FIGURE 10 Effect of temperature on the peak shear strength(k =1100kPa/mm,w =13%)
Figure 11 demonstrates the influence of water content on the interfacial shear strength at temperatures of 20℃ and -4℃. As shown in Figure 11(a) for room temperature conditions, with the increase in water content, the interfacial shear strength initially increases and then decreases, reaching a maximum at the optimal water content (w =13%). Correspondingly, the interfacial cohesion and friction angle also peak at the optimal water content. This is because when the soil water content is low, strongly bound water dominates around soil particles, forming a common bound water film between adjacent soil particles. The binding effect of the bound water enhances the interaction force between the soil, as well as between the soil and the concrete interface. As the water content increases, this interaction force gradually increases, leading to a corresponding increase in the interfacial shear strength. However, as the water content in the soil further increases, the weakly bound water film around the soil particles gradually becomes thicker. The binding effect of the weakly bound water is weaker, resulting in a gradual decrease in the strength of the soil and the interface. Additionally, as the water content gradually increases, the bound water film in the soil gradually forms, thickens, and even free water appears. In this process, the water in the soil acts as a lubricant, making the movement of soil particles relatively easier. Therefore, the interfacial shear strength exhibits a pattern of first increasing and then decreasing with the increase in water content 35,38.
Figure 11(b) illustrates the variation of interfacial shear strength at -4℃. It can be observed that the strength gradually increases with the increase in water content, and the increase is more significant under high normal pressure. Both the interfacial cohesion and friction angle also increase with the increase in water content.