What defines the effective unit weight of a soil?

What defines the effective unit weight of a soil?

• A. Saturated unit weight - water weight
• B. Saturated unit weight - gamma w
• C. Saturated unit weight + water weight
• D. Submerged unit weight + water weight

Answer: (B)

The effective unit weight of soil is a critical concept in geotechnical engineering, directly influencing the design and analysis of foundations, retaining structures, and other earthwork. It is defined as the weight of the saturated unit weight of soil minus the weight of the water in the soil pore spaces. This subtraction accounts for the buoyant force that water exerts within the soil, effectively reducing the stress exerted by the soil on underlying layers. The formula for effective stress, which is foundational in soil mechanics, is integral to understanding how soil behaves under load. When considering saturated soils, the unit weight of water is represented by gamma w (γw), which typically approximates 9.81 kN/m³ or 62.4 lbs/ft³ depending on the units used. By removing the water's weight from the saturated unit weight, the effective unit weight highlights the actual contribution of the soil particles to the overall stress within the soil mass. This distinction is important for analyzing the stability and strength of soil structures and effects on pore water pressure. This reasoning underscores why the answer that states the effective unit weight is defined as the saturated unit weight minus gamma w is the correct choice. The relationship clearly demonstrates how the components interact and provides practitioners with the necessary

The effective unit weight of soil is a critical concept in geotechnical engineering, directly influencing the design and analysis of foundations, retaining structures, and other earthwork. It is defined as the weight of the saturated unit weight of soil minus the weight of the water in the soil pore spaces. This subtraction accounts for the buoyant force that water exerts within the soil, effectively reducing the stress exerted by the soil on underlying layers.

The formula for effective stress, which is foundational in soil mechanics, is integral to understanding how soil behaves under load. When considering saturated soils, the unit weight of water is represented by gamma w (γw), which typically approximates 9.81 kN/m³ or 62.4 lbs/ft³ depending on the units used.

By removing the water's weight from the saturated unit weight, the effective unit weight highlights the actual contribution of the soil particles to the overall stress within the soil mass. This distinction is important for analyzing the stability and strength of soil structures and effects on pore water pressure.

This reasoning underscores why the answer that states the effective unit weight is defined as the saturated unit weight minus gamma w is the correct choice. The relationship clearly demonstrates how the components interact and provides practitioners with the necessary