Weak soil is a major obstacle facing the urban development of any site with other exceptional merits. The current study aims to investigate the utilization of nano-silica in enhancing the mechanical properties of weak kaolin soils. Design mixes using different percentages of nano-silica were investigated in the range between 0.25-1.20% from the dry weight of the kaolin soil. Various chemical, physical, and mechanical properties of each mixture have been investigated. The obtained results indicated that nano-silica addition to such kaolin soils decreased the plasticity index and the maximum dry density while increasing the plastic limit, the Liquid limit, and the optimum moisture content. In different curing days of the tested mixtures, maximum dry density was decreased, while the optimum moisture content increased. The optimum value of added nano-silica was less than 1% of the soil dry weight. In the modified kaolin soil with 0.9% nano-silica, the plastic limit was increased by 29%, while the liquid limit decreased by 13% in comparison with the untreated sample. After 28 days of the cured sample, the unconfined compressive strength readings increased by almost 14% compared to its reading on day one. Also, the California bearing ratio results recorded significant enhancement with nano-silica additives in comparison with the untreated kaolin soil. After 28 curing days, the sonicated samples recorded enhancement in the unconfined compressive strength readings by more than 5% and 9% with the additive N-Si (0.3% and 0.9%), respectively, when compared with the unsonicated samples.

Landslide mitigation is one of the major challenges occurring in hilly and mountainous regions worldwide. Various civil construction-based options, such as constructing walls and making fences using wires and metallic mesh, are regularly employed in attempts to reduce the hazard, but these measures are temporary solutions to stop the movement of unstable soil. The problem of unstable soils could be solved by increasing the vegetation on the hilltops and mountains where soil erosion and mass movements are predominant. A bioengineering approach could resolve this problem in a sustainable way and without damaging the environment. Various methods and approaches have been adopted worldwide for landslide mitigation and are discussed and critically analyzed in this article. The effectiveness of bamboo plantations on the hilltops and the use of specific species as determined by the soil characteristics are discussed and elaborated. Some research gaps in the existing bioengineering aspects and scope of research are highlighted for further improvement and refinement.