| Namphun mine locates in the north of Phongsali Province in Laos and in the south of Lanping-Simao basin. Presently,10ore bodies in the mine have been discovered. The veined or lentoid ore bodies were produced in the tectonic zone. They extend discontinuously downward from the surface to150meters. The surface portions of them have been strongly weathered. Currently, the mine is in the general exploration stage. There are7exploration tunnels and27geological drillings for controlling the ores. As the degree of exploration being in-depth, the mine is preparing for a large-scale mining.Hydrologic and engineering geological evaluation of Namphun mine is the theme of this thesis. By collecting relevant data and geological survey, and combining with prospecting works, drainage and pumping tests, laboratory tests, chemical analysis of water and other means, making use of large-well method, analogue method, RMR rock classification method, fuzzy comprehensive evaluation method and AHP method, a comprehensive system of mining technical conditions has been set up. It can be used for analyzing and evaluating the characteristics of geological environment of Namphun mine.On the hydrogeological evaluation, the aquifer and confining layers, mine water filling factors and water chemistry were analyzed detailedly, and large well method and hydro-geological analogy method were making used for predicting the mine water inflow. On engineering geological evaluation, engineering geological characteristics of the surrounding rock of ore body and structural plane were discussed systematically. The rock mass index (M), RMR rock classification method and fuzzy comprehensive evaluation method were utilized for rock steady performance evaluated.The study results showed that:①The water abundance of main aquifer in Namphun orefield are weak or moderate, so its hydro-geological complex level is the second class of the first type, that is, the water inflow will be mainly supplied by the water-filled fissure. Because deposit limited groundwater reserves, pit water inflow is not great, and does not have a serious impact on the ore mining. Mine water quality is good and clean, so it can be used for mine production and living water sources.②Because the structural planes were affected by the regional structure, most of them trend in NE or NW direction. The most dominant joint surface was also found to extend in NE and NW direction. According to the rock quality index (M), the surrounding rock of ore body is classified:the quality of sandstone is good, siltstone medium, fault fracture zone and mudstone bad. According to the RMR:sandstone is Ⅱ-Ⅲ (good rock), siltstone Ⅲ (generally rock), mudstone Ⅲ-Ⅳ (generally-poor rock), fault zone Ⅳ (poor rock). RMR classification results show that when the mining tunnel are layout in NWW and NE direction, it may will be not conducive to the stability of surrounding rock; be conducive to the stability of surrounding rock in NNW. Generally speaking, as the direction changing, the impact on the level of rock is not great, but it obviously affected by lithology. Especially, in the fault zone with lots of broken mud, intense deformation instability and sudden inrush of water will occur. So sufficient attention will be need in the mining process. Finally, the complexity of mining engineering geological exploration is medium type that mainly dominated by layered rocks. |
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