Theoretical analysis on electromagnetic emission of rock fracturing process

2013 ◽  
pp. 335-338
Author(s):  
P Lin ◽  
X Liu ◽  
S Kang ◽  
C Wang
Keyword(s):  
Theoretical Analysis ◽  
Electromagnetic Emission ◽  
Rock Fracturing ◽  
Fracturing Process

Numerical Prediction of Rock Fracturing During the Process of Excavation

2012 ◽  
pp. 225-237 ◽  
Author(s):  
Zhangtao Zhou ◽  
Zheming Zhu ◽  
XinXing Jin ◽  
Hao Tang
Keyword(s):  
Equation Of State ◽  
Numerical Model ◽  
Failure Criterion ◽  
Material Properties ◽  
Igneous Rock ◽  
Surrounding Rock ◽  
Rock Blasting ◽  
Rock Fracturing ◽  
Fracturing Process ◽  
Blasting Excavation

During the process of excavation, blasting can induce cracking inside the surrounding rock. Considering the effects of material properties and loading conditions, a rock blasting excavation model with two successive excavation steps was developed through the use of AUTODYN code. Four kinds of equation of state (EOS), linear, shock, JWL, and compaction were applied to the materials employed in this numerical model. A modified principal stress failure criterion was applied to determining material statuses, and TNT explosive and a relatively homogeneous igneous rock, diorite, were used in this numerical model. By using this numerical model, rock fracturing process during blasting excavation was simulated, and rock fracturing process during two successive excavations is presented.

scholarly journals Mutation effect of acoustic and electromagnetic emissions of hard rock impact failure

2019 ◽  
Vol 15 (1) ◽  
pp. 155014771882447
Author(s):  
Yang Liu ◽  
Cai-Ping Lu ◽  
Heng Zhang
Keyword(s):  
Acoustic Emission ◽  
Hard Rock ◽  
Acoustic Emissions ◽  
Electromagnetic Emission ◽  
Rock Fracturing ◽  
Impact Failure ◽  
Hard Roof ◽  
Micro Cracks ◽  
Roof Fall ◽  
Microseismic Event

To reveal acoustic emission and electromagnetic emission effects during hard rock impact failure is a crucial issue for monitoring and warning rockburst risk induced by hard roof fracture and fall. The presented research focuses on acoustic emission and electromagnetic emission and microseismic effects detected during laboratory tests and by in situ multi-parameter observations, and the field observations agreed satisfactorily with the experimental evidences. The following main conclusions were drawn: (1) the stress level, frequency of micro-cracks, and impact failure regularity of hard rocks can be revealed with electromagnetic emission and acoustic emission/microseismic parameters, respectively; (2) acoustic emission/microseismic event counts can directly reveal the cracks change in rocks, and the initiation, propagation, and coalescence of micro-cracks can be presented as first increase, followed by decrease in acoustic emission/microseismic event counts; (3) in most cases, only when stress suddenly decreases or the rock final collapses, acoustic emissions show obviously abnormal; and (4) acoustic emission/microseismic can be more effectively applied to warn rockburst danger. The above conclusions may shed light on the effective monitoring and warning methods of rockburst triggered by hard roof fall, and events contribute to some interpretations to originally transient precursors of hard rock fracturing.

Chip Removal by a Hydraulic Jet

1964 ◽  
Vol 4 (01) ◽  
pp. 21-25 ◽  
Author(s):  
J.B. Cheatham ◽  
J.G. Yarbrough
Keyword(s):  
Flow Rate ◽  
Particle Density ◽  
Experimental Studies ◽  
Fluid Viscosity ◽  
Drill Bit ◽  
Hole Size ◽  
Rock Fracturing ◽  
Fracturing Process ◽  
Jet Velocity ◽  
Chip Removal

Abstract Although adequate removal of cuttings from beneath a drill bit is important for efficient drilling operations, very little basic data are available relative to the fundamentals of chip removal by hydraulic jets. A discussion is presented in this paper of an experimental investigation of the jetting action of hydraulic jets in removing loose particles from the bottom of a cylindrical hole. Conditions for which the jet is no longer capable of removing chips from the bottom of the hole are determined. This situation represents equilibrium between the chip removal force and chip holddown forces such as gravity and pressure. In most of the tests loose particles were jetted with water or a water-glycerine mixture to determine the dependence of chip removal on hole size, jet size, height of jet off bottom of hole, flow rate, particle density and fluid viscosity. A test with a pressurized mud system indicated that relatively low pressures can completely overcome the removal action of a hydraulic jet. Although the system studied herein is not directly applicable to a rotary drill bit, the work with such simplified systems can provide a better understanding of the chip removal action of jets, and with logical extensions it may provide a reasonable basis for the best use of fluid jets in drilling. Introduction The primary deterrent to maximum drilling rates is the inability of the drilling system to remove rock cuttings efficiently enough to prevent interference with the drilling action. The objective of chip removal studies is to permit predicting and controlling removal forces under downhole drilling conditions. Conditions at the bottom of a hole during rotary drilling are exceedingly complex and are not likely to be described in a quantitative way by investigations in terms of the total drilling action until a better understanding is developed of the simplified components of the problem. The present study is concerned with the elementary condition of removal of chips by a single central jet. Even this relatively simple model provides mathematical difficulties because of the turbulent nature of the flow from the jet and because of the shape of the bottom of the hole beneath the jet. Theoretical and experimental studies have been made of turbulent jets impinging normally on an infinite body and deductions based on analytical solutions to simplified problems can give some insight into the problem of cutting removal by a jet. However, because of the present lack of understanding of the behavior of the interaction between the fluid jet and the chips being removed, an experimental approach was chosen for the present study. Methods have been developed for maximizing hydraulic horsepower, impact force and jet velocity; but whether maximizing these parameters maximizes chip removal with present drilling bits has not been demonstrated. Simplifying the problem of chip removal may make it possible to develop some understanding of the manner in which the jet velocity is dissipated. Better understanding of a simple case should materially assist in extending analysis to more complicated cases. Thus, we are not concerned in the present study with the rock fracturing process itself but only with the removal of the debris from the bottom of the hole. A problem which is quite similar to the chip removal problem is the suspension of solids in stirred vessels. This problem has been studied by the chemical industry and correlations have been obtained by dimensional analysis which permit the design of mixing vats. An approach similar to that used in the mixing vat problem is used in the analysis of the jetting data in the present paper. EXPERIMENTAL PROCEDURE The test equipment arrangement shown schematically in Fig. 1 allows the jetting action to remove particles until an equilibrium height is attained for each combination of hole size, jet size and flow rate.*** Equilibrium conditions require that the removal force is unable to remove additional particles. This balance between holddown and removal forces implies a relationship between the two forces which is constant for the particular system. When the holddown forces are constant, SPEJ P. 21ˆ

Elasto-Plastic Cellular Automaton Simulation of Fracturing Process in Single Pre-Fractured Rocks under Uniaxial Compression

2010 ◽  
Vol 34-35 ◽  
pp. 383-386 ◽  
Author(s):  
Hua Yan Yao ◽  
Peng Zhi Pan
Keyword(s):  
Cellular Automaton ◽  
Uniaxial Compression ◽  
Failure Modes ◽  
Fractured Rock ◽  
Failure Process ◽  
Great Influence ◽  
Rock Fracturing ◽  
Rock Heterogeneity ◽  
Fracturing Process ◽  
Rock Specimens

Rock is a natural heterogeneous material and presents complicated behaviors in the fracturing process. It is prevail to study the basic failure mechanism of rocks via numerical simulation. Based on the elasto-plastic cellular automaton (EPCA) model, this paper simulates single pre-fractured rock fracturing process with consideration of rock heterogeneity on the meso-scale. In this model, the Weibull’s distribution, which characterizes heterogeneity with the homogeneous index m and the random seed parameter s, is adopted to describe the distribution of mechanical parameters of rock specimens such as cohesive strength, Young’s modulus, etc. Pre-existing crack rock specimens with different homogeneous index or the different random seed are simulated by EPCA under uniaxial compression. Numerical results show that heterogeneity has great influence on pre-fractured rock failure process, final failure modes, and the uniaxial compressive strength.

Numerical Simulation for Rock Fracturing Process under Action of Disc Cutter

2013 ◽  
Vol 690-693 ◽  
pp. 3054-3058
Author(s):  
Li Juan Cao ◽  
Shou Ju Li ◽  
Zi Chang Shang Guan
Keyword(s):  
Numerical Simulation ◽  
Three Dimensional ◽  
Nonlinear Finite Element ◽  
Constitutive Relationship ◽  
Disc Cutter ◽  
Vertical Force ◽  
Nonlinear Finite Element Method ◽  
Rock Fracturing ◽  
Fracturing Process ◽  
Visual Description

Three-dimensional dynamic fracture process of rock under action of disc cutter is simulated by using nonlinear finite element method. Rock constitutive relationship is characterized by Drucker-Prager model. The influences of disc angular velocity and vertical force on the penetration depth and the specific energy are systematically investigated. The simulation results show that the rock fracturing process obviously presents properties of step crushing under action of disc cutter. The proposed numerical simulation presents an improvement on existing ones in terms of providing three-dimensional visual description of rock fracturing process.

Numerical Prediction of Rock Fracturing During the Process of Excavation

2010 ◽  
Vol 1 (2) ◽  
pp. 12-23 ◽  
Author(s):  
Zhangtao Zhou ◽  
Zheming Zhu ◽  
XinXing Jin ◽  
Hao Tang
Keyword(s):  
Equation Of State ◽  
Numerical Model ◽  
Failure Criterion ◽  
Material Properties ◽  
Igneous Rock ◽  
Surrounding Rock ◽  
Rock Blasting ◽  
Rock Fracturing ◽  
Fracturing Process ◽  
Blasting Excavation

During the process of excavation, blasting can induce cracking inside the surrounding rock. Considering the effects of material properties and loading conditions, a rock blasting excavation model with two successive excavation steps was developed through the use of AUTODYN code. Four kinds of equation of state (EOS), linear, shock, JWL, and compaction were applied to the materials employed in this numerical model. A modified principal stress failure criterion was applied to determining material statuses, and TNT explosive and a relatively homogeneous igneous rock, diorite, were used in this numerical model. By using this numerical model, rock fracturing process during blasting excavation was simulated, and rock fracturing process during two successive excavations is presented.

Development of Porosity Measurement Method Based on Modern Microscopic Techniques

2015 ◽  
Vol 240 ◽  
pp. 87-93
Author(s):  
Ewelina Małek ◽  
Tadeusz Niezgoda ◽  
Danuta Miedzińska
Keyword(s):  
Porous Structure ◽  
Innovative Technology ◽  
Rock Fracturing ◽  
Gas Recovery ◽  
Atomic Force ◽  
University Of Technology ◽  
Fracturing Process ◽  
Productivity Increase ◽  
Gaseous Hydrocarbons ◽  
Microscopic Techniques

The aim of the research, presented in the paper, is to show and to assess the porosity structure in accordance to the dimensions of carbon dioxide particle. The characteristic surface morphology of the sample and the visualisation of the coal porous structure have been obtained using the atomic force microscope (AFM). The presented study of the coal microstructure is a part of the concepts of the project which aim is to develop the guidelines for design of the innovative technology of shale gas recovery with the use of liquid CO2. The technology will be based on Military University of Technology invention which considers gaseous hydrocarbons recovery from at least two levels of lateral wellbores with the use of supercritical CO2, what will result with wellbore productivity increase, because CO2 will cause desorption of CH4 from the porous structure of shale rock and the thermodynamic transformation of CO2 in the reservoir will help the rock fracturing. The heat energy added for the fracturing process will be taken from the surrounding rock mass.

Experimental study on the damage process of marble under true triaxial pre-peak unloading conditions

2021 ◽  
pp. 105678952110207
Author(s):  
Yaohui Gao ◽  
Zhaofeng Wang
Keyword(s):  
Cyclic Loading ◽  
Principal Stress ◽  
Stress Test ◽  
Tensile Failure ◽  
Dissipated Energy ◽  
Rock Damage ◽  
Rock Fracturing ◽  
True Triaxial ◽  
Minimum Principal Stress ◽  
Fracturing Process

Stress-induced instability is associated with rock damage. Here, the progressive brittle fracturing process in Jinping marble is studied by introducing two types of true triaxial pre-peak unloading tests, namely, the incrementally cyclic loading-unloading minimum principal stress test (ICM test) and the incrementally cyclic loading-unloading maximum and minimum principal stress test (ICMM test). By comprehensively analysing the irreversible strains, dissipated energy, acoustic emission (AE) characteristics and scanning electron microscopy (SEM) results, the rock damage evolution can be quantified and divided into two distinctive damage stages. At the boundary point, the irreversible strain increments reach their minimum values. In the gentle damage stage, the normalized irreversible strains increase linearly, and this process is associated with a small number of AE hits with low amplitude. The rapid damage stage is characterized by a nonlinear increase in the normalized irreversible strains, and this process is associated with a large number of AE hits with high amplitude. The dissipated energy mainly increases in the rapid damage stage. In addition, the rapid damage stage in the ICMM test mainly occurs in the last five cycles, due to the differences in the deviatoric stresses in each cycle. In both of these tests, the failure mode is principally characterized by tensile failure. Moreover, the precursory signals of rock fracturing and the influence of the loading paths on the strength are discussed.

Real-Time Observations of Fracturing Processes of Brittle Rock in Compression by X Ray Computed Tomography

2011 ◽  
Vol 361-363 ◽  
pp. 171-178 ◽  
Author(s):  
Guang Zhu Cao ◽  
Yi Qiang ◽  
Feng Li
Keyword(s):  
Real Time ◽  
Process Model ◽  
Rock Sample ◽  
Failure Process ◽  
Brittle Rock ◽  
Ct Scanner ◽  
Rock Fracturing ◽  
Sandstone Sample ◽  
Initial Damage ◽  
Fracturing Process

In present，a series of uniaxial compressive experiments on sandstone samples have been conducted in the laboratory by using jointed devices of triaxial loading equipment and medical SOMTOM-plus CT scanner. Based on CT value, expression of density damage variables and density damage increments (DDI) of brittle rock and the method to determine the rock initial damage variables have been worked out. From real-time CT observations of sandstone sample under uniaxial compression condition and the analysis on CT digital images and the relation curve between sandstone density damage increment (DDI)and stress, the evolution process of fracturing in brittle rock sample can be divided into five stages, i.e. initial densification stage, crack occurrence-propagation, crack merging-bifurcation, crack rebifurcation-propagation, and crack cut-through-massive failure stage. Crack occurrence-propagation is a local phenomenon and the whole rock is still in the densification stage. Therefore, the rock failure process under compression is mainly including three stages, namely initial damage densification, local dilatation-bulk dilatation, and massive failure. The use of CT images and relation curve between density damage increment and stress in analyzing the meso-damage evolution processes of brittle rock sample is an important and effective method. As an important mechanics index in rock meso-mechanics, the density damage increment can be used to analyze the quantitative fracturing process in brittle rock under compressive condition, as well as being an important factor in a rock fracturing process model to be constructed.

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