The Netherlands aims to be CO2 neutral by 2050, aligning with the Paris Agreement. To achieve this, it is crucial to increase the contribution of geothermal energy to renewable energy sources, necessitating large-scale exploitation to speed up the energy transition. Only small-scale (1–2 km) geothermal field developments exist in the Netherlands primarily for heating. Expanding to extensive geothermal fields (10 km length) requires a strategic approach to well placement and consideration of the economic constraints associated with geothermal projects. The heterogeneity of the subsurface is a critical factor in developing large-scale geothermal reservoirs. This study introduces an innovative approach to optimising well placement based on geological trends, using a well-density function as a proof of concept. Implementing and optimising flexible well patterns for large-scale geothermal developments significantly enhances profitability compared to conventional oil and gas industry methods. Optimised flexible well patterns favour a long-term utilisation of energy recovered, minimise pressure extrema in the reservoir, and improve sweep efficiency. However, their application depends on reservoir operational decisions. The optimisation process ensures economic viability, even with lower heat prices. Broadly, this methodology could be key to scaling up geothermal developments to meet the objectives of the Paris Agreement.

Steel-Reinforced Resin (SRR) is a particulate material originally developed as an injectant for anchoring applications. More recently, it has been proposed as a filler material for cavities embedding mechanical connectors in FRP–steel hybrid bridges. In this context, the compressive behaviour of SRR becomes critical due to the multiaxial stress states and fatigue demands at a joint scale. This paper presents a comprehensive experimental and numerical investigation of SRR under monotonic, incremental cyclic, and fatigue compressive loading in unconfined conditions. A custom triaxial setup is also used to evaluate pressure sensitivity and strength enhancement due to confinement under monotonic loading. In parallel, micromechanical finite element models are developed to simulate the interactions between the resin matrix and the steel balls at the microscale, incorporating interface damage, friction, and cohesive failure. The models reproduce the observed nonlinear behaviour and reveal distinct Poisson's ratio responses in tension and compression, offering deeper insight into the mechanisms governing stiffness degradation, strain softening, and plateau behaviour.