To mitigate the negative environmental effects of the overuse of conventional materials—such as cement—in soil improvement, sustainable engineering techniques need to be applied. The use of biopolymers as an alternative, environmentally friendly solution has received a great deal of attention recently. The application of lignin, a sustainable and ecofriendly biobased adhesive, to enhance soil mechanical properties has been investigated. The changes to engineering properties of lignin-infused soil relative to a lignin addition to soil at 0.5, 1, and 3.0 wt.% (including Atterberg limits, unconfined compression strength, consolidated undrained triaxial characteristics, and mechanical properties under wetting and drying cycles that mimic atmospheric conditions) have been studied. Our findings reveal that the soil’s physical and strength characteristics, including unconfined compressive strength and soil cohesion, were improved by adding lignin through the aggregated soil particle process. While the internal friction angle of the soil was slightly decreased, the lignin additive significantly increased soil cohesion; the addition of 3% lignin to the soil doubled the soil’s compressive strength and cohesion. Lignin-treated samples experienced less strength loss during wetting and drying cycles. After six repeated wetting and drying cycles, the strength of the 3% lignin-treated sample was twice that of the untreated sample. Soil treated with 3% lignin displayed the highest erosion resistance and minimal soil mass loss of ca. 10% under emulated atmospheric conditions. This study offers useful insights into the utilization of lignin biopolymer in practical engineering applications, such as road stabilization, slope reinforcement, and erosion prevention.

Human activities have had a profound impact on the environment, particularly in relation to surface erosion and landslides. These processes, which are natural phenomena, have been exacerbated by human actions, leading to detrimental consequences for ecosystems, communities, and the overall health of the planet. The use of lignin (LIG) as a biopolymer soil additive material is regarded as an eco-friendly solution against soil erosion and slope failure which holds immense promise. However, significant research gaps currently hinder a comprehensive understanding of its mechanisms and effectiveness. Experimental studies offer a robust platform to address these gaps by providing controlled conditions for assessing soil stability, exploring mechanisms, and evaluating adaptability. Bridging these research gaps will contribute to the development of innovative and sustainable strategies for mitigating soil erosion and preventing slope failure, thereby promoting environmental resilience and resource conservation. This study aimed to investigate the effect of the LIG biopolymer on mitigation of soil erosion, slope failure and the enhancement of soil strength by conducting laboratory tests (UU triaxial, unconfined compressive strength (UCS), and soaking) as well as flume experiments under uniform rainfall events. The alterations in the engineering characteristics and erosion resistance of silty soil mixed with a LIG additive at concentrations of 1% and 3.0% by weight have been examined. The results show that the LIG-treated samples demonstrated an enhanced resistance to surface erosion and an enhanced prevention of slope failure, as well as improved shear stress, cohesion, stiffness, and resistance to water infiltration.

The improvement of soft clay and dredged soils to carry structures is increasingly important. In this study, the dynamic behavior of a crushed stone foundation wall in clay soil was analyzed using a 1g shaking table test. The response accelerations and spectra for three input ground motions were analyzed relative to the distance from the foundation wall, confirming that the acceleration was damped from the outside. The acceleration according to the distance from the wall was not significant under long-period motions, while different responses were obtained under short-period motions. The increased ground stiffness provided by the crushed stone wall lowered the natural period of the ground, and the acceleration amplification under short-period seismic waves was larger than that under long-period waves. Finally, equations were derived to describe the relationship between the acceleration amplification ratio and distance from the wall. The slopes of the proposed equations are larger under shorter periods, implying that the change in acceleration change with distance from the wall is more significant under shorter periods. The results of this study can be used to inform the design of soft soil improvements and the structures built atop them.

Ground liquefaction is causing great damage to the structure of land during earthquakes. Accordingly, various liquefaction damage reduction methods have been studied and developed. However, most of the ground liquefaction prevention methods have limitations in their application to existing structures. Therefore, in this study, a ground liquefaction damage reduction method, applicable to existing structures, was studied using the grouting method. A 1-G shaking table test was performed, and the ground was created with Jumunjin standard sand. A two-story model structure was manufactured by applying the similarity law, and an input wave applied a sinusoidal motion with an acceleration level of 0.6 g and a frequency of 10 Hz. The grouting chemical was produced by mixing water and cement, and the effect of reducing structural damage was analyzed according to various mixing ratios; in addition, the separation distance between the grouting chemical injection point and the structure was analyzed. As a result of the analysis, when the ground was reinforced by applying the grouting method, the settlement of the structure was about 84% smaller than when the ground was not reinforced, and the mixing ratio with the smallest settlement was 0.45. In addition, when there was no separation distance between the structure and the grouting chemical injection point, it was confirmed that the effect of reducing structural damage was the greatest. These research results will be used as basic data for developing a grouting method applicable to existing structures in the future.

Global warming is becoming worse owing to carbon dioxide emissions around the world, and eco-friendly energy for reducing carbon dioxide emissions is gaining importance. Wind power plants are the most representative of the environmentally friendly energy power plants built in the ocean. The fatigue loading and long-term dynamic behavior of offshore soils are important considerations in the construction of structures such as wind turbines in the ocean as they are subject to long-term loads such as wind and wave loads. A design graph presents the short- and long-term behaviors of soil. Several laboratory tests are typically conducted to create design graphs. In this study, a cyclic simple shear test conducted at various confining pressures and relative densities is presented in design graphs. The authors analyzed the sensitivity of the relative density and the confining pressure, and proposed a drawing technique to easily create two-dimensional design graphs. The authors found that the effect of the relative density on the design failure curve was higher compared with that of the confining pressure. The elliptic equation graph achieved the best match to the design failure curve, and the design failure curve drawing technique was summarized in five stages. In addition, the normalized cyclic stress ratio graph to distinguish safety or failure was presented.

Retaining walls are generally used for temporary installations during the excavation process of a construction project. They are also utilized to construct embankments in order to extend a railway facility. In this case, a retaining wall is installed during the construction process and contributes to the resistance of large amounts of stress, including the railway load. However, it is generally difficult to retain walls to maintain their stability. Therefore, alternative construction methods, such as the use of an inclined earth-retaining wall, have been utilized to suppress the lateral displacement. The stability is verified in advance through field tests; however, the maximum stress acting on the railway is thought to be the concentrated railway load. In this study, a two-dimensional numerical analysis was conducted by changing the railway load to a dynamic load. The analysis was applied according to the number of H-piles of the same length (10 m) when only the front wall was installed and when a back support was also applied. It was determined that the lateral displacement of the latter case is smaller than that of the former, whereas the resistance to dynamic loading of the former case is greater.