FIGURE 11 Effect of water content on the peak shear strength with temperature of 20℃ and -4℃(k =1100kPa/mm)
Figure 12 illustrates the influence of different temperatures and normal stiffnesses on the peak interfacial shear strength at a water content of 13%. Overall, as the normal stiffness increases, the interfacial shear strength also increases. Figure 12(a) shows the effect of various normal stiffnesses on the interfacial shear strength under room temperature conditions. It can be observed that under different normal pressures, the trend of the peak interfacial shear strength increasing with the increase in normal stiffness is consistent, exhibiting a gradual increase. This trend becomes more pronounced as the normal stress increases. This is because as the stiffness increases, greater normal stress is generated during the expansion of the specimen during shearing, thereby making the change in peak interfacial shear strength more significant. Under the same normal stiffness, the peak shear stress increases linearly with the increase in normal stress.
Figures 12(b-d) present the variation patterns under negative temperature conditions. The trends of stiffness and normal stress on peak shear strength are similar to those observed under room temperature conditions. However, under the same stiffness conditions, both cohesion and friction angles increase significantly. This is primarily due to the formation of ice cementation at the interface under negative temperature conditions, making the interfacial bonding tighter. As the temperature decreases, the peak shear strength gradually increases, and the cohesion also increases with the change in stiffness. Comparing stiffnesses of 200 and 1100, the increases are 9.9kpa, 12.6kpa, and 15.3kpa, respectively, showing a gradually increasing trend. This is because as the temperature decreases, the content of ice cementation between soil particles increases, allowing for a tighter bonding. As the stiffness of the soil gradually increases, it can exert a more concentrated force on the shear interface during sample expansion, resulting in a larger peak shear strength, thereby enhancing the influence of normal stiffness on cohesion.
As the temperature decreases, the internal friction angles of the interface with a normal stiffness of 1100 increase by 14.9%, 14.7%, and 7.7% compared to those with a normal stiffness of 200, showing a gradually decreasing trend. This is due to the increasing content of ice cementation at the interface. Since samples with high normal stiffness undergo greater shear strengths during shearing due to expansion and contraction, the ice cementation experiences brittle fracture. Consequently, the change in internal friction angle gradually slows down. This also explains why the internal friction angle at a normal stiffness of 1100 is slightly larger than that at a normal stiffness of 800 at -6℃.