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Joint roughness significantly affects the damage areas and peak shear strength of the rock joint. In this study, theoretical analysis and numerical simulations were carried out, and the results indicated that the resistance angles and heights of asperities quantified the damage range and damage degree, respectively, during the shearing process. Direct shear tests and 3D scanning tests were conducted on sets of mortar joint replicas and sandstone joints. By analyzing the test data, several morphological parameters were proposed to quantify the damage zone of the joint surface. Based on these morphological parameters, a new peak shear strength model, involving the effects of the height and dip angle of the joint surface, was constructed. Finally, the new model and previous classical models were compared. Moreover, the new model was used to predict the shear strength of other joint samples as well. The comparison and prediction results revealed that the new model is suitable for effective prediction of the peak shear strength of joints. [ABSTRACT FROM AUTHOR]

In this paper, we study a fifth order Camassa–Holm (FOCH) model with peakon solutions. Some interesting solutions are obtained including explicit single pseudo-peakons, two-peakon, and N -peakon solutions. In particular, detailed dynamical interactions for two-peakons and three-peakons are investigated numerically. [ABSTRACT FROM AUTHOR]

The numerical manifold method (NMM) simulates continuous and discontinuous problems in a unified framework; thus NMM has advantages in analysing crack propagation. However, calculation of the stress intensity factors (SIFs) when adopting the NMM requires additional procedures, such as the J-integral and the interaction integral. In this study, a hybrid crack element (HCE) method is incorporated into the NMM to directly obtain the SIFs; the new algorithm combines the merits of both the NMM and HCE method. In the proposed algorithm, the HCE is used in the crack-tip region while the NMM is applied in the remaining region. The SIFs at the crack-tip are calculated directly from the solution of the governing equation with less computational complexity relative to existing methods. The proposed algorithm does not require any changes to the initial mesh during crack propagation. It is verified by a few examples and the results show that the simulated crack propagation paths are in good agreement with the results from existing studies while the computational efficiency is improved due to the direct calculation of the SIFs and the consistency of the mesh system in the crack propagation process. [ABSTRACT FROM AUTHOR]

This paper introduces a simplified smooth rock reinforcement modeling approach based on the 2D combined finite discrete element method (FDEM). The goal is to facilitate modeling the end grouting process and the full grouting process of rock bolts reinforcement, and to improve further understanding of the interaction between bolt, grouting, and host rock based on material mechanical behavior. The study analyzed the mechanical model and fracture mode extracted from experimental results using the rebar bolt specimen. This facilitated the study of the bond strength component of the rib. Then, the bond force-slip relationship was explored using physical modeling with different combinations of bolt and cover constraints, with different types of grouts and rocks. Corroboration of the laboratory axial pullout test was then conducted. A power law for the stress-displacement of the radial component of bond force was generated, to elaborate simplified modeling method and the data range of parameters in the diverse combination of constraining forces. Then, the action law was implemented into the material rock reinforcement model in FDEM. The verification process, done by comparing the bond force-slip curve with the physical modeling, shows the model can effectively reflect the action rule of rebar bolts. The model simplifies rebar bolt modeling and adds a new ability to model rock reinforcement features into FDEM, making the FDEM technology extend fundamentally. [ABSTRACT FROM AUTHOR]

The effects of high temperature on rock strength and deformation, and hence the integrity of rock structure, have been a significant issue for rock mechanics and engineering. This article adopts a coupled thermomechanical (TM) solution method to explore the deterioration characteristics of heterogeneous rock under TM conditions. Based on the combination of damage mechanics and plasticity, a coupled material model with consideration of yielding, the plastic flow rule, damage evolution, the thermal effect, and heterogeneity was implemented in a commercial explicit finite-element code, LS-DYNA, through a user-defined material subroutine. Validation simulations indicate that the proposed model is capable of reproducing the mechanical behaviors of rock under unconfined compression and heating conditions. The effects of the heating temperature and homogeneity index on the mechanical properties were also investigated. The results indicate that rock exhibits prominent ductility characteristics with an increase in temperature regardless of the homogeneity index. With the same heterogeneity, monotonic reductions in unconfined compressive strength (UCS) and Young's modulus and an increase in peak strain were observed with an increase in the temperature. A single oblique fracture dominated the failure of the rock with lower homogeneity, whereas two conjugate fractures developed in the rock with more homogeneous strength. [ABSTRACT FROM AUTHOR]

A micro-mechanical based numerical manifold method (NMM) is proposed in this study to investigate the micro-mechanisms underlying rock macroscopic response and fracture processes. The Voronoi tessellation technique is adopted to create randomly-sized polygonal rock micro-grains. A rock micro-grain based broken criterion is proposed and a corresponding grain breaking technique is developed. To better represent the contact behavior of rock grain bonds, a cohesive fracture model that considers tensile, shear and compressive behaviors together, is adopted to interpret the failure of rock grain bonds. The developed program is first validated by reproducing biaxial tests of Transjurane sandstone. Finally, the influences of micro-parameters on the rock macroscopic response and failure modes are investigated. The results show that the developed micro-based model can mimic the deformation and failure characteristics of the test closely. A parameter study shows that the grain contact cohesion has significant effects on the model uniaxial compressive strength. The fracture process and failure mode of rock are dependent on the ratio of grain contact shear stiffness to normal stiffness. With the increase of the contact stiffness ratio, the failure mode of rock under uniaxial compression changes from a diffuse pattern to a concentrated shear band. [ABSTRACT FROM AUTHOR]

Rock slope failure is particularly detrimental to the safety of human life and engineering infrastructure. The pre-existing discontinuities in the jointed rock slopes play a key role in the slope stability, and the destabilization process often related to the complex interaction between the discontinuities and the intact rock bridge. Understanding the failure mechanism and accurately predicting the failure process are essential for the safety of jointed rock slopes. In this paper, a jointed rock slope analysis model (Y-slopeJ) is developed to evaluate the stability state and simulate the progressive failure process of jointed rock slopes based on the combined finite-discrete element method (FDEM). The accuracy and robustness of the proposed model are validated by numerical tests. Then this Y-slopeJ is applied to investigate the failure mechanism and failure process of rock slopes with various types of discontinuities, with an emphasis on crack initiation, propagation and coalescence. This work proposed a promising tool in understanding and predicting the progressive failure process of jointed rock slopes. [ABSTRACT FROM AUTHOR]

Recent attempts to solve rock mechanics problems using the numerical manifold method (NMM) have been regarded as fruitful. In this paper, a coupled hydro-mechanical (HM) model is incorporated into the enriched NMM to simulate fluid driven fracturing in rocks. In this HM model, a “cubic law” is employed to model fluid flow through fractures. Several benchmark problems are investigated to verify the coupled HM model. The simulation results agree well with the analytical and experimental results, indicating that the coupled HM model is able to simulate the hydraulic fracturing process reliably and correctly. [ABSTRACT FROM AUTHOR]