scholarly journals Negative Stiffness, Incompressibility and Strain Localisation in Particulate Materials

2021 ◽  
Vol 11 (18) ◽  
pp. 8751
Author(s):  
Arcady V. Dyskin ◽  
Elena Pasternak ◽  
Yuan Xu
Keyword(s):  
Compressive Loading ◽  
Peak Stress ◽  
Negative Stiffness ◽  
Particle Flow ◽  
Particle Flow Code ◽  
Strain Localisation ◽  
Isotropic Model ◽  
Single Strain ◽  
Bond Breakage ◽  
2D And 3D

In this paper, we consider two mechanisms capable of inducing strain localisation in particulate geomaterials in compression: the apparent negative stiffness and the incremental incompressibility caused by dilatancy. It is demonstrated that the apparent negative stiffness can be produced by the rotation of clusters of particles in the presence of compression. The clusters are formed by connecting the particles by the bonds that still remain intact in the process of bond breakage in compression. We developed a 2D isotropic model of incremental incompressibility showing that a single strain localisation zone is formed inclined at 45° to the direction of axial compressive loading. This mechanism of localisation was analysed through Particle Flow Code (PFC) 2D and 3D simulations. It is shown that, in the simulations, the peak stress (the onset of localisation) does correspond to the incremental Poisson’s ratio, reaching the critical values of 1 (in 2D) and 0.5 (in 3D).

Micro-Numerical Simulation of Anchorage Performance for Geotechnical Anchored Structure by Particle Flow Code

2011 ◽  
Vol 243-249 ◽  
pp. 3157-3166
Author(s):  
Si Feng Zhang ◽  
Yan Mei Li ◽  
Xiu Guang Song ◽  
Jian Zhou ◽  
Jian Cui
Keyword(s):  
Tensile Load ◽  
Reference Value ◽  
Peak Stress ◽  
Deformation Mode ◽  
Particle Flow ◽  
Particle Flow Code ◽  
Analysis Model ◽  
Interface Shear ◽  
Research Findings ◽  
Surrounding Soil

Based on the theory of particle flow code, the micro-numerical analysis model is established to study the anchorage performance of geotechnical prestressed anchorage structures. According to the numerical model tests, the development regularity of stress and displacement of surrounding soil around bar body under the effect of uplift loading is analyzed, and the interaction characters between anchor bolt and surrounding soil are also deeply studied. Conclusions can be drawn as follows: with the function of tensile load, two area of stress concentration form within the interior bond section of prestressed anchorage structure, and the soil porosity also changes accordingly. The interface shear stress peak point shift inward gradually with the increase of time-stepping, furthmore, the peak stress also enlarges gradually. According to the deformation mode, the surrounding soil can be divided into three zones. The radial displacement of soil between anchors is weakened because of the effects of group anchors, but the axial displacement is strengthened, which nominally is similar to the “single anchor character”. The research findings have a certain reference value for the study of anchorage mechanism.

scholarly journals Numerical Study of Damage to Rock Surrounding an Underground Coal Roadway Excavation

2020 ◽  
Vol 2020 ◽  
pp. 1-16 ◽  
Author(s):  
Jiangbo Wei ◽  
Shuangming Wang ◽  
Zhou Zhao ◽  
Delu Li ◽  
Lipeng Guo
Keyword(s):  
Field Survey ◽  
Numerical Study ◽  
Coal Mines ◽  
Circumferential Stress ◽  
Distribution Patterns ◽  
Particle Flow ◽  
Particle Flow Code ◽  
Stress Release ◽  
Coal Roadway ◽  
Shallow Coal Seam

In coal mines, underground roadways are required to transport coal and personnel. Such tunnels can become unstable and hazardous. This study simulates deformation and damage in the rock surrounding a shallow coal seam roadway using particle flow code. A numerical model of particle flow in the surrounding rock was constructed based on field survey and drilling data. Microcharacteristic indices, including stress, displacement, and microcrack fields, were used to study deformation and damage characteristics and mechanisms in the surrounding rocks. The results show that the stress within the rock changed gradually from a vertical stress to a circumferential stress pattern. Stress release led to self-stabilizing diamond-shaped and X-shaped tensile stress distribution patterns after the excavation of the roadway. Cracking increased and eventually formed cut-through cracks as the concentrated stress transferred to greater depths at the sides, forming shear and triangular-shaped failure regions. Overall, the roof and floor were relatively stable, whereas the sidewalls gradually failed. These results provide a reference for the control of rock surrounding roadways in coal mines.

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