Rock slope deformation mechanism in the Cihaxia Hydropower Station, Northwest China

Abstract

Complex block-flexure slope toppling is observed in interbedded sandstone and slate in the upper Yellow River, China. Block toppling is observed in the relatively hard sandstone and flexural toppling is observed in the relatively soft slate. The evolution of toppling slope deformation is characterized by long-term progress and spatial variability. In order to study these characteristics, field investigations, adit prospecting, borehole drilling, sonic tests and numerical simulation were carried out. In addition, the effect of the structure, the composite mode of the rock mass, the unloading fissures and geomorphology are discussed. Furthermore, we explored the toppling mechanisms and simulated it numerically; on this basis, the slope evolution is divided into four stages. Results obtained from the numerical simulation compared well with field investigation data (investigation data, rock sonic survey and strata dip statistics). Comparative studies have demonstrated that the analytical methods presented in this paper are appropriate for back analysis of the toppling evolution process. The result showed that this toppling slope has not yet entered the later progressivity failure stage and is currently limited to collapse at shallow levels, whereas the deep-seated rock mass will remain stable for a long time. This study might provide reference for a stability evaluation and hazard prevention analysis for rock toppling.

The Evolution Mechanism of the Slope Toppling Deformation for Early-Warning Analysis

“…In practical projects, the toppling boundary conditions are determined in different manners, including assuming nearly linear fracture planes or parabolic-like fracture planes (Zhang et al 2014;Liu et al 2016;Huang et al 2017). The insufficient adit exploration depth (approximately 200 m) and nonuniform toppling intensity zoning usually based on the rock quality classification can affect these determinations.…”

The Role of Water and Lithology on the Deformation and Failure of an Anaclinal Rock Slope in a Hydropower Reservoir

“…For the anaclinal slope, the soft plastic features of the rock masses and the thin stratified structure in the Baiguowan Formation favor the development of toppling deformation under long-term maximum principal stresses parallel to the slope surface [41,42]. Different processes of flexural toppling deformation of bedrock occur on the Zhengjiaping slope, which can be roughly divided into four categories: (1) the disintegration and relaxing deformation zone; (2) the strong toppling deformation zone; (3) the weak toppling deformation zone; and (4) the normal rock stratum zone (Table 2).…”

An Analytical Solution for Block Toppling Failure of Rock Slopes during an Earthquake

“…The width of block The height difference at the top of adjacent blocks under the slope crest a 2 The height difference at the top of adjacent blocks above the slope crest b…”

“…The joint connectivity rate of the block base ξ 1 − J c k 1 Seismic acceleration component parallel to the block base k 2 Seismic acceleration component orthogonal to the block base …”

“…This failure mode is one of the most common seen in natural or excavated rock slopes, e.g., rock slopes induced by construction including of hydropower stations [1][2][3], open-pit mines [4,5], railway [5] and other engineering works [6]. In recent years, quite a number of toppling failures occurred during earthquakes and caused huge losses to lives as well as infrastructures.…”