Which Eurocode 7 clauses does this pile capacity calculator follow?

The calculator is based on EN 1997-1:2004, particularly Section 7 (Pile foundations) and Annex D for static pile design. It implements the standard decomposition of pile resistance into base resistance and shaft resistance, and allows the user to apply partial factors according to the selected national design approach.

Can I use this tool for both bored and driven piles?

Yes. You can select the pile type (bored or driven) and adjust the base and shaft resistance coefficients accordingly. For driven piles, higher base and shaft factors are typically used than for bored piles, in line with common national annexes and worked examples.

Does the calculator replace a full geotechnical design?

No. The tool is intended as an educational and preliminary design aid. Final pile design must always be carried out and checked by a qualified geotechnical engineer, using site investigation data, load tests where appropriate, and the relevant National Annex to Eurocode 7.

Eurocode 7 Pile Capacity Calculator (Axial Bearing Resistance)

Compute characteristic and design axial pile resistance according to Eurocode 7 (EN 1997-1), including base and shaft resistance, partial factors and safety checks.

Pile Capacity Calculator

Pile & Design Settings

Pile type

Diameter d [m]

Embedded length L [m]

Groundwater level z_w [m]

Depth below ground surface (0 = at surface).

Unit weight of water γ_w [kN/m³]

Design approach

γ_R;b (base)

γ_R;s (shaft)

γ_F (actions)

Applied Design Loads

Enter characteristic axial loads at pile head (unfactored). The calculator will apply γ_F.

N_k (compression) [kN]

T_k (tension) [kN]

Start with ground surface at z = 0 m. Layers must cover the pile length.

Soil Layers Along Pile

Layer	z_top [m]	z_bot [m]	γ [kN/m³]	Soil type	c_u [kPa]	φ' [°]	α / β	N_q

For clays (undrained, c_u-based), set φ' = 0 and N_q ≈ 9. For sands (drained), set c_u = 0 and use φ'-based N_q (or leave blank to auto-estimate).

Results

Characteristic Resistance

Base resistance R_b;k: – kN

Shaft resistance R_s;k: – kN

Total compression R_c;k = R_b;k + R_s;k: – kN

Total tension R_t;k (shaft only): – kN

Design Resistance (ULS)

R_c;d (compression): – kN

R_t;d (tension): – kN

Design load N_d = γ_F·N_k: – kN

Design tension T_d = γ_F·T_k: – kN

Show layer-by-layer resistance breakdown

Eurocode 7 pile capacity – basic approach

Eurocode 7 (EN 1997-1) treats the axial resistance of a pile as the sum of base resistance and shaft resistance:

Compression (characteristic):

\( R_{c;k} = R_{b;k} + R_{s;k} \)

Tension (characteristic):

\( R_{t;k} = R_{s;k} \)

The calculator implements these expressions and applies partial factors according to the selected design approach (DA1-1, DA1-2 or custom). It is intended for preliminary design and educational use; final design must follow the relevant National Annex and be checked by a qualified geotechnical engineer.

Base resistance R_b;k

For piles in drained conditions (sands and gravels), the characteristic base resistance is commonly expressed as:

\( R_{b;k} = q'_{b;k} \, A_b \)

with \( q'_{b;k} = \sigma'_{v;b;k} \, N_q \)

\( A_b = \pi d^2 / 4 \) is the pile base area.
\( \sigma'_{v;b;k} \) is the effective vertical stress at pile base level.
\( N_q \) is a bearing capacity factor depending on effective friction angle φ′.

For undrained clays, a simple undrained expression is often used:

\( R_{b;k} = N_c \, c_{u;b;k} \, A_b \)

with \( N_c \approx 9 \) for deep foundations.

Shaft resistance R_s;k

Shaft resistance is integrated along the pile perimeter. In practice, it is evaluated layer by layer:

\( R_{s;k} = \sum_i q_{s;i;k} \, u \, \Delta z_i \)

with \( u = \pi d \) the pile perimeter and \( \Delta z_i \) the pile length within layer i.

Typical expressions for unit shaft resistance include:

Clays (undrained): \( q_{s;k} = \alpha \, c_{u;k} \)
Sands (drained): \( q_{s;k} = \beta \, \sigma'_{v;k} \)

The coefficients α and β depend on pile type, installation method and soil state. National Annexes and design guides provide recommended values.

Partial factors and design resistance

Eurocode 7 applies partial factors to actions and resistances. For axial pile resistance in compression:

\( R_{c;d} = \dfrac{R_{b;k}}{\gamma_{R;b}} + \dfrac{R_{s;k}}{\gamma_{R;s}} \)

\( N_d = \gamma_F \, N_k \)

ULS requirement: \( N_d \le R_{c;d} \)

For tension:

\( R_{t;d} = \dfrac{R_{s;k}}{\gamma_{R;s}} \)

\( T_d = \gamma_F \, T_k \)

ULS requirement: \( T_d \le R_{t;d} \)

The calculator lets you choose between two common sets of resistance factors (DA1-1 and DA1-2) or specify custom γ-values.

How to interpret the results

Characteristic values (R_b;k, R_s;k, R_c;k, R_t;k) are based on your soil parameters without partial factors.
Design resistances (R_c;d, R_t;d) include γ_R;b and γ_R;s.
Utilisation ratios (N_d/R_c;d, T_d/R_t;d) indicate how close the pile is to its design capacity.

Limitations and good practice

This tool focuses on axial capacity; lateral resistance, buckling and group effects are not covered.
Soil parameters should come from a properly interpreted site investigation (CPT, SPT, lab tests).
For critical projects, pile load tests and more advanced analyses are usually required.

FAQ

Can I model negative skin friction (downdrag)?

The calculator does not explicitly model negative skin friction. For conservative design, you can reduce the positive shaft resistance in compressible layers or treat downdrag as an additional action on the pile.

How are N_q, α and β chosen?

Default values are only placeholders. In practice, you should select N_q, α and β from your National Annex, design manuals or correlations with in-situ tests (e.g. CPT-based methods). The tool allows you to override these coefficients per layer.

Does this follow a specific National Annex?

No. The implementation is generic Eurocode 7. National Annexes may specify different partial factors, resistance models and parameter selection rules. Always adapt the inputs and factors to your jurisdiction.