# Mechanical Behavior of a Mine Tailing Stabilized with a Sustainable Binder
## 3 Experimental Program
### Results Analysis
#### 3.2.2 CU Triaxial Tests  
The evolution of the deviatoric stress (q) with the axial strain (\(\epsilon_{\mathrm{a}}\)) is shown in Figure 12. The analysis of the obtained results shows that the increase in the confining stress originated a respective increase in the values of q. For confining stresses of 50 kPa, 100 kPa and 200 kPa, the mine tailing showed typical behavior of a normally consolidated soil (NC), not showing peak deviatoric stresses, and with greater development of q between 0 \(<\epsilon_{\mathrm{a}}<\) 0.2%. During the shear phase, the specimen subjected to the OC ratio of 3.5 demonstrated a representative behavior of an overconsolidated soil, presenting a peak deviatoric stress (for \(\epsilon_{\mathrm{a}}=\) 6.9%) and residual deviatoric stress. A greater evolution of q between 0 \(<\epsilon_{\mathrm{a}}<\) 0.5% was observed for this specimen. This behavior can be explained by the fact that the overconsolidation of the specimens causes a greater rearrangement of the particles, which consequently causes a decrease in the void ratio and a respective increase in the mechanical strength of the specimen. Figure 13 shows the evolution of pore pressure (\(\Delta\)u) with axial strain (\(\epsilon_{\mathrm{a}}\)). It shows that the normally consolidated specimens present a contracting tendency with a positive evolution of the pore pressure throughout the shear phase. The overconsolidated specimen with \(\sigma_{3}=\) 200 kPa exhibits a dilating behavior, whereby the pore pressure evolution curve lies below the curve for the normally consolidated specimen, subject to the same confining stress. The peaks observed along the curves are due to the loading/unloading cycles performed. Figure 12: Evolution of the deviatoric stress with the axial strain. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Soil** & \(\Delta\) & \(\Gamma\) & **k** \\ \hline London clay & 0.16 & 2.45 & 0.062 \\ Kaolin & 0.19 & 3.14 & 0.050 \\ Glacial moraine & 0.09 & 1.81 & 0.014 \\ Santa Clara clay & 0.10 & 1.94 & 0.011 \\ River sand & 0.16 & 2.99 & 0.014 \\ Decomposed granite & 0.09 & 2.04 & 0.005 \\ Carbonate sand & 0.34 & 4.35 & 0.003 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Values of \(\lambda\), \(\Gamma\) and k for typical soils. Figure 14 shows the trajectories in terms of total and effective stresses. The trajectory in terms of total stresses (s\(-\)t) is determined from the stresses imposed during the shear phase using Equations (5) and (6). \[\mathrm{s}=(\sigma_{1}+\sigma_{3})/2 \tag{5}\]  
\[\mathrm{t}=(\sigma_{1}-\sigma_{3})/2 \tag{6}\]  
The trajectory in terms of effective stresses (s\(-\)t) is obtained by reading pore pressure throughout the shear phase. During this phase, the increase in pore pressure is not linear, causing curvature of the effective stress path. For the normally consolidated specimens, in terms of effective stresses, a trajectory was observed with the stresses moving to the left. This development of stresses confirms the contracting behavior of these specimens. The overconsolidated specimen resulted in a trajectory of effective stresses with curvature tending to the right, highlighting the dilating tendency of this specimen. From these stress trajectories, the failure points were identified for each of the specimens tested, allowing us to trace the failure envelopes of the mine tailing in terms of total and effective stresses. The shear strength parameters of the specimens reconstituted from tailings were obtained  
Figure 14: Mine tailing failure envelope. Figure 13: Evolution of pore pressure with axial strain. based on the deviatoric stresses of the specimens tested. Table 4 summarizes the shear strength parameters obtained (total cohesion (c), effective cohesion (c'), total friction angle (\(\phi\)) and effective friction angle (\(\phi\)') obtained from the resulting failure envelopes. The strength parameters were calculated using Equations (7) and (8).