DEL123 – 11205219 Soft Sediment Stability for Beneficial Use: innovative constitutive model development and numerical modelling
Aanleiding van het project
Turning fines and soft (dredge) sediments (also so-called unsuitable) to a useful resource for climate resiliency (e.g. clay for dikes), nature development (e.g. nature islands), or sustainable human activities (e.g. land reclamation or industrial waste basin closure) is a critical opportunity for sustainable development, in the Netherlands and internationally. Various Dutch and European projects (e.g. Markerwadden, Kleirijperij, Surricates) and international initiatives (PIANC Working Group (WG) 214 on Beneficial Sediment Use, or SedNet WG on Sediments and Circular Economy) are developing and collecting knowledge in this direction.
This project focuses on using soft sediments as a substrate for human (e.g. port) or nature development (e.g. natural islands, salt marshes and wetland), with specific focus on (sustainable) water and coastal infrastructure (main KIC line) in the context of circular economy and climate change adaptation. Lack of sand pushes land reclamation toward maximizing the use of fines dredge sediments. Likewise, climate change and decrease of water quality and biodiversity calls for building (coastal or inland water) islands or salt marshes in front of dikes with locally available (dredge) sediments to improve (secondary KIA lines).
Similar knowledge and technologies are applicable to other challenges world-wide, such as those in mine activities, where huge amounts of industrial waste, (i.e. a specific type of soft sediments) is produced as waste. These industrial wastes are generally discharged into large basins which must be eventually returned to nature. One potential solution to this, in which the mine industry is investing, is to find a way to use industrial waste as substrate for reclamation e.g. forest and or vegetation.
Many models have been applied (with success) to 1-dimensional (oedometric) compaction and consolidation problems. In oedometric compaction the deviatoric strain is of the same order of magnitude as the isotropic strain
Doel van het project
In this project we wish to better understand when and under which conditions a soft (dredge) sediments deposit can safely and effectively be used as the substrate for land reclamation, natural islands, wetland or salt marshes.
Specifically, we will develop innovative knowledge and tools to assess the stability and failure of a soft sediment deposit when subjected to an external load, for example a sand layer. Unlike typical soil, soft sediments may undergo significant deformation when exposed to load and before failure, expressing fluid-like behavior.
Objective of this project is also to develop a tool (constitutive model included in the numerical model MPM) to be added to the “Soft Sediment Toolbox (see Crossover section)” to maximize Beneficial Sediment Use.
Omschrijving van de activiteiten
Activity 1 (A1): Constitutive model development– Industrieel onderzoek.
Activity 2 (A2): Embedding it in and testing performance of the new constitutive mode in MPM-Anoura3D– Industrieel onderzoek.
The activities will begin in May 2020 with initial focus on Activity 1. The results of Activity 1 will be utilized in Activity 2, which will follow starting in the fall of 2020 to be finalized before the summer of 2021.
The existing constitutive models for geotechnical behaviour of soils have deficiencies when applied to soft fine sediments, and the deficiencies have the potential to result in unpredicted failures of loads placed on it. In particular, the formulations of long-term time-dependent stiffness, strength, viscosity and large strain behavior are in need of improvement. Hence, through a systematic and critical literature study, an attempt will be made to:
• identify physical processes and their constitutive model elements needed to model large deformation and softening.
• investigate to what extent available and suitable constitutive models cover these physical processes and identify the remaining gaps.
• prioritize the constitutive model elements that would most improve current modelling on the basis of their likely effect and importance.
• to develop, based on what have been learned in the above sub-tasks, a new formulation of constitutive model, aiming to provide the stakeholders with an improved constitutive model for soft fines-dominated sediments that is generic enough to possibly be implemented in various numerical models (e.g. not only MPM-Anoura3D specific)
Role of partners
The sub-tasks under activity 1 will be mainly carried out by Deltares with some considerable contribution of the University of Perugia (Prof. Claudio Tamagnini and his staff). University of Perugia will provide the project with summary of the state of the art of available constitutive models and governing processes. Moreover, they will play ad
1 From A1: Overview of most important physical processes to describe the stability of soft sediments – 2020
2 From A1: Formulation of the selected constitutive model to be embedded in the numerical models – 2020
3 From A2: The results of the updated version of MPM-Anoura3D, including the processes of A1 – 2021
4 From A2: Results of all relevant MPM-Anoura3D simulations. – 2021
5 A summary report with the main results of this projects (which will collect Deliverables 1, 2 and 4) – 2021
6 At least one (but likely more than one) conference or journal publication with the main outcome of this project. – 2021
The currently available geotechnical engineering stability tools are based on soil physics and numerical schematizations that approximate negligible to small deformations, in line with most conventional soils. Soft sediments, especially soon after dredging and with low to no sand content, express physics that resemble fluid-like behavior, and undergo very large deformations. Conventional geotechnical models lack the physics specific to this material and generally characterize large deformation as failure. This limits the applicability of beneficial use of soft sediments.
Over several years Deltares, within an academic-private consortium, has been developing a numerical tool (MPM-Anoura3D) to model large deformation with good success. This project intends to build upon this tool (and background knowledge) to include the necessary physical processes specific for large deformation of soft and fine sediments. This project will also utilize experimental tests recently carried out in Canada to verify the performance of the new model. These Canadian experiments and modeling are funded by the Institute for Oil Sands Innovation to bring forward the technology of sand capping of fluid fine industrial waste.
This project thus intends to push current available knowledge and tool one step further towards modeling stability and failure of soft sediment deposits with results that can be used for engineering applications.
1, 2, 4, 5
These products will be designed with an overview summary of findings followed by in-depth appendixes, for general practitioners and engineers, as well as scientific or specialist audience, to be used as background knowledge for further developments in the area.
These products will be made available in the Wiki by Deltares, cited in our publications, diffused by the consortium partners within their organizations and scientific network.
Part of the content of these deliverables will be utilized by Barr and delivered to IOSI as part of additional activities related to their sand capping of contaminated soft mud development project (part of which are offered as in-kind contribution to this TKI project).
This project therefore also facilitates exchange (import / export) of state-of-the-art knowledge between the Netherlands and Canada.
This information will also be included in university courses or seminars given by the expert staff in this consortium as much as possible.
After this project, MPM-Anoura3D will still likely be a tool dedicated to expert use, mostly used by Deltares and the University of Perugia. However, during the project Deltares will seek effective ways to transfer this tool to Boskalis and Barr for independent or collaborative use. The intention is to use this tool in Dutch and international projects should this project prove to produce the necessary accuracy and robustness.
During the project all consortium partners will be exposed and involved in selection of test cases of model application and model results. If feasible, some of the activities will be carried out by staff of the consortium partners to favor on-the-job training, and potential application to projects. If the new MPM-Anoura3D is proven accurate and robust, the executable code will be made freely available upon request.
Industry, public and academic practitioners outside the consortium.
The paper(s) will be published in journals or in conference proce