Seismic Wave Conversion Caused by Shear Crack Initiation and Growth

AbstractThe behaviour of a rock mass is determined not only by the properties of the rock matrix, but mostly by the presence and properties of discontinuities or fractures within the mass. The compression test on rock-like specimens with two prefabricated transfixion fissures, made by pulling out the embedded metal inserts in the pre-cured period was carried out on the servo control uniaxial loading tester. The influence of the geometry of pre-existing cracks on the cracking processes was analysed with reference to the experimental observation of crack initiation and propagation from pre-existing flaws. Based on the rock fracture mechanics and the stress-strain curves, the evolution failure mechanism of the fissure body was also analyzed on the basis of exploring the law of the compression-shear crack initiation, wing crack growth and rock bridge connection. Meanwhile, damage fracture mechanical models of a compression-shear rock mass are established when the rock bridge axial transfixion failure, tension-shear combined failure, or wing crack shear connection failure occurs on the specimen under axial compression. This research was of significance in studying the failure mechanism of fractured rock mass.

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Seismic wave conversion near the upper boundary of the Pacific plate beneath the Kanto district, Japan

Geophysical Journal International ◽

10.1046/j.1365-246x.2000.00086.x ◽

2000 ◽

Vol 141 (1) ◽

pp. 136-148 ◽

Cited By ~ 19

Author(s):

Shiro Ohmi ◽

Sadaki Hori

Keyword(s):

Seismic Wave ◽

Pacific Plate ◽

The Pacific ◽

Kanto District ◽

Wave Conversion ◽

Upper Boundary

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Brittle fracture of rock under combined tensile and compressive loading conditions

Canadian Geotechnical Journal ◽

10.1139/cgj-2016-0214 ◽

2017 ◽

Vol 54 (1) ◽

pp. 88-101 ◽

Cited By ~ 9

Author(s):

S.B. Tang ◽

C.Y. Bao ◽

H.Y. Liu

Keyword(s):

Friction Coefficient ◽

Brittle Fracture ◽

Crack Initiation ◽

Crack Extension ◽

Shear Crack ◽

Pressure Coefficient ◽

Compressive Loading ◽

Confining Pressure ◽

Loading Conditions ◽

Stress Criterion

The brittle fracture of rock with an angled crack under combined tensile and compressive loading conditions is studied using linear elastic fracture mechanics (LEFM). The modified maximum tangential stress criterion (MTSC) and the maximum shear stress criterion (MSSC) are used to check crack initiations in the tensile and shear modes, respectively. The effects of the friction coefficient of the crack surfaces and the nonsingular stresses (T stresses) on the crack initiation are studied for the cases of both low and high compressive confining pressure coefficients. The T stresses include those both parallel (Tx) and perpendicular (Ty) to the crack plane. The type of crack initiation under the combined tensile and compressive loading conditions is found to remain tensile dominated when the compressive confining pressure coefficient is small. However, shear crack extension becomes possible with the compressive confining pressure coefficient and friction coefficient increasing if the crack orientation angle is small. Moreover, the high compressive confining pressure and substantial friction are found to increase the possibility of shear crack extension. The theoretical predictions presented in this study move one step forward than the available analytical solutions for the angled crack subjected to general biaxial load and agree well with those from experimental tests.

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Numerical Analysis of Fracture Behaviour on Marble Samples Containing Two Flaws

Advances in Civil Engineering ◽

10.1155/2020/6278289 ◽

2020 ◽

Vol 2020 ◽

pp. 1-15

Author(s):

Lifei Zheng ◽

Dan Huang ◽

Xiaoqing Li ◽

Xuan Hu

Keyword(s):

Energy Dissipation ◽

Crack Initiation ◽

Critical Stress ◽

Shear Failure ◽

Shear Crack ◽

Crack Coalescence ◽

Tensile Failure ◽

Crack Evolution ◽

Rock Bridge ◽

Fracturing Process

Uniaxial compression tests were conducted on marble specimens containing two flaws. There are coplanar flaws and noncoplanar flaws. The inclination angle and spacing of flaws were considered of the coplanar flaws model, and the step angle and spacing of flaws were considered of the noncoplanar flaws model. Strength failure and crack coalescence behaviour were analysed in the paper. The crack evolution process containing microcrack initiation, coalescence, and failure is focused on the rock bridge coalescence and the extent of the pre-existing flaws. There are four forms of rock bridge coalescence: tensile crack coalescence, shear crack coalescence, mixed tensile and shear crack coalescence, and no coalescence. Also, there are four forms of the rock failure mode: tensile failure, shear failure, mixed tensile and shear failure, and split fracture. The outer end of the critical stress values were used to compare with the crack initiation strengths, and the crack initiation strengths were slightly larger than the critical stress. In addition, energy dissipation laws were analysed during the model fracturing process. The crack evolution mechanisms around the pre-existing flaw in the model were revealed by the distribution of microcrack and energy dissipation.

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Study on mechanical behavior and damage process of concrete with initial damage under eccentric load

Scientific Reports ◽

10.1038/s41598-021-95964-x ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Ge Lina ◽

Yi Fu ◽

Zhou Junxia ◽

Du Changbo

Keyword(s):

Crack Initiation ◽

Shear Crack ◽

Peak Stress ◽

Confining Pressure ◽

Type I ◽

Uniform Load ◽

Eccentric Load ◽

Initiation Point ◽

Initial Damage ◽

Damage Process

AbstractIn order to analyze the influence of eccentric load on mechanical properties and damage process of concrete with initial damage, the eccentric load compression tests of concrete under different confining pressures were carried out with the help of PFC particle flow program. The results show that: the eccentric load does not change the relationship between peak stress, crack initiation stress and confining pressure of concrete under uniform load, but decrease the value of them. The peak stress increasing coefficient under uniform load is higher than that under eccentric load, and the peak stress increasing coefficient increases in a linear function with the confining pressure, and the increasing rate is approximately the same. Under uniaxial compression of eccentric load, a type I shear crack approximately parallel to the loading direction is formed, while under biaxial compression, a bending type shear crack with the lower tip of the initial crack as the inflection point is formed. The number of microcracks in concrete under uniform load and eccentric load can be divided into three stages: the calm period at the initial loading stage, the pre-peak expansion period from crack initiation point to peak point, and the rapid increase period after the peak.

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