Soil Exploration MCQ with answer and solution

Concept

Soil exploration methods like SCPT have limitations regarding particle size; large coarse particles like gravel prevent the smooth penetration of the cone probe.

Step-by-step solution

1. Understand the working principle of the Static Cone Penetration Test (SCPT), which is pushed into the ground continuously. 2. Evaluate its suitability across different soil types based on grain size. 3. Fine-grained soils (clay, silt) and uniform sands offer smooth resistance without damaging the tip. 4. Coarse and hard particles like gravel cause high point resistance, potential damage, or refusal of the cone, making SCPT unsuitable for gravel.

Explanation

The Static Cone Penetration Test (SCPT) involves pushing a standard cone into the ground at a steady rate. While it works well in soft to stiff soils like clay, silt, and sand, the presence of large particles such as gravel, cobbles, or boulders can damage the equipment or obstruct penetration, making it unsuitable for gravelly soils.

Why the other options are wrong

A: Sand is suitable for SCPT as it allows smooth penetration and friction measurement. B: Silt is fine-grained and fully suitable for SCPT. D: Clay is soft and cohesive, making it ideal for SCPT.

Shortcut

Remember that penetrometer tests (CPT/SCPT) are generally restricted to soils without large coarse particles or gravel.

Common mistake

Confusing SCPT with Standard Penetration Test (SPT), which can handle gravelly soils to some extent with a solid cone drive point, though difficult.