Water Content Determination for Coarse-Grained Soil – Preferred Practical Method When a soil sample contains coarse grains (sands/gravels) and you need to determine its water content efficiently, which method is generally preferred in practice?

Introduction / Context:
Different water content methods suit different soil types and field conditions. Coarse particles complicate some procedures due to time, heat transfer, and representativeness issues; hence choosing the right method improves accuracy and efficiency.

Given Data / Assumptions:

• Soil has noticeable coarse fraction (sand or small gravel).
• Routine lab practice; not necessarily a time-critical site test.
• Need a reliable, repeatable result.

Concept / Approach:

The pycnometer method is well suited to coarse soils because drying can be slow and non-uniform in gravels, whereas measuring displaced water volumes and masses is straightforward. While oven-drying is a universal reference, large particles and trapped moisture may require long drying times and big ovens. The calcium carbide method is handy in the field but is more error-prone with coarse, non-uniform aggregates. The alcohol method is mainly used for fine sands/silts where ovens are unavailable.

Step-by-Step Solution:

Verification / Alternative check:

Standards and many lab manuals list pycnometer and oven-drying as acceptable; in comparative practice, pycnometer is often preferred for coarse fractions when quick, reliable results are needed without prolonged oven cycles.

Why Other Options Are Wrong:

Oven-drying is accurate but can be inefficient for coarse grains; calcium carbide can be affected by particle size and sample representativeness; alcohol method is less common for coarse soils.

Common Pitfalls:

Insufficient sample mixing; ignoring surface moisture on large particles; not correcting for absorbed water when using rapid methods.

Final Answer:

Pycnometer method