Example data table
| Item | Example value | Notes |
|---|---|---|
| Tank diameter | 18 m | Circular contact area assumed. |
| Total load | 8,500 kN | Use a service load for settlement checks. |
| Groundwater depth | 2.0 m | Affects effective stress and consolidation. |
| Layer 1 thickness | 3.0 m | Soft to medium soil zone near surface. |
| Layer 1 Cc / Cr | 0.22 / 0.04 | From lab tests or regional correlations. |
| Allowable settlement | 50 mm | Project-specific criterion. |
Formula used
How to use this calculator
- Enter the tank diameter and either total load or contact pressure.
- Provide groundwater depth if the site has a known water table.
- Fill layer thickness and consolidation parameters for each soil layer.
- Set an allowable settlement if you want a pass/fail indication.
- Press Submit to view results above the form.
- Use the CSV/PDF buttons to export the summary and layers.
Design context for tank settlements
Large-diameter tanks apply relatively low average pressure, but they influence a wide soil volume. Settlement control is often governed by serviceability, piping connections, and floor or shell tolerances. This calculator provides a transparent screening workflow that separates immediate (elastic) movement from time-dependent consolidation, helping teams focus on the most sensitive drivers early in design.
Input quality and field investigations
Reliable settlement estimates depend on credible geometry, loads, groundwater depth, and laboratory parameters. Use tank diameter and either total service load or measured contact pressure. Populate unit weights from site logs and confirm groundwater seasonality where possible. For compressibility, prefer oedometer test results for Cc, Cr, and preconsolidation stress; correlations should be treated as preliminary and verified during detailed geotechnical work.
Layered consolidation behavior
The layer table reflects how different strata contribute to total movement. Softer clayey layers with higher void ratio and compression index typically dominate consolidation settlement, even if thin. Preconsolidation stress distinguishes normally consolidated response from overconsolidated behavior, which usually settles less for the same stress increase. The mid-depth effective stress and stress increment outputs show why shallow groundwater and low overburden can increase predicted compression.
Interpreting results and tolerances
Compare the total settlement to the project’s allowable limit, and also review the split between immediate and consolidation components. A high immediate portion suggests stiffness assumptions (Es, ν, influence factor) deserve refinement or in-situ testing. A high consolidation portion highlights the need for ground improvement, preloading, vertical drains, or foundation alternatives. Use the layer breakdown to target improvement depth rather than over-treating competent strata.
Reporting, traceability, and exports
Construction decisions benefit from reproducible calculations. The CSV export supports quick peer review and can be appended to site reports. The PDF export provides a compact summary for approvals, RFIs, and design records. Keep a consistent naming convention for runs (e.g., “Tank A – Full – GW 2.0 m”) and store the exported outputs with the corresponding lab sheets and borehole logs for audit-ready documentation.
FAQs
1) Should I enter total load or contact pressure?
Enter either one. If contact pressure is provided, the calculator uses it directly. If you enter total load, contact pressure is computed from the circular tank area.
2) What does the groundwater depth change?
Groundwater reduces effective stress below the water table by using submerged unit weight. Lower effective stress generally increases consolidation settlement for the same stress increase.
3) Why are settlements computed at layer mid-depth?
Mid-depth is a common approximation for stress and compressibility within a layer. It provides a stable, easy-to-audit method for preliminary layered settlement estimates.
4) What is the immediate settlement factor Is?
Is is an influence factor used with the elastic screening equation. Use 1.0 for preliminary checks, then refine based on foundation shape, rigidity, and applicable guidance.
5) When will the result be conservative?
Conservative outcomes often occur if Es is too low, groundwater is assumed shallow, or soil parameters reflect softer conditions. Always align inputs with current field and lab evidence.
6) Can this replace a full geotechnical report?
No. It is a structured screening tool for scoping and comparison. Final design should follow site-specific testing, calibrated models, and professional geotechnical review.