| dc.description.abstract | The friction characteristics of landslide sliding surfaces are closely related to the slip velocity and the displacement. In the past, many scientists have used low to high velocity rotary shear apparatus to discuss and simulate the friction behavior of long-displacement landslides. The predecessors used air-dried kaolinite as the material to conduct rotary shear experiments at different slip velocity, and found that there are different friction coefficient-shear displacement curves in different slip velocity ranges. However, the previous studies focused on the establishment of friction laws, the generation and evolution of different friction coefficient-shear displacement curves have not been further studied. Therefore, this study attempted to conduct a more in-depth discussion on the friction coefficient-shear displacement curves of kaolinite at different slip velocity. Compared with the traditional soil shear test (direct shear test and triaxial shear test), the rotary shear apparatus has the advantage of being able to achieve long-displacement shearing. The Teflon ring which has the low friction characteristic is used to cover the test body. However, in the high velocity rotary shear test, the Teflon ring may contaminate the test body due to decomposition or shear wear, which may affect the experimental results. Therefore, this study will consider the effect of Teflon contamination on friction curve patterns, and the content of Teflon contamination in sheared kaolinite will be quantified. In addition, Since the microstructure reflects the mechanical properties of the experimental materials, this study also attempted to observe the microstructure at different shear displacements. The results show that the sheared kaolinite has 29.9% contamination at a slip velocity of 1 m/s, but the contamination content has no significant effect on the peak friction coefficient and the steady-state friction coefficient. It is also believed that the sheared kaolinite in other slip velocity conditions in previous studies has no pollution content according to the results, and even if it exists, the pollution has no significant effect on the experimental results. On the other hand, there is no obvious Riedel shear under the low slip velocity of 10^-6 m/s, and the deformation is uniform. At the slip velocity of 10^-5-10^-3 m/s, the friction curves present two peaks, and it is believed that the second peak is the shear displacement stage corresponding to the appearance of Riedel shear in the microstructural results of the previous study. | en_US |