## 4 Conclusions  
The primary goal of this study was to investigate the effect of XG biopolymer on the improvement of soil mechanical properties. UCS, CU, and UU triaxial tests were carried out to examine the soil strength. The durability of biopolymer-treated soil during cyclic processes of wetting and drying and susceptibility to water were also investigated. The following conclusions can be drawn:  
Adding XG caused substantial increases in LL and the plasticity index of soil. The UCS values of soil substantially increased with increasing the XG concentration and reached their peak value after a specific curing time depending on biopolymer concentration. The compressive strength of the soil increased 2.5 times after adding 2% XG. As a result of absorbing water during CU triaxial tests, the XG additive caused a significant reduction in soil strength and shearing parameters, including soil cohesion and friction angle. Results of UU triaxial tests for dried samples showed significant improvement in soil strength and soil cohesion due to the XG additive indicating promising results. Although during the wetting/drying cycles, the UCS values in all specimens were reduced by increasing the number of cycles, the biopolymer-treated samples exhibited higher soil strength than the pure soil samples. The XG-amended samples demonstrated strong resistance to the loss of compressive strength caused by repeated wetting and drying cycles. While the pure soil  
Figure 11: SEM images of the (**a**) untreated soil with a magnification of 2500; (**b**) untreated soil with a magnification of 15,000; (**c**) XG-treated soil with a magnification of 2500 (**d**) XG-treated soil with a magnification of 15,000.  
sample was fully disintegrated within 4 h of immersing in water, all XG-treated samples remained intact after 24 h and kept their shapes after two days of submerging in water. This proves the capability of biopolymer additives to keep soil structure once submerged in water.  
With respect to the overall results of conducted experiments, the XG additive has shown promising results in enhancing soil mechanical properties and can be an alternative sustainable solution for soil stabilization. The authors would suggest that for future studies, large-scale field experiments and in situ tests need to be conducted to obtain broader insight into the practical application of XG for soil stabilization. The suggestion would be to mix small amounts of XG with soil on the ground surface, followed by water application.  
[PERSON] designed and conceptualized the study, developed the research methodology, carried out the experiments, and data collection, developed the theoretical formalism, analyzed the data, and drafted the manuscript; [PERSON] coordinated and supervised the study and critically revised the manuscript; [PERSON] critically revised the manuscript. All authors have read and agreed to the published version of the manuscript. This research received no external funding.  
Not applicable.  
The data presented in this study are available on request from the corresponding author.  
This research was performed with the financial support of the Griffith University Postgraduate Research Scholarship (GUPRS).  
The authors declare no conflict of interest.