1. What is Optimum Moisture Content?

The Optimum Moisture Content (OMC) is the water content at which a soil can be compacted to its maximum dry density using a specific amount of compaction energy. It's determined through standard Proctor or modified Proctor tests.

2. How Does the Calculator Work?

The calculator identifies the OMC from compaction test data:

Where:

• \( OMC \) — Optimum moisture content (%)
• Maximum dry density — Highest density achieved in compaction test (g/cm³)
• Moisture content — Water content at maximum density (%)

Explanation: The OMC represents the water content that allows soil particles to be packed most densely under specific compaction effort.

3. Importance of OMC

Details: Knowing the OMC is crucial for earthwork construction, as it ensures maximum density and strength with minimum compaction effort. It affects bearing capacity, settlement, and permeability.

4. Using the Calculator

Tips: Enter the maximum dry density from your compaction curve and the corresponding moisture content. Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between standard and modified Proctor OMC?
A: Modified Proctor uses higher compaction energy, typically resulting in higher maximum dry density and lower OMC than standard Proctor.

Q2: How does soil type affect OMC?
A: Cohesive soils generally have higher OMC than granular soils. Clay soils may have OMC around 15-25%, while sands may be 8-12%.

Q3: Why is field moisture content often different from lab OMC?
A: Field conditions (compaction method, lift thickness, soil variability) differ from controlled lab conditions.

Q4: What's the acceptable range around OMC for field compaction?
A: Typically ±2% of OMC is acceptable, but specifications may vary by project.

Q5: How often should OMC be determined?
A: Whenever soil characteristics change significantly or at the beginning of major earthwork projects.