Experimental study on permeability of phyllite talus in Whenchuan-Maerkang expressway considering fragment orientation

The phyllite talus is widely distributed along the Wenchuan-Maerkang expressway. Considering that the phyllite has obvious flat geometric characteristics, most of its spatial distribution in the talus has a certain degree of directionality, so that the permeability of the phyllite talus will be different with that of the homogeneous talus. The angle between the maximum area of the flat fragment surface and the horizontal plane is defined as the fragment orientation angle, and the ratio of the directional fragments to the total ones in the talus is defined as the fragment orientation rate. The effects of the orientation angle and orientation rate on the permeability of the phyllite talus are investigated by using the customized large-scale permeameter. The test results show that with the increase of the orientation angle, the permeability coefficient increases, the critical hydraulic gradient decreases, and the failure hydraulic gradient presents a phased evolution trend of "decreasing-increasing-slowly decreasing". With the increase of the orientation rate, its permeability coefficient increases, and both the critical and the failure hydraulic gradients decrease. The research results may provide a reference for the researches on seepage deformation and the evaluation of hydraulic property of the phyllite talus.