scholarly journals Theoretical Study and Experiment Validation on Drilling Cutting Weight during the Whole Process of Drilling

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Z. H. Wang ◽  
J. Tan ◽  
Y. L. Tan ◽  
Y. H. Wu
Keyword(s):  
Theoretical Calculation ◽  
Radial Direction ◽  
Coal Mass ◽  
Theoretical Formula ◽  
Mining Engineering ◽  
Drilling Depth ◽  
Cutting Method ◽  
Drilling Hole ◽  
Prediction And Prevention ◽  
Laboratory Test Results

In mining engineering, coal and gas outburst is extremely dangerous dynamic disaster, which will cause serious casualties and property losses. As a method to predict coal burst, the drilling cutting method has been widely used in coal mines. The drilling cutting weight is an important index of the drilling cutting method. In theoretical calculation, scholars usually assume that the coal is isotropic and homogeneous before drilling to deduce the formula of drilling cutting weight. However, in actual mining engineering, drilling cutting is usually carried out in the plastic coal body in front of the working face. Therefore, in the present study, the theoretical formula of the drilling cutting weight in the plastic coal mass is deduced, as well as in the elastic coal mass. The results show that the drilling cutting weight calculated based on the deduced formula increases with the increase of drilling depth in the plastic coal mass, which is consistent with the field measurement results. The fragmentation degrees of coal around the drilling hole are also considered by introducing cohesion, which changes linearly along the radial direction of the drilling hole. The results show that the smaller the cohesion, the greater the drilling cutting weight. The calculation formula for drilling cutting in elastic coal mass is also given. The dilatancy effect of coal around the drilling hole is also considered by introducing expansion coefficient n, which changes linearly along the radial direction of the drilling hole. There is a good match between the theoretical calculation results and the laboratory test results. The obtained results are helpful for the prediction and prevention of coal burst.

PHYSICAL PREREQUISITES FOR GAS PERMEABILITY SIMULATION OF MINED ROCK MASS

2021 ◽  
pp. 78-84
Author(s):  
Oleksandr Shashenko ◽  
◽  
Vladyslava Cherednyk ◽  
Natalia Khoziaikina ◽  
Dmitro Shashenko ◽  
...  
Keyword(s):  
Rock Mass ◽  
Physical Model ◽  
Rock Sample ◽  
Coal Mass ◽  
Dynamic Processes ◽  
Deformation Diagram ◽  
Gas Dynamic ◽  
Laboratory Test Results ◽  
Deformation Properties ◽  
Complete Deformation

Purpose. Justification of the gas collectors formation physical model on the basis of research of conformity of permeability of rock mass to the full diagram of rock sample deformation. Methodology consists in sequential analysis of the stages of the complete deformation diagram of the rock specimen under “hard” loading, comparing them with the stages of formation of the high stress zone in front of the lava bottom and statistical analysis of laboratory test results. Results. Based on the rock’s deformation properties analysis and their comparison with the rock sample full deformation diagram, the physical model of formation of gas reservoirs during the development of gas-saturated coal seam is substantiated. Within the solved problem framework, four stages of the complete deformation process are analyzed, namely: elastic, at the limit of strength, out-of-bounds stage and equivoluminal flow zone. The gas collector boundaries, which are the characteristic points of the rock sample deformation diagram in specified deformations mode (the limit of elastic strength and the limit of final strength) are determined. It is proved that the structural and textural features of the coal mass in connection with the course of gas-dynamic processes are manifested in the change in the pores and cracks volume contained in it, which together make the filtration space. Knowledge regarding the transfer of the permeability changes established regularities and free methane accumulation zones formation to the real rock mass, if the process of its forgery is considered as a consistent change of geomechanical states of rocks, is obtained. Scientific novelty lies in the first substantiated possibility of modeling the stress state before the longwall face by equivalent stages of the rock sample destruction in the given deformations mode. Gradual comparative analysis of the internal mechanism of rock samples deformation along the complete deformation diagram allowed establishing causal relationships between geomechanical and gas-dynamic processes in coal mass, and qualitatively characterizing general trends in permeability and volumetric expansion in changes of these samples. Practical value of the work lies in the justification of the principle of construction of a digital geomechanical model for the detection of man-made gas collectors in a mined coal mass.

scholarly journals Optical rotatory power. I—A theoretical calculation for a molecule containing only isotropic refractive centres

1934 ◽  
Vol 144 (853) ◽  
pp. 655-675 ◽  
Keyword(s):  
Theoretical Calculation ◽  
Optical Activity ◽  
Chemical Structure ◽  
Central Atom ◽  
Optical Rotation ◽  
Rotatory Power ◽  
Theoretical Formula ◽  
Optical Rotatory ◽  
Present Communication ◽  
Optical Rotatory Power

Ever since the time of van’t Hoff and Le Bel the number investigations dependent on optical activity, or attempting to elucidate optical activity, has been very great, and it is remarkable that, even at the present time, there is no theoretical formula which gives the relation between the magnitude of the rotation and the chemical structure of the molecule concerned. The present communication supplies this want with regard to the molecule of the simplest asymmetric type: the molecule with four different groups attached to one central atom. Various special hypothese have been postulated to explain optical activity, but a few investigators have shown quite definitely that there is no necessity for any of these hypotheses. Born* and Oseen have shown independently that, if the molecule has a dissymmetric structure, the ordinary refractive properties of the atoms will account for an optical rotation. Gray* and de Mallemann have attempted calculations of formulæ for optical retatory power on this basis. However, it has not been possible to condense the numerous algebraic terms which occur in these calculaations into a compact form.

scholarly journals Study on the Evolution Law of Overburden Breaking Angle under Repeated Mining and the Application of Roof Pressure Relief

Energies ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 4513 ◽  
Author(s):  
Feng Cui ◽  
Tinghui Zhang ◽  
Xingping Lai ◽  
Jiantao Cao ◽  
Pengfei Shan
Keyword(s):  
Numerical Simulation ◽  
Coal Seam ◽  
Theoretical Calculation ◽  
Simulation Experiment ◽  
Elevation Angle ◽  
Theoretical Formula ◽  
Engineering Practice ◽  
Pressure Relief ◽  
Physical Similarity ◽  
Working Face

Aiming at the serious problems caused by coal mine mining activities causing the rock burst accidents, this paper is based on rock mechanics and material mechanics to establish the key layer breaking by the double-key layer beam breaking structural mechanics model of a single working face and double working face under repeated mining. The theoretical calculation formula of the angle was used as the theoretical basis for the elevation angle of the pre-reloading hole of the hard roof. The rationality and reliability of the formula were verified by the physical similarity simulation experiment and the 3 Dimension Distinct Element Code numerical simulation experiment, revealing the rock formation under the influence of repeated mining. The results show that the derived key layer breaking angle formula is suitable for the theoretical calculation of the breaking angle of the key layer of a single coal seam when the repeated disturbance coefficient is λ = 1; when it is λ = 2, it is suitable for the repeated mining of the short-distance double-coal mining. The rationality and reliability of the theoretical formula of the breaking angle of the double key layer of single coal seam and double coal seam were verified by the physical similarity simulation experiment. Through the 3DEC numerical simulation results and theoretical calculation results, the W1123 working face hard top pre-cracking pressure relief drilling elevation angle was 78°. The drilling peeping method was used to verify the results. The results show that the theoretical formula of the critical layer breaking angle is well applied in engineering practice.

Study of Hybrid Method on Beam Crack Evaluation

2012 ◽  
Vol 166-169 ◽  
pp. 1113-1116
Author(s):  
Chuang Du ◽  
Sen Li ◽  
Yan Yan Li ◽  
Zi Tao Du
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Numerical Calculation ◽  
Theoretical Calculation ◽  
Hybrid Method ◽  
Crack Width ◽  
Theoretical Method ◽  
Theoretical Formula ◽  
Calculation Formula ◽  
New Formula

Based on the numerical calculation and the theoretical formula for crack width,a new semi-numerical and semi-theoretical calculation formula for crack width of beam was given. By using this new formula,finite element method and theoretical method is combined. The method has been validated with the beam, it is indicated that the proposed method can be used to calculate the crack width of beam accurately and efficiently.

scholarly journals Theoretical Calculation and Analysis on the Composite Rock-Bolt Bearing Structure in Burst-Prone Ground

2015 ◽  
Vol 2015 ◽  
pp. 1-6
Author(s):  
Liang Cheng ◽  
Yidong Zhang ◽  
Ming Ji ◽  
Mantang Cui ◽  
Kai Zhang ◽  
...  
Keyword(s):  
Theoretical Calculation ◽  
Rock Burst ◽  
Mechanical Model ◽  
Surrounding Rock ◽  
Rock Bolt ◽  
Mining Engineering ◽  
Calculation Formula ◽  
Mining Depth ◽  
Rock Parameters ◽  
Bearing Structure

Given the increase in mining depth and intensity, tunnel failure as a result of rock burst has become an important issue in the field of mining engineering in China. Based on the Composite Rock-Bolt Bearing Structure, which is formed due to the interaction of the bolts driven into the surrounding rock, this paper analyzes a rock burst prevention mechanism, establishes a mechanical model in burst-prone ground, deduces the strength calculation formula of the Composite Rock-Bolt Bearing Structure in burst-prone ground, and confirms the rock burst prevention criterion of the Composite Rock-Bolt Bearing Structure. According to the rock burst prevention criterion, the amount of the influence on rock burst prevention ability from the surrounding rock parameters and bolt support parameters is discussed.

Tooth Cutting Method of Face Gear by Using CNC-Hobbing Machine

1992 ◽  
Author(s):  
Harumi Ishii ◽  
Shigeyoshi Nagata
Keyword(s):  
Processing Time ◽  
General Type ◽  
Radial Direction ◽  
Tangential Direction ◽  
View Point ◽  
Face Gear ◽  
Cutting Method ◽  
Cutting Resistance ◽  
Latent Ability ◽  
Tooth Cutting

Abstract At present, the research on a gear having special tooth profile a using CNC hobbing machine have been making progress. However, the method of tooth cutting with using CNC hobbing machine is not used the full for an inherent ability of itself. From the aforementioned view point, we have tried to test cut a face gear which is used an inherent latent ability of the CNC hobbing machine. The unipurpose device has been manufactured for the purpose of improving aforementioned defects of conventional tooth cutting method. Then we have used a fly tool instead of an unipurpose hob cutter. In general, a helicon gear has been cut by unipurpose hob cutter, giving vertical feed with using general type hobbing machine. In this way, not only the tooth roughness decreases, but also processing time increases for the tooth cutting because the size of cut has to be made very small due to heavy cutting resistance. In our research, the unipurpose device is attached to the CNC hobbing machine. Then a fly tool already located on the final point of full depth, translates along the tangential direction of the gear from an appointed position in the radial direction. In this way, we can expect the cutting resistance to be reduced during manufacture. Also the tooth roughness will be improved.

scholarly journals Combined Early Warning Method for Rock Burst and Its Engineering Application

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Zhongcheng Qin ◽  
Tan Li ◽  
Qinghai Li ◽  
Guangbo Chen ◽  
Bin Cao
Keyword(s):  
Rock Burst ◽  
Engineering Application ◽  
Prediction Method ◽  
Accurate Method ◽  
Deformation Energy ◽  
Microseismic Monitoring ◽  
Drilling Depth ◽  
Monitoring Method ◽  
Cutting Method ◽  
Drill Cutting

Rock burst is a common mine disaster often accompanied with casualties and property damage. In order to effectively predict and prevent the rock burst occurrence, an effective and accurate method for predicting rock burst is necessary. This paper first establishes the relationship between the drilling cuttings and the releasable elastic deformation energy. However, the traditional drilling cutting method has the defect that the drilling depth cannot reach the stress concentration area and the drilling cuttings cannot accurately reflect the internal stress variation in the deep part of coal body. So, an improved drill cutting method is presented to make up for these defects. Finally, the combined monitoring method based on the improved drilling cutting method and the microseismic monitoring method is established. It not only overcomes the limitations of a single prediction method but also effectively utilizes the advantages of improved drilling cutting method and the microseismic monitoring method. And this combined monitoring method is applied to the No. 3302 coalface of Xingcun Coal Mine. The obtained results indicate that the combined monitoring method can improve the prediction capabilities of the rock burst and provide novel insights for preventing the rock burst occurrence.

Drilling-Hole-Loading Method for Measuring Tensile Strength of Irregular Small Stones

2012 ◽  
Vol 239-240 ◽  
pp. 649-653
Author(s):  
Jin Chen ◽  
Ming Liu ◽  
Jie Min Liu
Keyword(s):  
Tensile Strength ◽  
Circular Hole ◽  
Standard Specimen ◽  
Hole Drilling ◽  
Theoretical Formula ◽  
Test Device ◽  
Drilling Hole ◽  
Loading Method ◽  
Set Up ◽  
Theoretical Stress

Drilling-Hole-Loading method is applied to predicting and measuring the tensile strength of irregular small-size stones. According to this method, a circular-hole must be drilled at the center of the irregular small-size stone. The mechanical model of the stone with a circular-hole and subjected to a pair of equivalent collinear pull forces is set up. The normal stress strain distributions on the critical section are anlyzed. Theoretical stress concentrated factor equation related to the hole diameter is calculated. Based on the static equilibrium theory, the theoretical formula of predicting the tensile strength of irregular small-size stones is established. Based on the theoretical formula, the test device for measurement of the tensile strength of the stone was designed. The tensile strength of a kind of bluestone was measured. The results show that the tensile strength predicted by Drilling-Hole-Loading method is a little lower than that of the standard specimen of stone without hole. Drilling-Hole-Loading method can be used to predict the tensile strength of brittle material and irregular small-size stones.

scholarly journals Dynamic Characteristics of Fault Structure and Its Controlling Impact on Rock Burst in Mines

2021 ◽  
Vol 2021 ◽  
pp. 1-7
Author(s):  
Tianwei Lan ◽  
Jiawei Sun ◽  
А. S. Batugin ◽  
Wenqi Zhao ◽  
Mancang Zhang ◽  
...  
Keyword(s):  
Coal Mining ◽  
Rock Burst ◽  
Treatment Plan ◽  
Geological Structure ◽  
Mining Engineering ◽  
Fault Structure ◽  
Safe Production ◽  
Geodynamic Environment ◽  
Controlling Mechanism ◽  
Prediction And Prevention

As one of the most serious shock dynamic disasters in coal mining, rock burst only occurs under the certain geodynamic environment. Geodynamic is the necessary requirement for the occurrence of rock burst, and the disturbance of mining engineering is the sufficient requirement. In terms of the fault structure, the method of geodynamic zoning is used to classify fault structure forms of rock burst in mines, and a model of geological structure is established to reveal the connection between fault structure and mine engineering. Besides, the influence of fault structure on rock burst is analyzed, and the controlling mechanism of the fault structure on the tectonic evolution of the mine area and the occurrence of rock burst is revealed. This research provides a treatment plan for the prediction and prevention of rock burst and guides the safe production in the coal mining engineering.

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