dc.description.abstract | The dip slope, oblique slope, and anti-dip slope may present different engineering behaviors, which are dominated by the oblique angle defined by the angle between discontinuities and slope orientations on a rock slope. Additionally, the angle between the direction of an engineering configuration and the dip direction of discontinuity also influences the engineering characteristics of a rock slope. These phenomena display the anisotropy of engineering behaviors.
Due to the slope stability analysis on the oblique angle needing a three-dimensional numerical simulation, the Particle Flow Code in Three Dimension (PFC3D) is adopted to simulate a three-dimensional synthetic rock slope model (SRSM) herein, including the parts of intact rocks and discontinuities, which are generated by the bonded particle model (BPM) and the discrete fracture network (DFN), respectively. This simulation technique can successfully simulate the planar and toppling failures that are consistent with the field observations. This paper conducts a series of parametric studies with the oblique angle (the absolute value of the angle between the dip direction of discontinuity, alpha_j, and the dip direction of a slope, alpha_s, left|alpha_j-alpha_s
ight|), the slope angle (eta_s), slope height (H), the dip of discontinuity (eta_j), and the friction angle on SRSM simulations to investigate the influences on engineering behaviors of planar failure and toppling failure by these parameters. In this paper, rock blocks sliding from planar failure or falling from toppling failure are referred to as collapse blocks. The impact area of landslide, the displacement vectors of collapse blocks, and the energy release of landslide are further analyzed during the simulation process. One of the analyzed results, the energy release of landslide, is employed to determine the “critical oblique angle” for planar failure and the “critical inverse oblique angle” for toppling failure.
According to the numerical simulation results, the following conclusions can be drawn: (1) For the planar failure simulated by SRSM under the friction angle of discontinuity ≥ 30˚, the dip of slope ≤ 75˚, and the slope height ≤ 60m conditions, the critical oblique angle simulated by this paper is consistent with the critical oblique angles revealed in engineering practical experiences and the national codes, which appear 20˚. However, the critical oblique angle may exceed 20˚ even near 40˚ when multiple unfavorable factors, i.e., a moderate dip of discontinuity, a steep slope, a tall slope height, and a low friction angle of discontinuity, appear. (2) For the toppling failure simulated by SRSM, the critical inverse oblique angle simulated by this paper is similar to that in engineering practical experiences and the national codes, the former appears 30˚ and the latter appears 30˚. Similarly, the critical inverse oblique angle may exceed 30˚ even near 50˚ when multiple unfavorable factors appear, such as a high dip of discontinuity, a steep slope, and a low friction angle of discontinuity. (3) When rock slope satisfies three conditions of planar failure, i.e., parallelism condition (left|alpha_j-alpha_s
ight|<left|alpha_j-alpha_s
ight|_{cri}), daylight condition(eta_s>eta_j), and sliding condition (eta_j>emptyset_j), the energy release of landslide increases with the decreasing dip of discontinuity and vice versa. (4) For toppling failure simulated by SRSM, the energy release of landslide increases with the increasing dip of discontinuity and vice versa. However, for toppling failure calculated by limited equilibrium analysis, the safety factor of a slope decreases with the increasing dip of discontinuity. (5) When oblique angle and inverse oblique angle=0°, the mean of displacement vectors of collapse blocks is consistent with the dip direction of a slope, and it appears near the middle of the dip direction of a slope and the dip direction of discontinuities under the other conditions. | en_US |