## 1 Introduction  
In recent years, due to the rapid growth of human engineering activities, the issue of slope instability has been on the rise annually. There is a common assumption that anti-dip slopes are inherently more stable, with shallower slip surfaces or a lower likelihood of mass sliding. In 1990, [PERSON] and [PERSON] provided a comprehensive overview of global landslide hazards, highlighting the widespread occurrence of toppling deformations worldwide [1]. [PERSON] and [PERSON] conducted a statistical analysis of 200 major landslides in China dating back to 1900 [2]. Among these, landslides or deformation issues in anti-dip slopes comprise approximately one-third of the total number of cases. It is evident that studying and analyzing the instability and deformation mechanisms of anti-dip slopes is essential for timely prevention and control. Owing to the perilous and unpredictable nature of anti-dip landslide events, scholars worldwide have undertaken numerous investigations. In early studies, the primary focus was on engineering geological descriptions [3; 4; 5; 6]. In 1976, [PERSON] and [PERSON] systematically examined the deformation and damage features of anti-dip slopes, classifying them into two groups: toppling and secondary toppling [7]. As the exploration of toppling deformation damage progressed, researchers initiated the examination of its deformation traits using physical experiments and numerical simulation methods. [PERSON] and [PERSON] [8] investigated and analyzed the deformation and damage mechanisms of anti-dip slopes using centrifugal simulation experiments. They also outlined the associated stability analysis methods. Numerical simulation has increasingly emerged as a vital tool for analyzing landslide deformation mechanisms, primarily because of the substantial costs and time needed for model test-based investigations. In 1995, [PERSON] and [PERSON] [9] employed 3D analysis software to simulate and analyze the instability progression of an anticline slope in Japan. In 2009, [PERSON] and [PERSON] [10] explored the impact of discontinuity orientation on the deformation mechanism of block topping, employing the discrete element software 3 DEC. In 2013, [PERSON] et al. [11] conducted a thorough analysis of the destabilization mechanisms in rocky slopes in Stampa by integrating various analytical approaches. In May 2009, destabilization damage occurred during the construction of a road in northwestern Spain, which was numerically simulated by [PERSON] et al. using the UDEC software to offer improved insights into the deformation damage features at the study site [12]. In 2016, [PERSON] et al. [13] applied a tension-weakening model in FLAC3D, using the Zhaogu No. 2 Mine as an example, considering the influence of fissures on the rock mass. Then, the deformation characteristics of the slope were analyzed, and the relationship between the fissure strength and the residual strength of the rock mass was established. In 2019, [PERSON] et al. [14] used the Xinyan landslide as a case study, uncovering the primary factors contributing to frequent landslides in the region via extensive indoor experiments, mineral analyses, and microstructural assessments. They also summarized the deformation and damage patterns. In 2020, [PERSON] et al. [15] used the Changshanhao Coal Mine as an example to determine the destabilization damage mode of the anti-dip slopes by using field investigations, physical exploration, and comprehensive analysis of FLAC3D (5.0) and 3 DEC (5.2) software. Since the beginning of spring 2022, extensive deformation and damage have occurred on the eastern pit slope of the Wolong Coal Mine in Ordos City, Inner Mongolia, posing a serious threat to personnel safety during operation. In this study, a thorough field engineering geological investigation and analysis were conducted for the eastern slope of the Wolong Coal Mine.