Implications of infinite rock slope analysis: Tension cut-off and graphical interpretation

Infinite slope analysis has been advocated and employed by many researchers because of its simplicity and conservative outcomes. Although the analysis has undergone extensive revisions with the assumption of linear failure criteria for soil slopes, it has rarely been used in rock engineering. This study proposes a theoretical framework for infinite rock slope analyses, particularly for rock masses weakened by weathering and other geological processes. The consequence of eliminating the tensile strength by assuming a highly fractured rock mass is examined using the exact solution obtained from both static and kinematic approaches. The analysis results indicate that the influence of tension cut-off becomes apparent due to reduction in the effective normal stress as a consequence of a steep slope and seepage flow. A unique characteristic of an infinite rock slope, where the length of the hypotenuse from the origin to the limit stress on the strength envelope is equal to the stability factor, is further discussed for various extents, such as seepage flow, factor of safety, and modified failure criterion with tension cut-off. Such graphical considerations clearly reveal the influence of various parameters involved in the analysis and provide useful insights into infinite rock slopes.