Step 1: Find the weight of water \( W_w \).

Weight of water, \( W_w = \) wet weight - dry weight = 120 g - 100 g = 20 g.

Step 2: Use the water content formula:

\( w = \frac{W_w}{W_s} \times 100\% = \frac{20}{100} \times 100\% = 20\% \).

Answer: The water content of the soil is 20%.

Step 1: Use the formula relating \( w \), \( S \), \( e \), and \( G \):

\( w = \frac{S \times e}{G} \times 100\% \)

Step 2: Rearrange to find \( S \):

\( S = \frac{w \times G}{e \times 100} \)

Step 3: Substitute values (convert \( w \) to decimal by dividing by 100):

\( S = \frac{15 \times 2.7}{0.75 \times 100} = \frac{40.5}{75} = 0.54 \) or 54%.

Answer: The degree of saturation is 54%.

Step 1: Use the formula:

\( w = \frac{S \times e}{G} \times 100\% \)

Step 2: Rearrange to find \( e \):

\( e = \frac{w \times G}{S \times 100} \)

Step 3: Substitute values (convert \( S \) to decimal):

\( e = \frac{18 \times 2.65}{80 \times 100} \times 100 = \frac{47.7}{80} = 0.596 \)

Answer: The void ratio is approximately 0.60.

Step 1: Calculate degree of saturation \( S \) using:

\( S = \frac{w \times G}{e \times 100} = \frac{30 \times 2.7}{0.9 \times 100} = \frac{81}{90} = 0.9 \) or 90%.

Step 2: Since \( S = 90\% \) < 100%, the soil is partially saturated, not fully saturated.

Answer: The soil is partially saturated with 90% saturation.

Step 1: Understand that soil strength depends on the interaction between soil particles and the presence of water.

Step 2: When saturation increases:

• Shear Strength: For unsaturated soils, some suction (negative pore water pressure) exists, which increases effective stress and shear strength. As saturation approaches 100%, suction decreases, reducing shear strength in some soils (especially fine-grained soils). Fully saturated soils rely on effective stress alone for strength.
• Compressibility: Increasing saturation generally increases compressibility because water is less compressible than air, but saturated soils can consolidate under load as water is expelled from voids, leading to volume decrease.

Answer: Increasing saturation reduces suction and can lower shear strength in unsaturated soils, while increasing compressibility due to consolidation effects in saturated soils.