Designing observation lines: a case study of the G9 seam in the Mong Duong colliery

Observation lines set up on the ground play an important role in the determination of rock deformation caused by underground mining, issuing timely warning notices and alleviating any impacts on surface engineering constructions. The main purpose of this study is to design three monitoring lines above the working (tunnel) with exact location of observation and control points on the topographical map as well as the profiles along the strike and dip directions. The initial determination of surface areas where the influence of coal extraction occurred based on geological parameters, extraction planning, topological maps, and limit angles of study areas is necessary before designing observation lines in order to accurately determine the deformation area. While common design methods have a problem of inaccurate control points, the method proposed in this study suggested adding a value to the angle of draw to solve the problem. The proposed method is applied to the seam G9 in the Mong Duong colliery to obtain the optimal design of monitoring lines. After taking several real conditions into account, the result design with the maximum and minimum distances between monitoring points of 28.5 m and 17.25 m, respectively, satisfied the standard requirement in Vietnam National Specifications on Mine Surveying