Frost action in soils — identify the correct statements regarding frost heave, volume change on freezing, suction below freezing, and the role of degree of saturation.

Introduction / Context:
In cold regions geotechnics, frost action can damage pavements, foundations, and utilities. Understanding frost heave mechanisms—ice lens formation, volumetric expansion of freezing water, and moisture migration due to suction—is critical for design and mitigation through soil selection, drainage, and insulation.

Given Data / Assumptions:

• Sub-freezing temperatures occur in the active layer.
• Soil contains frost-susceptible fines and access to moisture.
• Mechanisms include volume expansion and cryo-suction, not just simple freezing-in-place.

Concept / Approach:

Frost heave is the upward ground movement from ice lens growth. Water expands about 9% upon freezing, but the major heave is often due to ice lenses fed by water drawn through pores by suction gradients when the freezing front advances. Lower degree of saturation reduces available free water and capillarity, limiting heave potential.

Step-by-Step Solution:

Verification / Alternative check (if short method exists):

Empirical criteria (e.g., grain-size limits for frost susceptibility) and field observations corroborate that minimizing fines content and ensuring drainage (thus lowering saturation) mitigate heave.

Why Other Options Are Wrong:

Each individual statement is valid; selecting only one would ignore the comprehensive nature of frost action. Hence the inclusive option is correct.

Common Pitfalls (misconceptions, mistakes):

Assuming 9% expansion is the sole cause; neglecting water migration; overlooking that coarse non-frost-susceptible soils rarely heave even when freezing occurs.

Final Answer:

All of the above.