Highway Materials MCQ with answer and solution

Concept

Modulus of Subgrade Reaction

Formula

k = q / δ

Step-by-step solution

1. Identify the applied pressure (q) and the resulting settlement (δ) from the test data. 2. Divide the pressure (q) by the settlement (δ) using the formula k = q / δ to calculate the modulus of subgrade reaction.

Explanation

The plate load test is a field test that applies a vertical load through a steel plate onto the soil and measures the resulting settlement. The modulus of subgrade reaction (k-value) represents the stiffness of the soil support, calculated as the pressure applied divided by the settlement produced. Therefore, the plate load test is specifically designed to estimate this parameter for foundation and pavement design.

Shortcut

Remember "Plate = Subgrade": Think of placing a heavy Plate on the ground (Subgrade) to see how much it reacts or settles.

Common mistake

Students often confuse tests for modulus of subgrade reaction with laboratory shear strength tests like the Triaxial test or Direct shear test, or in-situ density tests like the Sand replacement test, incorrectly assuming subgrade reaction is measured from shear parameters rather than a field plate settlement test.