Understanding Soil Densification by Mechanical Manipulation

The question asks for the specific term used to describe the process of increasing the density of soil through the application of mechanical energy. This process is crucial in construction and geotechnical engineering to improve the soil's strength, reduce settlement, and control volume changes.

Analyzing the Options for Soil Densification

Let's examine each of the provided options to understand their meaning in the context of soil mechanics:

• Compressibility: This refers to the property of a soil that allows it to decrease in volume under applied pressure. It's a material property, not a process of mechanical manipulation.
• Soil stabilization: This is a broader term that involves improving soil properties (like strength, durability, or plasticity) by adding admixtures (like cement, lime, or asphalt) or by mechanical means (like compaction). While compaction is a form of mechanical stabilization, the term "stabilization" itself is more general.
• Compression: This is the decrease in volume of soil when subjected to stress. It occurs naturally under loads (like foundations) and over time, especially due to the expulsion of water from the voids. This is a phenomenon, not necessarily a process of mechanical manipulation aiming at densification.
• Compaction: This is the process of densifying soil by reducing the air voids within it using mechanical energy. This involves rearrangement of soil particles through techniques like rolling, tamping, or vibration. It is a controlled process done during construction to improve soil properties.

Comparing Soil Compression and Compaction

It's important to distinguish between compression and compaction in soil mechanics. A simple comparison helps clarify their differences:

As the table shows, compaction specifically relates to the mechanical process used to densify soil by reducing air voids.

Identifying the Correct Term for Mechanical Densification

Based on the definitions, the term that precisely describes the densification of soil through mechanical manipulation (like rolling, tamping, or vibrating) to reduce air voids and increase dry density is compaction.

Therefore, the densification of a soil by means of mechanical manipulation is called compaction.

Revision Table: Key Terms in Soil Mechanics

Additional Information on Soil Compaction Importance

Compaction is a critical step in civil engineering projects such as road construction, dam building, and foundation preparation. Proper compaction helps in:

• Increasing the shear strength of the soil, which improves its ability to support loads.
• Reducing the soil's compressibility, minimizing future settlement under structures.
• Decreasing permeability, which helps control water flow and reduces frost heave potential.
• Preventing excessive shrinkage and swelling caused by changes in moisture content.

The degree of compaction is usually measured by the dry density of the soil achieved in the field compared to a standard maximum dry density determined in a laboratory test (like the Standard Proctor test or Modified Proctor test).