Soil Excavation: Bank Volume, Loose Volume and Truck Loads

Bank volume, loose soil and swell

Bank volume describes material in its original in-ground state. Loose volume estimates its bulk after excavation and handling. Enter the project-specific percentage increase relative to bank volume: loose = bank × (1 + swell/100). A swell input of 20 means a multiplier of 1.20, not 0.20. Zero means no adjustment has been entered, not that every soil has zero swell. Soil type, moisture and handling affect the conversion. Compacted backfill and shrinkage require their own specified basis and are not calculated here.

Truck loads, density and payload

Optional load planning assumes all estimated loose material is removed. Volume-only mode divides loose volume by the usable volume per load and rounds up. Combined mode also uses entered loose bulk density and usable payload, then takes the larger volume-based or mass-based whole-load count. Density must describe the loose material in tonnes per cubic metre; do not substitute bank density without conversion. A truck body capacity is not proof that filling it is within legal or vehicle limits. Confirm usable capacities and loading arrangements with the haulier.

Excavation costs and disposal quotes

Choose whether the excavation quote is per bank cubic metre or per loose cubic metre. Haulage per load uses the optional calculated load count, while disposal per loose cubic metre uses loose volume. Add separately quoted other costs once. Use one VAT basis and avoid charging again for haulage or disposal already included in another quote. Prices are entered arithmetic inputs, not live South African rates. Zero cost lines remain unpriced. Retained soil, contamination, disposal acceptance, rock breaking, dewatering and minimum charges can change the actual scope.

Uneven ground, surveys and site assessment

This tool models level top and bottom planes with constant depth and straight faces. It does not calculate a varying natural-ground surface, a survey cut-and-fill difference, stepped benches, overbreak or intersecting trenches. For those conditions, obtain a measured quantity or divide the work into appropriate non-overlapping sections using the project’s measurement method. Excavation stability, shoring, access, buried services, water and nearby structures need a competent site assessment. A volume result does not approve an excavation method or determine a safe slope.

Worked haulage and quote example

Using 146.667 m³ bank volume before rounding and an entered 20% swell gives 176 m³ loose material. With 10 m³ usable capacity per load, the volume-only estimate is 18 loads. If loose bulk density is an illustrative 1.5 t/m³ and usable payload is 12 t per load, the estimated mass is 264 t and the payload-based count is 22. Combined mode therefore shows 22 loads. These are entered assumptions, not generic soil density or vehicle limits. Loads may be partially filled; actual routing and loading arrangements still need confirmation.

A checkable cost breakdown

For the same example, hypothetical quotes of R100 per bank m³ excavation, R500 per calculated load, R20 per loose m³ disposal and R100 other costs total about R29,286.67. The components are R14,666.67 excavation, R11,000 haulage, R3,520 disposal and R100 other. These are arithmetic examples, not market prices. A different quote per loose m³ must be compared on its stated basis. Keep the underlying volume unrounded until the final currency result, and avoid repeating items already included in a contractor’s rate.

Frequently asked questions

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