Rockfall occurs not only along the slopes of coastal and mountainous routes but also along the slopes of open pit mines. In this paper, research results and recent techniques concerned with falling behavior of rockfall, simulation methods, prevention measures, detection methods and protection measures are reviewed. It is considered, in general, that the engineering level for rockfall prevention, prediction and protection methods in Japan are not handicapped compared with those of Switzerland and other countries. However, accumulation of the data concerned with motion characteristics of rockfall is not so sufficient in Japan. Further tests on the motion characteristics of rockfall are expected to be continued because validity of simulation and other prevention and protection works can be confirmed only with reference to those field data. In the latter half of this paper, rock net system was discussed as an useful protection measure against rockfall. Ling net system which was developed in Switzerland is currently used as an effective mitigation method against rockfall energy in European Countries and high performance of the net has been tested also in Japan recently importing from Switzerland. It is considered that research works should be carried out intensively to develop other mitigation method of high performance against rockfall energy, not only because large amount of protection net is used every year in our country but also because the patent for the ling net was granted already in Switzerland.

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Geographic Information System (GIS) is widely used to input, store, retrieve, manipulate, analyze and present geographically referenced data. We adapted it in order to evaluate the aggregate resources potentiality.
By using GIS, aggregate resources database was constructed from the five information groups: geology, geographical features, development regulation zone, environment and economic value. These sub-systems were combined organically to search locations satisfying certain conditions for development of aggregate resources. Three kinds of raster data of 1 km meshes were produced from the database on rock distribution stage, development regulation zone and an area where economical development was possible. A combination of these data is enable to calculate the acceptable amount of resources. Minable meshes were extracted from the map by applying the map operation function of GIS to the three kinds of classified raster data.

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In Kamioka-mine, the conical-shaped steel reinforced concrete plug, whose length is only one thirds of the Japanese conventional standard, was designed and constructed, according to the principles proposed by the authors (see 1-st report). Pressure up to 4.5 MPa was applied in the pressurized cavern adjacent to the plug and the mechanical behaviors of the plug as well as the rock mass around the neighboring roadway were monitored.
It has been observed that both the plug and the rock mass around it, that is, the plug-rock mass structure behaves elastically without inducing the relative movement of the fissures in the rock mass beneath the plug, and that the pressure applied to the plug was resisted by the rock mass by inducing the compressive stresses. Since no symptoms indicating the unstableness of the plug-rock mass structure were observed,the plug has been proved to resist the pressure up to 4.5 MPa.

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An apparatus for the measurement of particle velocity and the diameter of a spherical particle (smaller than 10 mm) using acoustic emission due to the impact of the particle on a circular plate is developed. Based on the dropping experiments of nylon, high carbon chromium bearing steel (SUJ) and glass particles, the initial peak height (P₁) and the peak frequency (f_p) of the impact sound are related to the impact velocity (v), particle diameter (D), Young's modulus (E_p), Poisson's ratio (μ_p) and particle density (ρ_p). The P₁ and f_p are empirically expressed by Eqs.(6) and (15) respectively. If the properties of spherical particle are known, it is possible to estimate D and v from these equations by measuring P₁and f_p of the acoustic signal due to the impact of a particle. If a mass of spherical particle is known, it is also possible to estimate E_p and μ_p from these equations by measuring D and v using the apparatus.

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The classification and acidic leaching behaviors of phosphor sludge have been examined to establish the recycling system of rare earth components contained in fluorescent lamp waste. At first, separation characteristic of rare earth components and calcium phosphate in phosphor sludge was investigated by pneumatic classification. After pneumatic classification of phosphor sludge, rare earth components were leached in various acidic solutions and sodium hydroxide solution. For recovery of soluble component in leaching solution, rare earth component was recovered by treatment processes such as hydroxide and oxalate precipitations. The experimental results obtained are summarized as follows:
(1) In classification process, rare earth components in phosphor sludge were concentrated to 29.3 % from 13.3 %, and its yield was 32.9 %.
(2) In leaching process, sulfuric acidic solution was more effective one as a leaching solvent of rare earth components than other solutions. Yttrium and europium in phosphor sludge were dissolved in sulfuric acidic solution of 1.5 kmol / m³ concentration, and other rare earth elements were rarely dissolved in leaching solution. The leaching degree of yttrium and europium were respectively 92 % and 98 % in following optimum leaching conditions ; sulfuric acid concentration is 1.5 kmol / m³, leaching temperature 343 K, leaching time 3.6 ks and pulp concentration 30 kg / m³.
(3) In recovery process, yttrium and europium could be recovered to above 99.1 % by means of hydroxide treatment and oxalate precipitation method.
(4) Yttrium and europium from phosphor sludge contained in fluorescent lamp waste were recovered effectively by three processes of pneumatic classification, sulfuric acid leaching and oxalate precipitation methods. Their recovery was finally about 65 %, and its purity was 98.2 %.

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The physical properties such as moisture content, ash content, volatile matter, fixed carbon and specific surface area were investigated on the spent grain charcoal, Ca(OH)₂ added spent grain charcoal and the sawdust charcoal. Moreover, the burning properties of these charcoals were examined.
The spent grain charcoal contains fixed carbon of 81 % and ash of 12 %, and the ash content is fairly high compared with that in the sawdust charcoal. The ash content increases to about 16 % when Ca(OH)₂ is added to the spent grain charcoal. The ash of spent grain charcoal contains 47 % of P, 22 % of Ca, 14 % of Mg, 13 % of Si and others.
The thermal analysis gives a superior information on the ignition and burning properties. The spent grain charcoal is inferior to the sawdust charcoal in the burning property of the ignition temperature and the burning period, because the ignition temperature is higher and the burning period is longer. The addition of Ca(OH)₂ to the spent grain improves the burning property of the obtained charcoal due to an increase in the surface area.

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Investigation of overseas mine developments and operations is indispensable for the Japanese metal industry, which is heavily dependant on foreign mineral resources supply.
The first part of this paper provides an overview of the world metal mining industry in the 1990's focusing on globalization and sustainable development. Globalization of the mining industry has resulted in trends which include promotion of foreign investments in developing countries and merger and acquisition movements of the major mining companies. Concepts of the sustainable development and environmental issues with respect to the mining industry became important.
In the latter part of this paper, copper and gold open pit mines were studied worldwide from an economic point of view.
The main points resulting from the study include :
1) mines which have low ore value tend to have large mining capacity due to compensating productivity, and
2) the capacity of copper mines, even though ore reserves may be comparatively abundant, tend to be planned to postpone the mine life compared to that of gold mines.

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Although the general production scheduling problem, which seeks to maximize the NPV of a cash flow of a multi-period open pit mine development project, can be formulated as an IP problem, it can virtually not be solved by ordinary PCs. Therefore, the 4-D network relaxation method, in which production capacity constraints will be relaxed by a Lagrangian multiplier method so that the problem can be solved by LG method or Max-Flow method and in combination with a subgradient method iteratively converged to the optimum solution, has been developed. Akaike (1999) proposed a new 4-D network relaxation method, in which the processing method of each block will also be optimized, and further revised it to decrease the possibility of gap problem generation.
The algorithm to obtain the optimum production scale and the production schedule at the scale, using this revised 4-D network relaxation method, is proposed. Case study on a North American gold deposit apparently showed an influence of the discount rate on the optimum production scale. It took two and a half days approximately to solve a 5 period (10 years) project scheduling problem for an ore body model with 129,500 blocks.

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In this paper, a new concept for final pit shape in open pit design, Best Positive Inverted Truncated Cone (BPITC) algorithm, is presented for feasibility study and basic scheduling. Five mineral deposit models were used for eventual surface mine design optimization. Initially, geological reserve models were simulated by the utilization of GSLIB using randomly and regularly spaced drill hole data. Effects of varying anisotropy on the obtained metal quantities in reserves were also investigated. The BPITC was successfully applied to 100-times simulated deposit data set using Geostatistical simulation code GSLIB. The optimization results by BPITC were compared with those obtained by Positive Moving Cone (PMC) and Dynamic Cone (DC) based algorithms for the same mineral deposit models. The obtained results indicate that BPITC is superior to all the other optimizers. Concequently, the frequency distribution curves of profits and pit incremental feature by BPITC give effective information on mineral project decision-making and mining sequencing respectively.
The conclusions from this study are summarized as follows:
1. It was proved that for any type of deposit, the usage of correct anisotropic factors used in GSLIB lead to correct evaluation of reserves.
2. All the profits / benefits computed for all the five model deposits show that a newly developed scheme named as BPITC can always indicate optimal solutions for final pit designs.
3. Conclusively, the frequency distribution curves of profits and pit incremental feature by BPITC give effective information on mineral project decision-making and mining sequencing, respectively.

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Surface mine planning techniques are reasonably sequential and consist of geological modeling, deposit ranking, pit design and scheduling. In all deposits a pre-requisite is a sound geological model. Ranking uses such a model to find the economic pit limits and a broad mining path. The mine is then designed and scheduled, normally will involve a number of iterations to resolve issues such as blending of ore to a specification and smoothing ore and waste mining within a reasonably stable fleet capacity. In some cases these iterations are unsuccessful because the original ranking was flawed.
Dynamic commodity prices and increasing competition have reduced the technical staffing levels in many companies while increasing the requirement for faster mineral evaluations. Two recent developments in coal mine evaluation are presented. The first is a pit optimization method based on a variable block size to honor thin coal seam geology. The second is a scheduler using expert systems. Both techniques allow faster and more accurate coal project evaluations.
Z grid pit optimization is used in open pit mine planning to generate a pit, which is break-even at its limits. For a block model, coal values and mine costs; the optimum pit is the maximum revenue pit. A slightly smaller pit will leave revenue on the pit walls, while a slightly bigger pit is unprofitable at its limit. Pit optimization is also used to generate nested pits, which are optimum pits for incremental coal values. The smallest pit is the most profitable and to maximize NPV, and mitigate risk, should be mined first. Mining through the nested pits provides an initial schedule path
Life of mine (LOM) scheduling considers the planning, not as separate periods, but by simultaneously examining multiple periods on a project life basis. These LOM planning systems use mixed integer linear programming techniques to optimise the mine schedule, including blending. By considering multiple periods future profits and capital spending can be discounted and thus a LOM plan maximizes project NPV.

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