جستجوی مقالات مرتبط با کلیدواژه "support system" در نشریات گروه "مهندسی معدن"

The instability of the roof and walls of the tunnels excavated in coal mines has always attracted the attention of the miners and experts in this field. In this work, the instability of the main tunnels of the mechanized Parvadeh coal mine in Tabas, Iran, at the intersection with coal seam is studied. The main tunnels of this mine show significant horizontal displacements due to the complex ground conditions and great depth. The behavior of the rock mass surrounding the tunnel is investigated using various experimental methods, and according to the results obtained, the surrounding rock mass has squeezing conditions. In order to analyze the stability of the main tunnels, a series of 2D and 3D numerical modelings are performed using the FLAC2&3D finite difference software, and the results obtained are compared with the actual displacement values recorded in the walls of the main tunnels of the mine. The analysis results show that the tunnels under study are unstable with a steel frame support, and therefore, the use of different support systems for the stabilization is investigated. The results of modeling different types of support systems show that the use of shotcrete instead of galvanized sheet (as strut) does not have a significant effect on the reduced displacements. Also although the installation of steel sets is very effective in preventing the displacement of the walls, due to the swelling problems in the tunnel bottom and the placement of the conveyor and haulage rail, it cannot be used in practice. Finally, the use of truss bolt has yielded good results, and it can be proposed as a new support system in these tunnels. In addition, the modeling results show that in case the coal seam is higher than the tunnel foot, less displacement will occur in the tunnel walls compared to the other cases. In other words, changing the tunnel level in the future excavations can help reduce the displacements.

The main rock mass classification systems make use of similar rock mass parameters. Due to lack of comprehensive estimation systems, determining the real specifications of jointed rocks faces some difficulties. A vast number of parameters with various degrees of impact are involved in such definitions. Combination impact of all the effective parameters is to be figured out in order to come up with an acceptable value. Different classification systems have some well-known drawbacks and limitations mainly due to their empirical base. However, they are still very useful in practice. Therefore, there is a need to improve their efficiency. Two of these classification systems are the RMi and the Q-system. Bakhtiari dam site is located in the southwest of Iran. The project area consists of the sedimentary bedrocks of Sarvak and Garau formations. The Sarvak Formation is divided into 7 units from Sv1 (oldest) to Sv7 (youngest). Deviation system of Bakhtiari dam includes two tunnels, namely upper and lower tunnels. In this paper, the result of geological scanning of rock masses in seven geological zones hosting binary tunnels of Bakhtiari dam have been utilized. This information along with data produced from many different laboratory tests have been used to estimate the values of Q and RMi for each of the geological zones. The pros and cons of both systems are revealed and relationships are driven between the two systems through statistical analysis. The paper also shows that there are good correlations between the two systems. Finally, the support details suggested by each system are determined.