scholarly journals Johnson–Holmquist-II(JH-2) Constitutive Model for Rock Materials: Parameter Determination and Application in Tunnel Smooth Blasting

2018 ◽  
Vol 8 (9) ◽  
pp. 1675 ◽  
Author(s):  
Jianxiu Wang ◽  
Yao Yin ◽  
Chuanwen Luo
Keyword(s):  
Constitutive Model ◽  
High Pressures ◽  
Numerical Study ◽  
Parameter Determination ◽  
Economic Losses ◽  
Large Strains ◽  
Determination Method ◽  
Rock Materials ◽  
Rock Tunnels ◽  
Smooth Blasting

The Johnson–Holmquist-II(JH-2) model is introduced as the constitutive model for rock materials in tunnel smooth blasting. However, complicated and/or high-cost experiments need to be carried out to obtain the parameters of the JH-2 constitutive model. This study chooses Barre granite as an example to propose a quick and convenient determination method for the parameters of the JH-2 model using a series of computational and extrapolated methods. The validity of the parameters is verified via comparing the results of 3D numerical simulations with laboratory blast-loading experiments. Subsequently, the verified parameter determination method, together with the JH-2 damage constitutive model, is applied in the numerical simulation of smooth blasting in Zigaojian tunnel, Hangzhou–Huangshan high-speed railway. The overbreak/underbreak induced by rock blasting and joints/discontinuities is well estimated through comparing the damage contours resulting from the numerical study with the tunnel profiles measured from the tunnel site. The peak particle velocities (PPVs) of the near field are extracted to estimate the damage scope and damage degree for the surrounding rock mass of the tunnel on the basis of PPV damage criteria. This method can be used in the excavation of rock tunnels subjected to large strains, high strain rates, and high pressures, thereby reducing safety risk and economic losses.

A Computational Constitutive Model for Glass Subjected to Large Strains, High Strain Rates and High Pressures

2011 ◽  
Vol 78 (5) ◽  
Author(s):  
Timothy J. Holmquist ◽  
Gordon R. Johnson
Keyword(s):  
Constitutive Model ◽  
Strain Rate ◽  
High Pressures ◽  
High Strain ◽  
Material Strength ◽  
Large Strains ◽  
Single Element ◽  
Strain Rates ◽  
High Strain Rates ◽  
Third Invariant

This article presents a computational constitutive model for glass subjected to large strains, high strain rates and high pressures. The model has similarities to a previously developed model for brittle materials by Johnson, Holmquist and Beissel (JHB model), but there are significant differences. This new glass model provides a material strength that is dependent on the location and/or condition of the material. Provisions are made for the strength to be dependent on whether it is in the interior, on the surface (different surface finishes can be accommodated), adjacent to failed material, or if it is failed. The intact and failed strengths are also dependent on the pressure and the strain rate. Thermal softening, damage softening, time-dependent softening, and the effect of the third invariant are also included. The shear modulus can be constant or variable. The pressure-volume relationship includes permanent densification and bulking. Damage is accumulated based on plastic strain, pressure and strain rate. Simple (single-element) examples are presented to illustrate the capabilities of the model. Computed results for more complex ballistic impact configurations are also presented and compared to experimental data.

scholarly journals A 3DEC Numerical Analysis of the Interaction Between an Uneven Rock Surface and Shotcrete Lining

2021 ◽  
Author(s):  
Ping Zhang ◽  
Ering Nordlund
Keyword(s):  
Numerical Study ◽  
Support Effect ◽  
Influential Factors ◽  
Numerical Analyses ◽  
Numerical Code ◽  
Rock Surface ◽  
Stress Concentrations ◽  
Circular Tunnel ◽  
Rock Tunnels ◽  
Shotcrete Lining

AbstractRock tunnels excavated using drilling and blasting technique in jointed rock masses often have a very uneven and rough excavation surface. Experience from previous studies shows that the unevenness of a rock surface has a large impact on the support effect of shotcrete lining. However, clear conclusions regarding the effect of 2D and 3D uneven surfaces were not obtained due to limited studies in the literature. The numerical analyses reported in this paper were made to investigate the influence of the surface unevenness of a circular tunnel opening on the support effect of shotcrete using a 3D numerical code (3DEC). The models were first calibrated with the help of observations and measured data obtained from physical model tests. The influential factors were investigated further in this numerical study after calibration had been achieved. The numerical analyses show that, in general, the unevenness of a tunnel surface produces negative support effects due to stress concentrations in recesses (compressive) and at apexes (tensile) after excavation. However, shotcrete sprayed on a doubly waved uneven surface has better support effect compared to shotcrete sprayed on a simply waved tunnel surface. The development of shear strength (specifically frictional strength) on the uneven interface between the shotcrete and the rock contributes to this effect, in the condition where bonding of the shotcrete does not work effectively. The interface is a crucial element when the interaction between the rock and shotcrete is to be simulated. When an entire tunnel surface is covered by shotcrete with high modulus, more failures will occur in the shotcrete especially when rock surface is uneven. Based on the numerical model cases examined, some recommendations on how to incorporate tunnel surface conditions (2D or 3D unevenness) in the design of a shotcrete lining are given.

scholarly journals Rock Failure Analysis Based on a Coupled Elastoplastic-Logarithmic Damage Model

2017 ◽  
Vol 62 (4) ◽  
pp. 753-774
Author(s):  
M. Abdia ◽  
H. Molladavoodi ◽  
H. Salarirad
Keyword(s):  
Constitutive Model ◽  
Plastic Flow ◽  
Mechanical Response ◽  
Damage Model ◽  
Yield Function ◽  
Irreversible Thermodynamics ◽  
Stiffness Degradation ◽  
Shear Stresses ◽  
Rock Materials ◽  
Damage Process

Abstract The rock materials surrounding the underground excavations typically demonstrate nonlinear mechanical response and irreversible behavior in particular under high in-situ stress states. The dominant causes of irreversible behavior are plastic flow and damage process. The plastic flow is controlled by the presence of local shear stresses which cause the frictional sliding. During this process, the net number of bonds remains unchanged practically. The overall macroscopic consequence of plastic flow is that the elastic properties (e.g. the stiffness of the material) are insensitive to this type of irreversible change. The main cause of irreversible changes in quasi-brittle materials such as rock is the damage process occurring within the material. From a microscopic viewpoint, damage initiates with the nucleation and growth of microcracks. When the microcracks length reaches a critical value, the coalescence of them occurs and finally, the localized meso-cracks appear. The macroscopic and phenomenological consequence of damage process is stiffness degradation, dilatation and softening response. In this paper, a coupled elastoplastic-logarithmic damage model was used to simulate the irreversible deformations and stiffness degradation of rock materials under loading. In this model, damage evolution & plastic flow rules were formulated in the framework of irreversible thermodynamics principles. To take into account the stiffness degradation and softening on post-peak region, logarithmic damage variable was implemented. Also, a plastic model with Drucker-Prager yield function was used to model plastic strains. Then, an algorithm was proposed to calculate the numerical steps based on the proposed coupled plastic and damage constitutive model. The developed model has been programmed in VC++ environment. Then, it was used as a separate and new constitutive model in DEM code (UDEC). Finally, the experimental Oolitic limestone rock behavior was simulated based on the developed model. The irreversible strains, softening and stiffness degradation were reproduced in the numerical results. Furthermore, the confinement pressure dependency of rock behavior was simulated in according to experimental observations.

Experimental and Numerical Study of Soft Tissue Surrogate Behavior Under Ballistic Loading

2012 ◽  
Author(s):  
Ericka K. Amborn ◽  
Karim H. Muci-Küchler ◽  
Brandon J. Hinz
Keyword(s):  
Soft Tissue ◽  
Constitutive Model ◽  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Numerical Study ◽  
Constitutive Models ◽  
Material Behavior ◽  
Good Representation

Studying the high strain rate behavior of soft tissues and soft tissue surrogates is of interest to improve the understanding of injury mechanisms during blast and impact events. Tests such as the split Hopkinson pressure bar have been successfully used to characterize material behavior at high strain rates under simple loading conditions. However, experiments involving more complex stress states are needed for the validation of constitutive models and numerical simulation techniques for fast transient events. In particular, for the case of ballistic injuries, controlled tests that can better reflect the effects induced by a penetrating projectile are of interest. This paper presents an experiment that tries to achieve that goal. The experimental setup involves a cylindrical test sample made of a translucent soft tissue surrogate that has a small pre-made cylindrical channel along its axis. A small caliber projectile is fired through the pre-made channel at representative speeds using an air rifle. High speed video is used in conjunction with specialized software to generate data for model validation. A Lagrangian Finite Element Method (FEM) model was prepared in ABAQUS/Explicit to simulate the experiments. Different hyperelastic constitutive models were explored to represent the behavior of the soft tissue surrogate and the required material properties were obtained from high strain rate test data reported in the open literature. The simulation results corresponding to each constitutive model considered were qualitatively compared against the experimental data for a single projectile speed. The constitutive model that provided the closest match was then used to perform an additional simulation at a different projectile velocity and quantitative comparisons between numerical and experimental results were made. The comparisons showed that the Marlow hyperelastic model available in ABAQUS/Explicit was able to produce a good representation of the soft tissue surrogate behavior observed experimentally at the two projectile speeds considered.

scholarly journals Predicting the Mechanical Properties of Bimrocks with High Rock Block Proportions Based on Resonance Testing Technology and Damage Theory

2019 ◽  
Vol 9 (17) ◽  
pp. 3537
Author(s):  
Yuexiang Lin ◽  
Limin Peng ◽  
Mingfeng Lei ◽  
Xiang Wang ◽  
Chengyong Cao
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Constitutive Model ◽  
Uniaxial Compression ◽  
Rock Block ◽  
Dynamic Elastic Modulus ◽  
Parameter Determination ◽  
Design Parameters ◽  
Damage Theory ◽  
Design And Construction

Block-in-matrix-rocks (bimrocks) are very complicated geological masses that cause many challenging problems during the design and construction of engineering projects, such as parameter determination and landsliding. Successful engineering design and construction depends on a suitable constitutive model and reliable design parameters for geological masses. In this paper, the vibration attenuation signal of welded bimrocks was obtained and studied using resonance test technology. Combined with a uniaxial compression test, a constitutive model was proposed to describe the mechanical behavior of welded bimrocks. On this basis, the relations between the dynamic elastic modulus and the physical parameters of bimrocks were established, which included macroscopic mechanical parameters and damage constitutive parameters. Consequently, a new technological process was proposed to provide quick identification of the mechanical properties of welded bimrocks. The results indicate that the dynamic elastic modulus is highly correlated with the rock block proportion (RBP) and uniaxial compression strength (UCS). It is an effective parameter to predict the strength of the bimrocks with high RBPs. Additionally, the proposed constitutive model, which is based on damage theory, can accurately simulate the strain softening behavior of the bimrocks. Combining the resonant frequency technology and the proposed constitutive model, the complete stress strain curve can be obtained in a rapid and accurate manner, which provides a further guarantee of the stability and safety of underground engineering.

scholarly journals Numerical Predictions of a Swirl Combustor Using Complex Chemistry Fueled with Ammonia/Hydrogen Blends

Energies ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 288 ◽  
Author(s):  
Marco-Osvaldo Vigueras-Zuniga ◽  
Maria-Elena Tejeda-del-Cueto ◽  
José-Alejandro Vasquez-Santacruz ◽  
Agustín-Leobardo Herrera-May ◽  
Agustin Valera-Medina
Keyword(s):  
Boundary Conditions ◽  
High Pressures ◽  
Numerical Study ◽  
High Energy ◽  
Combustion Efficiency ◽  
Heat Losses ◽  
High Hydrogen ◽  
Numerical Predictions ◽  
Combustion Systems ◽  
Complex Chemistry

Ammonia, a chemical that contains high hydrogen quantities, has been presented as a candidate for the production of clean power generation and aerospace propulsion. Although ammonia can deliver more hydrogen per unit volume than liquid hydrogen itself, the use of ammonia in combustion systems comes with the detrimental production of nitrogen oxides, which are emissions that have up to 300 times the greenhouse potential of carbon dioxide. This factor, combined with the lower energy density of ammonia, makes new studies crucial to enable the use of the molecule through methods that reduce emissions whilst ensuring that enough power is produced to support high-energy intensive applications. Thus, this paper presents a numerical study based on the use of novel reaction models employed to characterize ammonia combustion systems. The models are used to obtain Reynolds Averaged Navier-Stokes (RANS) simulations via Star-CCM+ with complex chemistry of a 70%–30% (mol) ammonia–hydrogen blend that is currently under investigations elsewhere. A fixed equivalence ratio (1.2), medium swirl (0.8), and confined conditions are employed to determine the flame and species propagation at various operating atmospheres and temperature inlet values. The study is then expanded to high inlet temperatures, high pressures, and high flowrates at different confinement boundary conditions. The results denote how the production of NOx emissions remains stable and under 400 ppm, whilst higher concentrations of both hydrogen and unreacted ammonia are found in the flue gases under high power conditions. The reduction of heat losses (thus higher temperature boundary conditions) has a crucial impact on further destruction of ammonia post-flame, with a raise in hydrogen, water, and nitrogen through the system, thus presenting an opportunity of combustion efficiency improvement of this blend by reducing heat losses. Final discussions are presented as a method to raise power whilst employing ammonia for gas turbine systems.

Response of a polystyrene foam subjected to large strains and high pressures

2018 ◽  
Vol 227 (1-2) ◽  
pp. 61-71 ◽  
Author(s):  
G. R. Johnson ◽  
T. J. Holmquist ◽  
S. Chocron ◽  
N. L. Scott
Keyword(s):  
High Pressures ◽  
Large Strains ◽  
Polystyrene Foam
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