A Failure Criterion for Cracked Rock Mass under Seepage Pressure and Confining Pressure

2011 ◽  
Vol 225-226 ◽  
pp. 937-940
Author(s):  
Bi Yong Li ◽  
Zhe Ming Zhu ◽  
Zhang Tao Zhou
Keyword(s):  
Stress Intensity Factor ◽  
Rock Mass ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Failure Criterion ◽  
Crack Surface ◽  
Surface Friction ◽  
Confining Pressure ◽  
Seepage Pressure ◽  
Boundary Collocation Method

The existence of water affects the mechanical properties of cracked rock mass. Taking into account the friction generated by the crack closure, the stress intensity factor of the center cracked plate subjected to compression and seepage pressure was obtained through the theoretical analysis and numerical calculation of the boundary collocation method. The results show that crack tip stress intensity factor increases with the increasing of the seepage pressure, but decreases with the increasing of crack surface friction and the confining pressure. Finally a failure criterion for cracked rock mass under seepage pressure and confining pressure is developed.

scholarly journals Complex Analytical Study of the Stability of Tunnel-Surrounding Rock in a Layered Jointed Rock Mass

2020 ◽  
Vol 2020 ◽  
pp. 1-15 ◽  
Author(s):  
Su Wu ◽  
Kegang Li ◽  
Zaihong Yang ◽  
Shunchuan Wu ◽  
Ting Wang ◽  
...  
Keyword(s):  
Stress Intensity Factor ◽  
Rock Mass ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Inclination Angle ◽  
Failure Criterion ◽  
Mapping Function ◽  
Jointed Rock ◽  
Jointed Rock Mass ◽  
Structural Failure

A barrier function method based on the fmincon optimization function in MATLAB was used to determine the function to map a tunnel boundary to the unit circle in the complex plane, and a structural failure criterion of the mapping convergence was established based on the reliability theory of underground engineering. The joints were approximated as cracks around the tunnel, the anisotropy of the stress intensity factor due to the crack inclination and position changes was studied, and the modified scoring parameter of the layered joints around the tunnel for the rock geomechanics classification (RMR) was proposed and used at points around the tunnel. The calculation method for the supporting stress was required to balance the bias load. The results showed the following: (1) When taking the structural failure criterion as the convergence condition of the mapping function, the mapping function converged when the mapping accuracy was δ ≥ 31.74 % . (2) The crack with an inclination angle of β = 45 ° was the dominant structural plane of the jointed rock mass around the tunnel. The anisotropy of the stress intensity factor K II at the tip of the mode II crack indicated that the corresponding cracks at the various points around the tunnel had inconsistent influences on the tunnel. The position had the greatest influence, followed by the straight wall area, and then by the top and floor areas. (3) When the crack inclination β was equal to the inclination angle β 0 of the dominant joint plane, the secondary crack was parallel to the unloading surface of the corresponding tunnel. (4) The bias load formed by the layered joints around the tunnel reduced the stress threshold of the failure of the rib spalling.

Effect of the Crack Surface Friction on the Field Strength of Bi-Material-Interfacial Crack

2016 ◽  
Vol 713 ◽  
pp. 301-304
Author(s):  
You Tang Li ◽  
Lei Liu
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Effective Stress ◽  
Crack Surface ◽  
Interfacial Crack ◽  
Crack Tip ◽  
Surface Friction ◽  
Element Model ◽  
Crack Size

The stress field, displacement field and stress intensity factor are discussed based on elastic theory in this paper. The finite element model for interface crack of bi-material is set up, the friction phenomena of interface between two materials is simulated. The effect of crack size ratio and friction factor of crack surface on crack tip displacement, equivalent effective stress and stress intensity factor are analyzed. The results show that with the increase of the crack surface friction coefficient, the displacement and equivalent effective stress of the crack tip, and stress intensity factor will also increase under the condition of the same crack size. If the crack surface friction is ignored, the results will be not precise and are not in conformity with the practical engineering, even the significant impacts will disappear in the research for crack initiation, extension and fracture.

Effect of Confining Pressure on Stress Intensity Factors for Cracked Brazilian Disk

2015 ◽  
Vol 07 (03) ◽  
pp. 1550051 ◽  
Author(s):  
Wen Hua ◽  
Jigang Xu ◽  
Shiming Dong ◽  
Jizhou Song ◽  
Qingyuan Wang
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Confining Pressure ◽  
Mode Ii ◽  
Pure Mode ◽  
Intensity Factors ◽  
Brazilian Disk ◽  
Mode Ii Crack

An analytical model, verified by the finite element method, is developed to study the effect of confining pressure on stress intensity factors for the cracked Brazilian disk. The closed-form expressions for stress intensity factors under both confining pressure and diametric forces are obtained based on the weight function method. The results show that the confining pressure has no effect on the mode II stress intensity factor; however, the mode I stress intensity factor decreases with the increase of confining pressure and the change may be above 100% for a large confining pressure. In addition, the effect of confining pressure on the loading condition of pure mode II crack is also investigated. It is shown that the critical loading angle for pure mode II crack decreases as the confining pressure increases. Depending on the magnitude of confining pressure, the failure problem of a disk may be no longer a pure fracture problem. These results have established the theoretical foundation to measure the fracture toughness of materials under confining pressure.

Effects of Crack Surface Heat Conductance on Stress Intensity Factors

1990 ◽  
Vol 57 (2) ◽  
pp. 354-358 ◽  
Author(s):  
An-Yu Kuo
Keyword(s):  
Thermal Conductivity ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Crack Surface ◽  
Surface Heat ◽  
Mode Ii ◽  
Intensity Factors ◽  
Heat Conductance

Effects of crack surface heat conductance on stress intensity factors of modes I, II, and III are investigated. The crack problem is first solved by assuming perfect (infinite) heat conductance at crack surfaces. Finite heat conductance at crack surfaces is then accounted for by imposing a set of distributed dipoles at the crack surfaces. Distribution function of the dipoles is the solution of a Fredholm integral equation. It is shown that, for cracks in a homogeneous, isotropic, linear elastic solid, the degree of thermal conductivity at crack surfaces will affect the magnitude of mode I and mode II stress intensity factors but not mode III stress intensity factor. It is also shown that, for a geometrically symmetric cracked solid, only the mode II stress intensity factor will be influenced by different crack surface heat conductance even if the thermal loading is not symmetric. More importantly, for a given material thermal conductivity (K) and crack surface heat convection coefficient (h), effects of crack surface heat conductance on stress intensity factors is found to depend upon crack size. This “size effect” implies that, for a given set of K and h, an extremely small crack can be treated as if the crack surfaces are insulated and a very long crack can be treated as if the crack surfaces are perfectly heat conductive. As an example, the problem of a finite crack in an infinite plate subjected to a constant temperature gradient at infinity is studied.

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