Ground Support Design Calculator

Calculate rock bolt spacing, length, and shotcrete thickness from RMR and excavation dimensions.

RMR Value

Excavation Span

Excavation Height

Rock Density

kg/m³

Tab to move between fields

Support Class

Systematic Bolting + Shotcrete

Bolt Spacing1.5 m

Bolt Length4 m

Shotcrete Thickness50 mm

Bolts per Row5

Rows per Meter1

Rock Load59.6 kPa

Shotcrete Vol/m0.65 m³

How to Use This Calculator

Enter the RMR Value from your Rock Mass Rating Calculator output.
Set the excavation span (m) and height (m) for the tunnel or opening being designed.
Enter rock density (kg/m³) for load calculations.
Review Support Class, Bolt Spacing (m), Bolt Length (m), and Shotcrete Thickness (mm) for design specifications.
Use these outputs as preliminary design inputs to be verified by a geotechnical engineer.

What each input means

Identify Input Parameters
4 parameters
RMR Value = 55, Excavation Span = 5, Excavation Height = 4, Rock Density = 2700 = 4 input(s) provided
Calculate Support Class
Support Class
Systematic Bolting + Shotcrete = Systematic Bolting + Shotcrete
Calculate Bolt Spacing
Bolt Spacing
1.5 = 1.5
Calculate Bolt Length
Bolt Length
4 = 4

Engine last updated August 5, 2026. Checked against 3 independently-derived tests — how we verify calculators.

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