One of the key challenges in Delta Technology is related to possibilities of building on and with soft material. Soft materials (e.g. from dredged material and mine tailings) can be reused to form robust water defences enclosure dams and for land building. The material can be used to combat settlement in Sustainable Delta Cities as a cost-effective material for flood defences and as the basis for nature-based land reclamations like Marker Wadden. As such "Bouwen met Slib" has been identified as an important innovation to strengthen the international position of Dutch engineering companies. This project further explores the innovative use of worms and vegetation to enhance dewatering of sediment at disposal site deposits"

Sediment waste of mine processes (tailings) as well as dredged sediments are stored in dedicated deposits or beneficially re-utilized to build new lands (e.g. Marker Wadden) to improve resilience of flood defences or enhance habitat restoration. However these sediments and-or waste is characterized by a very high fines content and the accompanied very long consolidation times (e.g. the soil is very fluffy and not suitable for construction and it takes a lot of time for the soil to gain strength). This results in inefficiencies of the reclamation process deriving in very high operational costs. The ability to speed up the consolidation time of these deposits is crucial for the future of reclamation of mining areas and reclamation and flood protection projects with dredged sediment. The techniques being currently used by the industry are very high in costs and not very efficient in increasing the soil strength within a competitive time scale and thus there is room for improvement and for seeking new competitive and efficient technologies. This project builds up on the positive development and findings of the previous phase towards further improving consolidation of soft sediments in depositional processes at reclamation projects.

Here we report the detailed activities specific to the follow-up phase. For the activities of the first phase see DEL071. This project is designed to support the improvement of the understanding and quantification of:
• Combined effect of a plant-worm treatment in saturated and unsaturated conditions
• Achievable solids content and strength for a new worm species
• Provide a holistic view of an interacting biological systems of plants bacteria and worms and how this rudimentary ecosystem impacts key tailings properties (geotechnical and emissions) • Detailed analysis of worm’s tunnel formation dynamics and bed structure.

The scope of this study is divided in two tasks:
• Task A: Combining native vegetation and worms to enhance densification and strength in wetland and terrestrial conditions.
• Task B: micro-scale μCT imaging of tailings structure to understand enhanced dewatering of treated oil sands tailings
The objective of Task A is to evaluate the effect of introducing native plants and worms into thickened tailings. Specifically we will evaluate two different types of worms and vegetation that inhabit either (i) wetland environments or (ii) dry land soils in contrasting surface moisture scenarios and we will support the testing of the combination of these worms with several plant species. Task B includes μCT imaging of tailings structure. As a non-destructive 3D imaging tool μCT enables characterization of detailed spatial and temporal properties of environmental materials. In Task B μCT imaging will observe and quantify the evolution of the tunnel network that worms create over time the role of vegetation and their respective roles in determining bed properties. This will involve the repeat scanning of laboratory microcosms to investigate the impact of different treatments on the dewatering and densification of oil sands tailings deposits. Repeat μCT scanning will examine the 4D evolution of sediment structure over an experimenta

This project provides a foundational understanding for how to incorporate multicomponent natural systems into engineering designs for reclamation. Understanding the integrated role of biota and vegetation in dewatering and strengthening sediment is new and potentially very important knowledge. Involving natural systems at the engineering phase will speed up the reclamation process as a small ecosystem will already be established. This is consistent with the objective of prompt natural ecologically based reclamation. Deltares has a strong interest in this project as it may be useful for speeding up the reclamation of soft sediments in the Netherlands and for use in dike construction for flood protection and enhancing biodiversity in wetlands and offshore island environments.

Alle partijen krijgen alle resultaten van het Project ter beschikking. De resultaten van de samenwerking kunnen breed verspreid worden. Partijen kunnen over deze resultaten vrijelijk publiceren. De resultaten zullen volledig openbaar beschikbaar zijn, met uitzondering van ter beschikking gestelde achtergrondkennis.

De informatie over dit project wordt kenbaar gemaakt via de website van de TKI Deltatechnologie (projectbeschrijving) en de projectwiki van Deltares (projectvoortgang en resultaten).

Na de datum waarop deze Overeenkomst in werking is getreden, maar uiterlijk tot een jaar voor de beoogde datum waarop het Project zal zijn voltooid, kunnen ondernemers en/of onderzoeksinstellingen, die op het terrein van het relevante subsidieprogramma van het TKI werkzaam zijn alsnog als Partij toetreden. Een later toetredende Partij zal een nader overeen te komen bijdrage in kind en/of in cash moeten leveren die in redelijke verhouding staat tot zijn relatief aandeel in het Project na toetreding. De overige Partijen ontvangen vervolgens naar rato een terugbetaling en/ of gedeeltelijke vrijstellingen van hun nog te leveren bijdrage in kind, voor zover niet besloten wordt de bijdrage van de later toetredende Partij aan het projectbudget toe te voegen.