This book is open access book. The collaborative Pilot Project, titled “Comparison of Thermo-Hydro-Mechanical-Chemical (THMC) Processes in Bentonite Barrier Systems”, aims to investigate the fundamentals, conduct laboratory and field experiments, and develop numerical models for barrier systems that ensure the safe isolation of radioactive waste in deep geological repositories. This book compares methodologies and technologies used in experimental laboratory and field research, as well as systems analysis, in a collaborative work of German and Chinese scientists. Both parties have access to exceptional experimental and modelling research capabilities. The Beishan underground research laboratory (URL) is currently under construction in Gansu, China. It will serve as an international collaboration platform for URL research in the future. International cooperation is essential for excellent research and development due to the high cost of scientific programmes and technical operation of URLs, making it a precondition for providing secure solutions. This is important not only for deep geological repositories for radioactive waste disposal but also for other geoenergy applications, such as energy storage and geothermal energy utilization.