with the right solution for every challenge. The lines of communication are short." Very short we may say, because since the beginning of this year Voets Gewapende Grondconstructies has become the point of contact for all Terre Armee systems in the Netherlands and Dutch-speaking Belgium. "BAM Infra was convinced in the tender phase and tendered with our solution. After being awarded, we were invited in the first design rounds to convert the integral tender design into a DO and UO. A major advantage of sitting around the table early on is that you can get to work very quickly after the contract is awarded. After all, we don't build a work of art on our own. The integral collaboration makes you make the right assumptions together and led to a final design very quickly."

Showing guts

At the works of art in 't Gooi, 1,090 m² and 655 m2 of reinforced soil structures applied for the natural bridge and flyover, respectively. The natural bridge has a span of 42.6 meters with one intermediate support point and the fly-over has a span of 53.4 meters with also one intermediate support point. Jongmans: "We were not only guided by the technique, the landscape integration had to be met as well. The image quality plan included requirements for slope angles, sustainable construction methods, etc. The use of reinforced soil constructions saves on concrete and steel and you can build very quickly. In addition, we were all keen to keep spans as short as possible. Thanks to our years of experience, we are able to build within the sharply defined tolerances with Terre Armee. BAM Infra then showed the courage to place the abutment short of our structure, resulting in an extremely slim and integral design."

Building at the cutting edge does mean that we have very strict requirements for the quality of the backfill material, says Constant Brok of Voets Armed Ground Constructions. "We cannot haggle with assumptions. The quality of the backfill material is essential in reinforced soil structures. In this case, we found a suitable sand mixture in the area with a grain skeleton that fit together very well. This allowed us to make work with work. A nice bonus is that on this project, thanks in part to BAM Infra's good preparations, we also managed to certify ourselves as a company for Safety Ladder Step 3."