scholarly journals Modeling discrete fractures in continuum analysis and insights for fracture propagation and mechanical behavior of fractured rock

2019 ◽  
Vol 4 ◽  
pp. 100070 ◽  
Author(s):  
Goodluck I. Ofoegbu ◽  
Kevin J. Smart
Keyword(s):  
Mechanical Behavior ◽  
Fractured Rock ◽  
Fracture Propagation ◽  
Discrete Fractures ◽  
Continuum Analysis

scholarly journals Fracture Propagation Characteristic and Micromechanism of Rock-Like Specimens under Uniaxial and Biaxial Compression

2016 ◽  
Vol 2016 ◽  
pp. 1-11 ◽  
Author(s):  
Xue-wei Liu ◽  
Quan-sheng Liu ◽  
Shi-bing Huang ◽  
Lai Wei ◽  
Guang-feng Lei
Keyword(s):  
Fractured Rock ◽  
Fracture Propagation ◽  
Propagation Characteristic ◽  
Propagation Path ◽  
Biaxial Compression ◽  
Compression Tests ◽  
Microdamage Accumulation ◽  
Macroscopic Fracture ◽  
Crack Tips ◽  
Ae Location

This paper presents a set of uniaxial and biaxial compression tests on the rock-like material specimens with different fracture geometries through a rock mechanics servo-controlled testing system (RMT-150C). On the basis of experimental results, the characteristics of fracture propagation under different fracture geometries and loading conditions are firstly obtained. The newly formed fractures are observed propagating from or near the preexisting crack tips for different specimens, while the propagation paths are affected by the loading condition obviously. Then, by adopting acoustic emission (AE) location technique, AE event localization characteristics in the process of loading are investigated. The locations of AE events are in good agreement with the macroscopic fracture propagation path. Finally, the micromechanism of macroscopic fracture propagation under uniaxial and biaxial compression conditions is analyzed, and the fracture propagation can be concluded as a result of microdamage accumulation inside the material. The results of this paper are helpful for theory and engineering design of the fractured rock mass.

scholarly journals Experimental Study on Seepage Characteristics of Fractured Rock Mass under Different Stress Conditions

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Ma Haifeng ◽  
Yao Fanfan ◽  
Niu Xin’gang ◽  
Guo Jia ◽  
Li Yingming ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Permeability Coefficient ◽  
Fractured Rock ◽  
Axial Strain ◽  
Strain Curve ◽  
Confining Pressure ◽  
Strain Effect ◽  
Permeability Evolution ◽  
Hoop Strain ◽  
Permeability Characteristics

In order to obtain the mechanical behavior and permeability characteristics of coal under the coupling action of stress and seepage, permeability tests under different confining pressures in the process of deformation and destruction of briquette coal were carried out using the electrohydraulic servo system of rock mechanics. The stress-strain and permeability evolution curves of briquette coal during the whole deformation process were obtained. The mechanical behavior and permeability coefficient evolution response characteristics of briquette coal under stress-seepage coupling are well reflected. Research shows that stress-axial strain curve and the stress-circumferential strain curve have the same change trend, the hoop strain and axial strain effect on the permeability variation law of basic consistent, and the permeability coefficient with the increase of confining pressure and decreases, and the higher the confining pressure, the lower the permeability coefficient, the confining pressure increases rate under the same conditions, and the permeability coefficient corresponding to high confining pressure is far less than that corresponding to low confining pressure. The confining pressure influences the permeability of the briquette by affecting its dilatancy behavior. With the increase of the confining pressure, the permeability of the sample decreases, and the permeability coefficient decreases with the increase of the confining pressure at the initial stage, showing a logarithmic function. After failure, briquette samples show a power function change rule, and the greater the confining pressure is, the more obvious the permeability coefficient decreases.

scholarly journals Investigations of the mechanical behavior and failure mechanism of fractured rock samples

2021 ◽  
Vol 861 (4) ◽  
pp. 042109
Author(s):  
Chunping Wang ◽  
Liang Chen ◽  
Jian Liu ◽  
Xingguang Zhao ◽  
Jianfeng Liu
Keyword(s):  
Mechanical Behavior ◽  
Failure Mechanism ◽  
Fractured Rock ◽  
Rock Samples

Modeling snow slab failure in propagation saw test using Drucker-Prager model

2021 ◽  
Author(s):  
Agraj Upadhyay ◽  
Puneet Mahajan ◽  
Rajneesh Sharma
Keyword(s):  
Compressive Strength ◽  
Elastic Modulus ◽  
Mechanical Behavior ◽  
Brittle Failure ◽  
High Strain ◽  
Fracture Propagation ◽  
Strain Curve ◽  
Strain Rates ◽  
Stress Strain Curve ◽  
Natural Snow

<p><strong>Abstract</strong></p><p>Fracture propagation in weak snow layers followed by the failure of overlying homogeneous snow slab leads to the formation of snow slab avalanches. The extent of fracture propagation in the weak layer and size of the avalanche release area depends on the mechanical behavior of overlying snow layers. To model the snow slab failure in slab avalanche formation process, in present work, mechanical behavior of natural snow is studied through high strain rate (1×10<sup>-4</sup> s<sup>-1</sup> or higher) uniaxial tension and compression experiments on natural snow layers. Uniaxial loading and unloading experiments are also carried out to understand the permanent strains at high strain rates. Elastic modulus of snow is derived from loading unloading test data and compared with the tangent modulus obtained from maximum slope of the stress-strain curve. Tensile and compressive strengths are derived from peak load at failure and fracture energy is derived from post peak stress-strain curve. For a density range of 100-400 Kg/m<sup>3</sup> the range of obtained mechanical properties of natural snow are: Elastic modulus: 0.1-45 MPa, Tensile strength: 0.24-20 kPa, Compressive strength: 0.1-105 kPa, Fracture energy: 0.007-0.15 J/m<sup>2</sup>. For low density snow (<150 Kg/m<sup>3</sup>) tensile and compressive strength values are quite close but for higher densities compressive strength is significantly higher than the tensile strength. At low strain rates (<1×10<sup>-4</sup> s<sup>-1</sup>) snow generally exhibit no failure and large permanent deformations whereas, at high strain rates (1×10<sup>-3</sup> s<sup>-1</sup> or higher) failure strains are generally in the range 0.05-1.5 %. In all cases a sharp decrease in load at failure suggests a near brittle failure. By fitting the experimental dataset with power law, density dependent expressions for elastic modulus, tensile and compressive strength are obtained. On the basis of the experimental observations, a continuum elastic-plastic-damage material model is considered to model mechanical behavior of snow layers. To model the asymmetry in tensile and compressive strengths, pressure dependent Drucker-Prager model is considered for yield criterion and model parameters (friction angle and cohesion) are obtained using density dependent expressions of tensile and compressive strength of snow. Effective plastic strain based damage initiation and evolution models are used to model quasi-brittle failure of snow. This model has been used for modeling the snow slab failure in two dimensional propagation saw tests and the obtained results on the influence of slab density, thickness and slope angle on slab failure have been presented.</p><p><br><br></p>

scholarly journals Hydraulic and Mechanical Relationship of Individual Fracture in Rock under Compression and Shearing: Theoretical Study

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Zhiqiang Zhou ◽  
Yu Zhao ◽  
Chaolin Wang
Keyword(s):  
Normal Stress ◽  
Fractured Rock ◽  
Fracture Propagation ◽  
Nonlinear Behavior ◽  
Fracture Aperture ◽  
Fracture Permeability ◽  
Energy Principle ◽  
Permeability Model ◽  
Shear Dilation ◽  
Relationship Of

In this paper, a new approach has been developed for predicting the hydraulic and mechanical relationship of individual fractures subjected to normal stress and compression-shear stress. Considering that the closure process of rough fracture subjected to normal stress can be divided into two phases (linear behavior and nonlinear behavior), a relationship between normal stress and fracture aperture is derived through the minimum potential energy principle. Then, a formulation for calculating fracture permeability during shearing and compression processes is developed. Furthermore, a formulation for determining fracture aperture during the crack growth process is obtained, which is further implanted into the permeability model to predict the hydraulic behavior of fractured rock during fracture propagation. This new model not only considers the normal deformation of the fracture but also, and more importantly, integrates the effect of fracture propagation and shear dilation. Theoretical studies demonstrate that fracture permeability increases nonlinearly during fracture propagation. At last, experimental results and analytic results are compared to demonstrate the usefulness of the proposed models, and satisfactory agreements are obtained.

Interaction of a hydraulic fracture with parallel pre-existing fractures

2020 ◽  
Author(s):  
Haijun Wang ◽  
Shuyang Yu ◽  
Xuhua Ren ◽  
Lei Tang ◽  
Arcady Dyskin ◽  
...  
Keyword(s):  
Hydraulic Fracture ◽  
Fractured Rock ◽  
Fracture Propagation ◽  
Environmental Damage ◽  
Hydraulic Fractures ◽  
Main Attention ◽  
Fracture Interaction ◽  
Hydraulic Fracture Propagation ◽  
Fracture Coalescence ◽  
Fractured Rock Masses

<p>Formation and growth of hydraulic fractures can be strongly affected by pre-existing fractures in the rock mass. Until now the main attention was directed towards the investigation of the interaction between the hydraulic fracture and the pre-existing fractures intersecting its path, as they could significantly hamper its formation and growth, alter the geometry and produce additional leak-off. Less attention was paid to the interaction of the hydraulic fracture with parallel and coplanar pre-existing fractures, yet their interaction and coalescence can lead to unwelcome increase in the hydraulic fracture dimensions, change the direction of growth and in some cases result in undesirable effects such as environmental damage.  </p><p> </p><p>In order to investigate the hydraulic fracture interaction with parallel pre-existing fractures we conducted a series of tests on transparent rectangular samples with two artificial cracks. One of the crack was loaded with pressurised fluid. The types of interaction were classified and the conditions of fracture coalescence formulated. The results will contribute to the understanding of hydraulic fracture propagation in fractured rock masses and mitigating environmental damage.</p><p> </p><p><strong>Acknowledgements</strong>. Wang acknowledge support from the Natural Scinece Foundation of Jiangsu (BK20171130). The AVD and EP acknowledge support from the Australian Research Council through project DP190103260. AVD acknowledges the support from the School of Civil and Transportation, Faculty of Engineering, Beijing University of Civil Engineering and Architecture. Wang acknowledge support from the National Natural Science Fund (51409170,U1765204)</p>

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