[en] Coupled hydraulic, mechanical and chemical processes have to be considered for numerous subsurface utilizations and are crucial for analyzing the potential, safety and risks as well as the future development of a geosystem. Some subsurface applications, such as radioactive waste disposal, energy storage and geothermal energy usage, also play a key role in the transition to renewable energy resources as part of the global climate action. This thesis focuses on the development of methodological-analytical approaches and tools that can be used to characterize coupled processes in porous and fractured rocks. By investigating two different lithologies and observation scales in the μm- to m-range, this thesis contributes to a better understanding of coupled processes in reservoir and host rocks. The first part of the thesis considers hydraulic-mechanical (HM) processes and properties in fractured rocks. Fractures represent important flow paths in the rock but are also highly sensitive to mechanical influences. In the first study, a systematic method comparison for a non-invasive quantification of hydraulic fracture apertures is presented. Three different measuring instruments, a portable air permeameter, a microscope camera and a 3D laser scanner, are applied and evaluated on a natural single fracture in a well-known German reservoir analog (Flechtinger Sandstone). This case study shows that the air permeameter provides the most robust results, has the highest investigation depth, and offers substantial advantages in terms of mobility, time expenditure and data processing. For the optical fracture characterization approaches, the hydraulic aperture is determined indirectly by means of various model assumptions based on the mechanical aperture and the fracture roughness. This results in deviations of up to 27 % (microscope camera) and up to 260 % (3D laser scanner) compared to the results of the air permeameter. Based on the single fracture analysis, the presented methodology is transferred to the field scale and is optimized for application to a host rock formation for nuclear waste disposal. In the second study, a HM characterization of an excavation damaged zone in the Opalinus Clay of the Mont Terri rock laboratory in Switzerland is performed. The analysis of the discrete fracture network in the investigated EZ-B niche, consisting of tectonic and artificial discontinuities, shows that the uncovered excavation damaged zone is characterized by hydraulic apertures of up to 112 μm. Progressive desaturation of the tunnel walls over a period of about 15 years mostly prevented self-sealing processes. The physico-mechanical rock parameters determined on-site by using needle penetrometer tests also illustrate the sensitivity of the Opalinus Clay to tunnel ventilation and indicate a negative correlation of rock strength or stiffness and water content due to a pronounced hydromechanical coupling behavior. The second part of the thesis focuses on hydraulic-chemical (HC) processes in the porous medium and addresses reactive transport in a reservoir rock. In particular, porosity and permeability changes induced by dissolution or precipitation reactions can significantly alter reservoir properties. The third study investigates the dissolution of calcite cement in the Flechtinger Sandstone and the transferability of experimental reaction rates from the μm-mm-scale (mineral surface) to the cm-scale (core samples). Flow-through experiments on four sandstone cores are used to determine the range of dissolution rates on the cm-scale for different reaction time periods and varying hydraulic boundary conditions. This is contrasted with temporally and spatially resolved calcite dissolution rates at the μm-mm-scale from surface analyses using vertical scanning interferometry. Based on segmented X-ray micro- computed tomography scans of the core samples, a geometric approach is established to estimate the fluid-accessible surface area of the heterogeneously distributed calcite cement within the low-permeable and complex sandstone. Based on this introduced surface parameter, the rate information on the μm-mm scale is transferred to the core scale, yielding deviations of less than one order of magnitude between the upscaled and measured dissolution rates for all studied samples. Within the scope of this thesis, different measurement methods and approaches are identified, developed, optimized and validated, which can be used to describe and interpret coupled hydraulic-mechanical-chemical processes and to determine related key parameters in fractured and porous rocks. The investigative approach and the obtained results therefore provide a valuable basis for predicting the behavior of natural systems on higher length and time scales.