Axial capacity of driven, bored and CFA piles per EN 1997-1 §7 — both compression (R_c,k / R_c,d via DA1C1 or DA1C2) and tension / uplift (R_t,k / R_t,d via §7.7). Layered soil profile, α-method for cohesive layers and β-method (K·tan δ) for cohesionless, N_c·c_u or N_q·σ′_v for the base. Pile self-weight optional.
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EN 1997-1 §7.6 covers compressive pile resistance via shaft (R_s,k) and base (R_b,k). §7.7 covers tensile (uplift) resistance. R_c,k = Q_s,k + Q_b,k (compression) and R_t,k = Σ q_s,k·A_s (base ignored under tension). Design resistance is derived by Design Approach 1 (DA1C1 or DA1C2).
DA1C1 (A1+M1+R2) factors actions on the load side (γG=1.35, γQ=1.5) but uses characteristic material parameters and γ_R=1.0 on the resistance side. DA1C2 (A2+M2+R1) takes characteristic actions and applies material factors (γ_b=1.25 to base resistance for bored/CFA piles) on the resistance side. The plan instructs you to check BOTH combinations per EN 1997-1 §7.6 and the more onerous governs.
In tension (uplift), the base resistance R_b,k is conservatively taken as zero per EN 1997-1 §7.7. Only shaft friction and pile self-weight contribute to R_t,k. This is because pile base suction is unreliable under sustained tension — most failures in uplift occur at the pile-soil interface along the shaft.
The α-method (clay) sets q_s = α·c_u with α=0.50 for driven piles and α=0.45 for bored/CFA piles (compression); α is reduced to 0.35/0.40 under tension. The β-method (sand) sets q_s = K·σ′_v·tan(δ) with K=0.70 for driven and K=0.50 for bored, δ≈0.67·φ′. EN 1997-1 §7.6.2.3 limits σ′_v to 300 kPa for the β-method.
Pile self-weight W_p = γ_c·A_b·L (default γ_c=25 kN/m³ for reinforced concrete) is added to R_t,k when includeSelfWeight=true. This is appropriate for compression-light piles where uplift dominates — for example wind turbine foundations, transmission line anchors, and cantilever signs.
For pile groups with centre-to-centre spacing s < 3D, capacity is reduced by group efficiency η per CIRIA C580. η = 1 − (n−1)·(D/8s) for driven piles in clay. Use the Civil Pile Capacity (EN/AASHTO) tool for explicit group efficiency and static load test (ξ3/ξ4) handling.