Precast concrete piles: what is the maximum recommended taper along the length to ensure sound casting, handling, and driving performance?

Introduction / Context:
Precast reinforced concrete piles may be slightly tapered to facilitate driving and stress distribution. However, excessive taper can cause nonuniform stresses, driving damage, and casting difficulties. Codes and practice guides limit the taper.

Given Data / Assumptions:

• Precast R.C.C. piles (square or octagonal) with modest taper are considered.
• Good practice limits taper to a small value per metre length.
• Objective: ensure safe handling, uniform driving, and structural adequacy.

Concept / Approach:
A typical recommendation is that the taper of precast concrete piles should not exceed about 1 cm per metre of length. This small taper eases penetration while keeping cross-section changes gradual enough to avoid stress concentrations and reinforcement congestion.

Step-by-Step Solution:
List plausible tapers: 1, 2, 4, 5 cm/m.Adopt conservative practice for precast concrete: 1 cm/m.Therefore, the correct limit is 1 cm per metre.

Verification / Alternative check:
Comparatively, timber piles may have larger natural tapers; precast concrete members favor minimal taper for reinforcement layout and casting formwork stability.

Why Other Options Are Wrong:

• 2–5 cm/m: too steep for precast concrete, risking cracking and driving damage.
• No taper: permissible but not necessary; slight taper is common—question asks for the maximum recommended, not zero.

Common Pitfalls:
Applying timber pile taper limits to concrete piles; ignoring reinforcement detailing constraints in tapered sections.

Final Answer:
1 cm per metre length