Excavation Calculator: Bank vs. Loose Soil Volume

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What is Excavation Calculator: Bank vs. Loose Soil Volume?

The Excavation Calculator is a critical earthworks planning tool used to estimate the volume of soil to be removed or brought in for a project. In construction, dirt exists in three states: Bank (undisturbed), Loose (excavated), and Compacted. When you dig a hole, the soil expands because air is introduced between particles—a phenomenon known as 'swell' or 'bulking'. A 10 cubic yard hole might produce 13 cubic yards of loose dirt. Ignoring this factor leads to underestimating dumpster or truck requirements, causing significant project delays and budget overruns.

How it Works

The calculator starts with the geometric volume of the excavation (Length × Width × Depth). This gives the 'Bank Volume'. To determine the haul-off volume, it applies a 'Swell Factor' specific to the soil type (e.g., Clay swells ~40%, Sand ~15%, Topsoil ~25%). Formula: Bank Volume = L × W × D. Loose Volume = Bank Volume × (1 + Swell %). Truckloads = Loose Volume / Truck Capacity.

Step-by-Step Guide

1. Measure Excavation

Determine the length, width, and depth of the area to be dug in feet or meters.

2. Identify Soil Type

Select the material (Sand, Clay, Gravel, Topsoil) to apply the correct swell factor.

3. Calculate Volumes

The tool computes both the hole size (Bank) and the pile size (Loose).

4. Plan Logistics

Estimate the number of dump trucks or dumpsters needed based on the expanded loose volume.

Example

Input: 10ft x 10ft x 5ft (Clay)

Result: 18.5 yd³ Loose Soil (from 14.8 yd³ Bank)

FAQ

What is the difference between Bank and Loose volume?

Bank volume is the dirt in the ground (compacted by nature). Loose volume is the dirt after digging, which is fluffy and takes up more space.

How much does dirt swell?

It varies by type: Sand swells ~10-15%, common earth ~20-25%, and heavy clay or rock can swell 40-60%.

How many yards fit in a dump truck?

A standard dump truck typically holds 10-14 cubic yards of loose material. Smaller trucks may hold 3-5 yards.

What about backfilling?

If you are filling a hole, you need to account for compaction (shrinkage). You might need 1.2 cubic yards of loose dirt to fill 1 cubic yard of compacted space.

Does rain affect the volume?

Moisture increases weight significantly but doesn't change volume much. However, wet soil is much harder to transport.

Conclusion

Precise excavation estimates prevent the nightmare of having a pile of dirt with nowhere to put it. Always remember to 'Call Before You Dig' (811 in the US) to locate underground utilities. For backfilling projects, remember that soil shrinks when compacted, so you will need to order more loose soil than the hole's volume suggests (shrinkage factor).

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References & Standards

This calculator uses formulas and data standards from Standard References to ensure accuracy.

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