## 3 Results and Discussion
### Physical Properties of the TSF Tailings  
The results of particle size distribution are displayed in the curve semi-logarithmic mark of the cumulative percentage of passing grains as a function of particle size (Figure 9).  
Figure 8: Hydro-geotechnical behavior of the TSF mine tailings (**A**): Cracks formation at the disposal tailings ponds (TSF3); (**B**): significant precipitation and accumulation of salts on the surface (TSF2); (**C**): formation of drying scales on the surface of mine tailings (TSF1); (**D**): clogging of cracks (TSF2); (**E**): formation of highly indurated crusts (TSF3); (**F**): formation of wide and deep cracks (TSF2).  
Particle size and geotechnical parameters of the TSF tailings are given in Table 1. From the distribution curve, the main characteristics of the particle size parameters of the TSF, expressed as D10, D30, D50, D60, and D90, can be determined. They represent, respectively, the diameter of the grains for 10, 30, 50, 60 and 90% of the sieve (\(\mu\)m). D50 represents the average diameter of the grains, while that of the D90 represents the diameter of most of the grains constituting the TSF tailings. The coefficient of uniformity (Cu = D60/D10) and coefficient of curvature (Cc = (D30)2/(D10 \(\times\) D60) are quantitative indexes used to describe particle gradation. Considering the TSF1, TSF2 and TSF3 tailings, the coefficient of uniformity is 22.79, 20.02, and 14.19, respectively, and the coefficient of curvature corresponds to 1.24, 1.29, and 1.14, respectively. Based on these results, the Cu values are higher than 5 and the Cc values are between 1 and 3; all TSF tailings are classified as well-graded soils [73; 74; 75; 76; 77]. In terms of particle size distribution, all TSF tailings are of heterogeneous granulometry that consists of silt > sand > clay for the TSF1 and TSF2 tailings and silt > clay > sand for the TSF3 tailings. These results confirm that TSF3 tailings are finer with a P 80 of 100% (P 80 is the percentage of particles passing through an 80 microns sieve) compared to TSF1 and TSF2 tailings whose particle sizes show a P 80 of 66.67% and 73.39%, respectively. The use of the Soil Textural Triangle developed by the U.S. Department of Agriculture [78] according to the proportion of the granulometric fractions allows classifying the TSF3 tailings as silt, while the TSF1 and TSF2 tailings are classified as siltyo loam (Figure 10). The specific surface area (SSA) of all TSF tailings was 3 m\({}^{2}\)/g, which is attributed to their low clay minerals content.  
Figure 10: Positionning of the TSF tailings on the Soil Texture Triangle (USDA, 2017) [78].  
Figure 9: Particle size distribution of the TSF tailings.  
During the Atterberg limit tests, the liquidity limit of the TSF tailings could not be determined by the Casagrande cup due to their low clay content, but this test was performed using the cone penetrometer. The results of the Atterberg limit show that the plasticity index values (%PI = wL (%) \(-\) wP (%)) of the TSF1, TSF2 and TSF3 tailings are 5.11, 5.33, and 7.08% respectively. Some authors [12; 17] have argued that tailings from hard rock mining generally display low plasticity index values (PI! 10%). Here, [15] reports that the liquidity limit amounts to wL! 40% and the plasticity limit amounts to wP! 15%. These TSF tailings can be considered as very low (TSF1) to low in plasticity (TSF2 and TSF3) and showed silt-sized characteristics, which is in accordance with the data reported in the literature [15; 70; 79].