煤与瓦斯共采是采矿工程和安全科学与工程的综合性学科，目前和今后相当长的时期主要服务于煤炭安全开采、瓦斯(煤层气)资源的开发与利用和环境保护。煤与瓦斯共采以矿山岩石力学和渗流力学为基础，与矿业工程、安全工程、抽采工艺理论和实践相结合，是具有一定特色的基础理论学科与工程技术学科互相交叉的*立分支学科。《COAL AND GAS CO-EXTRACTION（煤与瓦斯共采）》共分九章，主要内容包括煤与瓦斯共采基础理论、煤与瓦斯共采设计原则、巷道法煤与瓦斯共采、无煤柱煤与瓦斯共采、地面钻井法煤与瓦斯共采、瓦斯抽采系统、煤矿瓦斯利用、煤与瓦斯共采成本和效益分析等。

Contents
Preface
Chapter 1 Introduction 1
1.1 Basic Concepts of Coal and Gas Co？extraction 1
1.2 Coal and Gas Co？extraction Models in China 4
1.3 History of Coal and Gas Co？extraction Technology 15
1.4 Research Methods of Coal and Gas Co？extraction 21
1.5 Research and Development Directions of Coal and Gas Co？extraction 22
References 24
Chapter 2 Basic Theory of Coal and Gas Co？extraction 27
2.1 Coal and Rock Mass Structure and Mechanical Characteristics 27
2.2 Strata Movement and Stress Distribution Characteristics 45
2.3 Coal Seam Gas Occurrence and Flow Theory 59
2.4 Theory of Mining "O" Ring in Coal and Rock 76
2.5 Theory of High？level Annulus in Coal and Gas Co？extraction 90
References 132
Chapter 3 Design Principles of Coal and Gas Co？extraction 135
3.1 Design Principles of Coal Mine 135
3.2 Design Principles of Mining Area 149
3.3 Design Principles of Working Face 158
References 169
Chapter 4 Coal and Gas Co？extraction by Roadway Method 171
4.1 Model of Coal and Gas Co？extraction by Roadway 171
4.2 Gas Extraction in First？mined Coal Seam 175
4.3 Gas Extraction in Stress？relief Coal Seam 199
4.4 Construction and Maintenance of Special Roadway for Gas Extraction 220
References 232
Chapter 5 Coal and Gas Co？extraction Without Coal Pillars 234
5.1 Principle of Surrounding Rock Control in Retaining Roadway along Goaf 235
iv COAL AND GAS CO？EXTRACTION
5.2 Surrounding Rock Control Technology for Retaining Roadway along Goaf 247
5.3 Method of Gas Extraction Without Coal Pillars 259
5.4 Safety Guarantee System for Mining Without Coal Pillars 267
References 276
Chapter 6 Coal and Gas Co？extraction by Ground Drilling 278
6.1 Pre？extraction of Coalbed Methane Technology Using Ground Drilling 279
6.2 Stress？Relief Gas Drainage Technology Using Ground Drilling 301
6.3 "Three？zone Linkage" Three？dimensional Gas Extraction Technology 319
References 325
Chapter 7 Gas Extraction System 327
7.1 Establishment of Mine Gas Extraction System 327
7.2 Equipment Selection of Gas Extraction System 332
7.3 Gas Extraction Drilling and Construction 348
7.4 Monitoring and Control of Gas Extraction System 373
7.5 Gas Extraction Standards 383
7.6 Gas Extraction Management 389
References 400
Chapter 8 Utilization of Coal Mine Gas 402
8.1 Classification of Coal Mine Gas Sources 402
8.2 Gas Safety Transportation and Pretreatment Technology 404
8.3 Low Concentration Gas Enrichment and Comprehensive Utilization 421
8.4 Resource Utilization of High Concentration Gas 434
8.5 Gas power generation Waste Heat Refrigeration Technology 445
References 452
Chapter 9 Analysis of Costs and Benefits of Coal and Gas Co？extraction 454
9.1 Costs Analysis of Coal and Gas Co？extraction 454
9.2 Benefits Analysis of Gas Drainage Utilization 465
References 472

Chapter 1 Introduction
　　1.1 Basic Concepts of Coal and Gas Co？extraction
　　1.1.1 The concept of coal and gas co？extraction
　　Coal is the main energy source of China. In China’s non？renewable energy consumption， coal accounts for approximately 66%， which is expected to be about 50% by 2050[1]. Coal seam gas refers to a hydrocarbon gas stored in coal seams， with methane as its main component. It mainly exists adsorbed on the surface of coal matrix particles， while part of it is in a free state in coal pores or dissolved in coal seam water. It is an associated mineral resource of coal， classified as unconventional natural gas， and is also known as coalbed methane. Coal and gas simultaneous extraction refers to a method that exploits both coal and gas as resources. By adopting the forms of coal mine gas drainage or coalbed methane extraction， it maximizes the amount of gas drained， thereby achieving the goal of developing and utilizing both coal and gas (coalbed methane) as resources in phased or simultaneous stages[2].
　　According to the sequence of coal mining and gas extraction， coal and gas co？extraction could be divided into the following three categories[3，4].
　　(1) Gas extraction before coal mining. In the original coal， coal seam gas exists in the porous media of coal seam and its surrounding rocks. The adsorbed gas amount usually accounts for 80%？90%， and the free gas amount accounts for 10%？20%. According to Articles 2 and 7 of "Interim Provisions on the Standardization of Gas Extraction in Coal Mines"， coal seams with high gas content and high proneness to coal and gas outburst must be effectively drained before mining.
　　Gas extraction before coal mining is generally used in mining areas of coal seams with high permeability and shallow burial depth. The main methods of gas extraction in the case include pre？drainage with surface vertical wells and surface directional long borehole， pre？drainage with underground to in？seam (UIS) boreholes and pre？drainage with roof and floor cross？measure boreholes.
　　(2) Coal and gas co？extraction. Coal mining will break the balance of the original stress field， causing strata movement and stress redistribution of surrounding rocks，forming stress relief zones and stress concentration zones， and leading to the generation， closure and expansion of cracks in the surrounding rocks. In the stress concentration zones， new cracks are generated. Meanwhile， the cracks may be closed and gas permeability is reduced， transforming part of the gas from a free state to an adsorption state. In the stress？relief zones， the cracks open and expand， and coal permeability is enhanced; gas is desorbed and moved in the mining？induced fractures， forming gas？rich zones. Coal and gas co？extraction is to make full use of the stress relief， the evolution of stress field and fissure field on gas， as well as the law of gas storage and transportation during coal mining， to establish two complete production systems of coal mining and gas extraction.
　　Coal and gas co？extraction is generally used in multi？seam environment with high gas content， low permeability and high coal and gas outburst potential. Gas extraction methods in this case mainly include roadway extraction， pillar？free drilling and ground drilling. The principles of these coal and gas co？extraction technologies are shown in Figure 1？1？1[5，6].
　　Figure 1？1？1 The principles of these coal and gas co？extraction technologies
　　(3) Gas extraction after coal mining. For coal seams with no coal and gas outburst proneness and high gas content in the adjacent strata， the method of coal mining before gas extraction is often adopted. After coal mining is completed， the goaf is drained. Extraction methods mainly include roadway (drilling) extraction， sealed wall pipe extraction and ground drilling extraction.
　　1.1.2 The idea of coal and gas co？extraction
　　Coal and gas resources are characterized by co？existence. Extracting them separately will inevitably affect each other. When coal and gas in multiple seams of low permeability and high gas content are mined， it will be difficult to directly extract gas due to the low permeability， and it is difficult to eliminate the risk of coal and gas outburst in coal mining. If coal is mined directly and the gas content in the coal seam is not reduced prior to coal mining， the coal and gas outburst or gas explosion may occur[7？9].
　　Separate operations of coal mining and gas extraction could either positively or negatively affect each other. Coal and gas co？extraction integrates independent coal mining with gas extraction. Coal mining causes the movement and stress redistribution of the coal seam， promotes gas desorption and flow， and creates favorable conditions for gas extraction. At the same time， the mining system and ventilation system provide space for gas extraction. In turn， the efficient gas extraction reduces the gas concentration in the working space and g