The clay adhesion phenomenon has been problematic in multiple engineering projects involving soft cohesive soils. In this dissertation, the adhesive characteristics of offshore high plasticity clay will be analyzed in support to deep sea mining applications. Adhesion of clays are particularly relevant in 2:1 swelling clays, where the magnitude of the force is highly dependant on the clay properties itself, working conditions and the soil engaging component surface material. The most prevalent force in offshore saturated conditions arises from the suction forces between micro-channels in the clay and the soil engaging component. Methods to reduce this adhesive force were assessed, ranging from solutions such as vibrations and electro-osmosis, to modifying the soil engaging surface to break continuous contacts between the clay and component. The natural adhesion of two typical offshore clays were experimentally determined by interface shear tests for the shear adhesion and pull-out tests for tensile adhesion. Interfacial shear strength was measured for typical materials found in the offshore industry, that being steel, aluminium, rubber and a polymer coating. Results from the tests showed that materials do have an impact on adhesive stresses. Similarly, pull-out tests showed this variation pattern. The influence of pull-out rates and contact time on adhesive tensile strength were also assessed and showed to increase with faster rates and longer contact times, respectively. In application to a typical rotational cutterwheel in deep sea mining, a scaled test-setup of a rack of cutter-teeth was dragged through the test clay to acquire horizontal cutting forces with the utilization of the experimentally found natural adhesion in the interface tests. The found adhesion value for the test clays were utilized to validate the cutting clay model from "The Delft Sand, Clay & Rock Cutting Model" (Miedema, 2019). Practical results from the scaled experiment seemed to coincide relatively well with the theoretical model. It is therefore recommended to further investigate the use of experimental means to determine adhesion of clays to develop an even more accurate empirical model.

Over the last decade, interest in deep-sea mining of Polymetallic Nodules (PN) has reignited. It is driven by an increasing demand of metals that are critical for the digital economy and modern technologies such as batteries. Methods for resource estimation of PN are known and commercially available. There is however no standard method of a planning a deep-sea mining operation. This is an essential step to define mineable reserves. To address this problem, an existing concept has been applied in this thesis. This planning concept was inspired by agriculture and subdivides a mining license area into large scale mining sites, which are in turn subdivided into smaller, continuouslymineable areas calledmining fields. The subdivision is illustrated in figure 1. The contribution of this thesis is the development of a methodology for this concept. The concept was applied to a framework based upon a license area in the Clarion-Clipperton Zone (CCZ) in the Pacific Ocean. The mining will be done using a Nodule Collector (NC), which is a self-propelled machine that continuously gathers PN on the ocean floor and transports them upwards to a vessel at the ocean surface. Certain areas are deemed constrained by slopes or nodule types. Mining sites wherein the NC will operate were outlined within the license area using those constraints and Nodule Abundance (NA).Within the mining sites, a new metric was introduced for assessing the mineability for the NC: the Straight-Line Distance (SLD). The next step down from mining sites are the mining fields. The operation of the NC within them is approximated by two different driving patterns. Different field shapes are also analyzed, along with the impact of obstacles inside the field. Different methods of creating fields inside the mining sites were considered. The procedure relied upon the SLD to define the boundaries between fields. Two sets of field are created: with elongated shape and compact shape. The best set of fields was selected using the approximation of NC operation. Lastly, a method for determining the sequence of fields is developed that uses a Genetic Algorithm (GA) as optimization method. It takes into account constraints for mining rate, operational hours, nodule targets and travelling time. The methods outlined in this thesis are flexible and can be applied in a variety of circumstances. The selection of mineable areas turns out to be the must crucial step. The subsequent delineation of mining fields and sequencing does not make or break the profitability of the operation, although they are essential steps for the definition of mineable reserves.