scholarly journals Numerical Modelling of Microwave Heating Assisted Rock Fracture

2021 ◽  
Author(s):  
Martina Pressacco ◽  
Jari J. J. Kangas ◽  
Timo Saksala
Keyword(s):  
Tensile Strength ◽  
Microwave Heating ◽  
Solution Method ◽  
Numerical Study ◽  
Rock Fracture ◽  
Model Performance ◽  
Mechanical Problem ◽  
Mechanical Parts ◽  
Tension Tests ◽  
Rock Specimens

AbstractThis paper presents a numerical study on the effects of microwave irradiation on the mechanical properties of hard rock. More specifically, the weakening effect of microwave heating induced damage on the uniaxial compressive and tensile strength of granite-like rock is numerically evaluated. Rock fracture is modelled by means of a damage-viscoplasticity model with separate damage variables for tensile and compressive failure types. We develop a global solution strategy where the electromagnetic problem is solved first separately in COMSOL multiphysics software, and then provided into a staggered implicit solution method for the thermo-mechanical problem. The thermal and mechanical parts of the problem are considered as uncoupled due to the dominance of the microwave-induced heat source. The model performance is tested in 2D finite element simulations of heterogeneous numerical rock specimens subjected first to heating in a microwave oven and then to uniaxial compression and tension tests. According to the results, the compressive and tensile strength of rock can be significantly reduced by microwave heating pretreatment.

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.

scholarly journals Dynamic Indentation Characteristics for Various Spacings and Indentation Depths: A Study Based on Laboratory and Numerical Tests

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Jie Liu ◽  
Wen Wan ◽  
Yu Chen ◽  
Jun Wang
Keyword(s):  
Crack Propagation ◽  
Laboratory Tests ◽  
Indentation Depth ◽  
Numerical Study ◽  
Stress Concentrations ◽  
Dynamic Indentation ◽  
Indentation Force ◽  
Numerical Tests ◽  
Crack Tips ◽  
Rock Specimens

Laboratory and numerical study tests were conducted to investigate the dynamic indentation characteristics for various spacings and indentation depths. First, laboratory tests indicate that the increase in the indentation depth first resulted in enlarged groove volumes, caused by fiercer rock breakages between indentations for a fixed spacing; then, the groove volume slightly increased for further increase in indentation depth, whereas the increase in spacing restrained rock breakages and resulted in shrunken grooves. In addition, the numerical study agreed well with laboratory tests that small chips formed at the shallow part of the rock specimen at the early indentation stage, and then, larger chips formed by the crack propagation at deeper parts of the rock specimens when the indentation depth increased. With further increase in indentation depth, crushed powders instead of chips formed. Moreover, the numerical analysis indicates that crack propagation usually leads to the decrease of the indentation force and the dissipation of the stress concentrations at crack tips, whereas the cessation of crack propagation frequently resulted in the increase of the indentation force and the stress concentrations at crack tip with the increase in indentation depth.

Experimental Study on Bedding Plane Interfacial Slip

2012 ◽  
Vol 256-259 ◽  
pp. 298-301
Author(s):  
Shu Hong Dai ◽  
Ying Sun ◽  
Zi Xian Dong
Keyword(s):  
Rock Fracture ◽  
Correlation Method ◽  
Bedding Plane ◽  
Image Correlation ◽  
Interfacial Slip ◽  
Practical Applications ◽  
Three Point Bending ◽  
Natural Interface ◽  
Extension Direction ◽  
Rock Specimens

Interfacial slip in rock was studied utilizing digital image correlation method (DICM). Notched rock specimens consisting of a natural interface under three point bending were employed for researching the characters and mechanisms of the interfacial slip. The displacement and strain fields on the surface of specimen were measured accurately by DICM. The experimental results show that the interfacial slip can change the crack extension direction and mode. The results are helpful in researching the mechanism of interfacial slip and practical applications in rock fracture problems.

Tensile strength of sands treated with microbially induced carbonate precipitation

2020 ◽  
Vol 57 (10) ◽  
pp. 1611-1616 ◽  
Author(s):  
Ashkan Nafisi ◽  
Douglas Mocelin ◽  
Brina M. Montoya ◽  
Shane Underwood
Keyword(s):  
Tensile Strength ◽  
Large Earthquake ◽  
Carbonate Precipitation ◽  
Direct Tension ◽  
Sem Images ◽  
Cemented Soil ◽  
Tension Tests ◽  
Deformational Behavior ◽  
Microbially Induced Carbonate Precipitation ◽  
Sand Type

During large earthquake events where bending moments within soil cements are induced, the tensile strength of cemented soil may govern the deformational behavior of improved ground. Several studies have been conducted to assess the tensile strength of artificially cemented sands that use Portland cement or gypsum; however, the tensile strength of microbially induced carbonate precipitation (MICP)-treated sands with various particle sizes measured through direct tension tests has not been evaluated. MICP is a biomediated improvement technique that binds soil particles through carbonate precipitation. In this study, the tensile strength of nine specimens were measured by conducting direct tension tests. Three types of sand (coarse, medium, and fine) were cemented to reach a heavy level of cementation (e.g., shear wave velocity of ∼900 m/s or higher). The results show that the tensile strength varies between 210 and 710 kPa depending on sand type and mass of carbonate. Unconfined compressive strength (UCS) tests were performed for each sand type to assess the ratio between tensile strength and UCS in MICP-treated sands. Scanning electron microscopy (SEM) images and surface energy measurements were used to determine the predominant failure mode at particle contacts under tensile loading condition.

Determination of Rock Fracture Toughness K IIC and its Relationship with Tensile Strength

2011 ◽  
Vol 44 (5) ◽  
pp. 621-627 ◽  
Author(s):  
Yan Jin ◽  
Jianbo Yuan ◽  
Mian Chen ◽  
K. P. Chen ◽  
Yunhu Lu ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Tensile Strength ◽  
Rock Fracture ◽  
Rock Fracture Toughness

scholarly journals Numerical Study of Microwave Heating of Micrometer Size Metal Particles

2008 ◽  
Vol 48 (5) ◽  
pp. 681-684 ◽  
Author(s):  
Motoharu Suzuki ◽  
Maxim Ignatenko ◽  
Masashi Yamashiro ◽  
Motohiko Tanaka ◽  
Motoyasu Sato
Keyword(s):  
Microwave Heating ◽  
Numerical Study ◽  
Metal Particles ◽  
Micrometer Size

scholarly journals Experimental and Numerical Study on Tensile Strength of Concrete under Different Strain Rates

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Fanlu Min ◽  
Zhanhu Yao ◽  
Teng Jiang
Keyword(s):  
Tensile Strength ◽  
Strain Rate ◽  
Numerical Study ◽  
Material Behavior ◽  
Constitutive Law ◽  
Test Machine ◽  
Strain Rates ◽  
Dynamic Tensile Strength ◽  
Dynamic Increase Factor ◽  
Versus Strain

The dynamic characterization of concrete is fundamental to understand the material behavior in case of heavy earthquakes and dynamic events. The implementation of material constitutive law is of capital importance for the numerical simulation of the dynamic processes as those caused by earthquakes. Splitting tensile concrete specimens were tested at strain rates of 10−7 s−1to 10−4 s−1in an MTS material test machine. Results of tensile strength versus strain rate are presented and compared with compressive strength and existing models at similar strain rates. Dynamic increase factor versus strain rate curves for tensile strength were also evaluated and discussed. The same tensile data are compared with strength data using a thermodynamic model. Results of the tests show a significant strain rate sensitive behavior, exhibiting dynamic tensile strength increasing with strain rate. In the quasistatic strain rate regime, the existing models often underestimate the experimental results. The thermodynamic theory for the splitting tensile strength of concrete satisfactorily describes the experimental findings of strength as effect of strain rates.

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