Exploitation of developed coal mine pillars by shortwall mining-a case example

The shortwall mining technique is similar to longwall mining but with shorter face lengths, ranging between 40 and 90 m, with the aim of controlling the caving nature of the overlying upper strata, the load on support and the overall operation of the supports applied at the face. Field observations and three-dimensional numerical modelling studies have been conducted for the longwall panel extraction of the Passang seam at Balrampur Mine of SECL to understand the caving behavior of the overlying upper strata. A large area of the Passang seam adjacent to the longwall panels has already been developed via bord and pillar workings. In this paper, numerical modelling studies have been conducted to assess the cavability of the overlying strata of the Passang seam in the mine over developed bord and pillar workings along with the support requirement at the face and in the advance gallery. The caving nature of the overlying rocks characterized by the main fall is predicted for varying face lengths, strata condition and depths of cover. The support resistance required at the face, the load in the advance gallery and its optimal obliquity were estimated for faster exploitation of the developed pillars in the Balrampur mine by shortwall mining.