# Triaxial Experimental Study of Zinc Contaminated Red Clay under Different Temperature Conditions
## 3 Results and Discussion
### Changes in Shear Strength of Zn-Contaminated Red Clay under Different Temperature Conditions
#### 3.3.1 Effect of Temperature on the Shear Strength Index of Zinc-Contaminated Red Clay  
According to the data-processing method of the triaxial compression test in the Standard for Geotechnical Test Methods (GB/T 50123-2019), the values of the damage points in the test data are obtained, calculated, and processed in accordance with the relevant formulas, the total stress circle of damage under different circumferential pressure is drawn, and the common tangent is drawn, and finally, the values of cohesion and internal friction angle under each condition are obtained. Figure 7 illustrates the variation curves of the shear strength index of Zn-contaminated red clay at various temperatures. In Figure 7, it can be seen that when the concentration of zinc contamination in the red clay remains constant, the cohesive force exhibits an overall increasing trend with the increase in temperature, whereas the internal friction angle exhibits a first increasing and then decreasing trend with the increase in temperature. Due to the thermal consolidation, as the ambient temperature rises, the volume of particles and pore water within the soil expands, the bound water between soil particles is converted into free water, the hydration film surrounding soil particles gradually decreases, the diffusion layer becomes thinner, and the hydrogel connection force between soil particles increases, resulting in a strengthening of the cohesion of red clay. Due to the confining effect of the surrounding pressure on the soil body during the heat consolidation stage, more pore water is discharged from the soil body, resulting in a decrease in pore pressure and an increase in pressure to be borne by the soil body, prompting the volume reduction of the soil body, the enhancement of the occlusion and friction between the soil particles, and a rise in the increase of the internal friction angle between the soil particles; after that, as the pore water continues to be discharged, the soil body deforms seriously, leading to the destruction of the occlusion point between the soil particles. Therefore, the internal friction angle of the red clay maintains the trend of first increasing and then decreasing with the increase of temperature. Figure 7: Curve of influence of temperature on the shear strength index of red clay. (**a**) The graph of the change of cohesion force with temperature; (**b**) The graph of internal friction angle with temperature. 3.2 Effect of Pollution Concentration on the Shear Strength Index of Red Clay under the Same Temperature Condition  
Figure 8 depicts the variation curves of shear strength index of red clay with different Zn contamination concentrations at the same temperature condition. From Figure 8, it can be shown that when the red clay is at the same ambient temperature, its cohesive force basically shows a decreasing trend with the increase of zinc contamination concentration, while its internal friction angle shows a trend of first increasing and then decreasing with the increase of zinc contamination concentration in the soil. This is because, when the ambient temperature of the red clay remains constant, with the increase of Zn contamination concentration in the soil, more Zn ions react with the cemented material within the soil and destroy its structure, reducing the attraction between soil particles, and the macroscopic expression of the cohesion of the red clay gradually decreases with the increase in Zn contamination concentration.