Scale-Size and Structural Effects of Rock Materials

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Scale-Size and
Structural Effects
of Rock Materials
Copyright
Contributors
About the authors
Preface
Acknowledgments
1
Size effect of rock samples
	Chapter outline
	Size effect law for intact rock
		Introduction
		Background
			Descending models
				Statistical models
				Fracture energy model
				Fractal and multifractal models
				Empirical and semiempirical models
			Ascending model
		Experimental study
			Rock sample selection
			UCS results
			Point load results
				Diametral loading
				Axial loading
		Unified size effect law
		Reverse size effects in UCS results
		Contact area in size effects of point load results
			Conventional approach to highlight size effects
			A new approach incorporating contact area
		Conclusions
	Length-to-diameter ratio on point load strength index
		Introduction
		Background
			Point load test size effect
			Size effect models
		Methodology
		Valid and invalid failure modes
			Failure mode in axial testing
			Failure mode in diametral testing
			Impact of stress distribution on failure mode
		Conventional point load strength index size effect
			Axial and diametral point load strength index results
			Applicability of existing size effect models
		Size effect of point load strength index
			Axial and diametral point load strength index
			Applicability of existing size effect models
		Conclusions
	Plasticity model for size-dependent behavior
		Introduction
		Notation and unified size effect law
		Bounding surface plasticity
		Model ingredients
			Elasticity
			Bounding surface and image point
			Hardening law
			Plastic potential and elastic-plastic matrix
			Model outputs and parameter sensitivity
			Initial stiffness
			Incorporating size effects
		Model calibration
			Fitting the unified size effect law
			Simulation for 96-mm diameter samples
			Simulation for 50-mm diameter samples
			Simulation for 25mm diameter samples
			Comparing models for different diameter samples
		Conclusions
	Scale-size dependency of intact rock
		Introduction
		Rock types
		Experimental procedure
			Point load testing
			Indirect tensile (Brazilian) testing
		Comparative study
			Size effect models
				Statistical model
				Fracture energy model
				Multifractal model
			Existing size effect models to point load
			Existing size effect models to tensile strength
		Conclusion
	Scale effect into multiaxial failure criterion
		Introduction
		Background
		Scale and Weibull statistics into strength measurements
			Scale effect in uniaxial compressive strength
			Scale effect in point load strength index
			Scale effect in tensile strength
			Scale effect in pure shear strength
		The modified failure criteria
		Comparison with experimental data
		Conclusions
	Size-dependent Hoek-Brown failure criterion
		Introduction
		Background
			Analytical study
			Experimental study
			Testing procedure
			Experimental results
		Size-dependent Hoek-Brown failure criterion
			Model development
			Model calibration
		Example of application
		Conclusions
	References
	Further reading
2
Rock fracture toughness
	Chapter outline
	Fracture toughness of splitting disc specimens
		Introduction
		Preparation of disc specimens
		Fracture toughness of five types of specimens
			Fracture toughness formula of FBD and HFBD
			Fracture toughness formula of CCNBD
			Fracture toughness formula of CSTBD and HCFBD
		Load-displacement curve of disc splitting test
		Comparison of disc splitting test results
		Conclusions
	Fracture toughness of HCFBD
		Introduction
		Test method and principle
		HCFBD specimens with prefabricated cracks
		Calibration of maximum dimensionless SIF Ymax
		Results and analysis
		Conclusions
	Crack length on dynamic fracture toughness
		Introduction
		Dynamic impact splitting test
			Configuration and dimensions of specimens
			Dynamic test process
		Results and discussion
			Comparison of dynamic and static fracture toughness
			Fracture mode of specimens
		DFT irrespective of configuration and size
		Conclusions
	Crack width on fracture toughness
		Introduction
		NSCB three-point flexural test
			Specimen preparation
			Test equipment and test plan
		Width influence on prefabricated crack
		Width influence of cracks on tested fracture toughness
		Method for eliminating influence of crack width
		Conclusions
	Loading rate effect of fracture toughness
		Introduction
		Specimen preparation
		Test process and data processing
			Test method
			Fracture toughness calculation formula
		Results and analysis
			Load-displacement curve
			Fracture toughness test value
				Loading rate effect on fracture toughness
				Size effect on fracture toughness
				Discussion on loading rate and size effects
		Conclusions
	Hole influence on dynamic fracture toughness
		Introduction
		Dynamic cleaving specimens and equipment
		SHPB test and data record
			Pulse signal on elastic pressure bar
			Determination of cracking time
		Dynamic finite element analysis
			Load determination of model
			Dynamic loading of model
			Dynamic stress intensity factor
		Results analysis and discussion
			Central aperture influence on test values
			Final fracture mode of specimen
		Conclusions
	Dynamic fracture toughness of holed-cracked discs
		Introduction
		Dynamic fracture toughness test
			Test specimens
			Test setup
		Experimental recordings and results
			Strain signals on bars
			Fracture patterns of specimens
			Test results analysis
		Dynamic stress intensity factor in spatial-temporal domain
		Conclusions
	Dynamic fracture propagation toughness of P-CCNBD
		Introduction
		Experimental preparation
			P-CCNBD specimen
			SHPB loading device
			Strain gauges and crack extension meters
		Experimental recording and data processing
			Load determination
			Determination of cracking time
			Determination of crack propagation speed
		Numerical calculation of dynamic stress intensity factor
			Loading of model
			P-CCNBD numerical model
			Dynamic stress intensity factor
		Determine dynamic fracture toughness
			Universal function
			Dynamic cracking and propagated toughness
			Loading rate effect on dynamic cracking toughness
			Crack propagation speed on dynamic expansion toughness
			Dynamic crack arrest and DFT rationality
		Conclusions
	References
	Further reading
3
Scale effect of the rock joint
	Chapter outline
	Fractal scale effect of opened joints
		Introduction
		Scale effect based on fractal method
			Scale dependence of joint roughness
			Peak shear displacement for field-scale rock joints
		Constitutive model for opened rock joints
		Validation of proposed scaling relationships
			Validation of scale dependence of joint roughness
			Predictive equation for peak shear displacement
		Conclusions
	Joint constitutive model for multiscale asperity degradation
		Introduction
		Quantification of irregular joint profile
		Description of proposed model
		Joint model validation
			Model implementation
			Model validation
				Correlation with JRC-profiled rock joints
			Correlation with experimental data
				Simulation of Bandis direct shear test
				Simulation of Flamand et al.s direct shear test
		Conclusions
	Shear model incorporating small- and large-scale irregularities
		Introduction
		Constitutive model for small-scale joints
			Mobilized shear strength
			Asperity degradation
			Dilation
		Constitutive model for large-scale joints
			Evaluation of peak shear strength
			Evaluation of peak shear displacement
			Degradation in dilation and postpeak strength
			Summary of proposed joint models
		Correlation with experimental data
			Simulation of Flamand et al.s test
			Simulation of Yang and Chiangs test
			Simulation of Bandiss test
		Conclusions
	Opening effect on joint shear behavior
		Introduction
		Constitutive model for joint opening effect
		Opening model performance
			Initial joint opening effect
			Joint opening effect induced by excavation
		Discussion
		Conclusions
	Dilation of saw-toothed rock joint
		Introduction
		Constitutive law for contacts in DEM
		Model calibration
		Direct shear test simulation
			Joint surface calibration
			Parametric study on dilation of rock joints
				Relative confining pressure effect
				Asperity wavelength effect
				Effect of multifaceted factors
		Conclusions
	Joint mechanical behavior with opening values
		Introduction
		Normal deformation of opened joints
			Semilogarithmic model
			Experiments and correlation
				Compression tests
				Results analysis
			Shear deformation of opened joints
		Direct shear tests
		Results analysis and discussion
		Conclusions
	Joint constitutive model correlation with field observations
		Introduction
		Model description and implementation
		Stability analysis of large-scale rock structures
			Rock slope case
				Site description
				Properties of rock mass
				Comparison numerical results with site investigation
			The underground powerhouse case
				Site description
				Properties of rock and joints
				Excavation process and reinforcements
				Site monitoring and result analysis
			The gold mine case
				Site description
				Rock mass properties
				Comparison between predicted and measured performance
		Conclusions
	References
	Further reading
4
Microseismic monitoring and application
	Chapter outline
	Acoustic emission of rock plate instability
		Introduction
		Materials and methods
			Samples of rock plates
			Equipment and AE acquisition system
			Numerical simulation scheme
			Computational model and parameters
			Loading and boundary conditions
		Results analysis
			AE in the failure process of the rock plate
			AE characteristics in numerical simulation test
		Discussion of the magnitudes of AE events
		Conclusions
	Prediction method of rockburst
		Introduction
		Microseismic monitoring system
		Active microseismicity and faults
			Microseismic event distribution
			Fault structures on rockburst distribution
		Rockburst prediction indicators
			Constructing prediction indicators
				Average number N and average released energy E
				Seismological parameter b and its decrease Deltab
				Potential maximum magnitude Mm
			Assessing prediction indicators
		Conclusions
	Near-fault mining-induced microseismic
		Introduction
		Engineering situations
		Computational model
		Result analysis and discussion
			Average energy of microseismic events
			Different characteristics of parameter b value
			Local-mechanism solutions and fracture modes
			Distribution of microseismic events
			Principal stress difference and elastic energy
			Sensitive factors of microseismic events
		Conclusions
	Acoustic emission recognition of different rocks
		Introduction
		Experiment preparation and methods
			Laboratory experiments
			AE signals
				AE signals in the time domain
				AE signals in different domains
			Artificial neural network
		Results and discussion
			Mechanical experiment results
			AE characteristics
		AE signal recognition using ANN
			ANN structure
			BP network training
			ANN recognition
		Conclusions
	Acoustic emission in tunnels
		Introduction
		Rockburst experiments in a tunnel
			Sample preparation
			Laboratory equipment
			Loading condition
		Experimental results
			Rockburst tendency
				Mineral composition analysis
				Analysis of rockburst tendency
			Destruction phenomenon of rockburst
			Horizontal stress and rockburst intensity
			Macroscopic morphology of rockbursts
		AE characteristics of rockburst
			AE characteristics under different horizontal stresses
			Rockburst fracturing model
		Discussion
			Tunneling model of excavation mechanics
			Key areas of rockbursts
		Conclusions
	AE and infrared monitoring in tunnels
		Introduction
		Simulating rockbursts in a tunnel
			Sample preparation
			Laboratory equipment
		Experimental results
			Rockburst evolution process
			AE characteristics
			IR characteristics
		Rockburst characteristics in tunnels
		Conclusions
	References
	Further reading
5
Structural effect of rock blocks
	Chapter outline
	Cracked roof rock beams
		Introduction
		Mechanical model of a cracked roof beam
			Formation of cracked roof beam
			Model of roof rock beam
			Instability process of cracked roof beam
			Voussoir beam of cracked roof beam
		Instability feature of cracked roof beams
			Influence factors of critical deflection
			Hinged blocks structure after roof instability
		Mechanical analysis of roof rock beams
			Building computational model
			Results analysis and discussion
		Conclusions
	Evolution characteristics of fractured strata structures
		Introduction
		Engineering background
		Mechanical and computational model
			Simplified mechanical model
			Building computational model
		Results and discussion
		Conclusions
	Pressure arching characteristics in roof blocks
		Introduction
		Pressure arching characteristics
			Symmetric pressure arch of two key blocks
			Step pressure arch structure of key blocks
			Rotative pressure arch structure of key blocks
			Key block stability of initial fractured roof
			Key block stability of periodic fractured roof
		Evolution characteristics of pressure arch
			Building computational model
			Evolution process of key blocks pressure arch
			Structure characteristics of symmetrical pressure arch
		Results and discussion
		Conclusions
	Composite pressure arch in thin bedrock
		Introduction
		Engineering background and pressure arch structure
			Engineering background
			Macroscopic pressure arch in far field
			Fractured pressure arch in near field
		Computational model and similar experiment
			Building a computational model
			Similar materials experiment
		Results and discussion
			Structures of symmetrical and stepped pressure arches
			Stress distribution of rotating-squeezed pressure arch
			Experimental verification on strata fracture structure
		Conclusions
	Pressure arch performances in thick bedrock
		Introduction
		Engineering background
		Pressure-arch analysis and experimental methods
			Theoretical analysis
			Building computational model
			Similar materials experiment
		Results and discussion
			Arching characteristics of principal stress
			Characteristic parameters of pressure arch
			Relationships between pressure arch and caving arch
		Conclusions
	Elastic energy of pressure arch evolution
		Introduction
		Engineering background
		Pressure-arch analysis and computational model
			Pressure-arch analysis
			Computational model
		Simulation results and discussion
		Conclusions
	Height predicting of water-conducting zone
		Introduction
		High-intensity mining in China
		OFT influence on FWCZ development
			Processes of overburden failure transfer
			Division of OFT into stages
			Development characteristics of FWCZ
		Development mechanism of FWCZ based on OFT
			Maximum unsupported and overhang lengths
			Failure criteria of stratum
			Mechanical models of OFT
				Model of unsupported strata
				Model of overhanging strata
		Example analysis and numerical simulation
			Example analysis
				General situation
				Calculation of maximum unsupported and overhang lengths
				Height calculation of FWCZ
			Numerical simulation of FWCZ height
				Numerical simulation model
				Simulation results analysis
		Engineering analogy
			Predicted FWCZ height
			Overall comparison and analysis
		Conclusions
	References
	Further reading
Index
	A
	B
	C
	D
	E
	F
	G
	H
	I
	J
	L
	M
	N
	O
	P
	R
	S
	T
	U
	V
	W
	Y
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