Geomaterials are materials inspired by geological systems originating from the billion years long history of the Earth. However, with the industrialization, these materials are artificially processed to the outputs as construction materials or by-product wastes. The cognition on the observed behavior of geomaterials should be upgraded by new developed multi-phase/scale analysis methods. It could be of great benefit to enhance the safety and reliability of geotechnical infrastructure built on/by geomaterials if a clear understanding can be achieved. Furthermore, with the updated cognition, the applications of geomaterials in geotechnical engineering can be expanded and enriched.

Therefore, the micro-macro behavior, interpretation and modelling, modification, and engineering application of multiphase geomaterials should be systematically studied by the new testing technologies, new theoretical frameworks, and new analysis tools. In particular, as environmental requirement and engineering availability of by-product waste, the efficient recycling of the waste for geotechnical infrastructure is included in this issue.

This special issue aims to collect new innovations on multiphase geomaterials before and after modifications. The theoretical studies from micro to macro scales and experimental investigations in laboratory and in situ are welcome. Additionally, engineering practices of geomaterials in different fields and objectives are encouraged. The geomaterials may include rock, clay, granular materials, treated soils, and industrial waste.

Potential topics include but are not limited to the following:

• Geotechnical testing in laboratory and in situ
• Thermal-hydro-mechanical-chemical coupled behavior and modelling
• Modification of problematic geomaterials
• Waste recycling in geotechnical engineering
• Applications and case studies in geotechnical engineering