Geology & Geotech Calculators | High Valley Geosystems

Built by Jack & Tony Johannsen

For education only. These calculators are simplified teaching aids. They are not a substitute for site-specific investigation, engineering judgment, or review by a licensed Professional Engineer (PE) or Professional Geologist (PG).

RQD & core recovery

Core run length Total core recovered Sum of intact pieces ≥ 10 cm (4 in)

Use the same units for all three.

TCR (%) = recovered / run × 100
RQD (%) = Σ pieces ≥ 10 cm / run × 100 (Deere, 1964)

Rock Mass Rating (RMR89)

Intact rock strength (UCS) RQD Discontinuity spacing Discontinuity condition Groundwater Joint orientation adjustment

RMR = R1 + R2 + R3 + R4 + R5 + adjustment (Bieniawski, 1989). Classes: I 81–100 very good, II 61–80 good, III 41–60 fair, IV 21–40 poor, V ≤ 20 very poor.

Slope angle / percent / ratio

Enter one value

% = tan(θ) × 100 · H:V = 1 / tan(θ) : 1 · θ = atan(%/100)

Infinite-slope factor of safety

Slope angle β (°) Depth to slip plane z (m) Unit weight γ (kN/m³) Effective cohesion c′ (kPa) Effective friction angle φ′ (°) Saturated fraction m (0–1, slope-parallel seepage)

FS = [c′ + (γz cos²β − u) tanφ′] / (γz sinβ cosβ), with u = γ_w m z cos²β, γ_w = 9.81 kN/m³

Unit conversions

Length ft = m Stress psi = MPa = kPa Mass short tons = tonnes Grade oz/t = g/t

1 ft = 0.3048 m · 1 psi = 6.894757 kPa = 0.006894757 MPa · 1 short ton = 0.907185 t · 1 troy oz per short ton = 34.2857 g/t