Strength Failure and Crack Evolution Behavior of Rock Materials Containing Pre-existing Fissures


Price: $60.00


Author: Yang Shengqi
Language: English
ISBN/ISSN: 9787030448606
Published on: 2015-11

According to AE monitoring results in the process of deformation failure, the AE characteristics of intact and flawed sandstone containing single fissure can be approximately divided into three typical periods, i.e., quiet period, active period, and remission period.In quiet period, for hard and brittle sandstone material, the AE events are not very active and the AE counts are very small, which results from the occurrence of fissure closure.Moreover, the AE behavior in quiet period is not dependent on the fissure length and fissure angle.In the active period, the AE counts of intact specimen are very dense and stable, but the AE behaviors of flawed specimens are different from that of intact specimen, which is distinctly related to fissure length and fissure angle.The AE counts of flawed specimen with single fissure are more decentralized than that of intact specimen; moreover, the AE counts of all flawed specimens with single fissure have several larger peak values before peak strength, which correspond to the crack initiation and propagation in the specimens.However, in the remission period, the AE counts and energy of intact specimen are rare, but AE behaviors of flawed specimen with shorter fissure
(2α = 5 mm) or higher angle (αa = 60°) approximate the one of intact specimen,which results from little occurrence of macroscopic cracks after peak strength.While the AE behaviors of flawed specimen with medium fissure (2α=15 mm) are not dependent on the fissure angle, which shows that the AE counts undergo first a relative steady phase and then increase abruptly with increasing time.For flawed specimen with longer fissure (2α = 20 and 25 mm), the AE counts are more and relatively denser, which results from gradual crack coalescence in the specimens after peak strength.

1.1Experimental Studies for Rock—Like Materials
1.2Experimental Studies for Real Rock Materials
1.3Numerical Studies for Crack Evolution Behavior
1.4Study of Fracture Coalescence Behavior by AE Technique
1.5Main Contents in This Book
2Experimentallnvestigation on Strength Failure and Crack Evolution Behavior of Brittle Sandstone
Containing a Single Fissure
2.1Experimental Studies
2.1.1Sandstone Material
2.1.2Preparation for Specimen with Single Fissure
2.1.3Experimental Equipment and Procedure
2.2 Strength and Deformation Behavior
2.2.1Uniaxial Stress—Strain Curves of Sandstone
2.2.2Effect of Single Fissure Geometry on Mechanical Parameters of Sandstone
2.3Crack Evolution Behavior
2.3.1Crack Coalescence Type of Sandstone Specimens Containing a Single Fissure
2.3.2AE Behaviors oflntact and Flawed SandstoneSpecimens with Single Fissure Geometries
2.3.3Real—Time Crack Evolution Process of Sandstone Containing a Single Fissure
3Experimentallnvestigation on Crack Evolution Behaviorof Brittle Sandstone Containing Two Coplanar Fissuresin the Process of Deformation Failure
3.1Experimental Material and Procedure
3.1.1Physical Behavior of Tested Specimens
3.1.2Specimens Containing Two Coplanar Fissures
3.1.3Testing Equipment and Procedure
3.2Influence of Coplanar Fissure Angle on Strength and Deformation Behavior
3.2.1Deformation Failure Behavior oflntact SandstoneSpecimen
3.2.2Deformation Failure Behavior of Flawed Sandstonewith Two Coplanar Fissures
3.2.3Relationship Between Coplanar Fissure Angleand Mechanical Parameters
3.3Crack Initiation and Coalescence Behavior Analysis
3.3.1Crack Coalescence Type of Sandstone Containing Two Coplanar Fissures
3.3.2Crack Initiation and Coalescence Behaviorof Pre—fissured Sandstone
4Experimentallnvestigation on Fracture Evolution Behavior of Brittle Sandstone Containing Three Fissures
4.1Specimen Preparation and Testing Procedure
4.1.1Sandstone Material and Specimen Preparation
4.1.2Testing Procedure
4.2Analysis of Experimental Results
4.2.1Axial Stress—Strain Curve oflntact Specimen
4.2.2Axial Stress—Strain Curve of Flawed SpecimensContaining Three Fissures
4.3Crack Initiation Mode and Analysis of the Coalescence Process
4.3.1Crack Initiation Mode and Stress Analysis
4.3.2Real—Time Crack Coalescence Process of Specimensfor β2 = 75° and 90
4.3.3Real—Time Crack Coalescence Process of Sandstone Specimens Containing ThreeFissures (β2 = 105° and 120°)
4.4Crack Coalescence Type and Strain Evolution Analysis
4.4.1Crack Coalescence Type Analysis
4.4.2Strain Evolution Analysis
5Experimentallnvestigation onFracture Coalescence.Behaviorof Red Sandstone Containing Two Unparallel Fissures
5.1Experimental Material and Loading Procedure
5.1.1Experimental Material and Specimen Preparation.
5.1.2Loading Procedure and AE Monitoring
5.2Strength and Deformation Behavior
5.2.1Axial Stress—Axial Strain Behavior
5.2.2Strength and Deformation Parameters
5.3Cracking'Mode and Characteristics
5.4Crack Coalescence Process and AE Behavior
6Discrete Element Modeling on Fracture Coalescence Behavior of Red Sandstone Containing Two Unparallel Fissures
6.1Discrete Element Modeling Method
6.1.1Micro—Bond Model
6.1.2Numerical Specimen
6.1.3Simulation Procedure
6.2Confirmation for Micro—Parameters of Red Sandstone
6.2.1Confirming Method for Micro—Parameters of Red Sandstone
6.2.2Calibrating Micro—parameters by ExperimentalResults of Intact Specimen
6.3Numerical Results of Red Sandstone Containing Two Unparallel Fissures
6.3.1Strength and Deformation Behavior
6.3.2Cracking Characteristics
6.4Stress Field in Red Sandstone Containing Two Unparallel Fissures
7Fracture Mechanical Behavior of Red Sandstone Containinga Single Fissure and Two Parallel Fissures After Exposure to Different High—Temperature Treatments
7.1Rock Material and Testing Procedure
7.1.1The Experimental Material and Heating Procedure
7.1.2Specimen Preparation and Fissure Geometry
7.1.3Testing Procedure and AE Monitoring
7.2Strength and Deformation Behavior
7.3Fracture Evolution Behavior
7.4Interpretation and Discussion
8Experimentallnvestigation on Strength and Failure Behavior of Pre—cracked Marble Under Conventional Triaxial Compression
8.1Experimental Methodology
8.1.1Marble Material
8.1.2Pre—cracked Sample Preparation
8.1.3Experimental Procedure
8.2Triaxial Experimental Results of Pre—cracked Marble
8.2.1Brittle—Ductile Transition Mechanism oflntact Marble
8.2.2Triaxial Stress—Strain Curves of Pre—cracked Marble
8.3Strength Behavior of Pre—cracked Marble
8.3.1Strength Behaviorin Accordance with Mohr—CoulombCriterion
8.3.2Strength Behaviorin Accordance with Hoek—Brown Criterion
8.3.3A New Evaluation Criterion Based on OptimalApproximation Polynomial Theory
8.4Failure Mode of Pre—cracked Marble
9Numericallnvestigation on the Failure Mechanical Behaviorof Red Sandstone Containing Two Coplanar Fissures UnderConventional Triaxial Compression
9.1Discrete Element Model and Micro—Parameters
9.1.1Intact Red Sandstone Material and Micro—Parameters
9.1.2Comparison ofTriaxial Experimental and NumericalResults of Intact Specimen
9.2Macroscopic Strength and Deformation Behavior
9.2.1Triaxial Deformation Behavior of Red Sandstone Containing Two Coplanar Fissures
9.2.2Triaxial Strength Behavior of Red Sandstone Containing Two Coplanar Fissures
9.3Fracture Evolution Behavior
9.3.1Fracture Evolution Process oflntact Specimen
9.3.2Fracture Evolution Process of Flawed Specimen
9.3.3Effect of Confining Pressure and Coplanar Fissure Angle
9.3.4Stress and Displacement Field

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