Influence of Xanthan gum biopolymer-based Soil Treatment on Particle Level Inter-Binding and Shear Behaviour of Soils

With the growing demand for sustainable construction materials, microbial biopolymers have been recently introduced in geotechnical engineering. Indeed, many researchers have conducted relevant studies to investigate the effects of biopolymer treatment on soils. The various types of biopolymers have shown their competitiveness compared to conventional binders such as cement. In this study, xanthan gum biopolymer was chosen because of workability and economic feasibility. From the understanding of rheological properties, applicability of xanthan gum on Tunnel Boring Machine (TBM) slurry additive was suggested in accordance with the shear thinning characteristics of xanthan gum. As a parallel section, the soil strengthening effect in terms of erosion behaviour and shear behaviour was assessed through the experimental program. Indeed, biopolymer treatment with less than 2.0% in mass ratio was effective on soil strengthening effects, resulting in erosion resistance and shear resistance improvement. In addition, this study aims to achieve a better understanding of xanthan gum biopolymer film matrix formation in soils in the manner of quantitative analysis. The biopolymer film matrix formation pattern was quantitatively analysed using a laboratory microscopic observation test. The newly introduced parameters (i.e., degree of biopolymer filling, dehydrated biopolymer concentration, connectivity) from the microscopic observation test were assessed, and those parameters were correlated with the erosion parameter and the shear parameters from the laboratory assessment. Porosity was applied as a main variable for the analysis of each correlation. While the porosity was an influential factor, different soil packing conditions (i.e., simple cubic soil packing and rhombohedral soil packing) showed the effect of pore size between sand particles on xanthan gum biopolymer film matrix. For another feasible application, the feasibility of xanthan gum on road shoulder pavement was basically assessed in the laboratory. While it remains difficult to simulate practical ground conditions to develop a highly reliable relationship between engineering properties and parameters for the biopolymer film matrix formation pattern, this research would be worthwhile to initiate an attempt for quantitative analysis of xanthan gum biopolymer film matrix formation