Specific gravity of sands (particle density): What approximate value of Gs is typically used for clean quartzose sands in soil mechanics calculations?

Introduction / Context:For clean, quartz-rich sands, the particle specific gravity (Gs) clusters around a well-known value. This index is needed to translate between dry unit weight, void ratio, and saturation relationships, especially during preliminary design and quality control on earthworks and foundations.

Given Data / Assumptions:

• Sand is predominantly quartzose (silica-based).
• No significant heavy mineral content is assumed.
• Typical laboratory reference temperature conditions.

Concept / Approach:

Quartz has Gs ≈ 2.65; sands composed primarily of quartz are commonly taken as Gs ≈ 2.65 in textbooks. Among the given discrete options, 2.6 is the closest practical choice and is often rounded to in problem sets and field approximations.

Step-by-Step Solution:

Verification / Alternative check:

Materials data sheets and soil mechanics texts agree on Gs ≈ 2.65 for silica sands; rounding to 2.6 is common when coarse options are provided.

Why Other Options Are Wrong:

1.6 and 2.0 are far too low for mineral grains; 2.2 and 2.4 are also below typical quartz values and would imply significant light minerals.

Common Pitfalls:

Using bulk aggregate specific gravity (which includes absorption) instead of particle Gs; assuming the same Gs for iron-rich or heavy-mineral sands which can be higher.

Final Answer:

2.6