Trench Backfill Calculator
Excavation, bedding, embedment and general backfill volumes for a pipe trench.
Inputs
Results
Excavation volume
81.00m³
Theoretical in-situ volume, no bulking allowance
Theoretical in-situ volumes. No allowance for bulking, compaction, shrinkage or loss is included. The pipe is assumed circular and seated directly on the bedding.
Calculation details
Engineering equations
V_excavation = W · D · L
V_bedding = W · t_b · L − A_pipe(z ≤ t_b) · L
V_embedment = W · h_e · L − A_pipe(t_b < z ≤ t_b + h_e) · L
V_backfill = V_excavation − V_bedding − V_embedment − V_pipe above embedment
Variables
- W
- Trench width (m)
- D
- Trench depth (m)
- L
- Trench length (m)
- t_b
- Bedding thickness below the pipe (m)
- h_e
- Embedment height above the bedding (m)
- A_pipe
- Circular segment area of the pipe below a given level (m²)
Assumptions
- Volumes are theoretical in-situ volumes.
- No allowance for bulking, compaction, shrinkage or loss is included.
- The pipe is circular and sits directly on the bedding layer.
- Trench walls are vertical with a constant width and depth.
Worked example
L = 50 m, W = 0.9 m, D = 1.8 m, outside diameter 300 mm, bedding 100 mm, embedment 200 mm
Excavation = 0.9 × 1.8 × 50 = 81.0 m³
Bedding = 4.5 m³, embedment = 6.5 m³
General backfill = 69.0 m³
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Results are preliminary engineering estimates based on the stated assumptions. Confirm inputs, assumptions and requirements against the applicable standards and authority requirements before use in design or construction.