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.     

Simulation of coal and gas outburst with different gas pressure

To discuss the mechanism of gas pressure in coal and gas outburst process,with the constant of moulding pressure,moisture and forced status of the outburst coal sample, five outburst experiments of the different gas pressure are simulated by the independently developed coal and gas outburst simulation test device and the same coal sample. It is found that coal and gas outburst could produce pyriform or elliptic holes with small mouth and big belly. And the volume of hole to the volume of outburst coal is from 1/2 to 2/3. Moreover, there is a threshold value of gas pressure for coal and gas outburst and greater with the increase of outburst intensity. As the force of outburst, the gas pressure has a certain effect of ejection and porphyrization on the outburst coal powders. The coal sample temperature varies continuously with the trend of rising firstly and decreasing subsequently. And the grads of coal temperature can be adopted for predicting the coal and gas outburst.     

穿层钻孔煤巷条带水力压裂防突技术及应用

针对低渗高突煤层煤巷条带预抽区域瓦斯治理难题,运用弹性力学理论,结合高压水动力特性,提出穿层钻孔煤巷条带水力压裂防突技术,建立计算目标煤层起裂压力计算模型,集成配套井下压裂成套设备,并进行工业性试验。试验结果表明：技术实施后,压裂钻孔的瓦斯抽采浓度和抽采纯量曲线呈现“高—低—高”特点,体现了压裂改造的双重作用;相比于水力割缝孔和普通穿层孔,压裂孔的瓦斯抽采纯量分别提高了20倍和133倍;预掘煤巷处的残余瓦斯含量降到8 m 3/t以下,穿层钻孔煤巷条带水力压裂增透技术消突效果显著。     

An analysis on the energy of coal and gas outburst process

Based on the hypothesis of the synthetic coal and gas outburst operating, we study the work done by elastic energy of coal mass and methane expansion energy in the coal and gas outburst process through theory and experiment. By using MTS815 rock mechanics test system, the triaxial compression test of the coal sample is carried out under different confining pressures and the power function relation between coal bodys elastic energy per unit volume and body stress is worked out. It shows there is a linear relation between methane expansion energy and methane pressure obtained by testing methane expansion energy under different moisture contents, different methane pressures and different compactness of coal mass, with the help of self-developed methane expansion energy testing device. The temperature change in the system is about 1 ℃ when methane does work in expansion. The result also shows that it could be regard as an isothermal process during coal and gas outburst. The results from experiment do great help in researching the mechanism of coal and gas outburst and establishing energy criterion.     

Numerical simulation of outburst prevention air door destruction by coal and gas outbursts

We explore the destruction of outburst prevention air doors by coal and gas outbursts using numerical simulation. The reflective overpressure when an outburst acts on doors is elucidated, and its formula is obtained. The destruction of outburst prevention wind doors by coal and gas outburst are simulated using ANSYS software based on data of wind door pressure obtained by similarity simulation experiment. The simulation results show that the weakest place of gate posts is where the wind tube is. Simulation results also show the first shock wave pressure that acts on an outburst prevention wind door is not the maximum one. Due to the effect of reflected overpressure, the outburst prevention wind door pressure will reach the maximum in several milliseconds. This finding is similar to the experiment result.     

Analysis on AE characteristic and its confining pressure effect of outburst coal containing gas

Briquette samples made of outburst coal are taken as study objects to study AE characteristic and its confining pressure effect by using self-developed equipment, Shimazu servo test machine and AE monitor system, and the characteristic of AE parameters are analyzed, too. The results show that in the process of outburst coal containing gas triaxial compression, there is no serious dense or sparse area of AE events, but three relative dense appear in compression phase, middle area of linear elastic stage and near peaking phase area so that the characteristic of AE events look like three peaks. But the amplitude of AE events is small and the good consistency between energy change and amplitude change is showed. Microstructure change caused by external stress field change, fracture and fragmentation of particle of samples, movement besides particle of samples and microstructure change caused by dissipation of gas are the sources of AE events. The number of AE events is reduced as the confining pressure is increased, but the influence on total number of AE events caused by confining pressure show nonlinear, expressed by quadratic function. The number of larger amplitude of AE events show decreasing tendency as the confining pressure is increased, the relation between numbers of AE events whose amplitude is more than certain value and confining pressure is expressed by quadratic function.     

煤与瓦斯突出综合预测指标临界值的优化

为了提高煤与瓦斯突出预测的准确性、保障采掘工作面的安全、高效推进和降低防突工程成本,根据“三率”(预测突出率、突出预测准确率、不突出预测准确率)各自具有的合理区间属性和权重,以张集煤矿采掘工作面为例,采用区间数关联决策方法,得出综合预测指标 F ′的最优化区间为［370,380］;根据加权灰靶决策方法,得出预测指标临界值排序为400、390、380等;取最优化区间和排序靠前的临界值的交集,得到煤与瓦斯突出综合预测指标 F ′的临界值为380,并开展现场应用。结果表明,考虑评价指标的区间属性,并取预测指标区间与排序靠前的临界值的交集作为煤与瓦斯突出预测综合指标 F ′的最优临界值方法是合理的。     

Clogging mechanical model and its application in gas extraction borehole

A clogging segment mechanical model is established on gas extraction horizontal borehole. Based on the air pressure extremes pmax of the construction site, we solve the corresponding critical clogging length L0 and find clogging will occur when L> L0. With the clogging segment mechanical model, we analyze the calculation method of the retreat drilling rod resistance in borehole. The influence rule of clogging length and air supplying system pressure on retreat drilling rod resistance is analyzed. Analysis results show that the main reason for difficult drilling clogging and retreat drilling rod is the higher pressure in borehole clogging segment. The retreat drilling rod resistance is especially sensitive to the change of air supplying system; therefore, the effective method of reducing the retreat drilling rod resistance is reducing the air supplying system pressure in borehole. The drilling construction status in Jiulishan coal mine is analyzed by using the clogging segment mechanical model, and three technical measures are put forward, including increasing slagging space, reducing slagging resistance and increasing drilling rod strength. When the improving measures are adopted, the pipe-sticking phenomena decreases, the drilling rod broken phenomenon are averted and the drilling efficiency increases by 17%.     

The Experiment of Prevention Accumulated Methane by Means of Abnormal Y Pattern Ventilation Method

In this paper, according to the experiment of abnormal Y pattern ventilation method in Coal Face 22160, Mine 10, Pingdingshan Coal Group Ltd. Co. , it is discussed that the effect of ventilation method on fugitive air and gas emission. It is discovered that Y pattern ventilation method can not only decrease air break in mine goaf by means of declining intake air in drawing road, and alleviate gas emission in gob area, but also wash the accumulated methane in upper corner by means of fresh air in middle road, and reduce the gradient of gas concentration greatly in direction of dip in upper half part of mining face and the gas concentration in upper corner. That can effectively prevent gas accumulation in mechanized high gas faces and provide reliable guarantee for high production and high effectiveness in mechanized high gas faces.     

Key Layer and Stress Dike Mechanism of Coal and Gas Outbursts

The outburst coal mass is a geologic body which had objectively existed before outbursts occurred.The authors think the occurrence and development of coal and gas outbursts are controlled by comprehensive factors according to a host of facts of outbursts in their researches,and all the factors belong to the system of "rock coal gas rock".Therefore the authors put forward a completely hypothesis,i.e.key layer and stress dike mechanism of coal and gas outbursts.This hypothesis emphasizes that the outbursts are the result of comprehensive action by coalbed gas,abutment stress and physical and mechanical properties of coal.Of special interest is emphasizing the geologic backgroud and conditions of outbursts to a great extent.Any phenomenon of outbursts which a person could observe could be qualitatively explained with the hypothesis so that the hypothesis can serve the study of geophysical field of outbursts perfectly.     

The effect of original moisture content in coal beds on coal and gas outburst risk level

By using self-made “Coal Containing Gas Thermal-Hydrological-Mechanical (THM) Coupling Experimental Equipment”, an experimental study is carried out to investigate the gas seepage law of containing-gas coal during the complete stress-strain process with different original water contents. Under the conditions of constant gas pressure and confining pressure, and the experimental results are compared with the field test of the gas emission variation of coal seams before and after being infused. The research results show that the triaxial compressive strength and the elastic ratio of coal decrease with the increase of original water content in coal, but the axial strain of coal increases and the absolute value of transverse strain and volume strain of coal increases at the triaxial compressive strength; the methane effective permeability of coal decreases throughout the complete stress-strain process. Outburst prevention by coal seam infusion attributed is analyzed from two aspects: the mechanics of coal and the gas flow in the coal seams. The higher original water content in coal seams is, the smaller the risk of coal and gas outburst becomes. So the original water content in coal seam can be treated as a significant criterion for the judgments of coal and gas outburst criticality.     

Analysis and Calculation of Ventilation System of Xuefengshan Highway Tunnel

Some problems about ventilation in extra long highway tunnels have been discussed in this paper. The ventilation modes and geometry parameters of longitudinal blow-suction ventilation of Xuefengshan Tunnel in Hunan Province (7 000 m) have been studied and calculated. Based on this, the general design, principle design, technical design and relative structural design of ventilation for the tunnel have been successfully done.     

Technique of Classification of Coal and Gas Outburst Mines

managing the coal mines according their dangerous grade determined. can decrease the engineering quanity and lessen the sightless characteristic. It has marked benefit for community and great economic benefit. The dangerous grade of outburst mines are determined Outburst coal mines are classified into mines with serious outburst hazard, mines with middle outburst hazard and mines with ordinary outburst hazard. Twelve classification indicators are used in comprehensively evaluating the dangerous grade of outburst mines. The dangerous grade of outburst mines are determined according to the principle of the most subjection with fuzzy comprehensive evaluation method, on the basis of the classification indicators and its quantification. By the model founded, some coal mines are studied and the research results are accordant with the fact.     

Study on the Chemical Composition and Macromolecular Structure of Outburst Zone Coal

In the light of ultimate analysis data and density of specific gravity liquid, we put forward a formula to calculate the real density of vitrinite, and get a relatively exact computational formula of condensation ring index. The molar fraction of carbon atom ( x C ) could be used to describe the metamorphic degree of coal. Relationship between the macromolecular structure and the probability of coal outburst has been discussed.     

高大平房仓立体机械通风技术研究

为解决高大平房仓机械通风不均匀等问题，在原有平面通风道的基础上，于粮堆中增设相应数量的直竖式通气竹笼，使之形成粮堆立体通风网络。试验表明：可提高通风效果和均匀度，消除死角，加快降温速度，缩短通风时间，节约费用，为立体通风提供一条新途径。     

包装稻谷采用不同通风方式的通风效果对比试验

采用不同风机和不同的通风方式,对包装稻谷在高大平房仓进行储粮通风降温的尝试,选择适合本地区较为合理的风机和通风方式,能取得较为理想的降温、控水、调质的效果,为安全储粮、节省费用开支做了初步尝试。     

高大房式仓增设辅助通风笼储粮试验

在高大房式仓机械通风网络中存在的“死角”问题极不利于粮食的安全储藏。根据途径比理论,在“死角”部位设计并安装了一种辅助径向通风笼,取得很好的效果。本文通风笼的安装部位和尺寸进行了理论推算,对其在运用过程中的合理性和科学性进行了探讨。     

移动组合立体通风就仓干燥高水分稻谷试验

为了解决一般深层粮堆通风干燥中存在的水分垂直分层问题 ,开发了移动组合式立体通风系统 ,并应用该系统在江西南昌进行了稻谷通风干燥试验。试验原粮 15 33t,平均水分 17.4 %。从 2 0 0 3年 1月 2 5日到 4月 2 4日 ,利用地上笼风道通风 198小时 ,移动组合式立体通风 2 0 0小时 ,各层水分分别降低为表层 15 .3% ,上层 14 .7% ,中层 13.7% ,下层14 .4 % ,全仓平均 14 .5 % ,水分梯度小于 0 .6 % /m粮层 ,各层水分最大相差 1.6 % ,明显改善了水分的垂直分层现象。试验共耗电 190 6 8kW·h ,单位能耗 0 .37kW·h/kg水。干燥前后稻谷的发芽率等品质指标无明显变化 ,较好地保持了粮食的原始品质。