Weight and volume relationships in soil mechanics form the foundation of geotechnical analysis, organizing soil as a three-phase system of solids, water, and air. This concept map connects five core domains: soil phases, volumetric ratios, gravimetric ratios, fundamental indices, and soil properties, showing how void ratio, porosity, water content, and unit weights derive from basic phase composition. Understanding these relationships is critical for calculating bearing capacity, settlement, and shear strength in foundation design and earthwork projects. Fork this diagram on Diagrams.so to customize soil classification thresholds, add site-specific parameters, or integrate with your geotechnical reporting templates. The framework applies equally to saturated, unsaturated, and dry soil states.