At the Hijiori Hot Dry Rock (HDR) field in Yamagata prefecture, the Long-Term Circulation Test (LTCT, Term 2 and Term 3) was conducted from December 23, 2001 to August 31, 2002. The test used two injection wells SKG-2 and HDR-1, and two production wells HDR-2a and HDR-3. At the beginning of this test, water was injected at a constant flow rate of 8.35 kg/s into SKG-2 and HDR-1. The ratio of injection flow rate at wells, HDR-1: SKG-2 was changed from 1:1 to 3:1 during the test, and production flow rate of HDR-2a decreased from 8 kg/s to 6kg/s. Production rate in HDR-3 remained almost constant during the test.
Because of difficulties in obtaining a match between the simulated and measured pressure of HDR-1 in the Term 1 of LTCT, the Bed-of-Nails model for fracture flow was modified. We re-developed a simple multi-reservoir model and simulated the test data using the FEHM (Finite Element Heat and Mass transfer) code developed at Los Alamos National Laboratory.
In addition, to estimate the productivity and the heat extraction of the multi-reservoir system during the long-term circulation, we studied four different injection scenarios by changing the ratio of injection rate or wells.
The two most important conclusions of the calculation are:
1) Production flow rate of HDR-2a decreased under the influence of decrease the injection rate of SKG-2, and
2) one of these four scenarios is recommended because of its high recovery and thermal output.

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An improved crack projection method for the analysis of open crack was introduced by applying image subtraction technique. In order to evaluate crack opening in the heterogeneous materials such as rocks, X-ray CT image subtraction method was introduced in the data processing together with necessary noise reduction method, using the 3-dimensional data given by X-ray CT. This is a promising method to analyze open cracks in the heterogeneous materials from the difference of X-ray CT images. The characteristic point of the method is that the reduction and the elimination of fatal noise related to X-ray CT images are possible and that the accurate image processing is expected. The fundamental formulae of noise reduction technique were firstly described and applicability for the rock sample was discussed. Then, formulae for X-ray CT image subtraction method were introduced as well as the necessary data processing for the crack opening measurement. In this study, artificial cracks were simulated by a couple of semilunar shaped rock samples. In order to verify the applicability of the method to the hetelogeneous materials, the rock samples were made of granite. The subtraction method was applied to the rock samples and the accuracy of the method was discussed. It was found that the influence of noises was clearly eliminated and that the crack opening distribution was accurately evaluated. This technique was also applied to the orthorhombic rock sample and it was also proved that crack opening could be evaluated by the same procedure in the case that tomography and data processing were conducted in the same condition.

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To clarify the characteristics of pumpage and drainage in mined areas, underground mining data, drainage data, and weather data in a coal mine were collected.
The pumpage rate is divided into two parts, the first is pumped under the seafloor and the second is pumped under the land. At the land, the pumpage rate has a correlation with annual precipitation. However, the pumpage rate from seafloor has no relationship with annual precipitation, cumulative mined area, or annual mined area.
The sources of drainage are classified based on main drifts, faults, and mined coal seams. Bar graphs for the variation of drainages from the sources show the movement of drainage peaks with development of new mined areas.
Numerical analyses about mine drainage are carried out to estimate and to make modeling the hydrogeological conditions. The records of drainage and the results of numerical analyses reveal the hydrogeological characteristics around mined areas. From the variation of drainages, the feature of drainage was simply modeled. These models are useful to predict the drainage in a new developed mining area.

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Effective utilization of tunnel muck was discussed. In the system proposed by the authors, the muck is reused as concrete aggregate and the muck waste is considerably reduced. This muck utilization system was examined from economical and technical viewpoints.
As the results of carefully investigation of tunnel muck, it was found that relatively small particle was short and the shape was not appropriate to concrete aggregate. Therefore the tunnel muck cannot be used directly as concrete aggregate and, at least, a simple crushing plant with an impact crasher and screens is necessary.
The muck was gathered in a tunnel and several experiments and testing including crushing, sieving and quality verification were conducted to obtain the data required to discuss the feasibility of this system. Finally, it was found that utilization of tunnel muck as concrete aggregate is possible with reasonable benefit.

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Dry gravity concentration method using a fluidized bed is being investigated. We employ polystyrene (PS) balls and glass beads (GB) as a fluidizing medium. Pieces of corrugated cardboard, paulownia wood, polypropylene (PP), polyvinyl chloride (PVC) and Al are employed as test materials. The separation efficiency is experimented and vertical position of separated materials in the fluidization bed is simulated, by changing the superficial velocity. It is found by experiment that high recovery (>90%) of sink products and float products is achieved, even if the density difference between them is slight. These high recoveries are achievable when the superficial velocity is slightly higher than the minimum fluidization velocity.
The recovery of float products is found to be sensitive to the superficial velocity: i.e., the recovery is low when the superficial velocity is either too high or too low. In order to examine the influence of the superficial velocity on the recovery of float products in detail, we employ two-dimensional simulation based on the discrete element method (DEM). The grater the superficial velocity is, the wider the vertical positioning of float materials becomes. It is found by DEM simulation that the recovery of float products tends to be low when the superficial velocity is too high, because the lowest vertical position during separation test is lower than that when the superficial velocity is optimal.
It is found from these series of experiments and simulation in this study that high efficient separation by dry gravity concentration using a fluidized bed is possible.

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Interaction forces between a bubble and a particle are critical for various industrial processes that handle colloidal dispersions, especially for froth flotation. Therefore, it is fundamentally important to understand the surface force between a bubble and a particle to control froth flotation process effectively. In this study, we conducted direct measurements of interaction forces between a spherical solid particle (silica and iron oxide) and a small air bubble in aqueous electrolyte using atomic force microscope (AFM). Interaction forces were measured between the particle attached on the top of AFM probe and air bubble generated on the flat surface. The forces between the silica and the bubble were repulsive over the wide range of the conditions of present experiments. The origin of the force was considered to be electrostatic force. In the case of iron oxide-air bubble system, the interaction forces were attractive when the pH was lower than isoelectric point (iep) of the ion oxide, while the forces were repulsive when the pH exceeded the iep. The attractive forces were stronger and longer-ranged than the force predicted by heterocoagulation theory. It was found that these interaction forces could explain batch column flotation results with nitrogen gas bubbles qualitatively.

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In many industrial processes, surfactants are used to control the dispersion and coagulation of particles in aqueous solutions. Especially, surfactants have critical effects in flotation separation. To investigate the effects of surfactants to the surface force between bubble and particle, which is critical for the particle recovery in flotation, we conducted direct measurements of the interaction forces between a spherical silica particle and an air bubble in dodecylamine hydrochloride (DAH) solution using atomic force microscope. Interaction forces were measured between the particle attached on the top of AFM probe and bubble generated on the flat surface.
When a hydrophilic silica particle was used, electrostatic force was observed at large separation distance on approach of the silica and the bubble. Then long-range attractive force acted between the surfaces even when DAH concentration was low. The range of attractive force includes the penetration distance of particle into the bubble. The relation between the floatability of silica particle in batch column flotation and the interaction force was discussed.
On the other hand, when the hydrophobized silica was used, the range of attractive force became short with the increase of DAH concentration. The repulsive force before attraction became very strong at high DAH concentration. The origin of the strong repulsive force is assumed to be the steric force between adsorbed dodecylammonium ions. These interaction forces cause the depression of the particle in flotation.

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Hydrometallurgical process as like a solvent extraction is very important to recovery precious metals from raw materials and metals scraps. Recently, authors have ever indicated the leaching process of gold by using ammonium thiosulfate solution from sponge gold, low concentrate ore and electronics scrap.
In this study trioctylmethylammonium chloride (TOMAC, (C₈H₁₇)₃CH₃NCl) was used as an extractant to extract gold from ammonium thiosulfate leaching solution. The influence of TOMAC concentration, retention (shaking) time, stripping process, multi stage extraction tests were investigated. It was found that the effective conditions for gold solvent extraction by TOMAC, such as 0.18 mol / l TOMAC diluted with n-octane at organic and water phase ratio of 1 : 1 could extract more than 99% of gold from the ammonium thiosulfate leaching solution at standard leaching condition (1.0 mol / l S₂O₃^2-, 0.03mol / l Cu²⁺ ion and 3.0mol / l NH₃/NH₄⁺ at pH10.5).

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