Abstract
Abstract. Calcareous mountainous areas are highly prone to geohazards, and rockslides play an important role in cliff retreat. This study presents three examples of failures of limestone cliffs with subhorizontal bedding in the southwestern calcareous area of China. Field observations and numerical modeling of Yudong Escarpment, Zengzi Cliff, and Wangxia Cliff showed that pre-existing vertical joints passing through thick limestone and the alternation of competent and incompetent layers are the most significant features for rockslides. A "hard-on-soft" cliff made of hard rocks superimposed on soft rocks is prone to rock slump, characterized by shearing through the underlying weak strata along a curved surface and backward tilting. When a slope contains weak interlayers rather than a soft basal, a rock collapse could occur from the compression fracture and tensile split of the rock mass near the interfaces. A rockslide might shear through a hard rock mass if no discontinuities are exposed in the cliff slope, and sliding may occur along a moderately inclined rupture plane. The "toe breakout" mechanism mainly depends on the strength characteristics of the rock mass.
Highlights
The southwestern calcareous area of China covers a large area of 54.4 × 103 km2, and it is highly prone to geohazards
Considerable research on cliff failure has been conducted in similar areas around the world (Abele, 1994; Von Poschinger, 2002; Rohn et al, 2004; Embleton-Hamann, 2007; Ruff and Rohn, 2008; Palma, et al, 2012), such as the North Calcareous Alps in Austria
This study focuses on the failure mechanisms of cliffs with subhorizontal bedding in the southwestern calcareous area of China and the recognition of these features in field investigations
Summary
The southwestern calcareous area of China covers a large area of 54.4 × 103 km, and it is highly prone to geohazards. Many multilayered carbonate rocks with subhorizontal bedding have been deeply cut by rivers during crustal uplift and form significant topographic relief in steep slopes and cliffs. Rockslides from subhorizontally bedded cliff failure and resulting catastrophes have occurred widely and frequently in the southwestern calcareous area of China. It is believed that water, lithology, geological structure, and karstification are of primary importance in triggering rockslides from cliff failure (Kay et al, 2006) These factors dominate the tearing and shearing failure mechanism of the rock masses and joints, which are directly displayed in the consequent failure behavior of the cliff slopes. This study focuses on the failure mechanisms of cliffs with subhorizontal bedding in the southwestern calcareous area of China and the recognition of these features in field investigations. Post-failure behavior, such as rock avalanches and debris flows, is not included in descriptions of
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