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This paper develops an improved three-dimensional sphere discontinuous deformation analysis (SDDA) model and uses UAV-based photogrammetry to enable SDDA to numerically analyze potential long-runout debris flows in Zheduotang area along the Sichuan-Tibet railway. First, the original SDDA is improved by proposing a sphere-sphere bonding algorithm to bond spheres with tetrahedral layout to form four-sphere clusters to approximate non-sphere particles in debris flow. Second, the capacity of the improved SDDA is verified by comparing modelling results with four groups of laboratory tests of granular flow. Third, UAV-based photogrammetry is used to obtain the real morphology of the extremely complex terrain surface of Zheduotang area which is finally transferred into a large number of triangular faces as the fixed boundary faces of SDDA. Then, three potential debris flow scenarios on this terrain surface are numerically studied, and some suggestions for engineering disaster prevention are drawn. Model performance shows that, the improved SDDA is a feasible tool to simulate debris flows. With the help of UAV-based photogrammetry, it shows significantly helpful for geohazard prevention for infrastructures in mountainous areas like the Sichuan-Tibet railway. • An improved sphere discontinuous deformation analysis model is proposed. • The validation of the improved model in debris flow simulation is verified. • UAV-based photogrammetry to parameterize the extremely complex terrain surface of mountainous area is used. • Engineering-scale long-runout debris flow simulations are carried out. [ABSTRACT FROM AUTHOR]

Landslides are frequent and devastating geological hazards that cause significant economic and human losses annually. The selection of appropriate shear strength parameters is crucial for evaluating and preventing landslide failure. Considering the nonlinear characteristics of rock-mass material, a rock slope stability analysis model was built using the nonlinear Hoek‒Brown failure criterion. A Geological Strength Index–material constant (GSI–mi) curve, based on a deterministic method, was proposed to back analyzed the Geological Strength Index (GSI), which is consistent with a trial-and-error method, but simpler to implement. The back analysis can be extended to other parameters in addition to the GSI. Furthermore, considering the randomness and uncertainty, a reliability-based back analysis method for nonlinear strength parameters of the sliding surface was proposed. The optimal parameter combination that corresponded to the minimum reliability index was determined, which could serve as reasonable values of the nonlinear strength parameters for landslides. A comparison of different failure criteria also suggested that the stress level at the sliding surface should be accounted for in landslides using the significant nonlinear characteristics of strength parameters. [ABSTRACT FROM AUTHOR]

Granite rocks are subjected to exogenic forces, such as tectonic stress and chemical weathering, which cause them to weather differentially, forming boulders that are common in temperate and humid regions. The presence of a large boulder on a slope can significantly impact slope stability, resulting in the formation of what is known as a solitary boulder slope. This study is dedicated to investigate the large-deformation instability characteristics of such slopes. In pursuit of this objective, our study first validates an adapted material point method through laboratory experiments. Subsequently, utilizing the inverse discrete Fourier transform theory, boulders with varying shapes were synthesized and further transformed into material point method models. Finally, the material point method was employed to analyse the impact of boulder position, shape, and incline on the large deformation characteristics of the slope. The results show that: (1) The closer a boulder is to the plastic zone of the slope, the stronger its reinforcement effect on the slope. (2) As the shape of boulders becomes more complex, the run-out distance of the slope tends to decrease, but the variability in run-out distances increases. (3) The slope plastic zone moves around the boulder, and its distribution undergoes alterations based on the boulder's shape. This study investigates the instability characteristics of large deformation in boulder slopes with varying boulder shapes, which provides a reference for the stability assessment of solitary boulder slopes. [ABSTRACT FROM AUTHOR]

In this paper, the pullout factor and failure mode of circular anchor plate at an inclined angle with the horizontal ground under the normal stress are studied with the method of the upper bound finite element limit analysis. The effects of soil cohesion, internal friction angle, anchor plate inclination angle, and embedded ratio on the pullout factor are investigated to reveal the evolution of fracture surface of the soil around anchor plate under limit state. It is noted that the analysis of variance is adopted to process a series of data related to pullout capacity for obtaining the expression of the anchor plate's pullout factor. The results show that the internal friction angle is the key factor determining the pullout characteristics of the anchor plate. Particularly, the effect of the inclination angle on pullout capacity is highly correlated to the internal friction angle. For φ = 0 ° , failure zone around anchor plate is presented as localization plastic zone and pullout capacity is linearly related to soil cohesion. The effect of inclination angle on pullout resistance is less significant. For φ ≠ 0 ° , the failure mode around the anchor plate is developing into full failure zone extending from both sides of anchor plate to ground. It is clearly noted that angle between the failure surface and horizontal line is greatly affected by the inclination of the anchor plate. Moreover, the effect of the inclination angle on pullout factor increases with increasing internal friction angle, which should be considered in the evaluation of the pullout bearing characteristics of the inclined circular anchor plate. [ABSTRACT FROM AUTHOR]