SYNERGISTIC EFFECTS OF LIME, CRUSHED SAND, AND GEOFIBER ON STRENGTH AND BEARING CAPACITY OF EXPANSIVE SOILS

Abstract

Black cotton (BC) soil, a highly expansive clay prevalent across the Deccan Plateau of India, poses serious challenges in geotechnical and pavement engineering applications due to its high plasticity, low strength, and significant swelling–shrinkage behavior. The present study investigates a hybrid stabilization approach incorporating lime, crushed sand, and polypropylene geofiber to improve the engineering properties of BC soil. A comprehensive experimental work was conducted using varying proportions of lime (2–10%), crushed sand (5–40%), and geofiber (0.1–0.5%). Standard Proctor compaction tests, unconfined compressive strength (UCS) tests at 28 and 56 days of curing, and soaked California Bearing Ratio (CBR) tests were performed.

The results shows that increasing lime content reduces maximum dry density (MDD) while increasing optimum moisture content (OMC), attributed to flocculation–agglomeration and pozzolanic reactions. Significant improvement in strength characteristics was observed, with UCS increasing from 142 kPa for untreated soil to 1345 kPa at 28 days for an optimal mix of 6% lime, 15% crushed sand, and 0.3% geofiber, representing an enhancement of approximately 847%. The soaked CBR value improved from 1.8% to 28.5%, far exceeding the minimum requirement of 8% as per IRC: 37-2012 guidelines for subgrade materials.

The results confirm that the combined effect of chemical stabilization, granular modification, and fiber reinforcement produces a synergistic improvement in soil performance. The proposed ternary stabilization system offers a scalable, cost-effective, and sustainable solution for enhancing the load-bearing capacity and durability of expansive soils in pavement subgrade applications.