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Here they mix 600 cubes of sand-bentonite mixture (ZBM) per day!

SiteTec is a company that specializes in the HDD industry, but we like to use our expertise for other industries as well. This is why Marcel Bijleveld product specialist at CEBO, put us in contact with Wim Mulder and Alex Puls of the company Van Heteren 3 years ago. Not to mix bentonite for horizontal drilling, but to use bentonite to ensure that the Canal of Twente does not leak in anymore.

At the start of the project, SiteTec was asked to develop a custom built mixing installation that could mix large amounts of bentonite. Three years later, together with Alex Puls and Wim Mulder, we can proudly conclude that we have succeeded. Nowhere else in the Netherlands, more than 600 cubic meters of bentonite-slurry mixed per day.

Who is Van Heteren?
Van Heteren is a company with 90 years of experience in civil engineering. Specializing in water engineering, civil concrete construction, bridges, explosives research, remediation and infrastructure. Driven specialists work at Van Heteren, who know what it’s all about when it comes to collaboration: thinking in solutions, trust in competent people.

The Twente Canal
Businesses along the Canal of Twente are growing.In order to continue growing whilst becoming more sustainable, the transport on the Canal of Twente must be optimized. The ships are becoming bigger. As a result, less transport movements are needed. At the same timemore can be transported. For this, the Canal of Twente must get dredged deeper and wider. Controlling the groundwater level is a crucial part of the final phase of this project. A tender that Van Heteren received from Rijkswaterstaat. The work consists of replacing the current sheet piles over a length of 35 kilometers and widening the canal; from the application of a self-sealing layer for groundwater management in the vicinity of the Twente Canals. The self-sealing layer is a thoroughly tested mixture of bentonite mixed with sand. The bentonite is supplied by CEBO and it is mixed with SiteTec mixing units.

The installation
At the CO2 neutral location, lots of techniques from different industries come together. At the base of the electrical mixing installation are 4 silos filled with bentonite, which lead to 2 SiteTec mixing tables. The mixing table MT8x6E has a centrifugal circulation pump with a capacity of 5.4 m³ per minute with a 55kW electric motor. Here, bentonite and water are fully automatically and unmanned mixed and pumped into the first mixing basin surrounded by concrete. The bentonite is kept in motion by a venturi system. After this, the bentonite slurry is ​​pumped to a maturation basin surrounded by sheet piles. The different basins ensure that the bentonite mix can swell and ripen in a structured way and is only used when the mixture is optimal. For the Canal of Twente an extensively tested mixture of bentonite and sand is used. Testing was done in Delft at Deltares, an independent knowledge institute for applied research in the field of water and subsurface. Sand is added after the ripening process by an industrial mixing machine, also used for example by bakeries.

The process is fully automatic, the flow and sand supply are matched in a certain ratio, the viscosity is measured; all to make sure the recipe of the extensively tested mixture is monitored and maintained constantly. This happens at the heart of the installation; a very advanced electrical, control and monitoring room. All machines and installations on site are electrically powered, which is in line with Van Heteren’s sustainable ambitions.

Application in the Twente Canal
After the production of the sand – bentonite mixture, it is applied at the bottom of the canal. The canal is dredged to the desired depth, after within 12 days a minimum of 10 centimeters is applied to the canal bottom. The sand is used to give weight to the mixture. As a result, it sinks to the bottom faster, the bentonite provides a closing effect. Van Heteren transports the mix to the destination at the canal with 1 of their 3 ships and applies I with 2 sets. Monitoring wells besides the canal are used to check in real-time whether the function of the bentonite is being realized.

The implementation of the innovative solution by Van Heteren is progressing very well! There is still a long way to go in the Twente Canal, but other canals in the Netherlands will possibly use this innovative solution as well. The bentonite solution is functional, natural and considerably less expensive than other solutions for sealing the canal. For SiteTec it was very interesting to be involved in this process, and we are proud of the end result! Would you like to receive more information about this project, or do you have any questions? Mail to info@sitetec.nl

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