Control on mine pressure of thick and strong roof stratum movement in long wall thick coal caving face

The caving of thick and strong roof stratum causes tremendous rock pressure in mine.The results of the analysis on dynamic natures of actual measurements of some fields,of which the roof pressure can be caused by thick and strong stratum in long wall thick coal caving face,could present the relation between the collapse and movement of thick and strong roof strata and surrounding rock pressure.In order to control the roof pressure effectively,the thick and strong roof strata,can be fractured and softened previ- ously by hydraulic fracturing and low-high pressure water infusion,fracturing and softening method.The results of study can provide basis for strata control and safe management in long wall thick coal caving face.

Pressure-relief effect of coal rock body of long distance lower protective seam mined based on FLAC^(3D)

According to the specific geological condition, analyzed the stress distribution of the overlying strata, the displacement of pressure released seam, thickness variation and the distribution of plastic zones by FLAG3D software to simulate mining of the long-distance lower protective seam. The research results show that the distribution of vertical stress appears as a ＂Double-hump＂ within the pressure-relief range of the protected coal seam and the swelling deformation curve of coal bodies takes an ＂M＂ shape. The swelling is divided into initial swelling, swelling increase and swelling compression stability. The maximum swelling ratio of the pressure released seam is 1.84%, protection angle of the lower protective coal seam along the strike direction is about 55°, protection angle below the dip direction is about 50°, protection angle above the dip direction is about 55°, and the coal seam compression zone resembles a ＂U＂ shape.

Distribution pattern of front abutment pressure of fully-mechanized working face of soft coal isolated island

The front abutment pressure of a fully-mechanized workface of 11061 soft coal isolated island of Liangbei Coal Mine was measured and studied using a self-developed mining-induced stress monitoring system associated with electromagnetic radiation technology, and the effects of abutment pressure distribution on strata behavior we discussed. The results indicate that the miningdnduced influencing distance advanced at the fully-mechanized working face of soft coal isolated island is larger than that at the gen- eral working face at the isolated island, besides the fracture zone in front of working face was widened to some extent, and the influencing range caused by relaxations on both roadways became bigger with the advancing working face. Moreover, it can be indicated that mining has significant effect on strata behav- ior of fully-mechanized working face of soft coal isolated island, which is mostly distributed in the area of stress concentration. The research results have an important reference value for revealing the distribution pattern of the front abutment pressure of a fully-mechanized working face of soft coal isolated island, and controlling the coal-rock dynamic disaster occurrence under similar mining conditions.

STUDY ON LAWS OF UNDERGROUND PRESSURE APPEARANCEIN THE DEEP ENTRIES OF COAL MINES

Based on a large amount of field investigation and observations, the paper analyzes and summarizes the mining depths and depth distribution of coal mines in China, discusses the characteristics of undrground pressure appearance in the entries of deep mining, points out some characteristics of surtounding rocks when rHo> =0.5, such as obvious rheologital deformation,and puts forward the main principles of supporting the entries in deep mining

DETERMINATION METHOD OF OPTIMAL SUPPORTING TIME IN HEADING FACE

This paper has put forward a concept of optimal supporting time through analysing the influence of the supporting time in the heading face on the supporting result of surrounding rock.The method Of the optimal Supporting time determined by graphical method is discussed, and the calculating formula for determining the optimal supporting time through the analysis method is derived.

THE RELATION BETWEEN THE CHAIN PILLAR WIDTH AND THE SURROUNDING ROCK DEFORMATION OF ROADWAY

Based on the analysis and research into ground pressure behavior law and surrounding rock deformation of a large number of roadways affected by mining activity,this paper proposed a relation between the surrounding rock deformation during mining ,the surrounding rock deformation rate during stable stage of mining and the chain pillar width. Moreover,it established the relation between the total amount of surrounding rock deformation during service period of roadway and the chain pillar width,which provides a principal basis for choosing the chain pillar width.

Drainage feature about coalbed methane wells in different hydrogeological conditions in Fanzhuang area

It is an important guarantee to enhance the production of coalbed methane （CBM） and reduce the project invest- ment by finding out the drainage feature about CBM wells in different hydrogeological conditions. Based on the CBM explora- tion and development data on the Fanzhuang block in southeast Qinshui Basin and combined with the seepage principle and lithology on the roof and the bottom coalbed, the mathematical model of integrated permeability was established. By perme- ability experiments of the different lithologies on the roof and the floor within the 20 m range combined with the log curves, the integrated permeability of different lithological combinations were obtained. The starting pressure gradient and permeabi- lity of the roof and the floor for different lithologies was tested by ＂differential pressure-flow method＂. The relationships be- tween the starting pressure gradient and the integrated permeability were obtained. The critical distance of limestone water penetrating into coal reservoirs was calculated. According to the drainage feature of CBM wells combined with the drainage data of some CBM wells, the results show that, when limestone water can penetrate into coal reservoirs, the daily water production is high and the daily gas production is low although there is no gas at the beginning of the drainage process, the CBM wells stop discharging water within 6 months after the gas began to come out, and the gas production is steadily improved. When limestone water can not penetrate into coal reservoirs, the daily water production is low and the daily gas production is high at the beginning of the drainage process, and it almost stops discharging water after some time when the gas come out, the daily gas production increases, and the cumulative water production is much lower.

Current situation of simultaneous coal and methane extraction tech- nology in pressure-relieved coalbed group

The importance of simultaneous coal and methane extraction and its significance on green exploitation is stated, and current research situation of simultaneous coal and methane and faced new problems are introduced. The research progress on movement of overlying strata and stresses change in them, cracks development during mining in overlying strata and meth- ane emission under disturbance of mining as well as the changing rules of permeability and methane flow under the disturbance of mining is analyzed. The progress on practice of simultaneous coal and methane extraction is analyzed. The deficiencies of current research and further researching fields on simultaneous coal and methane extraction are pointed out.

Influence of Lithological Characters of Coal Bearing Formation on Stability of Roof of Coal Seams

Lithology is one of the important factors influencing the stability of roof of coal seams. In order to investigate this, the phenomenon of underground pressure and distribution of pressure were studied by using the local observation and simulation test with similar materials. The observation results show that the distance of initial weighting and periodic weighting of the mudstone roof is shorter than that of sandstone roofs. The sandstone roof with a high strength has a longer distance of initial weighting and periodic weighting, the abutment stress on the working face is big and the height of caving and fracture zone is high. The peak point of abutment stress in the sandstone roof is near to the working face and the pressure bump is inclined to occur. The result is contrary to that in case of the mudstone roof with a low strength. While in the transition zone of nipped sandstone, roof rock-mass is broken and is poor in stability, therefore, it is difficult to hold the roof.

Test studies of gas flow in rock and coal surrounding a mined coal seam

An analysis of the variation rule of abutment pressure at the mining working face in a single coal seam and the mechanical behavior of surrounding rock during stoping is presented. Consideration of the elastic and plastic deformation zones that develop during the mining process allowed the determination of a relationship between horizontal stress and vertical stress. Based on this, a confined pressure unloading test was conducted by the use of the ＂gas-containing coal tbermo-fluid-solid coupling 3-axis servo seep- age＂ experimental apparatus. Thus, gas flow patterns in the elastic and plastic zones were derived from an experimental point of view. Darcy＇s law and the Klinkenberg effect were used to derive a gas flow equation for the elastic and plastic stress fields. The study of gas flow phenomena at the working face during coal mining is of great importance for the study of gas migration and enrichment patterns.

小间距大断面巷道群围岩控制技术研究

为有效控制潘家窑矿小间距大断面巷道围岩变形,基于普氏理论、强帮强角理论、锚杆悬吊理论,以巷道极限平衡拱、附加平衡拱下部围岩压力为主要控制对象,通过巷道帮部、角部支护以抑制极限平衡拱的形成,从而降低巷道顶部、帮部围岩压力。根据潘家窑矿巷道围岩地质力学参数试验结果,分析巷道围岩普氏拱形成过程,确定普氏拱曲线方程,研究开拓巷道顶部、帮部受力状态,计算巷道支护参数。研究结果表明:潘家窑矿开拓巷道附加平衡拱跨度为47.34 m、高度为14.241 m;附加平衡拱附加压力最大值为99.886 kPa;巷道顶部、帮部压力最大值位于主要运输巷,分别为198.608 kPa、74.8343 kPa。因此,提出了巷道顶板、帮部采用锚杆支护,同时巷道角部及帮部采用锚索加强支护的巷道支护方案。现场监测数据证明,支护后巷道整体变形量普遍较小,锚杆(索)受力稳定,围岩结构保持了较好的完整性。