A wide range of microorganisms produce extracellular polymeric substances (EPS), highly hydrated polymers that are mainly composed of polysaccharides, proteins and DNA. EPS are fundamental for microbial life and provide an ideal environment for chemical reactions, nutrient entrapment and protection against environmental stresses such as salinity and drought. Microbial EPS can enhance the aggregation of soil particles and benefit plants by maintaining the moisture of the environment and trapping nutrients. In addition, EPS have unique characteristics, such as biocompatibility, gelling and thickening capabilities, with industrial applications. However, despite decades of research on the industrial potential of EPS, only a few polymers are widely used in different areas, especially in agriculture. This review provides an overview of current knowledge on the ecological functions of microbial extracellular polymeric substances (EPS) and their application in agricultural soils to improve soil particle aggregation, an important factor for soil structure, health and fertility.

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Microbial Extracellular Polymeric Substances: Ecological Function and Impact on Soil Aggregation.

Three-dimensional numerical simulation of a mechanized twin tunnels in soft ground

The inter-particle coefficient of friction at the contacts of Leighton Buzzard sand quartz minerals

Experimental tests on effect of deformed prefabricated vertical drains in dredged soil on consolidation via vacuum preloading

Various applications of biopolymer-based soil treatment (BPST) in geotechnical engineering have been implemented in recent years, including dust control, soil strengthening and erosion control. Despite BPST methods can ensure the effectiveness of engineering while meeting environmental protection requirements, BPST technology requires further validation in terms of site applicability, durability, and economic feasibility. This study aims to provide a state-of-the-art review and future prospective of BPST. Current biopolymer types, engineered and assessed in laboratory scales, are described along with site implementation attempts. The effect of biopolymers on soil behavior is reviewed with regard to geotechnical engineering application and practice, including soil consistency limits, strength parameters, hydraulic conductivity, soil-water characteristics, and erosion control. The economic feasibility and sustainability of BPST application in ground improvement and earth stabilization practices is discussed. This review postulates biopolymers to be a promising new, environmentally friendly ground improvement material for geotechnical and construction engineering practice.

https://koasas.kaist.ac.kr/bitstream/10203/276070/1/000559046300002.pdf

Review on biopolymer-based soil treatment (BPST) technology in geotechnical engineering practices

Strength durability of gellan gum biopolymer-treated Korean sand with cyclic wetting and drying

Effects of spatially variable weathered rock properties on tunnel behavior

By quantifying the displacement and crack propagation during the excavation of a new tunnel constructed near an existing tunnel, the influence of the size of the existing tunnel, the distance between tunnel centers, and the earth pressure coefficient, K on the mechanical behavior of existing and new tunnels was investigated and analyzed. A series of experimental model tests was performed and analyzed. It was found that the displacements decreased and stabilized as the distance between tunnel centers increased depending on the size of the existing tunnel. Consequently, a 3.0D distance between tunnel centers for Model Test I and 1.2D for Model Test II are required conservatively to avoid the tunnels being influenced by each other. It was also found that regardless of the distance between tunnel centers, displacements are reduced and hence the stability of the pillar can be secured as the earth pressure coefficient increases. This fundamental insight provides the basis for a more rational design of closely spaced twin tunnels.

Influence of existing tunnel on mechanical behavior of new tunnel

By quantifying the evolution of void ratio in granular soils of different angularity under different normal stress levels adjacent to geomembranes of varying roughness at different stages of shearing, the effect of geomembrane surface roughness on the interface shear mechanisms between granular materials and geomembranes was investigated. The extent of the shear zone thickness at the interfaces between combinations of round/angular particles and smooth/textured geomembrane surfaces were evaluated. For smooth geomembranes, the interface shear strength is developed by sliding and plowing of sand particles, while for textured geomembranes, the strength results from the interlocking and dilation of sand particles. Study on the effect of particle angularity showed that more angular sand particles resulted in larger plowing effects with smooth geomembranes which in turn yielded higher residual friction angles than with rounded to sub-rounded sand. Higher normal stress produced larger plowing effects for a given sand sheared against a smooth geomembrane and reduced the amount of dilation adjacent to textured geomembranes.

Microscale geomembrane-granular material interactions

https://www.jstage.jst.go.jp/article/sandf/51/4/51_4_701/_pdf

Seok-Won Lee

Papers

Strength durability of gellan gum biopolymer-treated Korean sand with cyclic wetting and drying

Effects of spatially variable weathered rock properties on tunnel behavior

Influence of existing tunnel on mechanical behavior of new tunnel

Microscale geomembrane-granular material interactions

Particle shape and crushing effects on direct shear behavior using dem