Question

A terrace is being proposed to be constructed for a land slope of 20% medium-textured soil with 0.5 m depth of cut. What would be the width of the terrace if the terrace cut is vertical?

• A. 5 m
• B. 0.5 m
• C. 1 m
• D. 2.5 m

Hint:

Terrace width shortcut: $W = \frac{2 \times \text{Depth of cut}}{\text{Slope (fraction)}} = \frac{2 \times 0.5}{0.20} = 5\text{ m}$.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
In bench terracing design with vertical cut and balanced cut-and-fill excavation on sloping ground, the vertical interval and terrace width depend on the depth of cut and original land slope.
Key Formula or Approach:
\[ \text{Vertical Interval } (VI) = 2 \times d \]
\[ \text{Width of Terrace } (W) = \frac{VI}{S} = \frac{2d}{S} \]
where \(d\) is depth of cut (m), and \(S\) is land slope (fraction).

Step 2: Detailed Explanation:
Given parameters:
- Land slope: \(S = 20\% = 0.20\)
- Depth of vertical cut: \(d = 0.5\text{ m}\)
For balanced earthwork with vertical cuts, the total height of riser vertical interval is twice the depth of cut:
\[ VI = 2 \times d = 2 \times 0.5\text{ m} = 1.0\text{ m} \]
The bench terrace width \(W\) is given by:
\[ W = \frac{VI}{S} = \frac{1.0\text{ m}}{0.20} = 5.0\text{ m} \]

Step 3: Final Answer:
Thus, the width of the terrace would be 5 m, matching option (A).