This study conducted an experimental and numerical investigation on the stabilization of clayey subgrades using nano-silica and geogrid reinforcement. Nano-silica was incorporated in varying contents (0-4%) to assess its effects on Atterberg limits, compaction behavior, shear strength, and California bearing ratio. The results showed optimal performance at 2.5% nano-silica, with reduced plasticity index and enhanced dry density, cohesion, friction angle, and bearing capacity. A three-dimensional finite element model was developed to simulate subgrade behavior under cyclic loading, incorporating the effects of both nano-silica and geogrid layers. The model was calibrated using laboratory data to reflect observed settlement and stress distribution. The numerical results confirmed that nano-silica reduced settlement significantly up to the optimal content, while geogrid reinforcement further enhanced load distribution and reduced displacement. The combination of nano-silica and geogrid resulted in improved mechanical performance of the subgrade. These findings demonstrate the effectiveness of integrating chemical stabilization and mechanical reinforcement in clayey soils to improve structural capacity and reduce long-term deformation, providing a viable solution for pavement subgrade enhancement.

Soil stability is crucial for construction, traditionally achieved with cement, lime, and fly ash. However, challenges with weak subgrade soils have led to nanomaterials as a promising alternative. This review critically evaluates the application of nanomaterials in improving the physicochemical, mechanical, and microscopic properties of subgrade and underlying soils, based on 136 peer-reviewed studies published between 2002 and 2025. Eighteen nanomaterials were identified, with nano-silica being the most studied. Other notable ones include nano-clay, carbon nanotubes, nano-alumina, nano-magnesium oxide, nano-copper, and polymeric nanomaterials. The review reveals a predominant focus on fine-grained problematic soils, particularly soft clay and silty sand, primarily in research from Iran. Nanomaterials improved soil by reducing plasticity, enhancing compaction, boosting strength (unconfined compressive strength, California Bearing Ratio, shear strength), and lowering permeability through void-filling, pozzolanic reactions, and Calcium Silicate Hydrate gel formation. They also increased durability under freeze-thaw and wet-dry cycles while reducing cement usage. However, concerns remain about cost, scalability, and environmental safety, with gaps in field-scale studies and limited research on nano-ZnO, nano-CuO, and nano-graphene oxide. This review serves as a reference for sustainable geotechnical engineering.

This study evaluated the performance of cement-based grouts in compaction grouting. In the experimental study carried out, the simultaneous effects of fly ash (FA) and nano-silica (NS) on rheological and fresh-state as well as strength performances were investigated. In this context, 16 samples were prepared using 0%, 10%, 20%, and 30% FA replacement levels and 0%, 1%, 2%, and 3% NS content ratios at w/b = 0.75. Rheological characteristics and behavioral performance were defined with shear stress, apparent viscosity, yield stress, and plastic viscosity. Fresh-state performances, flow time with mini-slump, stability capacity with bleeding, and hardening periods with setting time were determined. In terms of mechanical performance, 28-day unconfined compressive strength (UCS) tests were carried out on grout samples. After the tests, the correlation relationship between them was examined using experimental data. The experimental results were performed with statistical analysis, and then, the contribution and impact levels of important parameters were evaluated. Test results showed that the simultaneous FA and NS influence resulted in reasonable outcomes in both the rheological and fluidity properties and caused a visible enhancement in the strength features., Statistically, NS content was dominant in rheological and fresh-state performance, while FA replacement was effective in strength features.

This research investigates the stabilization of infinite slopes in the Lesser Himalayan region using nano-silica (NS), employing analytical, numerical, and experimental techniques. The findings demonstrate significant improvements in slope stability, including an 800.3% increase in soil cohesion, a 320% rise in the factor of safety (FOS), and a 75% reduction in pore water pressure. These enhancements ensure the stability and safety of slopes in vulnerable terrains. This study aligns with multiple United Nations' Sustainable Development Goals (SDGs): fostering resilient infrastructure and innovation (SDG 9), enhancing community safety (SDG 11), supporting climate adaptation strategies (SDG 13), conserving land resources (SDG 15), and promoting sustainable material use (SDG 12). By addressing environmental challenges and advancing sustainable geotechnical solutions, this work contributes significantly to global efforts towards resilience and sustainability.

This study investigated the stabilization of fine-grained soil from the Indo-Gangetic plain using nano-silica (NS) and predicted the unconfined compressive strength (UCS) using advanced machine learning techniques. Experimental investigations were conducted on 118 UCS samples with NS contents varying from 0.5 to 4%. The results showed significant improvements in the soil plasticity, compaction characteristics, and UCS with NS incorporation. NS acted as a reinforcing agent, filling void spaces and improving interlocking between soil particles, leading to increased maximum dry density, reduced optimum moisture content, and notable improvements in the UCS. Microstructure analysis revealed the positive impact of NS on soil properties, attributed to enhanced durability, reduced swell strains, and improved strength due to the synergistic effects of NS particles. Furthermore, five innovative hybridized models based on artificial neural networks (ANN) and nature-inspired optimization algorithms were developed to predict the UCS of NS-stabilized fine-grained soils. The models demonstrated high accuracy, with R2 values exceeding 0.96 and 0.89 for the training and testing dataset. The ANN-Firefly algorithm (ANN-FF) model emerged as the most proficient predictor. This study highlights the importance of input parameters in model development and suggests that further research should focus on expanding experimental data to enhance model flexibility. The proposed approach offers significant implications for cost and time savings in experimental sample preparation and demonstrates the high capability of ANN to determine optimal values for soil stabilization techniques in the Indo-Gangetic plains.

Soil modification is an effective method for enhancing the mechanical properties, including its strength, deformation capacity, and dynamic mechanical stability. Nanomaterials have broad prospects in soil modification due to their small particle size, large specific surface area, and non-toxic and harmless properties. Using the laboratory dynamic triaxial test method, this paper presents a scientific evaluation on the dynamic stability and freeze-thaw resistance of loess modified with nano-silica. This study has investigated the effects of nano-silica content, dynamic stress amplitude, confining pressures, and freeze-thaw cycles on the cumulative deformation behavior of nano-silica modified loess subjected to cyclic loading. Based on the shakedown theory, the shakedown state of 60 samples was evaluated, and an equation for the critical dynamic stress of modified loess was established under the shakedown limit state. The experimental results show that nano-silica can effectively fill the micropores in soil and form a cohesive gel that enhances the bonding between soil particles, significantly increasing the cohesion of the loess due to its nanoscale (10- 9) small size. The 2.5 % content of nano-silica is the optimal dosage for reinforcing loess. Under the same confining pressure condition, the failure strength of the 2.5 % nano-silica modified loess is about 1.4-2.1 times that of the loess, and the residual strength is about 1.2-1.5 times that of the loess. The incorporation of nano-silica significantly improves the dynamic stiffness and freeze-thaw resistance of loess, increasing the reinforcement factor by 51 %-69 % under unfrozen conditions and still increasing it by 43 %-64 % after experiencing one freeze-thaw cycle. Similarly, nano-silica significantly enhanced the dynamic strength and strength parameters of loess. Nano-silica exerts an influence on the shakedown state of the soil, wherein the impact becomes more significant with increasing dynamic stress amplitude.

The Lesser Himalayan regions face significant geotechnical challenges due to unstable and erosive soil. This study investigates stabilizing these soils with Nano-silica (NS), a reliant additive that has been demonstrated to enhance soil mechanical properties. A comprehensive set of investigations, including multiple laboratory analyses, was conducted to evaluate the mechanical and physical characteristics of problematic soil stabilized with NS. The study also includes reliability analysis to assess the long-term performance and durability of the treated soil. The results of the experiment showed that adding NS greatly increased the soil's compressibility. More precisely, the right amount of NS increased the strength of the problematic soil and resulted in a notable rise in compressibility. According to the durability test results, stabilizing problematic soil with NS and allowing it to cure preserves its improved properties for an extended length of time. Reliability research utilizing probabilistic methodologies showed that applying NS considerably decreased the likelihood of problematic soil failure. The findings show that NS has the potential to be a stable, troublesome soil stabilizer that can lower the probability of soil failure in the Lesser Himalayan regions over the long run. This work provides a foundational understanding for future applications and paves the way for the construction of more robust infrastructure in mountainous terrain.

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.

This paper examines the effect of nano-silica and cement on the geotechnical properties of bentonite, both individually and in combination. For this objective, the nano-silica and cement contents were adjusted from 0.2 to 1% and from 4 to 8% by dry weight of bentonite, respectively. This investigation revealed that the plasticity index reduced from 243.82 to 215.19% and then from 243.82 to 201%, equivalent to a nano-silica and cement content of 0.8% and 8%, respectively. The mixture containing 8% cement and 0.8% nano-silica in bentonite had the lowest plasticity. Raising the amount of nano-silica, cement, or their combination in bentonite enhanced both the optimum moisture content and the dry unit weight. The compressive, tensile and CBR strengths of bentonite were improved after addition of nano-silica, whereas further enhancement was noticed after additional mixing of cement. The maximum axial stress, tensile stress and bearing ratio were measured in 0.8NS8C mix after 28 days. After 28 days of curing, the axial stress of mix 0.8NS4C was 1.44, 1.22 and 1.09 times, whereas tensile stress for the same was 1.24, 1.12 and 1.04 times greater than 4C, 6C and 8C, respectively. The CBR % in 0.8NS8C mix observed increment from 27.11 to 60.9% and 22.5% to 44.51% in un-soaked and soaked condition, respectively, after 28 days. The improved strength properties were attributed to the advance bonding characteristics due to formation of pozzolanic products (calcium silicate hydrate) after curing. SEM images of treated bentonite reveal denser and stiffer matrix with detection of newly formed pozzolanic products (calcium silicate hydrate gel). FTIR spectrum also reveals formation of new chemical compounds after ion exchange process indicated with broader band width in the region of wavenumber between 600 and 1500 cm-1 as noticed in 0.8NS and 0.8NS8C mixes.

Because soft clays have a greater tendency to swell and shrink, structures constructed on them face the danger of suffering uneven settlement, which may result in structural damage. Numerous attempts have been made to stabilise the soil by the mean of mechanical and chemical stabilization. In recent years, several researchers intended to change the geotechnical characteristics of problematic soils with the help of Nano-additives such as Nano-silica, Nano-clay, Nano-lime, Nano-carbons. This study is focused on summarising the change in strength, mineralogical and morphological behaviour of soil with the incorporation of Nano-silica and Nano-silica-based compounds reported by researchers. It was observed that strength of soil improved drastically with the addition of Nano-silica and Nano-silica-based compounds up to optimum dosages. The inclusion of Nano-silica densifies soil due to the filling effect, formation of better interparticle bond and pozzolanic products. From the detailed review of literature, it can be concluded that it is advantageous to incorporate Nano-silica and Nano-silica-based compounds to improve the geotechnical properties of problematic soils.