Pressure grouting is a ground improvement and excavation stabilization technique, which has been widely used to improve the mechanical properties of loose soil and to prevent ground movement. In soft or loose soils, grout with various additives is injected to increase cohesion and densify the porous medium, enhancing the bearing capacity. The injectability and replacement ratio are the main focuses to evaluate the efficiency of improvement. Compensation grouting is an important alternative for the prevention of significant deformation and collapse in long-term loading, shield tunnelling, and construction in karst areas. The action of grouting is also applied to develop joints and fissures in hard soil and rock matrixes to bond the fragments, increase integrality, and prevent instability and collapse during excavation. In addition, the combination of grouting with geotechnical structures such as piles and soil nails are a widely adopted approach in improving bearing capacity. Therefore, grouting techniques are increasingly becoming effective and frequently used methods in geotechnical, geological, and hydraulic engineering.

Permeation, compaction, and fracturing are the three diffusion patterns during pressure grouting through which the flowing grout and the surrounding soil or rock interact differently. For each grouting action, these three diffusion behaviors are involved, and the factors that govern the dominant diffusion pattern are the water-cement ratio, the different additives in the grout, the surrounding matrix, and the grouting pressure. The quasi-permeation, compaction, and fracturing mechanisms are microscopic scale processes, while the actions and surrounding responses in practice must be evaluated based on macroscopic parameters. Therefore, multi-scaled studies on distinguishing the grouting diffusion pattern and its performance on the surrounding soils/rocks are required in order to clarify the unclear connection between grouting mechanisms and grouting performance and efficiency.

The aim of this Special Issue is to bring together original research and review articles discussing the surrounding response of rock and soil matrixes during grouting under different diffusion patterns of permeation, compaction, and fracturing. Submissions showcasing laboratory testing, field investigations, theoretical analyzing, numerical modeling, and big data-driven computational intelligent simulating are welcome.

Potential topics include but are not limited to the following:

• Fluid mechanics and flow rules for grout in soil and rock
• Flowing behavior, propagation, and enhancement effects under various fluid components
• Stress and deformation responses and characteristics under dynamic and static grouting
• New grouting materials and additives for special functions
• Grouting procedures, technologies, and equipment in practice
• Laboratory or physical model tests for ground improvement with grouting
• Numerical simulation for grouting with coupled hydro-mechanical conditions
• Studies on grouting in excavation, backfilling, and reinforcement
• Big data-driven characterization, estimation, prediction, determination, and control of grouting parameters in achieving best performance in practice