Steel Piles – Preferred type for soft clay or loose sand with low capacity Which steel (or metal) pile is most commonly used in soft clay or loose sand where the natural bearing capacity is low?

Introduction / Context:
Different pile types suit different soils. In very soft deposits, gaining end bearing or uplift resistance by enlarging the effective base area is advantageous. Screw (helical) piles accomplish this with helix plates that engage the soil during installation and under service loads.

Given Data / Assumptions:

• Soil: soft clays or loose sands of low bearing capacity.
• Construction aims: achieve capacity without relying only on weak skin friction.
• Pile material: steel or cast metal shaft with helices.

Concept / Approach:
Screw piles develop significant capacity by the helix plates acting as bearing surfaces and by improved shaft-soil interaction. They are efficient in weak soils and can be installed quickly with torque monitoring.

Step-by-Step Solution:
Match soil condition to pile type that provides enlarged base area.Identify screw pile as best fit.Exclude H- and pipe piles unless driven to firm strata; disc piles are uncommon choices.

Verification / Alternative check:
Case histories show screw piles supporting boardwalks, sign gantries, and light buildings in soft ground with minimal spoil and vibration.

Why Other Options Are Wrong:

• H/pipe piles: may work but often require deeper penetration to competent layers.
• Disc pile: nonstandard in many modern practices.
• None of these: incorrect because screw piles are a recognized solution.

Common Pitfalls:
Ignoring potential negative skin friction where future consolidation occurs; connection details to the superstructure must be designed for torque/axial demands.

Final Answer:
Screw pile