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This paper proposes a modified Hybrid Finite-Element Material-Point Method (HFEMPM) for analyzing reinforced slopes. The method discretizes the soil using material points, and employs bar elements in the finite-element method to represent geosynthetics that can only withstand tensile loads. The interaction between geosynthetics and soil is naturally captured using the same background grid by HFEMPM. To capture their frictional contact more precisely, a specific procedure to evaluate the maximum frictional force of the bar exerted by the soil is proposed in this paper, which makes the modified HFEMPM more applicable in modelling reinforced soil. The μ (I) rheology from granular mechanics is introduced for stress updating of soil. The method is applied to simulate the experimental collapse of rod piles and centrifuge tests of reinforced slopes. Incorporating the μ (I) rheology for stress updating into the HFEMPM not only enables including the influence of particle size and initial soil strength on the stability of slopes, but also describing the effect of strain rate strengthening during the collapse process. Based on calculated results of stability with various reinforcement lengths and number of layers, a reference chart designed to summarize the optimal reinforcement scheme is provided as a guide in reinforced-soil engineering. [ABSTRACT FROM AUTHOR]

The Bisection Method is a common search strategy implemented as part of the shear strength reduction procedure for finite element slope stability analysis. Despite the Bisection Method's simplicity and reliability as a root finding technique, it is generally accepted to achieve slower rates of convergence than many alternatives. The aim of this paper is the description of an efficient method for performing shear strength reduction using root bracketing techniques, specifically for Finite Element slope stability analysis. The False Position (regula falsi) Method enables computationally intensive slope models to be simulated by minimising the total number of solver iterations required to determine the factor of safety. Several finite element models are presented to highlight the applicability of the given methods, with significant savings made (in the order of 50 percent) with respect to two of the most common strength reduction procedures − uniform incrementation and the Bisection Method. In all cases, strong agreement in safety factors is observed between traditional strength reduction methods and the proposed techniques. [ABSTRACT FROM AUTHOR]

Local instability of a compound slope is commonplace in practice. Extant analytical solutions only considered the single global failure pattern, which results in an inaccurate assessment of slope stability. This paper develops a unified analytical framework to account for the local and global instability of a compound slope. A failure pattern coefficient is proposed for the determination of instability behaviors. On this basis, the kinematically admissible three-dimensional (3D) failure mechanism is modified to describe the collapse of slopes. Under the framework of the upper-bound theorem of limit analysis, the external work rates and the internal dissipation rates can be calculated from the unified failure mechanism. The strength reduction technique is introduced into the work rate balance equation, and then the explicit solution of the safety factor is derived. The critical safety factor and slip surface are obtained through a hybrid optimization of the objective function. By way of example, the present solutions are compared with previous solutions and the results of the finite element method. Good agreements of the safety factor and slip surface show the good capability of this study to implement the stability analysis of compound slopes. A detailed parametric study is carried out to reveal the influence of slope geometry, soil strength, and external excitation on slope stability and failure pattern. The method presented in this paper provides a more rigorous solution for the stability assessment of compound slopes. [ABSTRACT FROM AUTHOR]

The meshless numerical manifold method (MNMM) inherits the advantages of handling continuous and discontinuous problems uniformly, improving interpolation precision, and avoiding linear dependence issues. This paper refines the MNMM method for slope stability analysis to overcome the dependence and sensitivity of the strength reduction method of the finite element method on the number of finite element meshes and the algorithm for solving the nonlinear equations when calculating slopes with soft and weak interlayers. First, the strength reduction method (SRM) was incorporated into MNMM to create the numerical model called MNMM-SRM. Based on the MNMM-SRM, a complementary Mohr-Coulomb (M−C) control equation compliant with Koiter's rule of multi-yielding surfaces was established. In the principal stress space, the subspace tracking method was used to track the eigenvalues and eigenvectors of the stress tensor, thereby addressing the corner problem of M−C multi-yield surfaces. Combining the k-means clustering algorithm with wavelet transformation and employing the slope's total nodal displacement field as an input variable, an intelligent and efficient critical slip surface (CSS) automatic extraction method was developed. Three typical cases were used to validate the accuracy of the numerical model. This numerical model has a wide range of potential applications in slope stability research. [ABSTRACT FROM AUTHOR]

Pre-existing (open) cracks at slope crests, especially tension cracks, are a significant factor in the transition from shallow to deep-seated landslides in unsaturated soil slopes induced by rainfall. This paper presents an analytical framework to assess the stability of unsaturated soil slopes for deep-seated rotational failure considering arbitrary crack depths and unsteady infiltration, and its effectiveness is verified by previous literature and finite element analysis. A closed-form formula is proposed for the maximum depth of cracks in unsaturated soils by the stability of the vertical crack boundary. A parametric study is performed to investigate the impact of some key parameters on the stability of unsaturated soil slopes with cracks. Dimensionless stability charts are developed, which can calculate the factor of safety for the slopes with cracksof any depth and can reflect that the potential slip surfaces through or without passing through the crack tip. In addition, given the existence of a critical crack depth and maximum crack depth, with a ratio ranging from 0.5 to 0.6 based on the stability charts, deep-seated rotational failure is more likely to occur than failure caused by a crack boundary. [ABSTRACT FROM AUTHOR]

A fresh slope stability analysis method is proposed in this paper, with combining scaled boundary finite element method (SBFEM), strength reduction method (SRM) and polytree-based mesh refinement algorithm. Firstly, SBFEM and SRM (SBFEM-SRM) formulation are innovatively combined to conduct the slope stability analysis with a coarse analysis mesh. Secondly, a shear-strain-based refinement indicator is introduced to determine the elements that need to be refined, then multistage local mesh refinement can be implemented recursively on-demand via the independently developed polytree-based refinement algorithm. The accuracy and superiority of SBFEM-SRM are firstly verified using a simple slope example. The effectiveness and applicability of SBFEM-SRM combined with the polytree-based refinement algorithm is demonstrated by using two examples, including a multilayered nonhomogeneous soli slope and an actual test embankment. The advantages of different methods can be inherited in the presented method, wherein flexible polygonal elements can be solved directly, and making a strong adaptability for complex geometry equipped. Moreover, the computational burden would be alleviated efficiently without compromising accuracy, benefiting from local adaptive mesh refinement strategy. And inspired by this, the proposed method can be briefly extended to 3D slope stability analysis, wherein the application performance will be more significant. [ABSTRACT FROM AUTHOR]

Many rainfall-induced landslides are reported to be shallow. Therefore, when regional slope stability analysis, or landslide hazard mapping is carried out, simple approaches, such as the infinite slope model, are often used. However, the infinite slope model is known to underestimate the factor of safety due to the absence of boundary effects. More sophisticated methods that account for the boundary effects at the toe and head of the landslide are much more computationally expensive. In this paper upper bound limit analysis (UBLA) is presented with a novel failure mechanism which consists of a translational parallelogram in the middle slope and two log-spiral components at the slope crest and slope toe to capture the boundary effect. The new approach is derived for a full range of pore water pressure conditions and validated by finite element limit analyses. For shallow landslides the translational UBLA is found to outperform the conventional log-spiral UBLA. The results of a large parametric study using the translational UBLA are then used to develop a novel analytical shallow landslide model which retains the simplicity of the traditional infinite slope model, but yet improves accuracy considerably, making this an attractive alternative for routine analysis such as landslide hazard mapping. [ABSTRACT FROM AUTHOR]

This paper proposes a novel optimization-based finite element method with a mixed constant-stress smoothed-strain element to solve elastoplastic problems. The proposed computational framework has three advantages: (1) in the proposed mixed constant-stress smoothed-strain element, the strain is smoothed on the edge-based smoothing domain, and the stress is assumed to be constant in each smoothing domain; (2) the cubic bubble shape function is introduced at the centroid of the element to enrich the displacement field. This makes the proposed approach accurate and free of volumetric locking for low-order elements; (3) the discrete elastoplastic boundary-value problem is formulated as a standard second-order cone problem based on the generalized Hellinger–Reissner variational principle, which is quickly and efficiently solved by the primal-dual interior-point algorithm. The proposed approach is validated on several classical problems of geotechnical engineering: the bearing capacity of footing and pipe under small deformation and slope stability. All the obtained results demonstrate that the proposed method adopting the novel mixed constant-stress smoothed-strain element offers competitively high computational accuracy and efficiency. [ABSTRACT FROM AUTHOR]

This paper presents a numerical technique for geotechnical slope stability analysis, integrating digital image meshing with the scaled boundary finite element method, allowing site conditions such as complex stratigraphies, surface and internal geometry evolution to be simulated in a robust and straightforward procedure. The quadtree decomposition technique is used to automatically discretise the geometry directly from digital images using pixel information to accurately capture boundaries with fine-scale elements. The process allows complex numerical models to be generated from cross-section images of slopes, capitalising on the combination of the scaled boundary finite element method and quadtree meshing. The spatial distribution of the soil material properties can be represented by the colour of each pixel. A mapping technique is developed to integrate these parameters into the computational mesh. The feasibility of the proposed method is presented through case study simulations of an active large Australian open-pit mine, considering various aspects of complex features such as geometry, stratigraphy and material behaviour. [ABSTRACT FROM AUTHOR]

Numerical investigation on stability of the rock slope with densely distributed fractures is still challenging. To overcome the large computational requirements caused by the fracture representation, material heterogeneity and mathematical nonlinearity, an efficient discrete fracture network (DFN) based modeling scheme is developed in this paper. With DFNs stochastically generated according to the statistical distributions of the fractures for resembling the natural fractured rock slope, finite element method (FEM) based strength reduction analysis is conducted for locating the critical slip surface and assessing the factor of safety, where the rock blocks are discretized as solid elements while discrete fractures are practically modeled by frictional contact interface elements. The effectiveness of the proposed approach is validated by comparison against analytical and several numerical solutions. A case study is further performed to evaluate the effects of DFN realization number and geometrical configuration on the stability of the fractured rock slope. It shows that 20 DFN realizations are sufficient to obtain a statistically convergent mean of the factor of safety. The predicted critical slip surface displays to be non-circular but linear or broken line morphology along the fracture network. The proposed numerical scheme shows to be useful and promising in investigating the deformation response and sliding failure mode in highly fractured rock slope. Massive fractures disorder the displacement distribution of the slope and influence the overall factor of safety, and the estimated factor of safety decreases with the increase ofslope height and angle, indicating the fracture distribution and slope geometric features as the prominent influential factors. [ABSTRACT FROM AUTHOR]

Modelling of delayed failure of cut slopes in soft sensitive clays is a significant challenge because of three major features taking place simultaneously: large deformation of the slope up to failure, pore water pressure generation and dissipation in the slope, and complicated time-dependent deformation of sensitive clay. This paper proposes a novel fully hydro-mechanical coupled edge-based strain smoothed particle finite element (ES-PFEM) modelling approach for delayed failure of cut slope with three outstanding features: (1) the particle finite element method with low-order edge-based strain-smoothed element for large deformation analysis, (2) an efficient stabilization method for pore water pressure to circumvent the Babuška-Brezzi stability restriction and (3) the elasto-viscoplastic model considering time-dependency, anisotropy and destructuration of soft sensitive clays. The accuracy and efficiency of the proposed approach are first examined by simulating consolidation test and strip footing. Furthermore, an adaptive substepping algorithm is proposed for the elasto-viscoplastic model. Finally, a typical case of delayed failures of cut slopes with different angles in soft sensitive clays is simulated and analysed, demonstrating the predictive ability of the proposed approach. The relationship between slope angle, sensitivity of clay and time of failure occurring is obtained for predicting the slope failure time in practice. [ABSTRACT FROM AUTHOR]