CONTROL TECHNOLOGY FOR SOFT ROCK ROADWAY IN INCLINED COAL SEAM: A CASE STUDY IN NUI BEO MINE, QUANG NINH, VIETNAM

The large deformation of soft rock roadway is still a main concern for a large amount of coal mines, particularly in terms of these located at inclined seam with large section. This paper presented a successful case study conducted at Nui Beo coal mine in Vietnam. Borehole peep detector was firstly put in to application to investigate the distribution of fractures to clarify the influenced range of surrounding rock. Then, the finite element analysis software (i.e. RS2) program is adopted to establish the numerical model aiming at exploring critical parameters for bolt support. Finally, a combined support technology including primary support by using high prestressed bolt and reinforced technology by cable have been proposed and put in to application. The results revealed that 1) the rheological strain is closely related to time, it is about 105 days from the firstly caving to be stable, 2) the maximum displacement of the ribs and roof-to-floor are 28mm and 47mmrespectively. The deformation of surrounding rock obtained from case study was used to evaluate the effective of proposed support technology. The use of high prestressed bolt can maintain the stability of surrounding rock inincline coal seam. Moreover, the experience can be used as reference for other mines in Vietnam.