Upper-Bound Limit Analysis for Slope Stability Based on Modified Mohr–Coulomb Failure Criterion with Tensile Cutoff

Using the classical (linear) Mohr–Coulomb (M–C) failure criterion, the failure mechanism of slopes is commonly treated as a completely shear failure. However, the tension failure mechanism has also been commonly observed in landslides, especially for those covered by cemented soils geometrical. Considering only the shear failure would overestimate the tensile capacity of geomaterial, which can lead to an optimistic result. In this paper, a modified M–C failure criterion with zero or low tensile strength (tension cutoff) was introduced that can characterize the shear–tension failure feature of slopes well. Combined with the limit upper bound theory, the expressions of stability factor (Ns) for slopes were derived considering (1) only soil self-weight; and two external conditions, (2) surcharge load, and (3) seismic load. Further, a detailed parametric analysis was conducted. The results show that the slope stability was greatly influenced by the surcharge coefficient (qt) and the horizontal seismic acceleration coefficient (kh). The influence of the degree of tension cutoff (ζ) on the slope stability strongly depends on the values of slope angle (β) and internal friction angle (φ). The difference in Ns under two extreme cases (ζ = 0 and ζ = 1) was significant, and the difference was more pronounced with the introduction of surcharge and seismic load.