Section 4: Soil and Water Conservation Engineering
Soil Mechanics
Subtopic: Soil compaction and Proctor test
Question Statement:
With an increase in compaction energy applied to a soil mass in a laboratory compaction test, the optimum moisture content (OMC) and maximum dry density (MDD) behave as:
Options:
(A) OMC decreases and MDD increases
(B) OMC increases and MDD increases
(C) OMC decreases and MDD decreases
(D) Both OMC and MDD remain unchanged
Answer Key:
A
Step-by-Step Solution & Explanation
As the compaction effort/energy increases (e.g. from Standard Proctor to Modified Proctor):
• The soil particles are packed more closely, resulting in an increased Maximum Dry Density (MDD).
• Less lubricating water is required to achieve the peak density, shifting the peak to a lower Optimum Moisture Content (OMC).