DIRECT SHEAR TESTS STUDY FOR RELATIONSHIP BETWEEN SURFACE TEMPERATURE AND SURFACE ROUGHNESS OF ROCK JOINTS

Large-scale rock landslides always are accompanied by thermal effect. Reduction of friction coefficient caused by the thermal effect can be used to explain the phenomenon of high-speed and long travel distance of landslide debris. The objective of this study is to understand the characteristics of heat generating on the rock joint surface after shear failure. First, the temperature and geometric data with respect to discontinuities surface are investigated using infrared thermal radiation imager and three-dimensional(3D)laser scanner respectively. Secondly, based on the statistical methods, the surface temperature distribution of rock joint after shear failure is obtained. On the other hand, the improved 2D divider method is employed to estimate the rock joint surface roughness through calculation of fractal dimension value for each sample. Thirdly, combined with the direct shear tests, multiple regression analysis is conducted among average temperature, normal stress, and roughness on the surface of rock joint. Under the condition of low shear speed( at the primary stage of sliding), the following results are found that:(1)The average temperature on the surface increases with the roughness of rock joint. The heat is mainly concentrated in the convex parts of rock joint surface; (2)The average temperature on the surface is directly proportional to the normal stress loaded on the rock joint; (3)The effect of rock joint surface roughness on the heat generation after shear failure is slightly larger than that of the normal stress. The testing results can provide technical parameters and theoretical help for investigation of energy during failure of large-scale rock landslides.