# Enhancing the Strength of Mine Residue Soil by Bioremediation Combined with Biopolymers
## 3 Results
### Effect of the Stabilizers Applied Individually  
From Figure 1 and Table 3, the addition of the applied individually stabilizers is shown to have a tremendous impact on the stress-strain compressive behavior of the mine residue soil. The addition of Portland cement (the most common binder used in soil stabilization) enhanced the maximum unconfined compressive strength significantly, whereas stiffness  
\begin{table}
\begin{tabular}{c c c c c c c} \hline  & \multicolumn{2}{c}{**q\({}_{\text{u max}}\)**} & \multicolumn{2}{c}{\(\varepsilon_{\text{f}}\)} & \multicolumn{2}{c}{**E\({}_{\text{u 50}}\)**} \\ \hline
**Test ID** & **(kPa)** & **Average** & **(\%)** & **Average** & **(MPa)** & **Average** \\ \hline Control—T1 & 110.23 & 106.18 & 1.235 & 1.15 & 11.78 & 11.58 \\ Control—T2 & 102.13 & 1.073 & & 11.38 & & 11.38 \\ Cement—T1 & 165.27 & 175.48 & 1.388 & 1.58 & 14.10 & 12.51 \\ Cement—T2 & 185.68 & & 1.773 & & 10.93 & \\ CMC—T1 & 241.08 & 221.82 & 4.074 & 4.58 & 6.27 & 5.24 \\ CMC—T2 & 202.55 & & 5.087 & & 4.22 & \\ XG—T1 & 190.51 & 167.76 & 3.983 & 4.08 & 5.01 & 4.58 \\ XG—T2 & 145.01 & & 4.186 & & 4.14 & \\ \hline BS\_Control—T1 & 103.48 & 78.09 & 4.431 & 5.22 & 3.07 & 2.40 \\ BS\_Control—T2 & 52.70 & & 6.016 & & 1.73 & \\ BS\_Cement—T1 & 75.83 & 85.38 & 6.911 & 5.92 & 1.51 & 2.21 \\ BS\_Cement—T2 & 94.94 & & 4.932 & & 2.92 & \\ BS\_CMC—T1 & 47.20 & 47.28 & 4.581 & 4.56 & 1.44 & 1.49 \\ BS\_CMC—T2 & 47.35 & & 4.530 & & 1.55 & \\ BS\_XG—T1 & 118.85 & 99.99 & 3.657 & 3.70 & 4.57 & 4.40 \\ BS\_XG—T2 & 81.13 & & 3.742 & & 4.23 & \\ \hline BA\_Control—T1 & 104.70 & 102.66 & 5.191 & 3.66 & 2.61 & 4.32 \\ BA\_Control—T2 & 100.61 & & 2.121 & & 6.03 & \\ BA\_Cement—T1 & 142.75 & 142.82 & 5.249 & 5.04 & 3.42 & 3.94 \\ BA\_Cement—T2 & 142.88 & & 4.839 & & 4.46 & \\ BA\_CMC—T1 & 62.75 & 62.76 & 4.228 & 3.91 & 1.96 & 2.11 \\ BA\_CMC—T2 & 62.78 & & 3.593 & & 2.26 & \\ BA\_XG—T1 & 158.66 & 130.48 & 4.960 & 3.93 & 5.12 & 4.41 \\ BA\_XG—T2 & 102.29 & & 2.891 & & 3.71 & \\ \hline \end{tabular}
\end{table}
Table 3: UCS results.  
was enhanced only slightly. However, the addition of any of the biopolymers (XG or CMC) promoted significant changes in the stress-strain behavior, increasing the compressive strength and the strain at failure. Comparing both biopolymers, the CMC exhibits a better performance than XG, which may be explained by the higher viscosity induced by the CMC [14], conferring a higher adhesion/cohesion between particles. Indeed, in the case of CMC, the strength more than doubled the control value and is above the cement value, while for the case of XG, the results can be compared with the samples stabilized with cement, in agreement with the findings of [PERSON] et al. [8]. These results clearly show the good performance of both biopolymers, and their ability to be used as stabilizers in mine residue soils. The stress-strain curves also showed that the samples stabilized with biopolymers exhibit a more ductile behavior, characterized by a higher strain at failure. This means that the bio-stabilized material can deform as the compressive strength is mobilized, avoiding catastrophic failure without previous warning.