Study on the Flexural Toppling Mechanism of Dolomite Slopes within Steep-Dip Slopes in the Dengying Formation

The Sinian Dengying Formation is widely distributed in southwestern China. The dolomite of the Dengying Formation in the Leibo Majingzi Jinyang area of southwestern Sichuan often forms steep slopes and develops toppling deformation. There have been few reports on the non coordinated toppling deformation and the resulting high-level collapse mechanism of this type of anti dipping thick layer dolomite slope. This article reveals through systematic field investigations and analysis of the tilting deformation process that: (1) the upper part of the Dengying Formation dolomite is interbedded with several layers of 3~10mm shale, which were strongly folded under the action of a nearly east-west stress field during the Indosinian Himalayan stage. The dolomite was sheared along the shale interlayers to form feather thin sections; (2) Since the Quaternary period, under the influence of the stress field in the valley caused by the cutting of the Jinyang River, the anti inclined slope body composed of dolomite has undergone book oblique deformation or folding under the action of gravity, resulting in thinning of the thin layered feathered dolomite, providing deformation space for the fracture and toppling of the overlying thick jointed dolomite; (3) The thin layers of the feather column are further crushed into fragmented rocks, which undergo differential weathering to form concave rock cavities. The overlying fractured and toppling thick layer of dolomite rock has evolved into dangerous rock zones and dangerous rock monomers due to the loss of support in the concave rock cavities; (4) Dangerous rock zones and individual dangerous rocks are developed above the multi-layered concave rock cavity, becoming the biggest geological safety hazard in the towns below.