**1.1 Role of coal in India**

Through a sustained program of investment and greater thrust on the application of modern technologies, it has been possible to raise the all-India production of coal to 716.08 million tonnes in 2020−21 (provisional). The all-India production of coal during 2021−22 was 778.19 MT (provisional), with a positive growth of 8.67%.

Coal India Limited (CIL) and its subsidiaries accounted for 596.221 million tonnes during 2020−21 as compared to the production of 602.129 million tonnes in 2019−20, showing a negative growth of 0.98%. Coal production of CIL, during 2021−22, was 622.634 MT (provisional), with a positive growth of 4.43%.

**Figure 1.** *Sector-wise GDP in India.*

*Underground Coal Mining Methods and Their Impact on Safety DOI: http://dx.doi.org/10.5772/intechopen.109083*

Singareni Collieries Company Limited (SCCL) is the main source of the supply of coal to the southern region of India. The company produced 50.580 million tonnes of coal during 2020−21 as against 64.044 million tonnes during the corresponding period last year. SCCL production of coal during 2021−22 was 65.022 MT(Provisional), with a positive growth of 28.55%. Small quantities of coal are also produced by TISCO, IISCO, DVC, and others [4]. In India, the total geological reserves of coal are around 3,44,021 MT, as per reports of the Geological Survey of India (GSI) as of 01.04.2020. The coal reserves of coking and non-coking coal are around 35,004 MT and 3,09,017 MT, respectively. From 1950 to 2020−21, the total coal extracted was around 1,72,96,897 TT [5, 6].

In India, open cast and underground mining are the two major coal mining methods. Opencast mining contributes about 95.74% of the total production. In contrast, underground mining contributes to the rest of the production by 4.26% during 2021−22 (provisional). The major contributors of coal in India are CIL, SCCL, SAIL, etc., in the public sector, and Reliance Power Limited, TISCO, etc., in the private sector. The overall coal production vs. open cast coal production vs. underground coal production is plotted in **Figure 2**.

#### **1.2 Need to increase underground coal production**

In India, coal mining is primarily carried out by opencast mining and underground mining. According to the Indian Bureau of Mines, there were 455 operating coal mines in India, out of which 219 were opencast, and 213 were underground. The remaining 23 were mixed collieries [7]. Even though the number of underground coal mines is proportionately equal to opencast coal mines, their production rates are nowhere on a comparable scale. The share of opencast and underground coal

#### **Figure 2.** *Opencast and underground coal production from 1996 to 2021−22.*

production in overall coal production is nearly 95.64% and 4.36%, respectively [8]. However, the thrust on increasing underground coal production is being felt by the coal companies because of many critical issues, such as difficulty in land acquisition for opencast mining under the current sociopolitical environment, the severe threat of irreparable environmental damage due to opencast mining vis-à-vis the growing concern for mitigating the environmental impact due to opencast mining and its associated cost, depletion of shallower deposits amenable to opencast mining, and at the same time, increasing demand for quality of coal production to maintain economic sustainability of the country [9–12]. In order to increase coal production to meet the country's coal demand, there is no other future option but to go for the exploitation of deeper deposits by underground mining methods.

### **1.3 Conventional mining**

The majority of Indian underground coal mines are still working with conventional mining. This process involves drilling and blasting technology for the extraction of coal and LHD/SDL for conveyance/transport of blasted coal, followed by the installation of supports, which slows the rate of extraction and also becomes a source for adverse strata conditions in case of delay in the extraction of exposed pillar during the depillaring [13, 14]. A rib-and-slice method is commonly practiced in conventional depillaring [15, 16]. A rib/snook is left against the goaf along with breaker-line support in openings at the goaf edge [12, 17]. Left-out rib/snook is judiciously reduced at the time of retreat to facilitate the caving of the roof strata. This depillaring technique used to dominate in the past due to different techno-economic reasons, but the industry found it incapable of further incrementing coal production. The chronic problem of significantly less productivity leads to a considerable loss per ton of coal production and the lack of capability of the mass output by such technologies. Conventional mining methods and adopted low-level technologies result in a low production rate from underground coal mining [18].

It is high time to go for mass production from underground coal mining by adopting suitable technologies, such as longwall mining, shortwall/short longwall mining for developed coal pillars, room and pillar mining, and wongawilli or rib pillar extraction by continuous miner. Earlier attempts to develop mechanized underground mines were not very successful due to improper planning, lack of advanced geotechnical studies and R&D facilities, issues related to maintenance of the mechanized machinery implemented, technical lapses, high cost due to absence of indigenous equipment supplier, lack of understanding the nature of overlying strata concerning the depillaring method adopted and machinery implemented.
