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Geomechanics Studies On the Stability of Sub-level Open Stoping With Backfill In the Hishikari Mine
Hyun, K. (The university of Tokyo) | Yamatomi, J. (The university of Tokyo) | Murakami, S. (The university of Tokyo) | Kurakami, T. (Sumitomo Metal Mining Co.,Ltd.) | Sagawa, Y. (Sumitomo Metal Mining Oceania Pty. Ltd)
ABSTRACT The Hishikari Mine, the only gold mine operating in Japan, consists of epithermal gold-silver veins. In 2007, the mine produced 183,000 tonnes of ore, with gold grade of 46 g/t. The veins are extracted mainly by drifting and bench stoping with backfill. Blasted waste rocks are generally used as backfill materials and crushed waste rocks with cement are used for larger stopes. In order to extract one of the veins with wider mineralization and lower grade, closely located to the narrower vein with higher grade of gold, we have studied the applicability of the sub-level open stoping with backfill through in-situ measurements and numerical analyses. Backfilling controls the displacement of excavated surfaces and increases the stope stability, but practical evaluation of a larger open stope created by the sub-level open stoping than the conventional drifting and bench stoping in conjunction with supporting effects of backfilling has not been established yet. The paper presents an approach to estimate supporting effects of backfilling by using FLAC3D numerical analyses and design the backfill quality and mining sequence for more stable and steady operations. 1 INTRODUCTION The Hishikari Mine, the only gold mine operating in Japan (Figure 1), consists of epithermal gold-silver veins. In 2007, the mine produced 183,000 tonnes of ore, with gold grade of 46 g/t. The Hishikari gold deposit was discovered by the Metal Mining Agency of Japan in 1981. Subsequent exploration and development by Sumitomo Metal Mining Co., Ltd. (SMM), the property owner, have proved Hishikari to be one of the outstanding gold deposits in the Japanese mining history (Ueno 1993). The Hishikari Mine consists of three deposits, namely Honzan, Yamada and Sanjin (Figure 2). The veins are extracted mainly by drifting and bench stoping with backfill. Blasted waste rocks are generally used as backfill materials and crushed waste rocks with cement are used for larger stopes. In the earliest years, bench stoping of smaller dimension with the height of 11 m was adopted. Then the engineering evaluation of the rock mass was employed, and as the mining operators have advanced in skill and experience, the stope dimension has been getting larger (Sato et al. 2007). Today the height of stope dimension is 19 m in the Honzan district and 24 m in the Yamada district of the mine. Large stope dimensions in bench stoping and sublevel open stoping make it possible to achieve higher productivity, but have a risk of inducing instability of the stope. Backfilling controls the displacement of excavation surface and increases the stope stability, but practical evaluation for stope dimension in conjunction with backfilling effects has not been established yet. In this paper, we have proposed an approach to evaluate supporting effects of backfilling by using numerical analyses and design the backfill quality and mining sequence for more stable and steady operations. (Figure in full paper) 2 KE VEIN IN THE HISHIKARI MINE The KE vein, located in the sanjin deposit, is divided the KE-2 vein and KE-3 vein (Figure 3).
- Geology > Mineral > Native Element Mineral > Gold (1.00)
- Geology > Geological Subdiscipline > Geomechanics (1.00)
ABSTRACT Black sea coast line is a hazardous region in Turkey especially in winter due to the dominant wave action. Therefore, rubble mound breakwaters used as ship shelters are vital structures especially for the fisherman. Construction of the breakwater requires good quality durable armourstones. Due to the nature of the rubble mound breakwaters, the armourstones with various sizes and types are used in the construction of these structures. The deterioration of these armourstones with time may result in the failure of the breakwater. In this study, various field and laboratory tests suggested in CIRIA/CUR (1991) and Rock Engineering Rating System-RERS (Lienhart 1998) of five armourstones (mainly limestone, andesite and sandstone) are performed. The test results are compared with their site performances in breakwaters and used to evaluate the suitability of the test results. Among the studied stones, the sandstone displays very poor performance. The others are found to be relatively good. Based on the data obtained, it is observed that some of the physico-mechanical parameters of the armourstones are good at predicting the long-term field performance of the armourstones. This paper will discuss the parameters to be used in the durability assessments of the armourstones. 1 INTRODUCTION The coast has for many centuries been an area of importance for human development. It is attractive in terms of its flat, fertile land, as base for transport by boat and as a base of fishing (Thomas 1998). However, in order to benefit from the sources of the coast, the protective coastal engineering structures are needed. These structures involve large quantities of quarried rock (armourstone) due to the economical reasons and the demand to build environmentally compatible and suitable structures. In this respect, the use of armourstone (approximately $40–50 per cubic metre) is three times cheaper than the use of concrete blocks ($120–150 per cubic metre), especially in Turkey. Additionally, there is a demand to build environmentally compatible and suitable structures in the world (Mather 1985; Latham 1991; Poole 1991; Erickson 1993; Smith 1999). The issue of durability of an armourstone relates to the properties of the rock from which it is derived, the environment to which it is exposed, the loads that are applied to it, and the method by which it was extracted from the source and then handled prior to final placement. In time, depending on these properties and the influence of the external forces, the armourstone can loose its quality (Clark 1988; Clark and Palmer 1991; Lienhart 2003; Latham et al. 2006a, b; Ertas and Topal 2006, 2008; Ozden and Topal 2007). This situation directly affects the durability of the coastal structure and in long term the economy of the region. Especially in Black Sea region where in winter harsh climatic conditions with dominant wave influence are observed, these kinds of structures are under great amount of risk. Alapli, Hisaronu and Tarlaagzi rubble mound breakwaters (Figure 1) are good examples of such structures used as ship shelters.
- Geology > Geological Subdiscipline (1.00)
- Geology > Rock Type > Sedimentary Rock > Clastic Rock > Sandstone (0.47)
- Energy > Oil & Gas > Upstream (0.48)
- Food & Agriculture (0.34)
ABSTRACT This study was carried out to improve diagnosis and prediction of geomaterials status from coastal protection structures. A methodology is proposed for the characterization of rock materials and management of the structures. The characterization was organized in different phases: i) visual inspection; ii) field techniques to study geologic-geotechnical features; iii) in situ measurement of geomechanical parameters; and iv) development of GIS-based mapping and assessment of the block materials. The results obtained allowed to define a geotechnical zonation for the structure armor layer, according to the type of geomaterial source, weathering/degradation grade and geomechanical rebound values. The GIS project developed, combined an applied cartography of the groins' superficial layer with the results of the field techniques. The interactive base included the pilot case presented in this work, from Espinho coastal area (NW Portugal, Iberian Peninsula), which comprises four different sectors. The results of this work, support the need to apply geomechanic concepts to coastal structures, since they allow the evaluation of deterioration levels and improve the planning of intervention works. This methodology contributes to ameliorate the efficiency of monitoring and maintenance, in an economically beneficial mode. 1 INTRODUCTION 1.1Coastal geoengineering The coastal human population has been growing in many countries around the world. It is currently estimated that about half of the globe population lives in coastal zones, although there is large variation among countries. In several countries, coasts currently face severe sea-level rise problems as a consequence of tectonic and anthropogenically induced subsidence. Also, historically, many geoscientists and engineers had to deal with natural hazards, like landslides and river and coastal erosion which affect the shoreline. On the other hand, human activities and the development of urban areas, may also affect coastal zones, making this environmental issue one of the most serious problems of the world. From the geoengineering point of view, and in a scientific context, impacts caused by the construction of large structures and incorrect land use require comprehensive geological, geomechanical studies and engineering solutions for their mitigation (Bock, 2006). During the last decades, the importance of geotechnical and geoengineering matters for rock characterization, together with the need to provide for its development, has been recognized (Manoliu & Radulescu, 2008). The use of GIS (Geographic Information System) databases is nowadays considered a useful tool that provides scientific background to evaluate parameters used as well as the results produced (Burke et al., 2001). In this work, using guidelines and procedures for the evaluation of rocks, it was possible to develop a GIS-based methodology that establishes a bridge between specific geological construction materials (geomaterials) and the design of coastal protection structures. 1.2 The rock project:importanceofgeomaterials characterization/evaluation The main considerations for a rock project are its scale and the availability, quality and handling of materials (Dupray et al., 2004; Latham et al., 2006a,b). In fact, our ports and coastal defences are vital, among others, to the maintenance of trade and economic development.
- Construction & Engineering (0.89)
- Law (0.54)
ABSTRACT The support measures determined by two empirical rock mass classification methods, Rock Mass Rating (RMR) and Tunnelling Quality Index (Q), for an access tunnel driven through jointed sedimentary rocks were compared with the actual support installed and the results of a numerical simulation undertaken using UDEC software package. The study indicated that the support measures recommended by the RMR method are in general agreement with the support installed, albeit some differences in the bolt spacing and shotcrete thickness used. In contrast, the Q recommended by the RMR method are in general agreement with the support installed, albeit some difference in the bolt spacing and shotcrete and fibre/mesh reinforcement, fall well short of the extent of shotcrete and mesh installed in the tunnel. The support performance monitoring and the results of numerical simulation showed that the installed support measures were required for the rock mass conditions present in the tunnel. 1 INTRODUCTION This paper presents an evaluation of the support derived using two empirical methods, Rock Mass Rating (RMR) and Tunnelling Quality Index (Q), for an access tunnel to an underground power station driven through jointed sedimentary rocks. The RMR and Q methods used in this study were developed by Bieniawski (1973) and Barton et al. (1974), respectively, and were subsequently revised to enhance the reliability of their support predictions. Their current versions are RMR89 (Bieniawski, 1989) and Q94 (Barton & Grimstad, 1994). Despite the revisions, these methods have limitations some of which are discussed by Palmstrom & Broch (2006), Pells & Bertuzzi (2008) and Ranasooriya & Nikraz (2007), 2008). A practical approach to identify the limitations of the empirical design methods and suggest improvement, where necessary and possible, is to compare their support predictions with those derived by other applicable methods and also with the performance of the support installed. The paper compares the support derived by the two methods with those installed in the tunnel, and evaluated their adequacy by two dimensional numerical simulation of the rock mass behaviour around the tunnel. 2 PROJECT BACKGROUND The case tunnel considered is part of the Lam Ta Khong pumped storage project situated some 200 km northeast of Bangkok, Thailand. The major components of the project include an underground power station and several kilometers of tunnels and shafts. The D-shaped 6.8 m wide and 1390 m ling case tunnel driven by drill and blast methods is the main access route to the underground power station. The tunnel overburden varies from 15 m at the entrance portal to about 350 m at the powerhouse end. The general tunnel alignment is 107°. Throughout the project, standard support systems comprising rock bolt, shotcrete, wire mesh and steel sets were used and their performance was monitored. The geological conditions and construction details of the project, as well as the results of convergence and support performance monitoring, were reported by Jinye (1993), Sirikaew (1993), Praphal (1993), Tran (1994), Sriwisead (1996), Nitaramon (1997), Gurung and Iwao (1998) and Phienwej (1999).