Abstract:

Red-bed soft rocks belong to the layers which are susceptible to landslide and collapse. The micro-structural characteristics of the rock have an important impact on its macroscopic mechanical strength. In this paper, the micro-structural observation with scanning electron microscopy (SEM) and the angle-changed shear strength test of the Jurassic red-bed sandstone, siltstone and mudstone samples which were collected from Pingshan County in Sichuan Province and Suijiang County in Yunnan Province were conducted. A large number of microstructures of red-bed sandstone, siltstone and mudstone were analyzed and the shear strength values of the red-bed soft rocks were obtained. The microstructure parameters, i.e.porosity, particle roundness, particle orientation and the quantized value of Euler number of the red-bed sandstone, siltstone and mudstone were extracted based on MATLAB digital image processing techniques. Then the quantitative relationship between the above parameters and the shear strength were analyzed. The results show that the shear strength and porosity of the red-bed soft rock have a negative exponential relationship; the shear strength and particle roundness and particle orientation have a negative linear relationship; the shear strength and the Euler number have positively correlated linear relationship.

Key words: red-bed soft rock, shear strength, digital image, microstructure, correlation