排水碎石计算器 — 公式
## Drainage Gravel Calculation
**Gravel Volume = Trench Volume - Pipe Volume**
The perforated pipe displaces some of the trench volume. Subtract its cross-sectional area multiplied by the trench length to get the net gravel volume. Use washed, angular gravel (3/4 to 1-1/2 inch) for good drainage.
**Gravel Volume = Trench Volume - Pipe Volume**
The perforated pipe displaces some of the trench volume. Subtract its cross-sectional area multiplied by the trench length to get the net gravel volume. Use washed, angular gravel (3/4 to 1-1/2 inch) for good drainage.
计算示例
50 ft French drain, 12 in wide, 18 in deep, with 4-inch pipe.
- Trench volume = 50 x 1 x 1.5 = 75 cu ft
- Pipe volume = 50 x pi x (2/12) squared = 2.18 cu ft
- Gravel = (75 - 2.18) / 27 = 2.7 cu yd
- Weight = 2.7 x 1.4 = 3.8 tons