Biopolymer soil stabilization as protection from slope erosion and shallow sliding

Climate change has a significant impact on slope stability through atmospheric perturbations, water infiltration and soil erosion, which is often accompanied by local or shallow sliding of the slopes. Usually, the erosion is not seen as a stability-treating occurrence, but with time it can develop to a reduction of the shear soil strength and raise in the pore water pressure that can disturb the slope stability.

In order to overcome these problems, it is necessary to introduce techniques for surface stabilization of soil slopes that increase erosion resistance and reduce surface water infiltration. Moreover, they have to be environmentally friendly, thus recommendations refer to the application of natural polymer compounds that do not pollute the environment, and at the same time represent an effective and economical measure for slope stabilization. Very often, as an additional measure in the application of these biopolymer solutions on the surfaces of the slopes, at the same time, the application of seeds from low and medium vegetation is performed. In the first months, the biopolymers form a bond between the solid soil particles, which increases the erosion resistance and reduces the ability to infiltrate and absorb surface water. In parallel, the biopolymer helps and accelerates the growth of vegetation to ensure long-term erosion and slope stability.

The aim of the presented study was to investigate the effects of the xanthan gum as a compound and to develop an original biopolymer solution which will be later tested. The testing methodology was organized in two phases: laboratory tests on natural and biopolymer treated soil in the first phase, and experimental testing of biopolymer treated slope in the second phase.

In the first phase, the classification and strength parameters of treated and untreated soil were determined through standard laboratory tests. The tests were performed on specimens with various percentages of the xanthan gum additive, moreover, specimens were tested on days 1, 7, and 14 to examine the curing effects. From the results, it was observed that Xanthan gum has significantly increased the strength of the soil, up to 50% after the 14 days of curing time.

In the second phase, the erosion of treated and untreated soil was experimentally tested on the 1:1.5 slope during a rainfall of 10 liters per hour which was simulated for 180 minutes. The obtained results were better than expected showing a significant erosion resistance on the treated slope. During the 180 minutes of rainfall on the treated slope, there was no eroded soil registered. The Xanthan gum binder with a content of 1.0% filling the pores was able to limit the water infiltration into the soil, which improves interparticle cohesion and shows increased erosion resistance. In contrast, the amount of eroded soil on the untreated slope with an area of 1.0m² was about 1900gr or soil erosion of 9.5%.

Finally, from the study can be concluded that the proposed biopolymer is a natural-based solution for erosion control which has major potential because they represent efficient, economic and environmentally sustainable engineering solutions.