Longwall mining has somewhat a successful operating history in India, both under Coal India Limited and that of the Singareni Collieries Company Ltd. Planning for high capacity longwalls gave birth the dream concept of Adriyala longwall project in Ramatundam coal belt in Godavari coalfields into a reality which is the first major mechanised longwall mining in India. Commissioned in 2014, Adriyala longwall project is the examplar of appropriate technology for achieving bulk production.
With four workable seams in the mine with minimum geological disturbances having a total extractrable reserves of 78.597 Mt which attained high significance. The unique feature of the Adriyala is that it is accessible with four ‘punch entries’ and one return air shaft of 7.5m dia with 484m depth from surface. The success story of the project is best described in the technical presenations in this special issue. The Journal of Mines, Metals & Fuels is privileged to publish this special issue, papers for which are authoritatively written on the occasion of the International Mining Machinery Exhbition and Conference (IMME 2018) at Kolkata, and seeks to provide some salient features of the project. Hopefully, the issue will not only chart the direction in planning for future underground vis-à-vis longwall workings in India but also provide some essential inputs for planning and design of safe longwall panel layouts, assessing support requirements, etc.
Underground mining needs to have strategic focus in the context with challenges of growing demand, constraints of availability of lands, environmental issues and increasing deeper deposits for bulk production. Hats off to the project authority for adapting all these aspects appropriately, Adriyala longwall project is truly a feather in the cap of the Singareni Collieries Company Ltd.Read more
India’s proclivity with mechanized longwall started in Moonidih Colliery in 1978. Subsequently 33 longwall faces were introduced with overseas collaboration. The longwall production peaked up to 2.3 Mt in the year 1996-97. But later it went a steep decline and by 2008 with only three or four longwalls were in operation. Then after the longwall technology went through a hibernating phase with only two operating longwalls were in 2013. The reasons for this down trend are the selection of under rated powered roof supports, strata management issues, spares management issues, lack of indigenous manufacturing facilities and less than adequate trained man power etc. [1,2]. The need to curb this undesirable trend was recognized by Singareni Collieries Company Limited (SCCL), India making attempt to introduce a high capacity longwall, gave Adriyala longwall project. The impetus for the construction of highend longwall was to increase the share of underground coal production and to explore the deeper deposits with high productivity.
This paper explores the construction, ongoing operations and the challenges faced at India’s highest capacity longwall project. A brief review on various aspects in constructing the project right from the exploration stage to outbye belt laying and panel preparation is given followed by the operations in I and II longwall panels.Read more
The Adriyala longwall project is conceived by Singareni Collieries Company Ltd., (SCCL) in the early years of this millennium. This large underground project is a flag ship project not only for SCCL but also for Indian coal mining ndustry as a whole.
Coal is the prime source of energy in India and will remain for decades to come. The growing energy demand can be met only with increasing coal production. India currently produces about 7.8% of the global production with about 9.4% of global coal reserves. This is anticipated to grow rapidly as the country has shortage of other sources of energy. SCCL has produced about 62Mt in the year 2017- 18 amounting to about 9% of the Indian coal production. The underground coal production in SCCL is about 13.4% of the total production and in CIL it is about 5.3% for the year 2017-18. Most of the coal exploited so far is up to the depth of 300m only. With depletion of reserves at the shallow depth, the future coal production has to be met from the greater depths only. The longwall technology is the only suitable technology for achieving bulk production from such conditions. Hence the Adriyala project planned for extraction below 350m depth has attained such high significance.
The Adriyala longwall project is a feather in the cap of SCCL and will be a milestone in Indian coal mining industry. This shall drive the coal companies to relook for bulk and profitable underground mining where the conditions are suitable.
For longwall (LW) machinery and connected equipment transport, diesel driven free steered vehicles were used. The floor of the trunk gallery was concreted for 2.0 km to facilitate transport of such heavy equipment with free steered diesel vehicles.
This paper focuses mainly on requirements of diesel vehicles and transport of equipment with diesel vehicles in trunk roadway having 1 in 4.5 gradient and tail gate with undulated floor, uneven sides, water seepage from the floor and other associated problems.Read more
Longwall technology is one of the principal underground coal mining methods widely used around the globe which is not fully emerged in India. However, since the introduction of first self-advancing powered roof supports, there has been mixed experience of longwall technology. History of failure of some longwall panels desponded the success stories of others. Majority of longwall downtimes and/or failure had been attributed due to poor cavability of roof, inadequate capacity of supports, lack of knowledge on longwall caving mechanisms, less than adequate strata monitoring systems, etc.
Strata around coal seams in India are dominated by competent beds, which do not normally cave in immediately after face advance, rather it remains in hanging condition for certain length and break into large discrete blocks. This type of caving mechanics is irregular and complex. Fracturing of competent bed in the immediate roof zone is certain to manifest itself on face as heavy load on supports, bleeding of hydraulic legs of supports, aggressive face spall and guttering in gate roads and in worst conditions longwall face stoppage and sometimes even structural failure of supports as the severity may be.
This paper presents a case study of strata behavioural experiences gained while extracting a deep and wide longwall panel overlain by 3.0 to 3.5m coal roof as immediate roof and 20 to 28m thick competent sandstone bed as main roof with high capacity longwall equipment. While extracting the panel the precise strata monitoring and trigger action response plans are prepared and implemented successfully for negotiating all the strata control hindrances.
Keywords: Longwall, strata control, main roof, weighting
Longer panels and hot surface climates have combined with the traditional sources of mine heat to produce uncomfortable working environments on high production longwall faces. The heat load generated by increasing mining depths and mechanization in UG mines is becoming progressively more and more of a problem. Below a critical depth, which is a function of geothermal gradient, the rock thermal properties and level of mechanization, ventilation will continue to have a diminishing efficiency when combating this heat load. In such a case the solution is to invest in an artificial cooling system. This paper gives insight of the details of the project, heat generating sources, different air cooling systems, psychrometric studies and air cooling arrangement made in Adriyala longwall project, Singareni Collieries Company Limited.Read more
Modern mining methods create a higher risk of spontaneous combustion from fast moving faces and increased ventilation. If spontaneous combustion did occur, the consequences were costly in both lost equipment and lost production. The detection and management of explosive atmospheres in underground coal mines is critical to the safe operation of a mine. Underground coal mines contain potentially explosive gases. But monitoring on its own never prevents a mine fire or puts it out if it starts. What continuous monitoring offers is a means of identifying a problem early and subsequently an opportunity to take appropriate control action. This paper briefs about the tube bundle gas monitoring system and its introduction in Adriyala longwall project of Singareni Collieries Company Limited.Read more
High capacity longwall technology introduced at Adriyala longwall project with a rated capacity of 3.0Mt per annum. Huge machinery required to be installed in longwall face and gate roads. This machinery required wider gate roads of 5.2 to 5.5m widths. The immediate roof in gate roads is coal with thicknenss of 4.0mtr. Immediate roof consists of 2 clay bands of 0.3m and 0.7m thickness within the bolted and above the bolted horizon causing bed separation in the immediate roof, resulted in that, during development of gate roadways, 85% of roadways are good in condition, 15% of gate roads were observed with guttering, geological disturbances, water seepage, and in some areas horizontal stress effect is also noticed. While retreating of longwalls, major disturbances were observed in gallery ahead of the longwall face, and also in cut through galleries and adjacent gate roads subjected to abutment loading. To overcome the above issues, Pre-tensioned bulbed type cable bolting is introduced first time in India as secondary support in gate roads of longwall panel to ensure its stability over long period and also to eliminate standing support in gate roads ahead of the longwall face. In this paper, the installation and performance of bulbed type cable bolt is discussed in detail.Read more