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℃.