Empire Infrastructure Open-Cut Buried Pipe Calculator

Open-Cut Buried Pipe Calculator BOSSPIPE OT

AS/NZS 2566.1 — Spangler-Iowa · Leonhardt · Eqs 5.4(1)–(5) buckling · §5.3 hoop+flexural for pressure pipes

Key assumptions for reviewer scrutiny

This calculator implements AS/NZS 2566.1 §5 for buried CC-GRP open-trench pipe. The simplifications below are explicit so reviewers can scrutinise them against your own preferred methodology.

Soil dead load uses prism load: W_d = γ·H. Marston trench-friction reduction is conservative-side ignored. Embankment installations would need C_e > 1 per AS/NZS 2566.1 §3 — this tool covers trench only.
Live load distributed via standard Boussinesq-style pyramid spreading: W_l = W·(1+i)/[(a+2H·tanφ)(b+2H·tanφ)] with φ = 30°. Impact factor and contact patch per traffic preset (SM1600: 80 kN wheel × 1.4, 0.5×0.2 m patch). Multi-wheel grouping uses simple superposition only.
Bedding constant K default 0.10 (AS/NZS 2566.1 §5.2.1, applicable to standard side-support bedding). Range 0.083–0.110.
Deflection lag factor D_L set to 1.0 because the calculator uses long-term creep moduli (E_b50, S_D50) directly. Some practitioners use D_L = 1.5 with initial moduli — both routes are valid; this one is preferred when material data sheets give 50-year values.
Leonhardt correction ζ bilinearly interpolated from a 5×6 lookup of Fig 5.1 chart values. Chart values are typical of AS/NZS 2566.1; project-specific application may warrant deviation.
Native soil modulus E'_n from AS/NZS 2566.1 Table 4.1 presets; user override available.
Embedment soil modulus E'_e from AS/NZS 2566.2 Table-equivalent presets at the chosen Dry Density Ratio %.
Combined effective modulus E' = ζ × E'_e, capped at 2 × E'_e for very stiff native (typical practice).
Wall strain = combined ring strain (ν · σ_v/E_b) plus bending strain (≈ 4 · e/D_m · ΔY/D); long-term limit 1.0%.
Buckling Eq 5.4(1) for H ≥ H_w: q_cr = 5.65·√(R_w·B'·E'·S_DL) with R_w = 1 − 0.33·H_w/H and B' = 1/(1+4e^−0.213H). Eq 5.4(3) for H < H_w: same form with R_w recalculated. Eqs 5.4(4) and 5.4(5) apply FoS = 2.5 to obtain allowable q_all,1 and q_all,2.
BOSSPIPE OT catalogue covers gravity (PN1) DN300–DN3000 in SN5000/SN7500/SN10000 (69 SKUs) plus pressure DN300–DN3000 in PN6/8/10/12.5/16/20/25 (149 SKUs — PN6 in SN5000 and SN10000, others SN10000 only). Total 218 SKUs from BOSSPIPE English Catalogue (May 2026). FWC couplings assumed throughout; no joint capacity check beyond manufacturer specification.
Hoop + flexural check (pressure pipes) implements AS/NZS 2566.1 §5.3 in strain form: ε_combined = ε_hoop + ε_bending ≤ 1.0% / FS where FS = 1.5. ε_hoop = p·D_m/(2·e·E_b50) using long-term hoop tensile modulus (E_b50 as proxy). Internal pressure cross-checked against pipe PN rating.
Material modulus E_b ranges per BOSSPIPE Material-Constant Table: ~12,000 MPa apparent flexural at 23°C. Default creep reductions: 2-year ≈ 0.65 × initial; 50-year ≈ 0.50 × initial. Override per current BOSSPIPE data sheet values.

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Inputs

Pipe selection

Product

Application

Nominal DN (mm)

BOSSPIPE Stiffness Class SN (N/m²)

—

Outside diameter D_e (mm)

Wall thickness e (mm)

E_b initial (MPa)

Poisson's ratio ν

E_b 2-year (MPa)

E_b 50-year (MPa)

Installation (trench)

Trench width B' (mm) — auto if blank

Cover above crown H (m)

Ground water above pipe H_w (m)

Bedding constant K

Soil properties

Native soil (E'_n from preset)

E'_n override (MPa)

Trench fill γ (kN/m³)

Embedment soil (Pipe Zone Material)

Compaction Dry Density Ratio (%)

E'_e auto (MPa) — editable

Live load preset (AS 5100.2)

Internal working pressure (kPa)

Internal vacuum (kPa)

Additional long-term load (kPa)

Capacity safety factor (buckling)

Design checks (long-term)

All checks per AS/NZS 2566.1 §5. Updates live as inputs change.

Vertical Deflection

—%

Limit: ≤7.5%

Wall Strain (long-term)

—%

Limit: ≤1.0%

FoS Buckling

—

Min: ≥2.5

Capacity detail

Check	Calculated	Limit	Status

Loading summary

Component	Pressure (kPa)	Reference

Calculation breakdown AS/NZS 2566.1 §5 — equations cited

Pipe section properties

D_e outside diameter—

D_m mean diameter—

e wall thickness—

I = e³/12 per unit length—

S_D initial = E_b·I/D_m³ × 10⁶—

S_DL2 at 2 years—

S_DL50 at 50 years—

S_D [N/m·m⁻¹] = (E_b·e³)/(12·D_m³) × 10⁶

Vertical pressures

W_d soil (prism load)—

W_l live (Boussinesq)—

W_w water—

W_add additional—

W_t total vertical pressure—

W_d = γ·H · — W_l = W·(1+i) / [(a+2H·tanφ)(b+2H·tanφ)]

Soil moduli & Leonhardt

E'_n native—

E'_e embedment—

E'_n / E'_e ratio—

B' / D_e ratio—

Leonhardt ζ (Fig 5.1)—

E' combined effective—

E' = ζ · E'_e · capped at 2·E'_e

Deflection & strain (Spangler-Iowa)

D_L deflection lag factor1.0 (long-term moduli)

K bedding constant—

ΔY/D × 100% Eq 5.2.1—

Ring strain ε_r—

Bending strain ε_b = 4·(e/D_m)·(ΔY/D)—

Hoop strain ε_h = p·D_m/(2·e·E_b50) (pressure)—

Combined ε_hoop+ε_bend (pressure)—

FoS hoop+flex = 1.0% / ε_combined—

Total ε—

ΔY/D = D_L·K·W_t / (8·S_DL + 0.061·E')

Buckling — AS/NZS 2566.1 §5.4

R_w water buoyancy factor—

B' soil-arching coefficient—

Eq 5.4(1) q_cr case H ≥ H_w—

Eq 5.4(3) q_cr case H < H_w—

Eq 5.4(4) q_all,1 = q_cr,1/FS—

Eq 5.4(5) q_all,2 = q_cr,3/FS—

q_applied total external pressure—

FoS buckling = q_cr,governing / q_applied—

Eq 5.4(1): q_cr = 5.65·√(R_w·B'·E'·S_DL) · R_w = 1 − 0.33·H_w/H · B' = 1/(1+4·e^−0.213H)

Caveats. AS/NZS 2566.1 design check only — not a certified deliverable. Final design must be reviewed and signed by a registered RPEng/CPEng. BOSSPIPE OT geometry from Empire's published Open-Trench Pipe Specs (59 SKUs, DN300–DN2400, SN5000/10000/20000). FWC coupling capacity assumed to manufacturer specification; not separately checked. Cohesion contribution to friction not modelled — soil load uses prism approach. Live load uses Boussinesq pyramid distribution; multi-wheel grouping applied as simple superposition. Leonhardt ζ from chart interpolation — project conditions outside the chart range need standard reference. Soil moduli E'_e at the chosen DDR are from AS/NZS 2566.2-equivalent presets.

References:

AS/NZS 2566.1:1998 (R2018) — Buried flexible pipelines, Part 1: Structural design (Spangler-modified Iowa, Leonhardt soil correction, §5 deflection/strain/buckling)
AS/NZS 2566.2:2002 — Buried flexible pipelines, Part 2: Installation
AS 5100.2:2017 — Bridge design loads (SM1600, HLP320, HLP400, 300LA rail)
AS 4799:2000 — Installation of underground utility services within railway boundaries (300-A-12 rail)
BOSSPIPE English Catalogue (May 2026) — Empire Infrastructure (Bosspipe International): gravity 69 SKUs DN300–DN3000 in SN5000/7500/10000; pressure 149 SKUs DN300–DN3000 in PN6/8/10/12.5/16/20/25 (PN6 in SN5000 and SN10000; PN8+ in SN10000 only)
BOSSPIPE Material-Constant Table — Empire Infrastructure
BOSSPIPE Filament Wound Coupling-Couplings-Table — Empire Infrastructure