Learn: Pile total compression resistance
An axially compressed pile can transfer load through its base and along its shaft. This calculation adds those two supplied resistance components to obtain their combined value under a compatible pile model.
What the formula is saying
Rb is base resistance and Rs is shaft resistance. Addition is valid only when the two components use the same resistance basis and can be mobilized consistently at the displacement level being considered.
Read the symbols in plain language
- Rb
- Base resistance
Base resistance. Use the total base-force component at the same resistance level as the shaft value.
kNKilonewtons measure force; 1 kN = 1000 N.
- Rs
- Shaft resistance
Shaft resistance. The two force components combine only under the stated mobilization and design assumptions.
kNKilonewtons measure force; 1 kN = 1000 N.
- Rc
- Result to find
Pile total compression resistance. The two force components combine only under the stated mobilization and design assumptions.
kN
Sort out the units first
Both inputs and the output are forces in kN. They are total resistance components, not unit base pressure in kPa or unit shaft friction.
Assumptions before calculating
This is an idealized study model with supplied soil parameters and loading. Ground investigation, drainage condition, groundwater, geometry and the governing design approach must be established by the responsible geotechnical design process.
This is a first-generation Eurocode teaching relationship or an explicitly simplified coefficient calculation. The numbers supplied here are exercise data, not a recommendation for any country. Check the adopted edition, relevant clause, National Annex, applicability conditions and all other limit states before any real design.
Let’s solve one together
Read the given values, follow each operation, then check what the result means.
Read the supplied values as one complete study case. Find Rc and explain the result in the stated output unit.
- Rb · Base resistance
- 800 kN
- Rs · Shaft resistance
- 1200 kN
Identify the compatible base resistance
Use the total base-force component at the same resistance level as the shaft value.
(800) = 800 kNAdd the compatible shaft resistance
The two force components combine only under the stated mobilization and design assumptions.
(800) + (1200) = 2000 kN
Does this worked answer make sense?
If one component is zero, the total equals the other. With nonnegative compatible components, the sum cannot be smaller than either component.
A second worked example — different values
A second case uses different data. Predict which way the answer will change, then calculate it without reusing the first answer.
- Rb · Base resistance
- 600 kN
- Rs · Shaft resistance
- 900 kN
Identify the compatible base resistance
Use the total base-force component at the same resistance level as the shaft value.
(600) = 600 kNAdd the compatible shaft resistance
The two force components combine only under the stated mobilization and design assumptions.
(600) + (900) = 1500 kN
Now try your own values
Change a value or its unit. The same method will show your calculation, step by step.
Results update only when you calculate. The lesson example above stays unchanged.
Your turn — check your understanding
Solve this separate case yourself. Use only the values below; the two worked examples use different data. Give the requested result in the selected unit.
- Rb · Base resistance
- 1000 kN
- Rs · Shaft resistance
- 1500 kN
Find: Learn: Pile total compression resistance
A hint, not the answer
Rb is base resistance and Rs is shaft resistance. Addition is valid only when the two components use the same resistance basis and can be mobilized consistently at the displacement level being considered.
Both inputs and the output are forces in kN. They are total resistance components, not unit base pressure in kPa or unit shaft friction.
Show the full practice solution
Compare the steps with your work; revealing a solution does not mark the lesson complete.
Identify the compatible base resistance
Use the total base-force component at the same resistance level as the shaft value.
(1000) = 1000 kNAdd the compatible shaft resistance
The two force components combine only under the stated mobilization and design assumptions.
(1000) + (1500) = 2500 kN
Avoid the common trap
Do not add a unit pressure directly to a total force. Do not count downdrag as positive shaft resistance or apply a final safety factor without following the chosen design basis.
When this method applies — and when it does not
The input components must both be characteristic, nominal or design values consistently; do not mix them. Pile groups, settlement compatibility, negative skin friction, structural capacity, uplift and correlation factors need additional treatment.
For study and understanding, not approval of a real structure, site operation or design. Apply the correct standard, National Annex and professional review to actual engineering work.
One idea understood. Keep going.
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Sources & further reading
References open in a new tab and explain the underlying principles. The teaching text and examples here are SimpleFlick’s own; the source organisations have not endorsed this calculator.
Reading focus: Pile total compression resistance. Read the relevant soil phase, seepage, earth-pressure, settlement or foundation topic. Effective stress, drainage and idealized geometry determine whether the relationship applies.
- University of the West of England — GeotechniCAL: soil mechanics and foundations
- University of the West of England — GeotechniCAL: foundation types and piles
Lesson updated: · Both examples and the separate practice case are checked against an independent high-precision numerical implementation. This verifies arithmetic for the stated model, not engineering certification.