scholarly journals Particle Flow Code Simulation of the Characteristics of Crack Evolution in Rock-Like Materials with Bent Cracks

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Zhanguo Ma ◽  
Shixing Cheng ◽  
Peng Gong ◽  
Jun Hu ◽  
Yongheng Chen
Keyword(s):  
Elasticity Modulus ◽  
Gradual Increase ◽  
Simulation Method ◽  
Two Dimensions ◽  
Particle Flow ◽  
Particle Flow Code ◽  
Crack Evolution ◽  
Underground Engineering ◽  
The Stability ◽  
The Impact

The distribution and propagation of rock cracks have a significant impact on geotechnical engineering. Taking rock-like materials with bent cracks as the research object, the particle flow code in two dimensions numerical simulation method was used to study the impact of the bend number on rock-like materials strength and crack evolution. According to the results, when the bend number was 1, 3, and 7, the strength of the specimens gradually increased; the elasticity modulus did not change significantly with the crack bend number. Uniaxial compression generated tensile cracks in all the specimens with bent cracks, but in terms of failure mode, the specimens with 0 bend tended to suffer penetrating failure along the fracture strike, while the specimens with 1, 3, and 7 bend tended to suffer penetrating failure along the diagonal direction. Both the fractal dimension and bend number were positively correlated with strain; with the gradual increase of the stress percentage, the damage variable of the specimens gradually increased at a growing rate. The research results provide a reference for predicting the stability of the underground engineering surrounding rocks containing bent cracks.

Stability Analysis of Side Slope under Normal and Rainfall Conditions

2013 ◽  
Vol 275-277 ◽  
pp. 1383-1388
Author(s):  
Cheng Liang Zhang ◽  
Lei Liu ◽  
Chun Wang
Keyword(s):  
Numerical Simulation ◽  
Simulation Method ◽  
Unstable State ◽  
Electrical Method ◽  
Rainfall Condition ◽  
Long Term Stability ◽  
Side Slope ◽  
Numerical Simulation Method ◽  
The Stability ◽  
The Impact

The paper studied a side slope engineering of highway in K29+450~K29+900 sections by making an on-site survey of landform and geological features of the side slope. By combining drilling, high-density electrical method and numerical simulation method, the depth and range of the sliding surface were determined. The stability of the side slope after an excavation in a normal and a rainfall conditions was analyzed using numerical simulation method, and simulation results show that in the normal condition the safety factor of the side slope is 1.12, and it is 1.05 in the rainfall condition; the distribution of plastic zones is wide, especially in the rainfall condition, the side slope has a large deformation and is in an unstable state. When a program of side slope reinforcement is chosen, the impact under rainfall condition should be considered in order to ensure long-term stability of side slope.

scholarly journals Investigation of the Effect of Bedding Layer Angle and Tunnel Number on the Stability of Tunnel under Uniaxial Compression Using PFC2D

2021 ◽  
Author(s):  
Vahab Sarfarazi ◽  
Kaveh Asgari ◽  
Mahdiyah Azizian
Keyword(s):  
Mechanical Properties ◽  
Uniaxial Compression ◽  
Dominant Mode ◽  
Two Dimensions ◽  
Particle Flow Code ◽  
Concrete Layer ◽  
Tunnel Diameter ◽  
Tunnel Number ◽  
Crack Growth Path ◽  
The Stability

In this paper the effect of bedding layer angle on the stability of tunnel under uniaxial compression have been investigated using particle flow code in two dimensions (PFC2D). For this purpose, numerical rectangle models with dimension of 100*100 mm have been prepared. These models consist of layers with different mechanical properties i.e., concrete layer and gypsum layer. The angle of these layers related to horizontal axis change from 0° to 90° with increment of 15°. These models are consisting of one, two and three tunnel. The diameter of tunnel change based on the tunnel number. The tunnel diameter was 6 m, when one tunnel exists in the model. The tunnel diameter was 3 m, when two tunnels exist in the model. The tunnel diameter was 2 m, when three tunnels exist in the model. These models were subjected to uniaxial compression. The results show that tensile cracks are dominant mode of fracture occurred in the models. The joint angle and tunnel number have important effect on the failure pattern and failure strength. Also, the mechanical properties of beddings control the crack growth path. The crack grows through the weak layers when bedding angle was equal to 45° and 60°, but it intersects the layer for any other bedding angels.

scholarly journals Failure behavior of the surrounding rock of jointed rock masses in a gold mine under impact disturbance

2021 ◽  
Author(s):  
Peng Li ◽  
Yunquan Wu ◽  
Meifeng Cai
Keyword(s):  
Stress Wave ◽  
Shear Failure ◽  
Jointed Rock ◽  
Surrounding Rock ◽  
Tensile Failure ◽  
Tensile Shear ◽  
Underground Engineering ◽  
Impact Stress ◽  
The Stability ◽  
The Impact

Abstract The impact disturbance has an important influence on the safety of underground engineering openings. In this paper, based on the in-situ stress measurement and structural plane investigation, the model of jointed rock roadway was established using the discrete element method (3DEC) to study the instability and failure characteristic of roadway surrounding rock with dominant joint planes under impact disturbance and to further analyze the influence of different buried depths, impact stress wave peaks, and stress wave delays on the stability of the surrounding rock. The results show that the stability of the surrounding rock is poor, and the whole convergence deformation of the surrounding rock occurs under the impact stress wave. There are three failure modes in the surrounding rock: tensile-shear failure, tensile failure, and shear failure. Tensile-shear failure mainly occurs in a small range close to the roof and floor of the roadway and the free surfaces of the two sides, and tensile failure occurs locally, while shear failure mainly occurs along the joint plane outside this range. Moreover, the greater the buried depth and stress wave peak value, the more serious the deformation of the surrounding rock. With the increase of stress wave delay, the deformation of the surrounding rock shows complex characteristics. In addition, the impact failure mechanism of the surrounding rock in jointed rock masses was discussed. The research results have important guiding significance for the prevention and control of underground engineering cavern disasters.

scholarly journals Natural convection with mixed insulating and conducting boundary conditions: low- and high-Rayleigh-number regimes

2014 ◽  
Vol 742 ◽  
pp. 636-663 ◽  
Author(s):  
P. Ripesi ◽  
L. Biferale ◽  
M. Sbragaglia ◽  
A. Wirth
Keyword(s):  
Natural Convection ◽  
Rayleigh Number ◽  
Boundary Conditions ◽  
Two Dimensions ◽  
Turbulent Regime ◽  
Thermal Insulating ◽  
Pattern Length ◽  
The Stability ◽  
The Impact ◽  
Rayleigh Numbers

AbstractWe investigate the stability and dynamics of natural convection in two dimensions, subject to inhomogeneous boundary conditions. In particular, we consider a Rayleigh–Bénard (RB) cell, where the horizontal top boundary contains a periodic sequence of alternating thermal insulating and conducting patches, and we study the effects of the heterogeneous pattern on the global heat exchange, at both low and high Rayleigh numbers. At low Rayleigh numbers, we determine numerically the transition from a regime characterized by the presence of small convective cells localized at the inhomogeneous boundary to the onset of ‘bulk’ convective rolls spanning the entire domain. Such a transition is also controlled analytically in the limit when the boundary pattern length is small compared with the cell vertical size. At higher Rayleigh number, we use numerical simulations based on a lattice Boltzmann method to assess the impact of boundary inhomogeneities on the fully turbulent regime up to $\mathit{Ra} \sim 10^{10}$.

Modeling and Simulation Calculation of a Overwater Autonomous Air Defense Weapon System

2014 ◽  
Vol 556-562 ◽  
pp. 6407-6413
Author(s):  
Bo Wei Zhao ◽  
Fa Xing LU ◽  
Xiao Wei Tang
Keyword(s):  
Simulation Method ◽  
Weapon System ◽  
Floating Platform ◽  
Error Sources ◽  
Air Defense ◽  
Whole Process ◽  
Simulation Calculation ◽  
The Stability ◽  
The Impact ◽  
The Waves

According to the problems of island air defense, an air defense autonomous weapon system carried by a floating platform on the water is proposed. Compared with the traditional land-based air defense weapons, this weapon system has higher security and mobility. On the other hand, the waves would have a greater impact on the stability of weapons platforms. In order to demonstrate the feasibility of the weapon system in a variety of error conditions, the combat system model facing with the whole process from the sensors finding the target to the air defense weapons capturing the target. At the same time, the model of the chain of system accuracy is proposed by adding the various error sources generated by the waves and the system itself to the model. The quantitative assessment of the impact on accuracy system by each source of error is implemented with the system simulation method. Finally, the feasibility of using the weapons on the actual combat is demonstrated with the results of the accuracy analysis .

Numerical Analysis of Negative Skin Friction for Pile under Surface Loading by Particle Flow Code

2012 ◽  
Vol 166-169 ◽  
pp. 482-486
Author(s):  
Feng Xi Zhou ◽  
Yuan Ming Lai
Keyword(s):  
Numerical Analysis ◽  
Numerical Simulations ◽  
Skin Friction ◽  
Two Dimensions ◽  
Particle Flow ◽  
Particle Flow Code ◽  
Surface Loading ◽  
Negative Skin Friction ◽  
Pile Interaction ◽  
End Bearing Pile

Numerical simulations of soil-pile interaction under surface loading are performed by particle flow code in two dimensions. Considering an end-bearing pile subjected to flexible distribution load, the variety of negative skin friction is studied. Numerical results show that negative skin friction is variation with the increasing of surface loading, and the negative skin friction is decrease when the value is up to ultimate skin friction.

scholarly journals Research on the Influence of Moisture Condition on the Mechanical Properties and Microstructure of Sandstone

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Zuosen. Luo ◽  
Zuoxiang. Zhu ◽  
Hao Bai ◽  
Daxiang Liu ◽  
Qiancheng. Sun
Keyword(s):  
Water Content ◽  
Gradual Increase ◽  
Triaxial Compression ◽  
Point Of View ◽  
Three Gorges Reservoir Area ◽  
Moisture Condition ◽  
The Three Gorges ◽  
The Stability ◽  
Moisture Conditions ◽  
The Impact

The sandstone from the dry to saturated state shows obvious deterioration characteristics. Taking the sandstone of a slope in the Three Gorges Reservoir area as the research object, uniaxial/triaxial compression of sandstone samples with different water-bearing states (dry, natural, and saturated) is carried out to study the changes in macromechanical properties of sandstone under different water-bearing states. Combined with NMR and SEM, the characteristics of microstructure of sandstone under different moisture conditions were studied. The results show that, with the increase of water content, the macromechanical parameters of sandstone gradually decrease, and the fine and microstructure characteristics are characterized by the gradual increase in the number of pores and the gradual increase in pore size. Based on the PFC2D software, considering the weakening effect of water on the partial cementation from a mesoscopic point of view, it is proposed to use soft and hard contacts to simulate the changes in the degree of cementation between particles under different water-bearing conditions and to study the impact of sandstone micromechanical parameters with changes in water content. Related research results can provide theoretical guidance for the stability evaluation of wading rock mass engineering.

scholarly journals Thermal Cracking Analysis during Pipe Cooling of Mass Concrete Using Particle Flow Code

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Liang Li ◽  
Xinghong Liu ◽  
Vinh T. N. Dao ◽  
Yonggang Cheng
Keyword(s):  
Thermal Cracking ◽  
Numerical Approach ◽  
Two Dimensions ◽  
Particle Flow ◽  
Particle Flow Code ◽  
Mass Concrete ◽  
Concrete Gravity Dam ◽  
Thermal Cracks ◽  
Thermal Fields ◽  
Good Agreement

Pipe cooling systems are among the potentially effective measures to control the temperature of mass concrete. However, if not properly controlled, thermal cracking in concrete, especially near water pipes, might occur, as experienced in many mass concrete structures. In this paper, a new numerical approach to simulate thermal cracking based on particle flow code is used to shed more light onto the process of thermal crack propagation and the effect of thermal cracks on thermal fields. Key details of the simulation, including the procedure of obtaining thermal and mechanical properties of particles, are presented. Importantly, a heat flow boundary based on an analytical solution is proposed and used in particle flow code in two dimensions to simulate the effect of pipe cooling. The simulation results are in good agreement with the monitored temperature data and observations on cored specimens from a real concrete gravity dam, giving confidence to the appropriateness of the adopted simulation. The simulated results also clearly demonstrate why thermal cracks occur and how they propagate, as well as the influence of such cracks on thermal fields.

Dietary Vitamin and Stability of Oral Anticoagulation: Proposal of a Diet with Constant Vitamin K1 Content

1997 ◽  
Vol 77 (03) ◽  
pp. 504-509 ◽  
Author(s):  
Sarah L Booth ◽  
Jacqueline M Charnley ◽  
James A Sadowski ◽  
Edward Saltzman ◽  
Edwin G Bovill ◽  
...  
Keyword(s):  
Dietary Intake ◽  
Vitamin K ◽  
High Performance ◽  
Case Reports ◽  
Food Composition ◽  
Dietary Guidelines ◽  
Dietary Vitamin ◽  
Vitamin K1 ◽  
The Stability ◽  
The Impact

SummaryCase reports cited in Medline or Biological Abstracts (1966-1996) were reviewed to evaluate the impact of vitamin K1 dietary intake on the stability of anticoagulant control in patients using coumarin derivatives. Reported nutrient-drug interactions cannot always be explained by the vitamin K1 content of the food items. However, metabolic data indicate that a consistent dietary intake of vitamin K is important to attain a daily equilibrium in vitamin K status. We report a diet that provides a stable intake of vitamin K1, equivalent to the current U.S. Recommended Dietary Allowance, using food composition data derived from high-performance liquid chromatography. Inconsistencies in the published literature indicate that prospective clinical studies should be undertaken to clarify the putative dietary vitamin K1-coumarin interaction. The dietary guidelines reported here may be used in such studies.

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