scholarly journals Effect of Stress Path on the Failure Envelope of Intact Crystalline Rock at Low Confining Stress

Minerals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1119
Author(s):  
Shantanu Patel ◽  
C. Derek Martin
Keyword(s):  
Numerical Modelling ◽  
Uniaxial Tension ◽  
Laboratory Tests ◽  
Triaxial Compression ◽  
Stress Path ◽  
Crystalline Rock ◽  
Intact Rock ◽  
Particle Model ◽  
Underground Excavations ◽  
The Impact

Numerical modelling is playing an increasing role in the interpretation of geological observations. A similar phenomenon is occurring with respect to the interpretation of the stress–strain response of intact rock measured in laboratory tests. In this research, the three-dimensional (3D) bonded particle model (BPM) with flat-jointed (FJ) contact was used to investigate the impact of stress paths on rock failure. The modified FJ contact model used for these studies numerically captured most of the intact rock behavior of Lac du Bonnet granite observed in the laboratory. A numerical simulation was used to track the behavior of this rock for different stress paths, starting with uniaxial tension and compression loading conditions. The migration from uniaxial tension to triaxial compression is challenging to simulate in physical laboratory tests but commonly observed around underground excavations. The numerical modelling methodology developed for this research tracks this stress path and the impact of the intermediate stress on peak strength at low confinements, commonly found around underground excavations.

A Simple and Practicable Approach on Implementing for the Reduced Triaxial Extension by the Conventional Triaxial Apparatus

2011 ◽  
Vol 250-253 ◽  
pp. 2089-2092
Author(s):  
Rong Jian Li ◽  
Xi An Li ◽  
Gao Feng Che ◽  
Wen Zheng ◽  
Wen Jun Chen
Keyword(s):  
Triaxial Compression ◽  
Stress Path ◽  
Test Results ◽  
Triaxial Apparatus ◽  
Eolian Sand ◽  
Conventional Triaxial Compression ◽  
The Difference ◽  
Shear Behaviors ◽  
The Impact ◽  
Triaxial Extension

Stress path is one of the very important factors of soil strength. It is significant to study the strength and reveal the importance of the impact of sand in different stress path conditions. Firstly, an ameliorating approach on implementing for the reduced triaxial extension by the conventional triaxial apparatus was discussed. Then, In order to study shear behaviors of the eolian sand under different stress path, two monotonic shearing tests with the conventional triaxial compression and the reduced triaxial extension stress path were performed and analyzed. The test results not only indicate that the amelioration on conventional triaxial apparatus is simple, practicable and inexpensive, but also reveal the difference of strength’s parameter between the reduced triaxial extension and conventional triaxial compression stress path. In sum, the stress path has important effect on the strength of the eolian sand.

scholarly journals Aziznejad, S. and Esmaieli, K. 2015. Effects of joint intensity on rock fragmentation by impact, 11th International Symposium on Rock Fragmentation by Blasting, 24-26 August, Sydney, Australia

2017 ◽  
Author(s):  
Kamran Esmaieli
Keyword(s):  
Rock Mass ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Rock Fragmentation ◽  
Intact Rock ◽  
Particle Model ◽  
Rock Masses ◽  
Dynamic Mechanical ◽  
Bonded Particle Model ◽  
The Impact

Impact-induced rock fragmentation is a mechanism that is commonly used for rock breakage in drilling andcrushing. Additionally, rock fragmentation by blasting is frequently used in rock excavation operations.Experience shows that presence of discontinuities in rock can significantly influence the impact-induceddamage and fragmentation of rock. Quantification of the response of jointed rock masses to impact loads iscomplicated by the fact that the available laboratory tests are mainly designed for aggregates or intact rocks.It can be argued that neither of these tests adequately represent a jointed rock mass. This paper presentsthe results of a series of numerical simulations used to investigate the influence of pre-existingdiscontinuities on the impact-induced fragmentation of rock masses. The methodology includesdetermination of the static and dynamic mechanical properties of a rock unit by conducting a series oflaboratory tests on intact rock samples collected from a quarry in Canada. A 2D distinct element code,Particle Flow Code (PFC2D), was used to generate a bonded particle model in order to simulate both staticmechanical properties (Uniaxial Compressive Strength, Elastic Modulus, Poisson’s Ratio and indirect TensileStrength) and dynamic mechanical property (drop weight tensile strength) of the intact rock. The calibratednumerical model was then used to construct large-scale synthetic rock mass samples by incorporatingdiscontinuity networks of different intensity into the bonded particle model. Finally, the impact-inducedfragmentation inflicted by a rigid projectile particle on the jointed rock mass samples, simulated by asynthetic rock mass model, was determined. More fragmentation was observed for the rock mass sampleswith higher joint intensity.

Influence of the Deformation Method on the Microstructure Changes in AZ31 Magnesium Alloy Round Rods Obtained by the Rolling Process

2016 ◽  
Vol 716 ◽  
pp. 864-870
Author(s):  
Andrzej Stefanik ◽  
Piotr Szota ◽  
Sebastian Mróz ◽  
Teresa Bajor ◽  
Sonia Boczkal
Keyword(s):  
Magnesium Alloy ◽  
Numerical Modelling ◽  
Rolling Mill ◽  
Laboratory Tests ◽  
Effective Strain ◽  
Rolling Process ◽  
Az31 Magnesium Alloy ◽  
Deformation Method ◽  
Microstructure Changes ◽  
Skew Rolling

This paper presents the research results of the microstructure changes of the round rods of AZ31 magnesium alloy in the hot rolling processes. The rolling was conducted in duo mill and a three-high skew rolling mill. Numerical modelling of the AZ31 magnesium alloy round rods rolling process was conducted using a computer program Forge 2011®. The verification of the results of numerical modelling was carried out during laboratory tests in a two-high rolling mill D150 and a three-high skew rolling mill RSP 40/14. Distributions of the total effective strain and temperature during AZ31 rods rolling process were determined on the basis of the theoretical analysis. Microstructure and texture changes during both analysed processes were studied.

Fractality of Simulated Fracture

2009 ◽  
Vol 409 ◽  
pp. 154-160 ◽  
Author(s):  
Petr Frantík ◽  
Zbyněk Keršner ◽  
Václav Veselý ◽  
Ladislav Řoutil
Keyword(s):  
Numerical Model ◽  
Elastic Plate ◽  
Model Simulation ◽  
Element Model ◽  
The Other ◽  
Particle Model ◽  
Discrete Element Model ◽  
Fractal Nature ◽  
Discrete Elements ◽  
The Impact

The paper is focussed on numerical simulations of the fracture of a quasi-brittle specimen due to its impact onto a fixed rigid elastic plate. The failure of the specimen after the impact is modelled in two ways based on the physical discretization of continuum: via physical discrete elements and pseudo-particles. Advantages and drawbacks of both used methods are discussed. The size distribution of the fragments of the broken specimen resulting from physical discrete element model simulation follows a power law, which indicates the ability of the numerical model to identify the fractal nature of the fracture. The pseudo-particle model, on the other side, can successfully predict the kinematics of the fragments of the specimen under impact failure.

scholarly journals Experimental Study on Limestone Cohesive Particle Model and Crushing Simulation

2018 ◽  
Vol 2018 ◽  
pp. 1-12
Author(s):  
Huaiying Fang ◽  
Dawei Xing ◽  
Jianhong Yang ◽  
Fulin Liu ◽  
Junlong Chen ◽  
...  
Keyword(s):  
Particle Size ◽  
Simulation Model ◽  
Impact Velocity ◽  
Distribution Curve ◽  
Particle Model ◽  
Particle Sizes ◽  
Particle Crushing ◽  
Discrete Element Method Simulation ◽  
Impact Crushing ◽  
The Impact

This study investigates the effect of impact velocity and particle size on crushing characteristics. We use a discrete-element method simulation and construct cohesive limestone particles with internal microinterfaces and cracks for impact crushing experimentation. The simulation model follows the same process as the impact crushing experiment. Results show that, after crushing at impact velocities of 30 and 40 m/s, the simulated particle-size distribution curve matches experimental results as closely as 95%. For different particle sizes, results are more than 90% in agreement. These results indicate the feasibility of the cohesive-particle crushing simulation model. When the particle size is 15 mm, an approximate linear relationship exists on impact velocity and crushing ratio. For a constant impact velocity, the particle size of 18 mm results in the maximum crushing ratio.

scholarly journals Forecasting the impact of buildings with multi-storey underground parts on the displacement of subsoil using modern numerical tools

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Hanna Michalak ◽  
Paweł Przybysz
Keyword(s):  
Numerical Modelling ◽  
Numerical Models ◽  
Deep Excavation ◽  
Design And Implementation ◽  
Numerical Tools ◽  
Excavation Support ◽  
Area Of Influence ◽  
The Impact ◽  
New Buildings ◽  
Ground Part

Abstract The paper will analyse and review the experience to date in determining the impact range of implementation of deeply founded structures on the displacement of the subsoil in the vicinity. With the background of these experiences, primarily empirical, the present possibilities of using numerical modelling to forecast the displacements of the terrain surface in various stages of works, that is, execution of deep excavation support systems, excavation-deepening phases with successive adding of struts, construction of underground levels and erection of the above-ground part of the building, will be presented. Based on the results of own research, conclusions on the use of 3D numerical models in spatial shaping and designing the structure of underground parts of new buildings erected in dense urban development will be presented. The characterised 3D numerical models were verified, taking into account the actual results of geodetic measurements of the completed buildings. Determining the range and forecasting the displacements of the subsoil are necessary for the design and implementation of investments due to the need to ensure the safety of erection and use of a new building and the buildings located within the area of influence.

scholarly journals Cooling of Electrons in a Weakly Outgassing Comet

2020 ◽  
Author(s):  
Peter Stephenson ◽  
Marina Galand ◽  
Jan Deca ◽  
Pierre Henri ◽  
Gianluca Carnielli
Keyword(s):  
Solar Wind ◽  
Extreme Ultraviolet ◽  
Pure Water ◽  
Particle Model ◽  
Particle In Cell ◽  
Electron Sources ◽  
Cometary Plasma ◽  
Impedance Probe ◽  
Cold Electrons ◽  
The Impact

<p>The plasma instruments, Mutual Impedance Probe (MIP) and Langmuir Probe (LAP), part of the Rosetta Plasma Consortium (RPC), onboard the Rosetta mission to comet 67P revealed a population of cold electrons (<1eV) (Engelhardt et al., 2018; Wattieaux et al, 2020; Gilet et al., 2020). This population is primarily generated by cooling warm (~10eV) newly-born cometary electrons through collisions with the neutral coma. What is surprising is that the cold electrons were detected throughout the escort phase, even at very low outgassing rates (Q<1e26 s<sup>-1</sup>) at large heliocentric distances (>3 AU), when the coma was not thought to be dense enough to cool the electron population significantly.</p> <p> Using a collisional test particle model, we examine the behaviour of electrons in the coma of a weakly outgassing comet and the formation of a cold population through electron-neutral collisions. The model incorporates three electron sources: the solar wind, photo-electrons produced through ionisation of the cometary neutrals by extreme ultraviolet solar radiation, and secondary electrons produced through electron-impact ionisation.</p> <p>The model includes different electron-water collision processes, including elastic, excitation, and ionisation collisions.</p> <p> The electron trajectories are shaped by electric and magnetic fields, which are taken from a 3D collisionless fully-kinetic Particle-in-Cell (PIC) model of the solar wind and cometary plasma  (Deca 2017, 2019). We use a spherically symmetric coma of pure water, which gives a r<sup>-2</sup> profile in the neutral density. Throughout their lifetime, electrons undergo stochastic collisions with neutral molecules, which can degrade the electrons in energy or scatter them.</p> <p>We first validate our model with comparison to results from PIC simulations. We then demonstrate the trapping of electrons in the coma by an ambipolar electric field and the impact of this trapping on the production of cold electrons.</p>

scholarly journals Stability Assessment of Mining Excavations: the Impact of Large Depths

2018 ◽  
Vol 40 (3) ◽  
pp. 180-187
Author(s):  
Tadeusz Majcherczyk ◽  
Zbigniew Niedbalski ◽  
Łukasz Bednarek
Keyword(s):  
Rock Mass ◽  
In Situ Monitoring ◽  
Stability Assessment ◽  
Underground Excavations ◽  
Deformation Prediction ◽  
Large Depth ◽  
Coal Deposits ◽  
The Impact

AbstractBack in the early 1980s, coal deposits occurring at depths of ~700 m below surface were already regarded as large-depth deposits. Meanwhile, today the borderline depth of large-depth mining has extended to >1,000 m. Design, excavation and maintenance of mining roadways at the depth of >1,000 m have, therefore, become crucial issues in a practical perspective in recent years. Hence, it is now extremely important to intensify research studies on the influence of large depths on the behaviour of rock mass and deformation of support in underground excavations. The paper presents the results of the study carried out in five mining excavations at depths ranging from 950 to 1,290 m, where monitoring stations with measurement equipment were built. The analysis of data from laboratory and coal mine tests, as well as in situ monitoring, helped to formulate a set of criteria for stability assessment of underground excavations situated at large depths. The proposed methodology of load and deformation prediction in support systems of the excavations unaffected by exploitation is based on the criteria referring to the depth of excavation and the quality of rock mass. The depth parameter is determined by checking whether the analysed excavation lies below the critical depth, whereas the rock mass quality is determined on the basis of the roof lithology index (WL) and the crack intensity factor (n)

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