Aanleiding van het project
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.
Doel van het project
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
Omschrijving van de activiteiten
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
Products are here reported for this phase. For the product of the previous phase, refer to DEL071. Volgnummer Wat Wanneer (jaar) Task 1 Report with comparison of terrestrial, wetland worms and no-worms. Includes description of the experiment setup and results of (i) mudline and solids content evolution in time, (ii) strength and density profiles, (iii) survival rates of worms and (iv) consolidation parameters (saturated conditions). At least one conference publication 2022 Task 2 Report on the design, execution and results of the μCT analysis. This will evaluate the mechanisms and impact of selected treatment on the evolving sediment structure of tailings deposits during remediation. The innovative 4D methodologies used, as well as the outcomes of the research will also lead to submission for publication in a peer-reviewed journal. 2022
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.
This project will take advantage of the previous phase based on the collaboration with COSIA and Imperial and will add the experience of QMUL. COSIA will provide insight on geotechnical processes and background knowledge to the field (e.g. long and fruitful collaboration between COSIA and the industry). On the other hand, Imperial will provide testing materials and knowledge about the operational conditions. QMUL will make their innovative laboratory setup available to the project. The theory developed will be disseminated by Deltares at short courses, and when possible within the Living Lab for Mud initiative of EcoShape. Project results will be presented at various conferences worldwide (e.g. IOSTC;OSTRF; etc) and a Journal paper.