Sumitomo Metal Mining Co., Ltd. focuses on the "non-ferrous major class" mining company as its business strategy and the Pogo Gold Mine is situated at a very important position to achieve the goal. The mine was started with the grassroots exploration in 1991, as a first exploration project in which Sumitomo Metal Mining has majority share of project. A couple of gold deposits were discovered and defined during the exploration stage and the project was evaluated feasible to develop. The environmental permit process was started in 2000 and completed in 2004, in which especially the ore process flow was designed very carefully to prevent the surrounding nature from any impacts. The intensive construction works were initiated after approval of the environmental permits and twenty months had been spent to start ore processing in February 2006. The mine adopts the drift and fill mining method with paste backfill by using tailings from the ore process. Currently about 2,400tonnes/day of ore are mined and processed, which are above the plan in the feasibility study.

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We conducted Material flow/stock analysis, in order to estimate not only the in-use stock, but also waste flows of lead in Japan. Material flow analysis (MFA) quantifies flows of materials into, out of a system boundary. In this paper, all lead flows are captured throughout its lifecycle; from Raw Material Production, Material Production, Interim Product Production, Final Product Production, Use, to Waste management including Recycling. There are two motivations why we focused on lead. The first is that when exports of lead old scraps rapidly increased in 2005, changes of lead old scraps exports affect domestic lead refineries. This incident suggests the importance of analyzing the scrap trade flows. The second is its toxicity. This means the importance of appropriate management of waste flows. Currently, 80% of lead is being used as lead-acid batteries. As a consequence of MFA, We find that the stock of in-use lead in Japan is about 1.58 million tonnes in 2007. The batteries for Four-wheel cars (34%) and other vehicles (19%) are biggest form of lead in-use stock, followed by the stock in construction (18%) .

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In this study, we developed a method for creating on a computer a specimen of polycrystalline rock composed of monomineral, and using joint elements with normal (k_n) and shear (k_s) stiffnesses for the intergranular cracks, 3D finite element analysis was performed for the mechanical model of the polycrystalline rock in uniaxial compression to estimate the elastic properties and the stress distributions in the intergranular cracks. The effective Young's modulus of the polycrystalline rock is mainly governed by k_n of the intergranular cracks and increases with k_n, while the effective Poisson's ratio is mainly governed by the ratio of the shear stiffness to the normal stiffness (k_s/k_n) and increases with a decrease in k_s/k_n. As the ratio k_s/k_n decreases, the shear stress in the intergranular cracks decreases and the normal stress in the intergranular cracks with a large inclination angle relative to the loading axis increases in tension while that with a small inclination angle increases in compression. Thus, the normal and shear stresses in the intergranular cracks deviate more from the values in a homogeneous body as the ratio k_s/k_n decreases. Furthermore, it was found that the normal and shear stresses in the intergranular cracks that penetrate the upper and lower end surfaces, where the boundary conditions of displacement are given, are much smaller than those in other points, since the relative displacements in such intergranular cracks are constrained by the boundary conditions of displacement.

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Depressurization has been considered as a promising gas production technique from methane hydrate reservoirs. However, in the actual case of production from real reservoirs, there is still something to clarify. This research presents an experimental study to understand sand production phenomena from methane hydrate bearing sediments. The production of framework sands into a well is one of the problems plaguing the gas industry because of its adverse effects on well productivity and equipment. The aims of this study are to understand the sanding phenomena and clarify a driving force of sanding. In our experiments, we used an artificial sedimentary core and performed several depressurizing experiments under various conditions. The temperature, pressure, and production volumes of sand and water were measured. As the results, sand production is occurred during depressurizing process under the unstable condition of methane hydrate. The driving force of sand production is not a dissociation gas flow but a water flow through pore. It is determined by the water flow rate whether the sand production occurs.

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Particle transport with fluid flow in porous media is one of important problems in various engineering fields. The migration and sedimentation of micro particles through porous media affect strongly the hydraulic characteristics. The grout injection is performed to reduce the permeability of rock in civil engineering. In resource engineering, the decline of oil production might be due to the blockage of pore space caused by the asphaltene deposition in oil reservoir. Also, the transport of micro particles with water and gas flow could cause the production decrease in methane hydrate development.
This paper presents the simulation study of particle transport in porous media to understand the migration and sedimentation process of micro particles. In this study, we use a numerical simulation method based on the micromechanical fluid-particle system that couples the lattice-Boltzmann method (LBM) and the distinct element method (DEM) . LBM is known to be a suitable technique for simulating fluid flow in complex and time-varying geometries with boundaries. On the other hand, DEM has attracted much attention among many researchers as a useful simulation technique for large deformation problems. With the coupling of both methods, the complex motion of micro particles with fluid flow in porous media can be simulated.
To estimate the effect of particle concentration in the hydraulic characteristics such as permeability, we attempted to simulate the migration behavior of micro particles through porous media using this hybrid simulation method. As a result, it confirmed numerically that the migration and sedimentation of micro particles through porous media cause the decline of permeability. Also, it is cleared that particle concentration has a large impact on it.

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A force-penetration relationship is considered to be closely related to the deformation and fracture mechanism at the bit-rock interface. In this study, a testing machine in which a piston, a rod or a bit can be easily changed was developed for laboratory impact-penetration test simulating the in-situ percussive drilling. A series of percussive drilling tests with a button bit against Inada granite were carried out to examine and discuss the drilling performace. Stress waves were measured at two locations 1.91 m apart along the rod, and then force-penetration curve of the button bit was calculated by measured strain/stress wave. Main results are summarized as follows:
1) Delay of traveling time at bit can be expressed by a slit bit model.
2) Variation in the slope of force-penetration curves in laboratory tests was very similar to that in in-situ percussive drilling.
3) In spite of large scatter in the slope of force-penetration curves, the elastic deformations of rock surface were almost constant.

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The Hishikari Mine is the only major gold mine operating in Japan, whose production rate in 2008 was around 184,000 tonnes with the average gold grade of 42.8 g/t. The gold 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 (cemented rock fill) are used for larger stopes. In order to extract the KE-2 vein with wider mineralization and lower grade, being closely located to the narrower KE-3 vein with higher gold grade, we have studied the applicability of the sublevel open stoping (SLOS) with cemented rock fill through in-situ measurements of rock mass displacements and numerical stress analyses for evaluating the stability of the KE-2 large SLOS stopes and interaction with the KE-3 bench stopes.
We have used a bi-linear stress-strain characteristics of backfill for modeling the nonlinear compaction of cemented rock fill, whose stiffness increases with wall displacements of the backfilled stopes. The non-linear compaction may affect support characteristics of backfill, the present paper, therefore, incorporates the two-stage/bi-linear compaction modeling of backfill in FLAC3D in order to analyze the supporting effects of the cemented rock fill and to investigate the required backfill quality and mining sequence for more stable and steady operations of the KE-2 and KE-3 stopes.

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Predicting borehole temperature is a major concern when it is dealing with geothermal wells, deep wells, and methane hydrate wells during drilling operation. In geothermal wells and deep wells, the formation temperature exceeds usually heat-resistant temperature of drilling tools. In methane hydrate wells, it must cope with gas blowing out caused by resolution of the methane hydrate. Therefore predictions of borehole temperature precisely are very important. As fluids move through a borehole, there is transfer of heat between fluids and the surroundings due to the temperature difference between fluid and surrounding. In these applications the fluid behavior is non-Newtonian, and the pseudo-plastic flow in concentric annulus is used extensively, which assumed the rheological model of drilling mud in wells.
The aim of this paper is to investigate the Nusselt number concerned with heat transfer coefficient of pseudo-plastic fluid laminar flow in concentric annulus. Numerical results are obtained for different values of radius ratios and rheological constants, showing the importance of the duct geometric configuration and the little affect of the fluid rheology on the Nusselt numbers. Concentric annular duct has two limit configuration cases, i.e., when the radius ratio, ζ_A→0, the duct tends to be represented by a circular tube, and when ζ_A→1, by a parallel-plates channel, in these cases analytical results are expressed in functions of rheological constant.

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