Civil 200 - Soil Phase Relationships and Calculations (Notes) 4.1) Second Lecture

Phase relationships in soils: key ideas and calculations

  • Civil 200 core focus: relate soil weight and soil volume, soil mass and soil volume, and identify the soil phases (solid, water, air).

  • Soil can be treated as a two-phase material (solid + pore water) or a three-phase material (solid + water + air) depending on saturation and moisture.

  • Learning outcomes emphasize applying relationships between density, unit weight, porosity, void ratio, and saturation to compute unknowns from givens.

Foundational definitions and relationships

  • Phases and volumes

    • Total volume: V = Vs + Vw + V_a

    • In a saturated soil, Va = 0 \Rightarrow V = Vs + V_w

    • Pore volume (voids): Vv = Vw + V_a

  • Weights and unit weights

    • Weight and unit weight basics: $$W = ext{weight},\