THE STUDY OF THE RELATION BETWEEN COAL-GAS OUTBURST AND PHYSIC AND MECHANIC PROPERTIES OF COAL SEAM IN A COAL MINE

The experimental study of physic and mechanic properties of coal seam in a coal mine is presented, and the relation between coal-gas outburst and the strength, the elastic modulus, as well as the deformation property of coal seam is analysed on the basis of the experimental results.     

Experimental analysis of matrix shrinkage’s influence on mechanical permeability of gas filled coal

Based on the coal seam of Zhao zhuang coal mine and Si he coal mine belong to Jin cheng anthracite Mining Group in Shanxi province, by using the self developed three axial servo controlled seepage equipment for hot fluid solid coupling of coal containing methane, parallel experiments for permeability of helium and methane under different gas pressures are carried out to quantitatively study the influence of Klinkenberg effects on the permeability of coal. Meanwhile, the problem of permeability decreasing caused by fluid pressure decreasing and gas desorption is eliminated by controlling the effective stress. The results show thatthe Klinkenberg effect is obvious under low gas pressure. With the increase of gas pressure, the permeability of coal decreases at first and then increases. The inflection points of gas pressure for Klinkenberg effect are about 0.9 MPa both for coal samples in Zhao zhuang coal mine and Si he coal mine. When the effective stress is constant, with the increase of gas pressure, the permeability increment caused by Klinkenberg effect decreases, while permeability increment caused by coal matrix shrinkage increases. Coal matrix shrinkage has a close relationship with the mechanical properties of coal rock mass. For the coal sample with a poor mechanical property, coal matrix shrinkage is more obvious.     

近水平复合煤层露天矿备采煤量留设位置与保有期优化

为了确定经济合理的露天矿备采煤量留设位置和保有期,运用露天开采基本原理与统计分析方法,分析新时期露天煤矿的发展变化特点及其对备采煤量留设位置和保有期的影响;以经济效益最优为判断准则,研究复合煤层露天矿备采煤量留设位置与内排运距的关系,建立备采煤量留设位置优化模型;研究季节性剥离露天矿备采煤量保有期与剥离成本、运输成本以及资金时间价值的关系,建立备采煤量保有期优化模型。以内蒙古东部地区某露天矿为研究实例,确定了该矿经济合理的备采煤量保有期为6.5个月,备采煤量应全部留在1号煤层。研究结果表明：该优化模型可用于指导露天矿生产,有效降低剥离成本,提高经济效益。     

Mechanism analysis of permeability based on promoting coal matrix shrinkage by water jet

High pressure pulsed water jet (HPWJ) is a new technology of effectively improving coal seam permeability. However, the mechanism of increased permeability is not yet clear, which restricts the application of HPWJ in different coal seams. From the perspective of improving permeability by coal matrix shrinkage, the impelled dynamic equations is established based on analysis of coal dynamic effects by water jet. According to theoretical analysis of the stress state of coal matrix, it is concluded that HPWJ can promote coal matrix shrinkage, and the relationship equation between jet impact-coal matrix is derived. Besides, the gas seepage function in the coal slotted by the HPWJ is gained by using PM model, which provides theoretical support for generalizing the technology in the coal mine.     

Coal and gas outburst disaster early warning andemergency response decision support technology

In order to realize early warning of coal and gas outbursts, and take timely emergency response, the technology of coal and gas outburst early warning and emergency response decision support is brought forward. The characteristics of abnormal gas outburst are specially analyzed, thus methods are given to monitor and identify the coal and gas outburst disaster. Combined with existing safety monitoring system in the mine, researches of such techniques are carried out as outburst gas content predicting, spread range forecasting and regions of power cutoff. Through those techniques, the Daping coal mine gas explosion disaster is retrieved. In the process of simulation, gas spreading early warning and related emergency response proposals can be issued before the gas arrive.     

Exploration on the Principle of ECMB

ECMB, which is developed by Amoco company in USA, has very prospective. On the basis of the study on adsorption characteristics of mixture gas in coal, the principle of ECMB has been explored. The order of adsorption capacities of coal for several gases is: CO 2>CH 4>N 2>H 2 when coal adsorbs gas. In 2 member mixture gases, adsorption capacities of coal for mixed gases, methane and carbon dioxide tally with Langmuir equation, but not does for nitrogen and hydrogen. The substance of the increasing drawing ratio of coal seam gas by using ECBM is decreasing adsorption amount of methane in coal by emptying the other gas or gases into coal seam. N 2 is better gas than CO 2 in the process of using ECMB.     

露天矿过断层开采方式及生产能力接续分析

在露天开采过程中遇到断层时,由于煤层突然错位,造成剥采比剧变,工程接续困难。因此,过断层期间剥采比合理控制和矿山工程平稳过渡接续是露天开采的技术难题之一。笔者通过建立剥采比与断层落差、产状及煤层厚度数学模型,研究不同煤柱留设宽度对边坡稳定的影响;分析了矿山工程发展速度与同时采煤台阶数的关系,计算确定了过断层期间确保矿山工程平稳过渡接续的动态降深速度和生产能力接续方式。结合胜利东二号露天矿过F61断层进行实例研究。结果表明：过断层开采方式和生产能力接续方法可有效均衡生产剥采比,保证产量稳定,提高矿山经济效益。     

Application of A New Anchor Cable Mounting Rod in the Lower Soft Coal Seam of Splitting and Merging Coal

To obtain the deep displacement of the coal seam in the working face,multi-point displacements were installed in the coal seam, but the installation of multi-point displacement is differen tunder different geological conditions. This paper is based on the splitting and merging of 7_1 coal and 7_2 coal in Huaibei Mining(Group) Co., Ltd., and analyzes properties of the roof andcoal in the 7_2 coal of the lower coal seam of bifurcation area, and calculates the damage depth of the floor in the process of 7_1 coal mining. The multi-point displacement meter installation is often challenged by hole collapse, stuck pole and broken installation rod in 7_2 coal of the soft coal seam of bifurcation area, as a result, the base points can't be installed in the specified location. In view of this, this paper adopts a new anchor cable mounting rod which can install the whole base points to the specified location without stuck pole or broken mounting stem. All the basic displacement data can be obtained, and the law of mine pressure appearance in stope and tunnel can be accurately controlled, which can be used to maintain the stability of roadway and the safety of stope.     

A visco elasto plastic creep model of outburstprone coal under triaxial compression

Using self made creep seepage experimental apparatus, triaxial creep tests on outburst prone coal are carried out with coal samples taken from Songzao Coal Mine. It is found that the attenuation creep property is shown in the conditions of less than its long term strength load, while non attenuation creep property for the greater conditions. By introducing a visco elasto plastic body which can describe the deformation property of non Newtonian fluids, the visco elasto plastic creep model of outburst prone coal is put forward combined with a Poyting Thomson model. The model parameters were fitted out with Matlab programmer and validation is employed. It is found that the test results were in good agreement with those by the proposed model.     

The Influence of In-situ Stress Gradient and Geothermal Temperature on The Calculation of Coalbed Gas Pressure

On the basis of coal seam having outcrop of coal seam and outlet on ground,the method for calculating coalbed gas pressure from the one-dimensional stable gas flow equation by considering deeply the influence of in-situ stress gradient and geothermal temperature is presented. In some mine, the theoretically computing and measuring results of coalbed gas pressure show that the in-situ stress gradient and the geothermal temperature have important influence on the calculation of coalbed gas pressure, and if the factors are drew into the calculation of coaled gas pressure,it will make the results much more accurate.     

DEVELOPMENT AND EXPERIMENTAL ANALYSIS OF HYDRAULIC LOCK OF THE THINNEST COAL SEAM SHEARER

The structure and work theory of a new type of hydraulic lock of the thinnest coal seam shearer is described in this paper. Its performance tests have been done the test results show that the performance of hydraulic lock is satisfactory and can be fit for the needs of locking and floating of the cutting drum of the thinnest coal seam shearer     

The application of deep hole pre-split blasting to gas improved extraction in high hydrogen sulphide mine

As the present result of gas extraction by conventional methods in soft low permeability of high-gas mine is not satisfying, deep hole presplitting controlling blasting technology is adopted in Changwu Tingnan coal mine, Shaanxi province. The amount of a single drilling gas extraction increases by 1.36 times, face gas extraction rate edges up to 50% and seam permeability coefficient increases by 9 times. By taking some comprehensive measures, such as enhancing ventilation, drainage, extraction of hydrogen sulfide and lime slurry injection in the blast holes, the hydrogen sulphide is controlled in advanced and the concentration is controlled blow 2×10 -6~4×10 -6, thus the working environment is effectively improved and the safety in production is ensured.     

RESEARCH ON THE MECHANISM OF GAS OUTBURST INITATION IN MINES

The mechanism of coal-gas outburst iniration is comprehensively analysed. The direct courses of initating coal-gas outburst are the sudden loss of confining stresses and the gas pressure gradient in coal seam. The effects of working face's advancing rate, geological conditions and gas pressure gradient as well as mechanical & physical characteristics of coal on outburst initation are expounded by means of mathematic analyses about gas seepage which takes place in coal seams. The results are of certain practical significance and reference value to further quantitive study of outburst and its predication.     

THE EFFECT OF THE STRESS OF LONGWALL AND STRUCTURE OF COAL ON THE BUMP OF COAL AND METHANE

The problems that the bump of coal and methame in the mine is contraled by the stress of longwall and that the coal and methane bump in the mine is affected by the physical properties of the coal are analysed and discussed through some specific bump cases. It is shown that the compressive stress, the content of the methane of the coal, and the bump of coal and methane are directly affected by the content of the ash and the volatile of the coal.     

Analysis on rock cross-cut coal uncovering using high pressure water jet slotting in close distance seam group

Safe production and procedures at the driving face are restricted in mines of Guizhou province by the long periods required for rock cross-cut coal uncovering in high gas coal seam group. A new method is proposed to solve this problem using high pressure water jet slotting in penetration boreholes. This is proposed to increase the gas desorption rate and reduce drilling hole, which will shorten the cycle of rock cross-cut coal uncovering. Numerical simulation is used to compare the pressure relief effects of different slotting methods in penetration boreholes. The results show that the pressure relief effect of slotting all coal seams is more ideal. Field application indicates that high pressure water jet slotting has good effect of the pressure relief in coal seam group. The drilling number is reduced by 30, the drilling length is shortened by 610 m and the standard time of gas pre-pumping decreases by 39 days.     

Numerical Simulation of Strata Movement Behavior in Deep Excavation

According to the complex conditions of deep excavation in Nantong mine, FLAC program are carried out for strata movement, ground pressure and surface displacement due to coal extraction. Based on the analysis of Nantong mine, the basic features of strata movement, the fundamental behavior of ground pressure and the related parameters of surface displacement are obtained. The results are of referential value for mining, supporting and preventing of surface displacement.     

Study on Hydraulic Automatic Ranging Cutting Height of Shearer

A new method has been put forward to automatically adjust height of drum-typeshearer.The principle of this rnethod is that the boundary of coal and rock is recognized with thepressure changes resulting from the height adjustment of the oil cylinder exerted by the cutting forceswhile the shearer drum is cutting the pure coal seam and the rock.With the help of this the corre-spondent hydraulic serving system can be controlled to adjust the height of shearer drum automati-cally.In this paper, a mathematical model is established a nd experiments and researches have been al-so carried out.     

Analysis on the mechanical model in gob-side entry retaining of inclined coal seam

When gob-side roadways in inclined coal seam are retained by strike long wall mining method, the conveyor roadway are retained under ascending mining and the ventilation roadway is retained under underhand mining. In order to research the differences of roof activity in the two conditions, stack continuous layer boards model and load strips segmentation method are used and the influence of the coal seam dip angle is considered. Then the solving formulas of roadside support resistance under such conditions are obtained. Through comparison and analysis, it shows that roadside support resistance of conveyor roadway gob-side entry retaining is much greater than ventilation roadway gob-side entry retaining. When ventilation roadway gob-side entry retaining is used, roadside support resistance reduces with the coal seam dip angle increases. While conveyor roadway gob-side entry retaining is adoptel, roadside support resistance increases with the coal seam dip angle increases. But when the coal seam dip angle is larger than the natural repose angle of goaf caving gangue, the resistance can be reduced by considering the effect of goaf gangue accumulation. The conclusion provides reference for choosing mining sections order of gob-side entry retaining in inclined coal seam.     

Study on Adsorption Characteristics of Coal to Gas in Geophysical Field

It is very important to mine safe exploitation, gas drawing and predict of coal and gas outburst that adsorption characteristics of coal to gas in geophysical field are studied. Adsorption and desorption characteristics of coal to gas in geophysical field have been reviewed in detail, then it is obtained that adsorption characteristics of coal to gas in electromagnetic field should be further studied . Adsorption and desorption characteristics of coal to methane in alternating electric field (AEF) have been studied mainly. Adsorption characteristics of three coal samples in AEF have been studied by means of Volume Method. The result shows that chemical properties and matter constituent of coal surface are no changed , adsorption and desorption of the coal samples in AEF well accord with Langmuir equation and two constants empirical formula, and because coal potential energy is increased and coal temperature is raised caused by Joule heat effect , adsorption ability of coal is decreased, and the desorption process is slowed down in AEF.     

An Experimental Research on Coal base Reducing Poor Siderite to Sponge Iron

A series of experiments were carried out in the department laboratory and showed that using fixed bed jar method the coal base reduction of poor siderite can produce reduction ore.by ball milling and magnetic separation the sponge iron(TFe>80%,SiO 2<6%) was obtained.Thereby the scientific basis for developing and utilizing the low grade siderite were provided.