Development of Kinematic Criterion for Undercutting Induce Rock Failures

The interlayered soft and hard rocks exhibit difference in weathering rate. This differential weathering leads to various failure modes such as rockfall, rock-slides, plane fall/slide and wedge fall/slide in upper lying hard units, which is eventually induced by the erosion of the underlying weaker lithologies. However, the geometry and orientation of joints in hard rock play an essential role in causing these failures that were not reported previously. The current research focuses on developing a kinematic criterion for these undercutting-induced rock slope failures. In this study, the discontinuity data were gathered from the thirteen cut slopes along the Islamabad-Muzaffarabad Dual carriageway, Pakistan, where the rocks of Murree Formation of Miocene age are exposed. The discontinuity data was analysed in the DIPS software that indicated the three orthogonal joints along the slopes with the bedding of the rock unit dipping into the hill. The horizontal and into the slope orientation of the major joint is generally considered favourable; however, the field evidence is depicted otherwise in the interlayered lithologies. The results of this research showed that the undercutting is more pronounced along gentler bedding joints either into or out of the slope; on the other hand, it has less effect on the slope where the strike is across the hill, dipping on either side at steep to very steep angles.

Keywords:

Cut Slopes , Differential Weathering , Kinematic Criterion , Rock Fall , Undercutting Induced Failures , Slope Stability