Papers by Nilabjendu Ghosh
The presence of an overburden dump of considerable height on the surface adversely affects the st... more The presence of an overburden dump of considerable height on the surface adversely affects the stability of the barrier pillars of an underlying longwall working. The barrier pillars must remain stable during the extraction of both the adjacent panels; their premature crushing may lead to transfer of the side abutment stresses on to the face supports causing their structural damage ultimately leading to strata control problems at the face. In this paper, the effect of a 120 m high overburden dump on the stability of underlying workings and the barrier pillars has been discussed.
Mining, Metallurgy & Exploration, 2020
High-production methods like longwall mining with hydraulic powered supports are necessary to inc... more High-production methods like longwall mining with hydraulic powered supports are necessary to increase underground coal production in India. Longwall mining had a mixed success record for Indian geo-mining conditions. In this paper, an analysis is presented to optimally design an array of chain pillars in multi-seam longwall mining panels in the deepest coal mine in India. The study found that a chain pillar of 80-m width and 195-m length is necessary for long-term stability without any reinforcement. It was also observed that an optimum chain pillar can be designed by providing suitable side reinforcement (side bolting) which will reduce the chain pillar dimensions to 55-m width and 160-m length. Optimum design of chain pillars will reduce the coal locked up in these chain pillars by~77%. This will also reduce the gestation period of longwall mining panel development. This paper also evaluates the maximum tensile subsidence strain induced at the surface and finds that the values are within the safe working limit of 3 mm/m. Thus, this paper finds direct application in the design of future multi-seam retreating longwall mining panels in Indian geo-mining conditions.
Proceedings of the conference on Recent Advances in Rock Engineering (RARE 2016)
From the observations of caving of the overlying roof rock in longwall panels it can be inferred ... more From the observations of caving of the overlying roof rock in longwall panels it can be inferred that the caving is dominated by the weak parting layers, laminated nature and massiveness of the roof rock formation. This caving process is controlled by the presence and geo-technical properties of strong beds and weak parting beds in the roof rock layers. Based on the study conducted at different coalfields over longwall panels a 'Parting Plane Approach' has been developed for identifying the parting planes in the roof along with strong and weak rock beds. The strata caving behaviour over longwall workings is manifested by local and main falls. They are governed by the thickness, rock mass strength and the induced stresses in the Caving Layer 1 or the Immediate Roof and the Caving Layer 2 or the Main Roof respectively. A software has been developed in MATLAB platform to identify the rock beds as belonging to the Caving Layer 1 and the Caving Layer 2 or the Immediate Roof and the Main Roof. A parameter, Equivalent Main Fall Span (aeq), has been introduced for classifying the overlying roof rock. In this paper the various methods for determination of aeq, viz. an Empirical method, a Mathematical approach, and a Numerical modelling based approach have been discussed along with case studies.
Uploads
Papers by Nilabjendu Ghosh