Acid mine drainage is generally treated by neutralization process in which metal ions are precipitated as metal hydroxides, followed by settling of the precipitates. The treatment cost and the settling characteristics of the precipitates, such as settling velocity and sludge volume, depend on not only the concentration of metal ions, especially ferrous irons, but also the kind of neutralizing agent used and the introduction of various steps including oxidation, sludge recycle, etc. Neutralization process for mine drainage is outlined paying attention to the treatment cost and the sludge volume.

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Open pit quarries often form large slopes after a long-term excavation. In early 1990s, some large failures of those slopes in Japan occurred. Therefore a method for monitoring the slope stability is necessary and should be established immediately.
The Global Positioning System, a surveying system using artificial satellites, is a promising method for monitoring long-term stability of large slopes. The GPS offers several advantages which include: it is a three dimensional measurement system with high accuracy for a long baseline, and measurement can be taken during night and day under varying weather condition with portable equipment. The first and third authors have developed a new system by using the GPS for monitoring ground displacements at real-time.
In this paper, the GPS displacement monitoring system is outlined and a field experiment to investigate the applicability of the system at a practical slope is described and the results are discussed.

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In order to investigate the influence of faults on the spatial distribution of the initial rock stress, a simple model of faulted ground has been presented and the numerical solutions have been compared to the trends of the observed stress by means of the stress relieving method in the world. The observed stress data have been firstly presented and analyzed to make clear the trends of them. The significant difference between the observed vertical stress and the overburden pressure has been examined as shown in Fig. 3, and the non-linear characteristics of the horizontal maximum and minimum stresses as a function of the depth have been discussed by seting out their limitting envelope curves as shown in Figs. 4 and 5.
The numerical analysis has been performed by the Displacement Discontinuity Method. Practically, a twodimentional semi-infinite elastic ground model with two sets of parallel faults intersecting the surface has been presented as shown in Fig. 6, considering fractal geometry of faults, and the stress changes caused by the frictionless sliding on the fault surface have been analyzed under the various primary stress conditions. Numerical solutions show that the trends of the observation can be fairly well explained with the present model, and it has been concretely shown that the variation of the initial rock stress with location is closely depending upon the sliding mode of adjacent faults and the primary stress condition.

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The understanding of the fatigue failure characteristics istics in rock under shear stress is considered important in designing underground structures. However, the study on direct shear test under cyclic loading has not been carried out extensively. Therefore, in this paper, we have investigated the time-dependent behavior of Kimachi sandstone and Tohoku marble under loading shear stress.
Results obtained from the experiments are as follows;
(1) Upper and lower shear displacements decreased with increasing number of cycles.
(2) The shear displacement-number of cycles curve in the fatigue process of rock was found to consist of three stages as typically shown in Fig. 7 (A-B, B-D, D-E).
(3) Shear stress-shear displacement hysteresis loops of both rock specimens gradually becomes narrower with increasing number of cycles irrespective of the ratio of shear stress.
(4) AE activity is seen in the primary (A-B) and tertiary stages (D-E). Especially, AE events occurs drastically in tertiary stage.
Based on the above results, the fatigue process is believed to consist of the following steps;(a) in the primary stage, pre-existing cracks and pores in the rock become closed, then (b) in the secondary stage, micro cracks are developed and proceeded with increasing number of cycles, and (c) in the tertiary stage, micro cracks coalesce into macro cracks and lead to the failure of the rock specimen.

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A method to estimate rock strength with TBM cutting force is proposed. It is assumed that thrust force for a disc cutter increases linearly with product of rock strength and cutting depth. This assumption leads to the following equations:
(Rock strength)∝(Resultant thrust force)/(Penetration rate)
(Rock strength)∝(Resultant torque)/(Penetration rate) ^1.5
By the method, rock strength along Niken-goya tunnel was estimated. The tunnel mainly consists of sandstone and slate. Estimated rock strength well agreed with the results of geological investigation; extremely small strength in fragmented slate, on the other hand, very large while boring through massive sandstone. The estimated rock strength was compared with the results of Schmidt hammer test, and it was found that the correlation between the two was excellent. Correlation between estimated rock strength and rock classification was also examined. It was found that the correlation existed, however, the classification used was too rough to evaluate the proposed method precisely.
The proposed method is relatively simple and requires only three values: thrust force, torque and penetration rate. It can be said that the proposed method is promising for real-time estimation of rock strength on the face.

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To clarify the cutting mechanism of water jet, it is very important to know dynamic properties of stagnation pressure of water jet. This pressure includes wide range frequency components, such as pulsation of a plunger pump and impact pressure caused by impingement of droplets, and so on. In this case the transducers' characteristics affect the source wave, and the detected wave of pressure differs from source wave. The system and method to obtain the source wave of stagnation pressure from detected wave are presented in this paper. Their characteristics are in using a digital filter for deconvolution. And the accuracy of the present method is examined by comparing its result with that of other method. In addition, relationship between characteristics of the stagnation pressure and the flow structure of water jet is examined by flash photography using pulsed laser light. As a result, it is elucidated that the fluctuation of stagnation pressure is caused by wavy motion of water jet

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磁気分離法を利用して, 鉄セン亜鉛鉱, 硫ヒ鉄鉱などから構成される亜鉛硫化鉱中のヒ素を分離除去する実験を行った。分離試験は, フランツ等磁力選別試験機を用い, 分離場の磁界強さを2, 0000e, 5, 0000e, 10, 0000eの3段階に変化させ, 鉱石を空気中で分離した。硫ヒ鉄鉱などのヒ素化合物は, 非磁着物中に濃縮される。磁着物中のヒ素の品位は磁界強さの増大とともに0.12%から0.04%まで減少した。磁界強度10, 0000eでの非磁着物は供給試料重量の8.26%となり, そのヒ素品位は0.96%に達した。これは, 試料に含まれる全ヒ素の約63%が分離除去可能となることを意味する。それに伴って, 磁着物中の亜鉛品位とその重量は, 磁界強度とともに増大し, 10, 0000eではそれぞれ48.46%と66.90%となる。このことは亜鉛回収率が約96%にも達することを示唆する。

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Intermediate products such as smelting dust and scraps of semiconductors contain lead, silver, gold and many other kinds of valuable metals as well as arsenic and antimony. In order to recover these valuable metals from the secondary materials, a by-production process is required to avoid recirculation of arsenic and antimony back into the smelting of the base metals. In this process, the valuable metals are recovered by dissolving in the metallic lead which is formed. The arsenic and antimony are eliminated into the speiss phase. To analyze the behavior of the minor elements between the molten speiss and metallic lead, the distribution ratios were established in the Pb-Fe-As ternary system. Bi, Ag, Cd, In, and Au are collected in the metallic lead phase and can be rec, vered from the bullion in the lead refining process while Co, Ni, S and Ga are concentrated in the speiss phase. Cu, Sb, Se, Sn and Zn are however distributed in both phases. Effective recovery of these elements can not be expected in this process.
The activity coefficient of minor elements in the speiss phase of the Pb-Fe-As system are estimated by means of the distribution coefficients and activity coefficients of minor elements in molten lead.

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The suction and extrusion pressures were measured by using a vaned disk and a plate turbine as an impeller of mixer-settler extractor. The suction effect by a vaned disk and extrusion effect by a plate turbine are strongly dependent on the rotation speed, and they slightly decrease with an increase in the flow rate due to the pressure drop. When the flow rate is zero, the maximum suction and extrusion pressures are obtained. The both pressures at a certain flow rate are in good agreement with the difference between the maximum pressure and the total pressure drop. The maximum suction and extrusion pressures are nearly proportional to the third power of rotation speed. The suction pressure is also dependent upon the distance from the vaned disk to the bottom of the mixing space, and in the same manner the extrusion pressure depends on the distance from the plate turbine to the extrusion pipe of the mixing space. When the distance is shorter, the effect becomes higher. If the rotation speed is fixed, the desired suction and extrusion pressures are obtained by adjusting the distance.

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In order to recover Ti as TiN powder from Ti based Fiber Reinforced Metal (FRM) scrap for recycling, the reactive gas atomization process by using laser was investigated. A double tapered nozzle was effective to atomize the melted TiN produced by the interaction of Ti and N₂ gas, and favorable spray was accomplished.
Consequently, Ti as matrix was converted to TiN by reacting with N₂ gas, the melted TiN was atomized by high pressure N₂ gas, and atomized droplets were rapidly cooled on a dryice. Color of powders was gold or brown, and the shape of powders was oval or spherical, and the size of powder was in the range from several tens of μm to several hundreds of μm. Such an eutectic crystal or an equiaxed crystal was seen in the microstructure through an optical microscope.
By X-ray diffraction pattern analysis and Electron Probe X-ray Micro-Analyzer-Energy Dispersive X-ray Spectroscopy (EPMA-EDX), it was found that the microstructure consisted of TiN_0.7C_0.3, Ti₅Si₃ and TiN_0.3, and Ti based FRM after laser irradiation presented a similar microstructure.

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The glass-formation region of the SnCl₂-P₂0₅-SbCl₃ system has been investigated. Glass was obtained in the composition range of 0-20 mol% SbCl₃, however, some of the glasses contained black crystallites of Sb. The content of Sb in the glasses obtained decreased with increasing SnCl₂ content.

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