Abstract
Due to its abruptness and extensive occurrence, slope toppling failure has become a typical deformation pattern requiring urgent attention in engineering construction and disaster prevention within the geologically complex mountainous regions of southwestern China. To thoroughly investigate its underlying mechanism, the limestone sliding mass and shale slip bed from the Guang'an Village landslide were selected as prototype materials, and physical models of anti-dip limestone slope and anti-dip shale slope were respectively constructed, with loading tests employed to simulate gravitational effects during geological history. By integrating digital photography, non-contact deformation measurement techniques, and miniature pressure sensors, real-time image, displacement, and pressure data during the slope toppling deformation process were acquired. The experimental results comprehensively reproduced the anti-dip rock layer toppling and slope instability processes. The findings indicate that hard rock layers such as limestone are prone to brittle toppling-fracture failure, with slope instability dominated by shallow collapse; whereas soft rock layers such as shale tend toward long-term bending creep, ultimately leading to deep-seated sliding of the slope mass. As the toppling process continues to develop, multi-level fracture surfaces gradually form within the slope, dividing it into five zones with clear geological-mechanical significance. The study further proposes the rock layer overturning angle as a parameter for describing slope kinematic characteristics, and presents a staged discussion of the toppling deformation process for rock masses in both unstable and stable regions. In anti-dip limestone slopes, the dominance of the horizontal component of rock layer displacement vectors represents the key characteristic for rotational deformation about the toe following toppling-fracture; while in anti-dip shale slopes, the vertical displacement component gradually increases from the slope surface toward the interior, indicating a bending toppling characteristic. During loading, the internal pressure within rock masses at the slope surface and front edge of the slope crest exhibits a distinct stepwise variation trend, highlighting the dynamic interplay between tensile and compressive stresses. This experiment can serve as a typical case study for investigating deformation and failure mechanisms of anti-dip rock slopes, and provides important data support for stability assessment and risk prediction in geotechnical engineering.
Full Text
Physical Model Study on the Evolution of Toppling Deformation Mechanism and Failure Modes in Anti-dip Rock Slopes
Qian Zhao, Zhongping Yang, Shunbo Zhang
School of Civil Engineering, Chongqing University, Chongqing 400045, China
Abstract
Southwest China's mountainous regions feature complex geological structures, where slope toppling failures have become a critical deformation pattern requiring urgent attention in engineering construction and disaster prevention due to their suddenness and widespread occurrence. To deeply reveal the formation mechanism, this study selected the limestone sliding mass and shale sliding bed from the Guang'ancun landslide as prototype materials to construct physical models of anti-dip limestone and shale slopes, respectively. Loading tests were conducted to simulate gravity effects during geological history, while digital photography, non-contact deformation measurement techniques, and micro pressure sensors were employed to obtain real-time images, displacement, and pressure data during the slope toppling deformation process.
The experimental results successfully reproduced the toppling deformation and slope instability processes. The findings indicate that hard rock layers such as limestone are prone to brittle failure characterized by toppling-breaking, with slope instability dominated by shallow collapse. In contrast, soft rock layers like shale tend to undergo long-term bending creep, ultimately leading to deep-seated sliding of the slope. As the toppling process continues, multiple levels of fracture surfaces gradually develop within the slope, dividing it into five distinct zones with clear geological-mechanical significance. The study further proposes the layer overturning angle as a parameter to describe the kinematic characteristics of slope movement, enabling a staged discussion of the toppling deformation process for rock masses in both stable and unstable regions.
In the anti-dip limestone slope, the dominance of horizontal displacement vectors is the key characteristic of rotational deformation around the toe following toppling-breaking. In the anti-dip shale slope, the vertical displacement component gradually increases from the slope surface inward, indicating a bending-toppling deformation characteristic. During loading, the internal pressure within the rock mass at the slope surface and crest front edge exhibits a clear stepwise variation trend, highlighting the dynamic transition between tensile and compressive stresses. This experiment serves as a typical case study for investigating the deformation and failure mechanisms of anti-dip rock slopes, providing crucial data support for stability evaluation and risk prediction in geotechnical engineering.
Keywords: anti-dip rock slopes; physical model test; toppling deformation; failure mode