HDD Bore Profile Calculator
Conservative preliminary estimate of profile geometry, pull force and residual tensile capacity for HDD projects.
Notice: This quick check is for orientation purposes only. The results do not replace a project-specific design. Dimensioning and approval are the responsibility of the responsible engineering office. All information without guarantee. Full Disclaimer
Application & Background
The HDD Bore Profile Calculator provides a conservative preliminary estimate for a simplified HDD profile. It is neither a technical approval nor a complete HDD verification.
Unlike the Pull Force Calculator, this tool also estimates the required pull force along the profile and compares it with the calculated tensile capacity remaining after bending.
Calculation Model
The tool uses a simplified 4-point profile with tangential circular arcs. Force is estimated with the Euler–Eytelwein equation and a segment-based friction model:
Surface ──── Rollers ────╲ Entry (α₁)
╲
╲── Low point ─── Bottom (L₃) ─── Low point ──╱
╱ Exit (α₂)
╱── Surface
Radius, horizontal projection and arc length are derived from angle and cover depth:
$$R = \frac{H}{1-\cos\alpha}, \qquad x=R\sin\alpha, \qquad l=R\alpha$$
Bending and residual tensile capacity always use $R_{governing}=\min(R_{in},R_{ex})$. The minimum bending radius follows DVGW GW 321:2003, Table A.3: 50D at 0 °C, 35D at 10 °C and 20D at 20 °C. Intermediate temperatures use the next colder step.
The force balance along the 4 segment points considers:
| Force Component | Formula (simplified) |
|---|---|
| Roller friction | $\mu_{ground} \cdot w_a \cdot g \cdot L_{roller}$ |
| Capstan effect (curves) | $e^{\mu \cdot \alpha}$ — belt friction against the bore wall |
| Buoyancy/Weight | $w_b \cdot g \cdot H$ — net submerged weight |
| Borehole friction | $\mu_{mud} \cdot |
The required pull force $F_{req}$ is the cumulative force at exit point T₄.
Utilization Rate
$$\text{Utilization} = \frac{F_{req}}{F_{allow}} \times 100,%$$
| Range | Assessment |
|---|---|
| ≤ 60 % | Green — internal planning reserve available |
| 60–80 % | Amber — detailed verification required |
| > 80 % | Red — do not release at preliminary-planning stage |
The 60/80% thresholds are conservative internal planning thresholds, not GW 321 limits.
Sources & Standards
- DVGW GW 321 (10/2003), Annex A — Pull-force, duration and minimum-bending-radius values for PE pipes
- Euler–Eytelwein equation — Capstan/belt friction (basis for force calculation at bends)
Model Limitations
The model does not include reamer and cutting forces, hydrokinetic forces, breakaway and stationary friction, local deflections, borehole instability, or external-pressure and collapse checks. Friction coefficients and drilling-fluid density are project assumptions. Execution and rig selection require a project-specific HDD design check and field data.
All data provided without warranty. Full disclaimer