Experimental Investigation on the Use of Geogrid Between Pavement Layers for Subgrade Improvement

• Geogrid reinforcement significantly improves the engineering properties of black cotton soil stabilised with GGBS slag as pavement subgrade material. • CBR value shows a notable increase from soil alone to soil+slag+geogrid, confirming enhanced load-bearing capacity. • Peak shear stress improved from 0.54 to 0.60 kg/cm² at 1.5 kg/cm² normal stress with slag and geogrid addition. • Shrinkage limit increased from 9.82% to 11.82% with slag, indicating reduced volumetric change susceptibility of the expansive soil. • Geogrid is an effective, practical subgrade stabilisation solution offering higher strength and improved bearing capacity without mortar or specialised equipment. • Future work should extend to field-scale trials and evaluation of long-term performance under cyclic traffic loading.

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