In this study, a mixing procedure of sulfur-rich soil and cement-based binder to enhance the soil’s unconfined compressive strength (UCS) was tested in field conditions for geotechnical applications. The focus was to evaluate uniformity of industrial size soil-binder mixture, blended by existing method. This paper outlined sampling strategy and the number of samples needed for a valid uniformity evaluation. Moreover, this study emphasized the difference between field mixing and laboratory mixture preparation by comparing UCS of stabilized soil samples in the field and UCS of corresponding samples mixed and prepared in the laboratory environment. In the field, soil and cement were blended in two to four stages with 5% and 7% cement—the percentages being based on the soil’s dry weight under field conditions. Samples were taken from the field mixtures after each stage. Since the number of samples needed to be representative of mixture characteristics for large-scale mixing is not standardized, this field experiment included two phases. The first phase was dedicated to finding a sampling strategy for a large soil pile along with measuring UCS of collected samples. In the second phase, sample collection was conducted based on the results of sampling strategy from the first phase. In the laboratory, samples with percentages of binder similar to the amount of binder in the field were also prepared. Both field and laboratory samples were prepared using the tapping method in the laboratory for UCS test. Samples were cured under similar conditions for 28 days. The results showed that the uniformity of mixture improved after each additional mixing stage. In addition, while spots with low UCS were observed in the second mixing step, these spots were eliminated in the third mixing step, and results of the UCS tests were comparatively uniform. Moreover, comparison of the samples revealed that the UCS of the laboratory mixture is higher than that of the field mixture. This showed that even though the UCS is a good standard for comparing the strength of different soils stabilized with different percentages or types of binders in the field mixing, the actual strength of the stabilized mixtures under field circumstances is lower than that in laboratory prepared mixtures.

A laboratory investigation was conducted to identify principal variables-initial mixing water content, porosity, and binder content- impacting undrained shear strength (qu) of stabilized sulfur-rich silty soil. An equation for predicting qu of stabilized soil was established based on the experimental data. Initially, samples were prepared with soils sample with different initial water and binder contents. Multicem, a binder consisting of a mix of cement and cement kiln dust, was added to the samples. Three different percentages of Multicem were mixed at five different soil water contents to measure qu of stabilized mixtures to understand how water content and porosity levels in the samples affect the performance of the binder and their combined impact on the strength of the samples. The soil-binder mixtures were compacted and subsequently cured in laboratory-controlled environment. The prepared samples were tested in uniaxial compression test apparatus. The results evidenced that binder content and corresponding porosity affect the strength of specimens at an equal water content. The results showed that at equal initial mixing water content, the qu of a sample increased by increasing binder content. Furthermore, it was observed that increase of binder content has a reverse effect on porosity. It was appeared lowering the soil water content, initially increased the strength until an optimum water content. Further lowering water content increased the porosity and consequently decreased qu of samples. Moreover, a ratio of porosity/volumetric binder content was chosen to evaluate the impact of these two variables on strength of samples. This study showed that qu is an exponential function of porosity/binder volumetric content ratio which depends on initial mixing water content of mixtures. It was shown at water content lower than the optimum, results of stabilization are more effective than in soil at higher water contents. Therefore, reducing the water content and thereby porosity has more significant effect on improving qu than increasing the binder content.

Sulfide-rich soils contain iron monosulfides and disulfides, which can oxidize under aerobic conditions when the soil is drained, facilitating oxygen diffusion and leading to the acidification of surrounding watercourses. This type of soil is often excavated due to its unsuitable geotechnical properties. As a result, soils with acidification potential need to be safely transported and deposited in landfills. Moisture content plays a crucial role in controlling the oxidation process, as maintaining optimal moisture levels limits oxygen diffusion, thereby preventing oxidation and acid generation. This study uses numerical modeling using SEEP/W to predict moisture fluctuations in sulfide soil landfills under various conditions. It further investigates the effects of soil properties, weather conditions, and landfill cover thickness on landfill performance, focusing on their role in maintaining moisture levels that inhibit sulfide oxidation. Results indicate that soil hydrological properties have a significant impact on saturation levels in the landfill, independent of other parameters. Adding a capillary break positively affects the moisture levels period studied, and a thicker cover enhances moisture retention. Keeping the water table close to the surface helps the system recover water lost due to evaporation and weather changes. These findings showed the current cover design practices, mandating uniform 1-meter cover thickness for all sulfide soil landfills is over-design in some cases and provide helpful insights for developing effective management plans to mitigate environmental risks and optimize landfill construction.

Due to their silty texture and high organic content, sulfide soils are typically unsuitable for use as a foundation for construction projects. In most cases, excavation and replacement with other construction materials are needed to ensure the structural integrity of building or infrastructure. Landfills are commonly used for the disposal of excavated sulfide soil. Because of the chemical properties of these soils and the risk of acidification, these landfills need to be kept saturated to limit oxygen diffusion. However, the long-term behaviour of these landfills is not yet fully understood, highlighting the need for further research to investigate the fluctuation of the degree of saturation in the soil, under different conditions. This study examined the effect of seasons on the degree of saturation in sulfide soil landfills and its effect on oxygen transport. The objective of the current study was to validate a numerical model of a sulfide soil embankment, done using SEEP/W software, with data from the monitoring of a sulfide soil landfill, in Northern Sweden. A one-dimensional numerical model of the landfill was created using laboratory measurements of hydraulic conductivity and water retention capacity. This model was then validated by comparing it with data from installed sensors. The numerical model accurately predicted the degree of saturation changes over time in the landfilled soil. These findings allow engineers to optimize design and predict long-term performance under different environmental conditions. The study highlights the importance of numerical modelling in predicting long-term hydrological behaviour and offers valuable insights into sulfide soil landfill behaviour.