Which combined geotechnical and construction measures can significantly reduce the required structural thickness of a pavement while maintaining performance?

Introduction / Context:
Pavement thickness is dictated by support conditions and traffic loading. Improving subgrade quality and drainage often allows thinner, more economical pavement structures without compromising service life or performance.

Given Data / Assumptions:

• Traffic loading unchanged.
• Opportunity to improve subgrade properties and environment.

Concept / Approach:
Better compaction increases subgrade modulus and bearing capacity. Stabilisation (with lime, cement, or bitumen) further enhances stiffness and reduces plasticity. Effective drainage prevents saturation, reduces pore pressures, and increases resilient modulus. Combining these measures maximizes structural capacity for a given thickness, permitting thickness reduction safely.

Step-by-Step Solution:
Assess current subgrade CBR/modulus.Apply compaction to reach specified density (e.g., 98% MDD).Stabilise problematic soils to raise stiffness and reduce PI.Provide sub-surface and surface drainage to keep the water table low and layers dry.Redo pavement design with improved parameters; adopt reduced thickness if criteria are satisfied.

Verification / Alternative check:
Mechanistic–empirical design iterations show reduced layer thicknesses once resilient modulus/CBR improves and moisture is controlled.

Why Other Options Are Wrong:

• Each of A–C helps; the largest benefit arises from their combination, not from any single measure in isolation.

Common Pitfalls:
Ignoring drainage leads to seasonal failures; relying on compaction alone for highly plastic clays is inadequate.

Final Answer:
Combination of all the above