scholarly journals The Calculation of Coal Rock Fracture Conductivity with Different Arrangements of Proppants

Geofluids ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Yuwei Li ◽  
Wannong Meng ◽  
Ray Rui ◽  
Jinghui Wang ◽  
Dan Jia ◽  
...  
Keyword(s):  
Elastic Modulus ◽  
Theoretical Model ◽  
Poisson Ratio ◽  
Rock Fracture ◽  
Contact Deformation ◽  
Fracture Conductivity ◽  
Plate Fracture ◽  
Calculation Results ◽  
Coal Rock ◽  
Pore Flow

An accurate evaluation of coal rock fracture conductivity is an important prerequisite for predicting the productivity of CBM wells. Coal rock is soft and fragile, with low elastic modulus and high Poisson ratio. In the process of fracturing flowback, the contact deformation between proppant and fracture wall will affect the fracture conductivity when the proppant is embedded in the coal rock; thus the calculation method of plate fracture conductivity is no longer suitable for the evaluation of coal rock. Based on the contact deformation theory of elastic mechanics, a method for calculating contact deformation of proppant in fracture is proposed. Considering the effect of the deformation and embedded depth of proppant and the tortuosity of pore flow channel between proppant particles on fracture conductivity, a model for calculating fracture conductivity of coal rock fractures under three kinds of proppant arrangement (Model 4-1, Model 3-1, and Model 2-1) is established. Comparison of calculation results of theoretical model and experiments confirmed that the arrangement of proppant in coal rock fracture is closest to Model 3-1, and the influence of mechanical parameters of coal rock and proppant on fracture conductivity is calculated and analyzed by this theoretical model. The study shows that the coal rock fracture conductivity is affected little by Poisson’s ratio of coal rock and proppant, which is greatly influenced by the elastic modulus of them, and the effect of particle size of proppant is especially significant.

The Model for Calculating Elastic Modulus and Poisson's Ratio of Coal Body

2013 ◽  
Vol 6 (1) ◽  
pp. 36-43 ◽  
Author(s):  
Ai Chi ◽  
Li Yuwei
Keyword(s):  
Elastic Modulus ◽  
Poisson’S Ratio ◽  
Fractured Rock ◽  
Rock Block ◽  
Poisson's Ratio ◽  
Linear Elastic ◽  
Study Results ◽  
The Face ◽  
Block Face ◽  
Coal Rock

Coal body is a type of fractured rock mass in which lots of cleat fractures developed. Its mechanical properties vary with the parametric variation of coal rock block, face cleat and butt cleat. Based on the linear elastic theory and displacement equivalent principle and simplifying the face cleat and butt cleat as multi-bank penetrating and intermittent cracks, the model was established to calculate the elastic modulus and Poisson's ratio of coal body combined with cleat. By analyzing the model, it also obtained the influence of the parameter variation of coal rock block, face cleat and butt cleat on the elastic modulus and Poisson's ratio of the coal body. Study results showed that the connectivity rate of butt cleat and the distance between face cleats had a weak influence on elastic modulus of coal body. When the inclination of face cleat was 90°, the elastic modulus of coal body reached the maximal value and it equaled to the elastic modulus of coal rock block. When the inclination of face cleat was 0°, the elastic modulus of coal body was exclusively dependent on the elastic modulus of coal rock block, the normal stiffness of face cleat and the distance between them. When the distance between butt cleats or the connectivity rate of butt cleat was fixed, the Poisson's ratio of the coal body initially increased and then decreased with increasing of the face cleat inclination.

Study on the Dynamic Performance of Asphalt Concrete under Passive Confined Pressure

2012 ◽  
Vol 226-228 ◽  
pp. 1755-1759
Author(s):  
Hua Zhang ◽  
Fei Li ◽  
Yu Wei Gao
Keyword(s):  
Elastic Modulus ◽  
Asphalt Concrete ◽  
Poisson Ratio ◽  
Dynamic Properties ◽  
Dynamic Performance ◽  
Dynamic Strength ◽  
Confining Pressure ◽  
Mechanical Behaviors ◽  
One Dimensional ◽  
Stress States

An improved passive confining pressure SHPB method was used to study the dynamic mechanical behaviors of asphalt concrete under quasi-one dimensional strain state. The effect of confining jacket material and its geometrical sizes on the confining pressure were discussed. The dynamic strength, dynamic modulus of elasticity and dynamic Poisson ratio of asphalt concrete were obtained. The influential rules of confining pressure on the dynamic properties were studied by comparing the stress-strain curves of asphalt concrete under different stress states. The study found that passive confining greater impact on the strength of asphalt concrete than elastic modulus and Poisson ratio, but the elastic modulus improved with the increase of confining pressure.

An Evolutionary Multi-Objective Optimization Approach to the Topology Optimization of Auxetic Structures

2002 ◽  
Author(s):  
Ashraf O. Nassef
Keyword(s):  
Topology Optimization ◽  
Elastic Modulus ◽  
Finite Elements ◽  
Multiobjective Optimization ◽  
Poisson Ratio ◽  
Optimization Approach ◽  
Multi Objective Optimization ◽  
Finite Elements Analysis ◽  
Multi Objective ◽  
Auxetic Structures

Auxetic structures are ones, which exhibit an in-plane negative Poisson ratio behavior. Such structures can be obtained by specially designed honeycombs or by specially designed composites. The design of such honeycombs and composites has been tackled using a combination of optimization and finite elements analysis. Since, there is a tradeoff between the Poisson ratio of such structures and their elastic modulus, it might not be possible to attain a desired value for both properties simultaneously. The presented work approaches the problem using evolutionary multiobjective optimization to produce several designs rather than one. The algorithm provides the designs that lie on the tradeoff frontier between both properties.

scholarly journals Analysis of The Rock Fracture on Uniaxial Compressive Strength Test

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Edward Dinoy ◽  
Yohanes Gilbert Tampaty ◽  
Imelda Srilestari Mabuat ◽  
Joseph Alexon Sutiray Dwene
Keyword(s):  
Compressive Strength ◽  
Uniaxial Compressive Strength ◽  
Poisson Ratio ◽  
Rock Fracture ◽  
Strength Test ◽  
Maximum Pressure ◽  
Test Results ◽  
Average Value ◽  
Compressive Strength Test ◽  
Uniaxial Compressive Strength Test

The compressive strength test is one of the technical properties or compressive strength tests that are commonly used in rock mechanics to determine the collapse point or the elasticity of rock against maximum pressure. The rock collapse point is a measure of the strength of the rock itself when the rock is no longer able to maintain its elastic properties. The purpose of this test is to find out how long the rock maintains its strength or elasticity properties when pressure is applied, and to find out the difference between the strength of compact rock and rock that has fractures when pressure is applied. Rocks that have fractures will break more easily or quickly when pressure is applied compared to compact rocks. This analysis is carried out by comparing the rock strength of each sample, both those that have fractures and compact rocks. To find out these differences, laboratory testing was carried out. The test results show the value (compressive strength test 57.76 MPa), (elastic modulus 5250.000MPa), (Poisson ratio 0.05) and the average value of rock mechanical properties test (axial 0.91), (lateral-0.279), and (volumetric 0.252) . Based on the test results above, it shows that rocks that have fractures will break more easily when pressure is applied, compared to compact rocks that have a long time in the uniaxial compressive strength test.

scholarly journals The analysis of rheological damage of anchorage body based on visco-elasto-plastic model

2021 ◽  
Vol 303 ◽  
pp. 01060
Author(s):  
Qing-duo Wang ◽  
Feng-hai Yu ◽  
Aleksei Renev ◽  
Sergei Tsibaev ◽  
Xue-rui Yang
Keyword(s):  
Elastic Modulus ◽  
Constitutive Equation ◽  
Creep Curve ◽  
Damage Model ◽  
Rheological Characteristics ◽  
Plastic Model ◽  
Experimental Creep ◽  
Calculation Results

In order to study the rheological damage of anchorage body, rheological damage model of anchorage body is established in this paper, and it is based on visco-elasto plastic model that is often used to simulate rock rheological characteristics. The expressions of creep constitutive equation and elastic modulus of anchorage body are obtained through the analysis of rheological damage model of anchorage body, and by the fitting calculation results, finding that the theoretical creep curve is matched with the experimental creep curve under certain conditions. The research conclusions have critical significance to the bolting support and design.

scholarly journals Evaluation Method of Granite Multiscale Mechanical Properties Based on Nanoindentation Technology

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Man Lei ◽  
Fa-ning Dang ◽  
Haibin Xue ◽  
Mingming He
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Uniaxial Compression ◽  
Compression Test ◽  
Evaluation Method ◽  
Poisson Ratio ◽  
Nanoindentation Test ◽  
Uniaxial Compression Test ◽  
Displacement Curve ◽  
Mineral Contents

In order to study the mechanical properties of granite at the micro- and nanoscale, the load-displacement curve, residual indentation information, and component information of the quartz, feldspar, and mica in granite were obtained using a nanoindentation test, a scanning electron microscope (SEM), and X-ray diffraction (XRD). The elastic modulus and the hardness of each component of the granite were obtained through statistical analysis. Treating rock as a composite material, the relation between the macro- and microscopic mechanical properties of rock was established through the theory of micromechanical homogenization. The transition from micromechanical parameters to macromechanical parameters was realized. The equivalent elastic modulus and Poisson’s ratio of the granite were obtained by the Self-consistent method, the Dilute method, and the Mori-Tanaka method. Compared with the elastic modulus and the Poisson ratio of granites measured by a uniaxial compression test and the available data, the applicability of the three methods were analyzed. The results show that the elastic modulus and hardness of the quartz in the granite is the largest, the feldspar is the second, the mica is the smallest. The main mineral contents in granite were analyzed using the semiquantitative method by XRD and the rock slice identification test. The elastic modulus and the Poisson ratio of granite calculated by three linear homogenization methods are consistent with those of the uniaxial compression test. After comparing the calculation results of the three methods, it is found that the Mori-Tanaka method is more suitable for studying the mechanical properties of rock materials. This method has an important theoretical significance and practical value for studying the quantitative relationship between macro- and micromechanical indexes of brittle materials. The research results provide a new method and an important reference for studying the macro-, micro-, and nanomechanical properties of rock.

Investigation of grouting diffusion in a single rock fracture considering the influences of obstructions

2021 ◽  
Author(s):  
Wenqi Ding ◽  
Dong Zhou ◽  
Xiaoqing Chen ◽  
Chao Duan ◽  
Qingzhao Zhang
Keyword(s):  
Diffusion Process ◽  
Rock Fracture ◽  
Temporal Distribution ◽  
The Finite Element Method ◽  
Single Plate ◽  
Plate Fracture ◽  
Test Platform ◽  
Grouting Reinforcement ◽  
Spatio Temporal ◽  
Single Rock Fracture

Grouting reinforcement was used to improve rock strength and avoid seepage in rock engineering. A self-developed visualised test platform was developed and the influences of different fracture openness on grouting diffusion modes were revealed; the Bingham rheological model was imported to simulate the grouting diffusion process in a single plate fracture, the spatio-temporal distribution of the velocity field under different obstructions was determined using the finite element method. The results indicate that: 1) The grout diffuses faster with the increase of fracture openness, while a stagnation effect of the grouting diffusion velocity behind the obstruction occurs. 2) Due to obstructions, the grouting diffusion process can be divided into four stages: circular diffusion, flat diffusion, vortex diffusion, and butterfly diffusion. 3) The grouting diffusion area is divided into a fully-reinforced zone and a semi-reinforced zone, and the area of the latter increases with the fracture openness, while being little affected by the size of any obstruction. 4) Furthermore, some new grouting diffusion laws were revealed considering the asymmetrical arrangement of obstructions. The results presented in this work will be helpful for describing and predicting the grouting process in fracture networks.

Theory and Application of Stage-by-Stage Evaluation for Steam Turbine State-Line

1984 ◽  
Vol 28 (04) ◽  
pp. 240-260
Author(s):  
Robert Latorre ◽  
Zisimos Mourelatos ◽  
Efstratios Nikolaidis
Keyword(s):  
Theoretical Model ◽  
Computer Program ◽  
Steam Turbine ◽  
Heat Balance ◽  
Standard Heat ◽  
Balance Calculation ◽  
Calculation Results ◽  
Design Case ◽  
The Heat Balance

A theoretical model of a steam turbine is formulated based on idealized Curtis and reaction stages to obtain expressions for a stage-by-stage evaluation of the turbine state line. Using typical stage geometries and corrections a computer program was developed to size the turbine and evaluate its state line at design conditions. A comparison of the heat balance made with the stage-by-stage state line and the standard heat balance is presented. For the design case of 30 000 shp it is shown that the differences in the heat balance calculation results are within ±0.5 percent.

scholarly journals Theoretical Modeling of Rock Breakage by Hydraulic and Mechanical Tool

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Hongxiang Jiang ◽  
Changlong Du ◽  
Songyong Liu ◽  
Liping Wang
Keyword(s):  
Theoretical Model ◽  
Water Pressure ◽  
Rock Fracture ◽  
Superposition Principle ◽  
Specific Energy Consumption ◽  
Critical Length ◽  
Rock Fragmentation ◽  
Rock Breakage ◽  
Hydraulic Impact ◽  
Mechanical Tool

Rock breakage by coupled mechanical and hydraulic action has been developed over the past several decades, but theoretical study on rock fragmentation by mechanical tool with water pressure assistance was still lacking. The theoretical model of rock breakage by mechanical tool was developed based on the rock fracture mechanics and the solution of Boussinesq’s problem, and it could explain the process of rock fragmentation as well as predicating the peak reacting force. The theoretical model of rock breakage by coupled mechanical and hydraulic action was developed according to the superposition principle of intensity factors at the crack tip, and the reacting force of mechanical tool assisted by hydraulic action could be reduced obviously if the crack with a critical length could be produced by mechanical or hydraulic impact. The experimental results indicated that the peak reacting force could be reduced about 15% assisted by medium water pressure, and quick reduction of reacting force after peak value decreased the specific energy consumption of rock fragmentation by mechanical tool. The crack formation by mechanical or hydraulic impact was the prerequisite to improvement of the ability of combined breakage.

scholarly journals Experimental Research on the Mechanical Characteristics and the Failure Mechanism of Coal-Rock Composite under Uniaxial Load

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Ke Yang ◽  
Zhen Wei ◽  
Xiaolou Chi ◽  
Yonggang Zhang ◽  
Litong Dou ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Acoustic Emission ◽  
Elastic Modulus ◽  
Crack Propagation ◽  
Failure Mechanism ◽  
Poisson’S Ratio ◽  
Mechanical Characteristics ◽  
Poisson's Ratio ◽  
Energy Value ◽  
Coal Rock

Due to the influence of the component structure and combination modes, the mechanical characteristics and failure modes of the coal-rock composite show different characteristics from the monomer. In order to explore the effect of different coal-rock ratios on the deformation and the failure law of the combined sample, the RMT rock mechanics test system and acoustic emission real-time monitoring system are adopted to carry out uniaxial compression tests on coal, sandstone, and three kinds of combined samples. The evolution rules of the mechanical parameters of the combined samples, such as the uniaxial compressive strength, elastic modulus, and Poisson’s ratio, are obtained. The expansion and failure deformation characteristics of the combined sample are analyzed. Furthermore, the evolution laws of the fractal and acoustic emission signals are combined to reveal the crack propagation and failure mechanism of the combined samples. The results show that the compressive strength and elastic modulus of the combined sample increase with the decrease of the coal-rock ratios, and Poisson’s ratio decreases with the decrease of the coal-rock ratios. The strain softening weakens at the postpeak stage, which shows an apparent brittle failure. The combined sample of coal and sandstone has different degrees of damages under load. The coal is first damaged with a high degree of breakage, with obvious tensile failure. The acoustic emission energy value presents different stage characteristics with increasing load. Crackling sound occurs in the destroy section before the sample reaches the peak, along with small coal block ejection and the partial destruction. The energy value fluctuates violently, with the appearance of several peaks. At the postpeak stage, the coal samples expand rapidly with a loud crackling sound in the destroy section, and the energy value increases dramatically. The crack propagation induces the damage in the sandstone; when the energy reaches the limit value, the instantaneous release of elastic energy leads to the overall structural instability.

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