Parking garage Garenmarkt, Leiden | Varied foundation techniques for project Garenmarkt Leiden

Having previously supplied Dura Vermeer with the anchor piles for the Cornerstone (Rotterdam), TaTa Steel (Velsen), AFAS Experience Centre (Leusden) and Tournooiveld (The Hague) projects, Jetmix Funderingstechniek also laid a stable foundation under the Garenmarkt parking garage in Leiden. The Werkendam-based company was commissioned by the Dura Vermeer-BESIX construction consortium to supply and install no fewer than 369 anchor piles. Components that were installed using a self-designed and manufactured self-drilling grout injection system.

The steel sheet pile was realized vibration-free with a 100-ton foundation machine.

"In mid-2017, the Dura Vermeer-BESIX construction consortium asked us to quote for the supply and execution of anchor piles for the Garenmarkt parking garage project in Leiden," says head of business office Marinus de Heus on behalf of Jetmix. "Subsequently, we made a design regarding the required anchor piles and this was coordinated with the project team. Ultimately, this led to an agreement between the construction consortium and Jetmix Funderingstechniek. After obtaining the contract, we worked out the bid design, first in a final design and finally in the execution design."

369 anchor piles
Jetmix decided to install the anchor piles using a self-drilling grout injection system; a masterpiece designed and manufactured entirely in-house. "A total of 369 anchor piles of the Jetmix Ø76.1, Ø82.5 and Ø101.6 types with drilling points ranging from 300 to 380 millimeters were installed from a working level at N.A.P. with an excavated construction pit floor at N.A.P. -/- 18.50 meters," said De Heus. "The maximum computational values for the loads on the anchor piles are between 1,900 kN tensile in the construction phase and 1,500 kN pressure in the use phase. The pile tip level varies between N.A.P. -/- 43.0 and -/- 51.0 meters."

The very limited workspace resulted in the necessary challenges.

Challenges
The very limited workspace presented challenges for all parties during the project. So did Jetmix. "Part of the anchor piles were installed from the concrete strut frame in the middle of the construction pit, the rest from the water via linkable pontoons," says De Heus. "We also took care of the complete logistics and handling of all auxiliary works, equipment and materials. Furthermore, we were responsible for the dimensioning in the X, Y and Z directions."

Minimal transportation
In mid-2017, Jetmix chose to expand its business activities to include larger-scale foundation techniques. A decision that has since resulted in, among other things, the arrival of a 100-ton foundation machine. "At the same time, discussions were ongoing with the construction consortium about the foundation techniques needed around the construction of the entrance to the parking garage," De Heus said. "There was a strong preference to carry out the work with one machine, so that heavy transport movements in the city center would be minimized. In this context, Jetmix submitted additional bids for the supply and installation of sheet piling, soil displacement screw-comb piles and screw-tube piles, as well as the steelwork for the sheet piling. Ultimately, this too resulted in an order." Specifically, using the Woltman 90DR multi-purpose foundation machine, Jetmix brought approximately 1,800 m² steel sheet piles by pressing with a quatro-piler. In addition, both 112 soil displacement screw-comb piles type 455/555 with a precast concrete core and a drilling depth of 18.0 meters and four screw-tube piles type 762/950 with a length of 24.0 meters were used.  

Text | Chris Elbers   Image | Jetmix Foundation Technology
Featured image: The anchor piles were installed from the outrigger frame and from the pontoon.