Final answer:
To calculate the total unit weight of soil at 50% saturation and full saturation, we use the given soil properties, such as dry unit weight and porosity, and incorporate the unit weight of water. To find the specific gravity of the soil, we can manipulate the formula for dry unit weight.
Step-by-step explanation:
To find the total unit weight of the soil when the soil's degree of saturation (S) is increased to 50%, we must calculate the weight of the soil considering the added water content. The soil's dry unit weight (γ_d) is 15.8 kN/m³, porosity (n) is 0.40, and S is increased to 50% (or 0.5). The total unit weight (γ) can be calculated using the formula γ = γ_d + n * S * γ_w, where γ_w is the unit weight of water, which is approximately 9.81 kN/m³. For a fully saturated soil, S would equal 1. Using this information, we can calculate the respective total unit weights for both scenarios (a and b). For (c), the specific gravity (G) of the soil can be determined from the dry unit weight and the unit weight of water using the equation γ_d = (G * n * γ_w) / (1 + n).