Soil Stabilization Methods – What Is “Mechanical” Stabilization? In highway and geotechnical practice, mechanical stabilization of soils primarily involves which action to improve gradation and strength for bases/sub-bases or embankments?

Introduction / Context:
Stabilization improves soil performance by altering gradation, plasticity, or bonding. Broadly, techniques are categorized as mechanical (physical mixing and compaction) and chemical (additives such as lime, cement, fly ash, polymers). Understanding the distinction guides selection for cost, availability, and environmental constraints.

Given Data / Assumptions:

• Objective: Improve bearing capacity, stiffness, and durability of soil layers.
• Constraints: Prefer methods without chemical reactions for “mechanical”.
• Common field targets: sub-bases, bases, embankments.

Concept / Approach:

Mechanical stabilization blends soils of different particle-size distributions (e.g., well-graded gravel with fines) to achieve dense packing and lower void ratio under compaction. The improved gradation reduces permeability and increases shear strength without relying on chemical reactions. Chemical stabilization, in contrast, uses lime, cement, or other additives to alter clay mineralogy or create cementitious bonds.

Step-by-Step Solution:

Verification / Alternative check:

Gradation envelopes ( Fuller/ Talbot ) and Proctor compaction curves demonstrate improved maximum dry density and CBR after appropriate blends, confirming mechanical stabilization effects.

Why Other Options Are Wrong:

• Adding chemicals, lime, or cement: all are chemical stabilization, not mechanical.

Common Pitfalls:

Confusing “mechanical stabilization” with mechanical compaction alone; the term typically implies blending plus compaction.

Final Answer:

Mixing two or more types of natural soils