## 1 Introduction  
An anti-dip rock slope is a common geological structure where the stratum dips inward toward the outer surface of the slope [1; 2; 3; 4]. Generally, an anti-dip rock slope is more stable than a conventional dip rock slope. However, unstable anti-dip slopes and their related geohazards are also common in slope engineering due to excavation and disturbances. Statistical analysis shows that approximately \(\sim\)33% of slope failures occur on anti-dip rock slopes [5], and toppling is the primary failure pattern for anti-dip rock slopes [6; 7; 8]. A large displacement causes slope failure, which is induced by the nonhomogeneous rock joints and bedding plane [9; 10; 11]. The mechanical properties and failure modes of anti-dip rock slopes with different rock layers are more complex than a rock slope, which is only composed of one single rock layer [8]. Four different methods are commonly used to study the stability of anti-dip rock slopes: (a) in situ investigations [12; 13], (b) laboratory similar testing with rock-like materials [14; 15; 16], (c) theoretical and analytical methods (e.g., the limit equilibrium method) [17; 18; 19], and (d) numerical simulation methods [5; 20; 21]. In situ investigations can provide valuable information about a rock slope before (e.g., the geological condition)and after (e.g., the failure characteristics) slope failure but cannot reveal the evolutionary process or instability mechanism of the slope. Besides, the influence of different factors (such as different rock types, slope angles, and internal discontinuities) on rock slope stability also cannot be comprehensively considered. In laboratory similar tests, the size effect of the rock slope cannot be reflected, and the properties of similar materials also differ significantly from those of real rock materials. Similarly, the theoretical method cannot fully account for the heterogeneous characteristics and unconventional size of a slope. Considering the above limitations, numerical simulations based on on-site geological surveys play a prominent role in analyzing slope stability [22; 23; 24]. A number of studies have been conducted using the numerical simulation method to throw light on the stability and failure mechanisms of anti-dip rock slopes, and many meaningful results have been obtained [7; 25; 26]. Various numerical modeling approaches can offer different advantages. To solve the nonlinear stress distribution of anti-dip slopes, their toppling failure was first analyzed using the finite element method (FEM) by [PERSON] et al. [27]. Then, [PERSON] et al. [28] studied the seismic responses of anti-dip slopes using three-dimensional FEM. The seismic failure mode of these slopes was identified through analyses of the dynamic responses of the slopes. To further simulate the sliding, rotation, and collapse characteristics of anti-dip slopes, the discrete element method (DEM) has been gradually adopted by many scholars. [PERSON] et al. [7] employed the discrete element method to simulate the excavation process of an anti-dip slope, and the slope stability after excavation was analyzed and compared with the data from field monitoring. [PERSON] et al. [21] investigated the dynamic effects and failure mechanism of anti-dip bedding rock slopes under seismic loading using three-dimensional DEM, and the amplification effect, changes in the Fourier spectrum, failure mechanism, and permanent displacement of the slope caused by the applied seismic action were analyzed. In addition to the traditional FEM and DEM mentioned above, some novel numerical simulation methods (e.g., DDA, CDEM, and FDEM) have also been applied to analyze the stability of different rock slopes [3; 29; 30; 31]. In summary, although different numerical simulation methods have been extensively used in the stability analysis of anti-dip slopes, the complexity of their failure and instability can be attributed to different geological conditions.