Subballast Quantity Calculator

1. Choose Rectangular or Trapezoidal section method.
2. Add one or more segments and enter length, top width, and depth.
3. For trapezoids, define the bottom width using slope or bottom width.
4. Set track count if the same section repeats on parallel tracks.
5. Apply compaction and waste to estimate ordered quantity.
6. Optionally add density and truck capacity for mass and trips.
7. Press Calculate to view totals above, then export CSV or PDF.

Subballast quantity planning for trackbeds

Subballast is a structural layer below ballast that improves bearing capacity, drainage control, and long-term geometry. Quantity planning should align with design thickness, formation width, and any widening required for shoulders or transitions. This calculator estimates compacted geometry first, then converts to ordered quantity using project allowances.

Key inputs and recommended ranges

Begin with segment length, top width, and thickness from drawings, surveys, or chainage notes. Compacted thickness often falls between 150–300 mm for many renewal scopes, while top width typically reflects sleeper length and shoulder design. Where side slopes are specified, enter the H:V ratio; otherwise use bottom width to match the section.

Section methods and geometry checks

Rectangular sections suit uniform-width layers. Trapezoids suit widened bases or sloped shoulders. For slope-defined trapezoids, the base widens by 2·D·S, which should be checked against formation limits and adjacent utilities. Confirm thickness continuity through transitions to avoid over-ordering.

Ordering allowances, density, and haulage

Ordered material generally exceeds compacted volume due to bulking, moisture condition, and trimming losses. Apply a compaction factor commonly 1.05–1.25 and waste allowance often 2–8%, then validate against supplier delivery condition. If bulk density is known, mass estimates support weighbridge reconciliation. Truck capacity converts ordered volume into a practical trip plan.

Example data for review and audit

Use this example to verify inputs before exporting reports. Adjust values to your specifications.

Export CSV for procurement logs and PDF for site records. Compare segment totals to delivery tickets and chainage progress to confirm ordered quantity aligns with actual placement and compaction performance.

1) What is the difference between compacted and ordered volume?

Compacted volume is the placed geometry in the trackbed. Ordered volume adds compaction factor and waste allowance to reflect loose delivery volume needed for placement and trimming.

2) When should I choose rectangular versus trapezoidal sections?

Use rectangular when width is constant across the layer. Use trapezoidal when shoulders widen, side slopes are specified, or drawings show different top and bottom widths.

3) How do I interpret the side slope (H:V) input?

H:V means horizontal distance per one unit vertical. A value of 1.5 indicates 1.5 units horizontal for every 1 unit vertical, widening the base by 2·D·S.

4) Why does the calculator allow multiple segments?

Track sections often change by chainage due to transitions, turnouts, or widening. Segmenting improves accuracy by letting each portion use its own length, thickness, and geometry.

5) What density should I use for mass estimates?

Use the supplier’s tested bulk density for the delivered condition. If unavailable, start with a typical value and update once lab results or weighbridge tickets confirm actual density.

6) How are truckloads calculated?

Truckloads equal ordered volume divided by truck capacity in the same units. The result is a planning estimate; adjust for practical payload limits, moisture, and route restrictions.

7) What checks should I do before ordering?

Confirm chainage lengths, thickness, and section widths against drawings and site measurements. Review compaction and waste assumptions, then compare totals to previous projects or material take-offs.