Principles of the roof cut short-arm beam mining method (110 method) and its mining-induced stress distribution

Abstract

Since the 1960s, mining science and technology in China has experienced two technical innovations, i.e. the “Masonry Beam Theory (MBT)” and “Transfer Rock Beam Theory (TRBT)”. Based on those theories, the conventional mining method (being called the 121 mining method) was established, consisting of excavating two tunnels with a pillar left for mining a working panel. However, with increasing mining depth, engineering geological disasters in the underground caverns have been frequently encountered. In addition, the use of the coal-pillar mining results in a large amount of coal resources unexploited. In order to address the problems above, the “Roof Cut Short-Arm Beam Theory (RCSBT), being called the 110 mining method)” was proposed by He Manchao in 2008. The 110 mining method features the mining of one coal seam panel, excavating necessarily only one roadway tunnel and leaving no pillars. Realization of the 110 mining method includes the following steps: (1) directional pre-splitting roof cutting, (2) supporting the roof by using high Constant Resistance Large Deformation bolt/cable (CRLD), and (3) blocking gangue by hydraulic props. This paper presents an overview of the principles, techniques and application of the 110 mining method. Special emphasis is placed on the numerical simulation of the geostress distribution found in the mining panel using the 110 method compared to that of the 121 method. In addition, the stress distribution on the “short beam” left by the roof cutting when performing the 110 method was also investigated using both numerical simulation and theoretical formulation.