Reinforcement of soft clay soils with basalt geogrid

Soft clay soils are among the most challenging geotechnical materials due to their low bearing capacity, excessive settlement, and susceptibility to deformation under applied loads. These properties often necessitate soil improvement techniques to enhance the performance of infrastructure built on such soils. Various methods have been developed to address these challenges, with geosynthetics emerging as an effective and versatile solution. Geosynthetics are widely used in geotechnical engineering due to their functions of reinforcement, separation, filtration, drainage, and erosion control. This study focuses on the use of basalt geogrid, a geosynthetic material, to reinforce soft clay soils and evaluates its effectiveness through a series of laboratory and field tests. Basalt geogrids are produced from basalt fibers, which are derived from volcanic rocks. These fibers exhibit excellent mechanical properties, including high tensile strength, durability, and resistance to chemical and environmental degradation. Additionally, basalt geogrids are environmentally friendly, as they are made from natural materials and can be recycled. These attributes make basalt geogrids a promising alternative to traditional synthetic geosynthetics in soil improvement applications. In this research, soft clay soil with 69% fine content and low plasticity (classified as CL according to the Unified Soil Classification System) was selected as the test material. The soil's physical properties were determined through laboratory tests, including liqid limits, particle size distribution, and compaction characteristics. The optimum water content and maximum dry unit weight of the soil were found to be 17% and 16.65 kN/m3, respectively. To assess the reinforcing effect of basalt geogrid, California Bearing Ratio (CBR) tests were conducted under both dry and soaked conditions. The experimental program included three configurations: unreinforced soil, soil reinforced with a single layer of basalt geogrid, and soil reinforced with two layers of basalt geogrid. The geogrid layers were placed at specific depths within the soil specimens to optimize their reinforcing effect. In the unreinforced state, the dry and soaked CBR values of the soil were 7.24% and 6.44%, respectively. With the addition of a single geogrid layer, these values increased to 15.19% and 4.27%. When two geogrid layers were used, the dry and soaked CBR values further improved to 16.71% and 5.60%, respectively. These results demonstrate the significant enhancement in soil strength provided by basalt geogrid under dry conditions. The study also examined the swelling behavior of the soil during soaked CBR tests. The swelling values for all configurations were approximately 1.80 mm, indicating minimal variation in this parameter despite the presence of geogrid reinforcement. However, a notable reduction in CBR values was observed under soaked conditions, particularly for geogrid-reinforced specimens. This reduction suggests that the reinforcing effect of basalt geogrid diminishes in the presence of water, which could be attributed to the loss of interfacial friction between the geogrid and the surrounding soil. To better understand the performance of basalt geogrid in soil reinforcement, load-settlement behavior was analyzed. The load-settlement curves revealed that the inclusion of basalt geogrid significantly reduced settlement and increased the bearing capacity of the soil. This improvement was more pronounced under dry conditions, where the geogrid effectively distributed the applied load and limited soil deformation. In contrast, the presence of water weakened the soil-geogrid interaction, reducing the overall effectiveness of the reinforcement. Field tests were also conducted to validate the laboratory findings. Plate load tests were performed on natural and geogrid-reinforced soils to evaluate their bearing capacity and deformation characteristics. The results confirmed the laboratory observations, showing substantial improvements in bearing capacity and settlement reduction for geogrid-reinforced soils. These findings highlight the potential of basalt geogrid as a cost-effective and sustainable solution for reinforcing soft clay soils in various geotechnical applications. The performance of basalt geogrids was also evaluated in terms of their interaction with the soil particles. The apertures of the geogrid allowed for an effective mechanical interlock with the soil, contributing to enhanced load transfer and reduced deformation. This interlock mechanism proved to be more efficient under dry conditions, as the absence of excess water ensured stable soil-geogrid contact. However, under soaked conditions, the increased moisture content reduced interfacial friction, thus limiting the reinforcement efficiency. These findings underscore the importance of considering environmental factors, such as water table fluctuations, during the design phase. Additionally, the environmental benefits of basalt geogrids were highlighted in this study. Compared to traditional geogrids made from synthetic polymers, basalt geogrids are produced from a natural and abundant resource, making them a sustainable choice for soil reinforcement applications. Their high resistance to UV radiation and chemical degradation further enhances their suitability for long-term use in challenging environmental conditions. These properties position basalt geogrids as a promising alternative for geotechnical projects aiming to balance performance with sustainability. The results of this research suggest several avenues for future studies. For example, the long-term durability of basalt geogrids under cyclic loading and varying environmental conditions should be investigated. Furthermore, the combination of basalt geogrids with other soil stabilization techniques, such as chemical additives or prefabricated vertical drains, could be explored to optimize the reinforcement effects. Such hybrid solutions may mitigate the limitations observed under soaked conditions and further enhance the applicability of basalt geogrids in waterlogged or high-moisture environments. Another area for further exploration is the economic feasibility of large-scale applications of basalt geogrids. While their mechanical properties and environmental advantages are evident, a comprehensive cost-benefit analysis comparing basalt geogrids to conventional materials is essential. This would help establish guidelines for their use in infrastructure projects, particularly in regions with abundant basalt resources. Moreover, numerical modeling and simulation techniques could be employed to further investigate the interaction between basalt geogrids and various soil types. Advanced finite element analysis tools can provide valuable insights into the stress distribution and deformation mechanisms in reinforced soil systems. Such analytical approaches would enhance the understanding of reinforcement behavior under complex loading and boundary conditions, and support the development of design guidelines tailored to different project requirements. It is also recommended that future studies investigate the long-term environmental impacts of basalt geogrid usage, including lifecycle assessments and degradation patterns in different climates. Understanding how basalt geogrids perform over time, both structurally and environmentally, is crucial for establishing their reliability in sustainable infrastructure systems. In conclusion, the study demonstrated that basalt geogrids significantly enhance the bearing capacity and stability of soft clay soils, particularly in dry conditions. While their performance under soaked conditions is comparatively limited, basalt geogrids remain a viable and sustainable option for a wide range of applications, including road construction, embankments, and retaining walls. Future research should focus on hybrid reinforcement techniques, combining basalt geogrids with other soil stabilization methods to mitigate the effects of water and further optimize performance. Moreover, long-term field studies are recommended to evaluate the durability and effectiveness of basalt geogrids under varying environmental and loading conditions. This research contributes valuable insights into the potential of basalt geogrids and provides a foundation for advancing sustainable soil improvement practices in geotechnical engineering.