Four groups of large-scale triaxial consolidated-drained shear test were carried out on two types of incompact coarse-grained soil samples taken from the top and bottom of slope at a slag field. The relations of stress and strain, volumetric strain and axial strain, measured Poisson’s ratio against stress level, as well as the applicability of Duncan-Chang E-ν and E-B models were examined. Research results demonstrated that: 1) the stress-strain curve of the incompact coarse-grained soil displayed hardening features with no significant peak. Strength parameter φ was closely related to and augmented along with the increase of reference strain. 2) The incompact coarse-grained soil showed monotonous shear shrinkage in the whole process of shearing, which indicated that the structural compression caused by translational motion of particles dominated the whole process, while the particle rotation and force chain adjustment were negligible. 3) The measured Poisson’s ratio was in a linear relation with stress level, yet with an evident difference between top and bottom materials of slope. In addition, the Duncan-Chang E-B model had a good fitting result for the Poisson’s ratio of slope top materials, while the Duncan-Chang E-ν model was more applicable for slope bottom materials.