What are common ground improvement techniques and their applications?

Ground improvement methods: (1) Densification - vibrocompaction, dynamic compaction for loose sands, (2) Reinforcement - stone columns, soil nailing, geosynthetics, (3) Preloading - surcharge with wick drains to accelerate consolidation, (4) Grouting - cement, chemical, or jet grouting for strength and permeability, (5) Deep soil mixing - cement columns for soft clay, (6) Compaction grouting - controlled displacement for densification. Selection depends on soil type, improvement objective (strength, stiffness, permeability), depth, area, and cost.