Strength enhancement of geotextile-reinforced fly-ash-based geopolymer stabilized residual soil

Soils in their natural form are often deemed unsatisfactory to be directly used as a construction material for their respective applications. Under such circumtances, employment of ground improvement techniques to better suit the soil for its function is typically the most economical approach. Consequently, the present research investigated into the beneficial effect of modernized soil treatment techniques, i.e., geopolymer stabilization using fly ash as the precursor and geotextile reinforcement, on the strength enhancement of natural residual soil. A series of unconsolidated undrained (UU) triaxial compression tests were carried out to assess variation of geopolymer stabilized residual soil strength based on the varying number of geotextile layers, geotextile arrangement, and confining pressures. It was found that the increase in the number of geotextile layers resulted in a corresponding rise in soil strength and stiffness. It was also discovered that placement of geotextile layers at sample regions which suffered the maximum tensile stress–strain during loading was more effective compared to random placement. Soil strength was observed to reduce with increasing confining pressure which demonstrated the effectiveness of utilizing geotextile reinforcement at greater depths below the ground to be less. Failure patterns showed that while unreinforced soil resulted in failure along a shear plane at an approximate angle of 45 + φ/2 (φ: angle of internal friction), reinforced samples demonstrated a bulging failure where the soil between adjacent layers of geotextiles appeared to bulge. The findings deemed the employment of geopolymer stabilization and geotextile reinforcement on natural residual soil very effective with regards to the enhancement of soil strength and stiffness.