外文原文-动压作用下软岩巷道围岩控制综述

中国矿业大学2005届本科生毕业设计 第126页 Why Longwall in India has not Succeeded as in other Developing Country Like ChinaProf A K GhoseAbstract Of the global hard coal production of some 3300 million tonnes during 2000-2001, China headed the league table with a production of 970 million tonnes, and with a production level of 320 million tonnes India ranked third. Both of these developing nations have large resource endowment in bituminous coal, the proved recoverable reserves at end 1999 stood at 114500 million tonnes in China and at 84396 million tonnes in India according to Survey of Energy Resources 2001 of the World Energy Council1. Coal occupies the centre-stage in the energy economy of both the nations, coal has a share of 75% of the consumption of primary energy in China while in India the share of coal is around 64% in the current mix of commercial energy2. However, any comparison between the technology levels of the two giant nations in coal production would perhaps be invidious, dictated as these are by a whole host of imponderables including the site-specific conditions of the resource endowment, differing thrusts of national policy and the socio-cultural and political milieu. Underground coal mining has a predominant share of some 94% of Chinese coal production, while in India the share is only 21%. To examine and analyze the palpable reasons for not so successful application of Longwall technology in India vis-a-vis China, one needs to examine the chronological evolution of the technology in the two nations, appraise the technogenesis of Longwall technology in both the countries and then home in on the contributory factors. This paper attempts a foray in unravelling the reasons fully cognizant of the fact that any post hoc analysis, as of date, can only outline a hypothesis of the multitude of reasons behind the apparent failure of Longwall technology in India due to subjective interpretation and perception of the issues involved. It is also not always possible to reflect by hindsight on the compulsions of the planner/decision-maker in choosing a specific strategy at any given point of time. Be that as it may, we examine here on a broad canvass the remarkable saga of growth in Longwall technology in China and the apparent under-performance of Longwall in India.Keywords Longwall, Geotechnology, Moonidih colliery, Coal seamsLONGWALL TECHNOLOGY GENESIS AND EVOLUTIONFigure 1 Longwall tons (st) per 8-h machine shift (annual average for a single mine) since 1984The seventeenth century innovation of Longwall system in Shropshire in England has made giant strides over the past three centuries to emerge as the predominant bulk production system in global coal industry today with a share of nearly 70% of the aggregate production and is recognized as the safest, the most productive and cost effective method as well for extraction of coal seams by underground mining3. Longwall mining made its debut in Indian coal mining scene reportedly around 1870s; despite such head start however the progression of the technique in Indian coal industry milieu has been extremely slow and halting. From the early application to stowing faces, caved Longwalling was attempted only around early 1960s and the first mechanized powered support face, the new-age Longwall, was launched in August 1978 at Moonidih Colliery. While this marked the beginning of a major initiative in transfer of innovative Longwall technology in the relatively low technology milieu of Indian coal industry, the overall performance has fallen short of expectations and despite experiences in deploying some 33 mechanized powered support packages to date in Coal India and Singareni Collieries Company, Longwall technology in India remains a laggard, straggling miles behind the global best practices. One could cite the case of Console Energy which operated 14 Longwall mining systems of the 59 operating Longwalls in the United States in 2000, where the best Longwalls annual production average is close to 8100 clean tonnes per 8-h machine shift. Figure 1 shows the evolution of Longwall tons (short tons) per 8-h machine shift (annual average for single console mine) since 19845. There are examples galore of such high performance faces in the United States, Australia and even in China. In benchmarking the performance of Indian Longwall faces with those of China, it is necessary to examine the evolution of coal mining technology in India and China to provide a backdrop. India gained Independence in 1947 and commenced on the national economic planning journey in 1951. China as a nation-state came into existence in 1949 when its coal output was 32.43 million tonnes, very close to Indias coal output.While both the nations started almost at the same base level, Chinas coal odyssey has been marked by a quantum jump in production level which touched an all-time high of 1.3 billion tonnes in 1997 encompassing the three elements of the coal industry, the state-controlled mines, local mines and collective ownership and small mines. Since then, a massive restructuring of Chinese coal industry with closure of over 40 000 small coal mines has curtailed the production level to just around 970 million tonnes in 2000-2001. It is also important to highlight a major difference between Indian and Chinese Longwall experiences. Longwall mining, using the first generation mechanization systems comprising friction/hydraulic props, AFC, and shearer, kicked off almost contemporaneously around 1962-63 both in China and India. Since then, Chinas leap forward in Longwall has been phenomenal and while India has been toying with a handful of powered support Longwall faces with a production of 4.52 million tonnes from 14 faces during 2000-2001, in state-controlled mines in China in 1997 there were 238 fully mechanized faces with an average annual output of 784,000 tonnes. During 1997, more than 76 fully mechanized Longwall systems produced over 1 million tonnes, of which 12 faces produced over 2 million tonnes annually. During 1999, one team in Dongtan mine of Yangzhou Coal Mining Group, Shandong Province produced 5.12 million tonnes with an OMS of 246.96 tonnes6. Benchmarking Indian Longwall faces with those of China in effect is a comparison between unequals! Between 1978 and 1985, about 200 sets of Longwall face equipment were imported in China; such acquisition of technology not only had a direct impact on increased production, but also led to direct replication of imported equipment and the domestic manufacturing capacity was significantly upgraded7. In 1980, some 75% of fully mechanized Longwall equipment were imported in China; by 1995, with absorption of new techno-logy and sheer copying of imported equipment, the share of imported equipment fell to 13.8%6. Through sustained R&D efforts over the past three decades, China has made a major breakthrough in Longwall technology for thick seams using sub-level caving (soutirage) and has emerged as the world leader in this area with record production levels and manufacture of equipment packages for sub-level caving. In 1996, there were 86 fully mechanized sub-level working faces with an aggregate output of 67 million tonnes.Even if China lags behind the performance of the super heavyduty Longwalls in the United States or Australia, the policy thrust of the coal sector in China, the massive investment in imported and indigenous faces, the focus on walking on two legs, fast decision-making and above all the work culture in a mandarindominated society made it possible for China to launch the Longwall odyssey purposefully and achieve a quantum jump in production levels in Longwall, backed by a highly developed manufacturing base for mining equipment8. The critical success factors that were obtainable in China were simply missing in the Indian coal industry context. It is in this backdrop that one needs to appraise the less than adequate performance, an euphemism for poor performance, of Longwall technology in India.APPRAISING THE SCORECARD FOR LONGWALL TECHNOLOGY IN INDIAThe under-performance of Longwall technology, especially of the high-investment powered support Longwall face, which made its debut in August 1978 at Moonidih Colliery, has led to much soul- searching, introspection and articulation of concern over the past 25 years in India. The collapse of heavy-duty Longwall installations at Churcha West (1989) and Kottadih (1997) has merited the attention of the Government and a number of Committees have been appointed over the years to examine the entire gamut of problems of Longwall technology and to suggest remedial measures for bringing about performance improvement. These include the H B Ghosh Committee (1983-84), the Strategic Action Group under the Chairmanship of Shri K A Sinha (1988-89), the S K Chowdhury Committee (1990) to enquire into the circumstances leading to the collapse of Churcha West Face and finally the Mahendru Committee (1998) which, besides enquiring into the collapse of Kottadih face was also charged with the responsibility of studying the performance of all past and operating Longwall faces in the country to assess and recommend the applicability of Longwall technology under Indian geo-mining conditions.By and large, the contributory factors that have been identified for the not so successful operation of Longwall systems converge on the following: n Inadequacy of geological and geotechnical assessment of Longwall locales n Flawed equipment selection with inadequate rating of supports, shearers and coal clearance systems n Management failure in planning, operation, provision of service back-up and spares availability n Failure in inculcating a culture for mechanized Longwall and creating a cadre of Longwall personnel who could serve as change agents in implementing the technology n Issues of power supply, materials supply, ventilation, dust control and availability of clean water for hydraulic emulsions n Absence of a viable manufacturing capacity for Longwall equipment.All these factors culminated in either poor performance or led to collapse of faces which eroded the confidence of the industry on Longwall technology. In a number of papers, the author has undertaken critical studies on Longwall under-performance in Indian coal industry, analysed the problem dimension and pinpointed the major factors which have beleaguered Longwall technology in India8 - 11. The factors which conjointly have blighted Longwall technology can now be examined in depth under three main headings:a) Geological and geotechnical site factorsb) Flawed planningc) Management lacuna.Geological and Geotechnical Site factorsAnalysis of Longwall performance in 28 Longwall faces underscores the fact that investment in pre-mining geological and geotechnical investigations could have averted some of the face collapses or even reduced the risk of operations besides contributing to more careful selection of appropriate face equipment. Accurate and reliable delineation of the geology of a panel is sine qua non for establishing face and panel length avoiding any geological surprises. There are examples galore of disruptions to Longwall operations in practically every Longwall face. A few aberrant experiences include:n Faces at Moonidih encountered a series of step faults at the face and stringers of small dykes, the existence of which were not known at the time of face development.n The face at Seetalpur encountered an igneous intrusion at mid-height of the coal seam and also a massive inrush of water from an overlying seam.n Kottadih panel collapsed because of inadequate support capacity where the support design had been based on data from a single borehole which failed to detect the massiveness of the overlying strata.n At GDK-11A Incline in SCCL serious failure of Longwall units took place because of inadequate support capacity.Flawed PlanningLongwall technology has not been able to take its roots in Indian coal industry soil or establish itself as a preferred system primarily because of flawed planning in the first generation powered support Longwall faces.Instead of providing a conducive seed bed to germinate, to be absorbed and transferred, and then diffused, a large majority of Longwall faces was commissioned at sites where conditions were singularly adverse right from inception. In Seetalpur Longwall face, quite apart from the adverse mining conditions at the face, such as gassiness, and intrusion in the coal seam, the face performance was baulked by the outbye coal clearance capacity with multiple conveyors which constituted weak links in the evacuation system. The Gleithobel plough installed at Moonidih colliery in 1988 could work only two panels due to non-availability of suitable working areas. The coal seam hardness, structure and other workability indices were difficult for ploughing. Many of the sites selected for Longwall application were replete with adverse geological conditions, constrained by panel size and coal clearance system.In general, the parameters of Longwall technology were driven by equipment manufacturers under tied aids and no serious efforts were made by Indian planners to vet the plans, including the equipment specifications, keeping in view the then state-of-theart of Longwall technology. In the process, the coal industry was saddled with technology packages which were backdated (archaic?) in some cases, and often a complete mismatch with the site factors. There was no conscious effort either in choosing the best equipment or proven advanced mining technology. The mix of Longwall equipment, from British, German, Russian and Chinese suppliers compounded the problems.Management DeficienciesIndian coal industry failed in effective management of Longwall technology which could have opened a new window of opportunity for underground production and productivity and improving the bottom line. Bereft of a management vision to re-engineer the industry for a new Longwall culture and technological transformation, the Industry has been hesitant and cringed resorting to the syndrome of it does not work here instead of aggressively addressing the technological concerns of Longwall technology and adopting best practices. In fact coal industry failed to look out of the box. The research and academic institutions also failed in providing the necessary technical support to ensure successful transfer of high-tech Longwall technology. If management is the art of getting things done, the coal industry failed in providing the right seed bed for sowing, germinating and transferring Longwall techno-logy vis-a-vis the exemplar of Chinese coal ind