scholarly journals Numerical Study of Fracture Characteristics of Deep Granite Induced by Blast Stress Wave

2021 ◽  
Vol 2021 ◽  
pp. 1-22
Author(s):  
Zheming Zhu ◽  
Weiting Gao ◽  
Duanying Wan ◽  
Meng Wang ◽  
Yun Shu
Keyword(s):  
Shear Failure ◽  
Numerical Study ◽  
Numerical Models ◽  
Rock Fracture ◽  
Initial Pressure ◽  
3D Models ◽  
In Situ Stress ◽  
Vertical Pressure ◽  
The Difference ◽  
Radial Cracks

To study the characteristics of rock fracture in deep underground under blast loads, some numerical models were established in AUTODYN code. Weibull distribution was used to characterize the inhomogeneity of rock, and a linear equation of state was applied to describe the relation of pressure and volume of granite elements. A new stress initialization method based on explicit dynamic calculation was developed to get an accurate stress distribution near the borehole. Two types of in situ stress conditions were considered. The effect of heterogeneous characteristics of material on blast-induced granite fracture was investigated. The difference between 2D models and 3D models was discussed. Based on the numerical results, it can be concluded that the increase of the magnitude of initial pressure can change the mechanism of shear failure near the borehole and suppress radial cracks propagation. When initial lateral pressure is invariable, with initial vertical pressure rising, radial cracks along the acting direction of vertical pressure will be promoted, and radial cracks in other directions will be prevented. Heterogeneous characteristics of material have an obvious influence on the shear failure zones around the borehole.

Propagation Mechanism of Coal Rock Fracture under Gas Pressure

2011 ◽  
Vol 402 ◽  
pp. 626-630
Author(s):  
Zhi Gang Zhao ◽  
Di Di Gan
Keyword(s):  
Shear Failure ◽  
Shear Fracture ◽  
Rock Fracture ◽  
Pressure Coefficient ◽  
Maximum Principal Stress ◽  
In Situ Stress ◽  
Gas Pressure ◽  
Propagation Mechanism ◽  
Coal Rock ◽  
The Difference

The failure of coal rock under gas pressure and in-situ stress is an inevitable stage of coal and gas outburst. The propagation mechanism of coal rock fracture under gas pressure is studied in this paper using fracture mechanics. The expression of normal stress and shear stress is given first with the simplification that the fracture is elliptical. Then the relationship among critical gas pressure, fracture direction and side pressure coefficient is studied in two branches as tension-shear failure and compression-shear failure. For tension-shear fracture, the fracture will be easy to propagate while the fracture has the same direction as maximum principal stress. For compression-shear fracture, the propagation direction is determined by the difference of compression-shear parameter and friction coefficients.

scholarly journals Numerical Investigation of the Impacts of Borehole Breakouts on Breakdown Pressure

Energies ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 888 ◽  
Author(s):  
Hua Zhang ◽  
Shunde Yin ◽  
Bernt Aadnoy
Keyword(s):  
Hydraulic Fracturing ◽  
Shear Failure ◽  
In Situ Stress ◽  
Test Results ◽  
Breakdown Pressure ◽  
Borehole Breakout ◽  
Borehole Breakouts ◽  
The Difference ◽  
Mud Pressure

Borehole breakouts appear in drilling and production operations when rock subjected to in situ stress experiences shear failure. However, if a borehole breakout occurs, the boundary of the borehole is no longer circular and the stress distribution around it is different. So, the interpretation of the hydraulic fracturing test results based on the Kirsch solution may not be valid. Therefore, it is important to investigate the factors that may affect the correct interpretation of the breakdown pressure in a hydraulic fracturing test for a borehole that had breakouts. In this paper, two steps are taken to implement this investigation. First, sets of finite element modeling provide sets of data on borehole breakout measures. Second, for a given measure of borehole breakouts, according to the linear relation between the mud pressure and the stress on the borehole wall, the breakdown pressure considering the borehole breakouts is acquired by applying different mud pressure in the model. Results show the difference between the breakdown pressure of a circular borehole and that of borehole that had breakouts could be as large as 82% in some situations.

scholarly journals Influence of Patching on the Shear Failure of Reinforced Concrete Beam without Stirrup

2021 ◽  
Vol 6 (7) ◽  
pp. 97
Author(s):  
Stefanus Adi Kristiawan ◽  
Halwan Alfisa Saifullah ◽  
Agus Supriyadi
Keyword(s):  
Reinforced Concrete ◽  
Shear Failure ◽  
Numerical Study ◽  
Unsaturated Polyester ◽  
Reinforced Concrete Beam ◽  
Concrete Cover ◽  
Shear Capacity ◽  
Rc Beam ◽  
Shear Span ◽  
Shear Cracking

Deteriorated concrete cover, e.g., spalling or delamination, especially when it occurs at the web of a reinforced concrete (RC) beam within the shear span, can reduce the shear capacity of the beam. Patching of this deteriorated area may be the best option to recover the shear capacity of the beam affected. For this purpose, unsaturated polyester resin mortar (UPR mortar) has been formulated. This research aims to investigate the efficacy of UPR mortar in limiting the shear cracking and so restoring the shear capacity of the deteriorated RC beam. The investigation is carried out by an experimental and numerical study. Two types of beams with a size of 150 × 250 × 1000 mm were prepared. The first type of beams was assigned as a normal beam. The other was a beam with a cut off in the non-stirrup shear span, which was eventually patched with UPR mortar. Two reinforcement ratios were assigned for each type of beams. The results show that UPR mortar is effective to hamper the propagation of diagonal cracks leading to increase the shear failure load by 15–20% compared to the reference (normal) beam. The increase of shear strength with the use of UPR mortar is consistently confirmed at various reinforcement ratios.

scholarly journals Numerical Study on Damage Zones Induced by Excavation and Ventilation in a High-Temperature Tunnel at Depth

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4773
Author(s):  
Jianyu Li ◽  
Hong Li ◽  
Zheming Zhu ◽  
Ye Tao ◽  
Chun’an Tang
Keyword(s):  
High Temperature ◽  
Lateral Pressure ◽  
Numerical Study ◽  
Pressure Coefficient ◽  
Fracture Morphology ◽  
In Situ Stress ◽  
Surrounding Rock ◽  
Geothermal System ◽  
Mechanical Coupling ◽  
Lateral Pressure Coefficient

Geothermal power is being regarded as depending on techniques derived from hydrocarbon production in worldwide current strategy. However, it has artificially been developed far less than its natural potentials due to technical restrictions. This paper introduces the Enhanced Geothermal System based on Excavation (EGS-E), which is an innovative scheme of geothermal energy extraction. Then, based on cohesion-weakening-friction-strengthening model (CWFS) and literature investigation of granite test at high temperature, the initiation, propagation of excavation damaged zones (EDZs) under unloading and the EDZs scale in EGS-E closed to hydrostatic pressure state is studied. Finally, we have a discussion about the further evolution of surrounding rock stress and EDZs during ventilation is studied by thermal-mechanical coupling. The results show that the influence of high temperature damage on the mechanical parameters of granite should be considered; Lateral pressure coefficient affects the fracture morphology and scale of tunnel surrounding rock, and EDZs area is larger when the lateral pressure coefficient is 1.0 or 1.2; Ventilation of high temperature and high in-situ stress tunnel have a significant effect on the EDZs scale; Additional tensile stress is generated in the shallow of tunnel surrounding rock, and the compressive stress concentration transfers to the deep. EDZs experiences three expansion stages of slow, rapid and deceleration with cooling time, and the thermal insulation layer prolongs the slow growth stage.

scholarly journals Evolution of Meniscal Biomechanical Properties with Growth: An Experimental and Numerical Study

2021 ◽  
Vol 8 (5) ◽  
pp. 70
Author(s):  
Marco Ferroni ◽  
Beatrice Belgio ◽  
Giuseppe M. Peretti ◽  
Alessia Di Giancamillo ◽  
Federica Boschetti
Keyword(s):  
Mechanical Properties ◽  
Stress Relaxation ◽  
Developmental Stage ◽  
Mechanical Response ◽  
Numerical Study ◽  
Numerical Models ◽  
Mechanical Stimulus ◽  
Specific Response ◽  
Mechanical Parameters ◽  
Biochemical Analyses

The menisci of the knee are complex fibro-cartilaginous tissues that play important roles in load bearing, shock absorption, joint lubrication, and stabilization. The objective of this study was to evaluate the interaction between the different meniscal tissue components (i.e., the solid matrix constituents and the fluid phase) and the mechanical response according to the developmental stage of the tissue. Menisci derived from partially and fully developed pigs were analyzed. We carried out biochemical analyses to quantify glycosaminoglycan (GAG) and DNA content according to the developmental stage. These values were related to tissue mechanical properties that were measured in vitro by performing compression and tension tests on meniscal specimens. Both compression and tension protocols consisted of multi-ramp stress–relaxation tests comprised of increasing strains followed by stress–relaxation to equilibrium. To better understand the mechanical response to different directions of mechanical stimulus and to relate it to the tissue structural composition and development, we performed numerical simulations that implemented different constitutive models (poro-elasticity, viscoelasticity, transversal isotropy, or combinations of the above) using the commercial software COMSOL Multiphysics. The numerical models also allowed us to determine several mechanical parameters that cannot be directly measured by experimental tests. The results of our investigation showed that the meniscus is a non-linear, anisotropic, non-homogeneous material: mechanical parameters increase with strain, depend on the direction of load, and vary among regions (anterior, central, and posterior). Preliminary numerical results showed the predominant role of the different tissue components depending on the mechanical stimulus. The outcomes of biochemical analyses related to mechanical properties confirmed the findings of the numerical models, suggesting a specific response of meniscal cells to the regional mechanical stimuli in the knee joint. During maturation, the increase in compressive moduli could be explained by cell differentiation from fibroblasts to metabolically active chondrocytes, as indicated by the found increase in GAG/DNA ratio. The changes of tensile mechanical response during development could be related to collagen II accumulation during growth. This study provides new information on the changes of tissue structural components during maturation and the relationship between tissue composition and mechanical response.

scholarly journals Application of Artificial Neural Networks for Predicting the Bearing Capacity of Shallow Foundations on Rock Masses

2021 ◽  
Author(s):  
M. A. Millán ◽  
R. Galindo ◽  
A. Alencar
Keyword(s):  
Bearing Capacity ◽  
Analytical Solutions ◽  
Shear Failure ◽  
Numerical Models ◽  
Computational Effort ◽  
Shallow Foundations ◽  
Geological Strength Index ◽  
Rock Masses ◽  
Ann Model ◽  
Artificial Neural

AbstractCalculation of the bearing capacity of shallow foundations on rock masses is usually addressed either using empirical equations, analytical solutions, or numerical models. While the empirical laws are limited to the particular conditions and local geology of the data and the application of analytical solutions is complex and limited by its simplified assumptions, numerical models offer a reliable solution for the task but require more computational effort. This research presents an artificial neural network (ANN) solution to predict the bearing capacity due to general shear failure more simply and straightforwardly, obtained from FLAC numerical calculations based on the Hoek and Brown criterion, reproducing more realistic configurations than those offered by empirical or analytical solutions. The inputs included in the proposed ANN are rock type, uniaxial compressive strength, geological strength index, foundation width, dilatancy, bidimensional or axisymmetric problem, the roughness of the foundation-rock contact, and consideration or not of the self-weight of the rock mass. The predictions from the ANN model are in very good agreement with the numerical results, proving that it can be successfully employed to provide a very accurate assessment of the bearing capacity in a simpler and more accessible way than the existing methods.

COMPARATIVE ANALYSIS FOR THREE FIXTURES OF PAUWELLS-II BY THE BIOMECHANICAL FINITE ELEMENT METHOD

2019 ◽  
Vol 20 (01) ◽  
pp. 1950079
Author(s):  
MATTHEW JIAN-QIAO PENG ◽  
HONGWEN XU ◽  
HAI-YAN CHEN ◽  
XIANGYANG JU ◽  
YONG HU ◽  
...  
Keyword(s):  
Finite Element ◽  
Numerical Models ◽  
Femoral Shaft ◽  
3D Models ◽  
Procedure Time ◽  
Stable Fixation ◽  
Secondary Fracture ◽  
Solid Models ◽  
Acute Correction ◽  
Hip Screw

Little is known about why and how biomechanics govern the hypothesis that three-Lag-Screw (3LS) fixation is a preferred therapeutic technique. A series models of surgical internal-fixation for femoral neck fractures of Pauwells-II will be constructed by an innovative approach of finite element so as to determine the most stable fixation by comparison of their biomechanical performance. Seventeen sets of CT scanned femora were imported onto Mimics extracting 3D models; these specimens were transferred to Geomagic Studio for a simulative osteotomy and kyrtograph; then, they underwent UG to fit simulative solid models; three sorts of internal fixators were expressed virtually by Pro-Engineer. Processed by Hypermesh, all compartments were assembled onto three systems actually as “Dynamic hip screw (DHS), 3LS and DHS+LS”. Eventually, numerical models of Finite Elemental Analysis (FEA) were exported to AnSys for solution. Three models for fixtures of Pauwells-II were established, validated and analyzed with the following findings: Femoral-shaft stress for [Formula: see text](3LS) is the least; Internal-fixator stress (MPa) for [Formula: see text]; Integral stress (MPa) for [Formula: see text]; displacement of femoral head (mm) for a[Formula: see text](DHS+LS) = 0.735; displacement of femoral shaft (mm) for [Formula: see text]; and displacement of fixators for [Formula: see text]. Mechanical comparisons for other femoral parks are insignificantly different, and these data can be abstracted as follows: the stress of 3LS-system was checked to be the least, and an interfragmentary displacement of DHS+LS assemblages was assessed to be the least”. A 3LS-system should be recommended to clinically optimize a Pauwells-II facture; if treated by this therapeutic fixation, breakage of fixators or secondary fracture is supposed to occur rarely. The strength of this study is that it was performed by a computer-aided simulation, allowing for design of a preoperative strategy that could provide acute correction and decrease procedure time, without harming to humans or animals.

Analysis of TBM Tunnel Behavior in Jointed Rock Mass

2011 ◽  
Vol 90-93 ◽  
pp. 2033-2036 ◽  
Author(s):  
Jin Shan Sun ◽  
Hong Jun Guo ◽  
Wen Bo Lu ◽  
Qing Hui Jiang
Keyword(s):  
Rock Mass ◽  
Numerical Models ◽  
Jointed Rock ◽  
In Situ Stress ◽  
Jointed Rock Mass ◽  
Joint Orientation ◽  
Joint Spacing ◽  
Factors Affecting ◽  
Dip Angle

The factors affecting the TBM tunnel behavior in jointed rock mass is investigated. In the numerical models the concrete segment lining of TBM tunnel is concerned, which is simulated as a tube neglecting the segment joint. And the TBM tunnel construction process is simulate considering the excavation and installing of the segment linings. Some cases are analyzed with different joint orientation, joint spacing, joint strength and tunnel depth. The results show that the shape and areas of loosing zones of the tunnel are influenced by the parameters of joint sets and in-situ stress significantly, such as dip angle, spacing, strength, and the in-situ stress statement. And the stress and deformation of the tunnel lining are influenced by the parameters of joint sets and in-situ stress, too.

Experimental and Numerical Study on Grinding Temperature during Surface Grinding with Different Cooling Methods

2009 ◽  
Vol 416 ◽  
pp. 514-518 ◽  
Author(s):  
Qing Long An ◽  
Yu Can Fu ◽  
Jiu Hua Xu
Keyword(s):  
Numerical Study ◽  
Specific Energy Consumption ◽  
Ground Surface ◽  
Numerical Results ◽  
Surface Grinding ◽  
Grinding Temperature ◽  
Air Jet ◽  
The Difference ◽  
High Specific Energy ◽  
Cooling Methods

Grinding, characterized by its high specific energy consumption, may generate high grinding zone temperature. These can cause thermal damage to the ground surface and poor surface integrity, especially in the grinding of difficult-to-machine materials. In this paper, experimental and fem study on grinding temperature during surface grinding of Ti-6Al-4V with different cooling methods. A comparison between the experimental and numerical results is made. It is indicated that the difference between experimental and numerical results is below 15% and the numerical results can be considered reliable. Grinding temperature can be more effectively reduced with CPMJ than that with cold air jet and flood cooling method.

Numerical Study of Corrugated Metal Panels Subjected to Windborne Debris Impacts

2014 ◽  
Vol 626 ◽  
pp. 109-114
Author(s):  
Wen Su Chen ◽  
Hong Hao ◽  
Hao Du
Keyword(s):  
Extreme Event ◽  
Numerical Study ◽  
Numerical Models ◽  
Economic Loss ◽  
Wind Loading ◽  
Windborne Debris ◽  
Study Laboratory ◽  
The Impact ◽  
Metal Panels ◽  
Corrugated Metal

Hurricane, typhoon and cyclone take place more and more often around the world with changing climate. Such nature disasters cause tremendous economic loss and casualty. Various kinds of windborne debris such as compact-like, plate-like and rod-like objects driven by hurricane usually imposes localized impact loading on the structure envelopes such as cladding, wall or roof, etc. The dominant opening in the envelope might cause serious damage to the structures, even collapse. To withstand the impact of such extreme event, the requirements on panel capacity to resist windborne debris impact has been presented in the Australian Wind Loading Code (2011) [1]. Corrugated metal panels are widely used as building envelop. In a previous study, laboratory tests have been carried out to investigate the performance of corrugated metal panels subjected to a 4kg wooden projectile by considering various impact locations, impact velocities and boundary conditions. In this study, numerical models were developed to simulate the responses of the corrugated metal panels subjected to wooden debris impacts by using commercial software LS-DYNA. The predicted data from the numerical simulations were compared with the experimental results. The validated numerical model can be used to conduct intensive numerical simulation to study the failure probabilities of corrugated structural panels subjected to windborne debris impacts.

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