Compaction effects: identify the incorrect statement about how compaction influences soil structure and behavior.

Introduction / Context:
Field compaction controls density and water content to achieve desired strength, stiffness, and permeability. The resulting soil structure (flocculated vs. dispersed fabric) and pore-size distribution strongly affect engineering properties, so it is crucial to understand what changes compaction actually induces.

Given Data / Assumptions:

• Compaction curves (dry vs. wet of optimum) apply.
• Fine-grained soils show marked structural differences across the curve.
• Statements are evaluated for general, widely observed behavior.

Concept / Approach:

(a) is incorrect because compaction alters particle arrangement and fabric, changing macro- and microporosity. (b) is generally true for silts and clays: higher dry density reduces void ratio and permeability. (c) is true: wet-side (more dispersed) structures are weaker and more compressible; dry-side (more flocculated) are stiffer but may be more collapsible upon wetting. (d) is true: dry-side compacted soils tend to swell more when later wetted due to collapsible structure and suction effects.

Step-by-Step Solution:

Verification / Alternative check:

Laboratory Proctor data and oedometer tests confirm differences in compressibility and swell between wet- and dry-side compaction.

Why Other Options Are Wrong:

(b)–(d) reflect standard observations; (e) is wrong because exactly one statement (a) is incorrect.

Common Pitfalls:

Overgeneralizing to coarse-grained soils (permeability trends are less pronounced in clean sands).

Final Answer:

Compaction has no effect on the structure of a soil