Old concrete specimens were examined carefully under a stereomicroscope and with an image analyzer to clarify the characteristics of durability failure related to age. Microcracks and pores in concrete specimens more than forty years old were coated with cyanoacrylate mixed with fluorescent paint, and then microscopically visualized under ultraviolet light. Various patterns of cracks or pores in old concrete specimens, such as typical microcracking and rims within the outer parts of aggregates, were revealed. However, clear distinction of these microacracks and pores in usual thin or polished sections was difficult. Image analysis including image sharpening, edge preserving smoothing, thresholding, and line thinning reveals that the total microcrack length per square millimeter in specimens of old concrete shows good agreement with P-wave velocity determined by the usual method.
This method is useful in the observation and evaluation of durability failure in old concrete specimens.

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The slag samples from various non-ferrous metallurgical smelters have been characterized by determining Bond's work index, density and Vickers hardness coupled with X-ray powder diffraction and optical microscopic observation. Bond's work index for a slag consisting almost of glassy phase shows relatively higher index value than that of the crystalline slags and brittle minerals like quartz and feldspar, although a consistent index for zinc slag could not be obtained due to a large amount of co-existing metallic phase.
The following empirical equation for crystalline brittle materials has been developed to describe the correlation between work index; Wi [kWh/t] and the product of Mohs' hardness; H_M and density;ρ[Mg/m³]. Wi=0.42 (H_M·ρ) +6.56
This equation is suitable for the range up to 30×10³ in the values of H_M·ρ with corresponding correlation coefficient of 0.83. Using this equation, the work index for the brittle portion of zinc slag, which is mainly constituted of oxide and silicate minerals, was estimated to be 16 kWh/t.

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The final goal of this study is to develop the computer-controlled robots for finishing the inside surfaces of tunnels as are expected.
In this study, some control algorithms to measure the distance between the head of the ultrasonic sensor and a point on the surface of an object were developed, and the outlines of some objects with the surfaces of simple slopes and rocks have been measured by using the robot manipulator with the ultrasonic sensor.
When the sloped surfaces of the objects are covered with some emery papers and measured by the robot system, very accurate values on the shapes of surfaces of the objects can be obtained automatically and speedily. Especially, the time required to measure every shape of the objects can be reduced remarkably by the continuous measurement of the above-mentioned control algorithms where the ultrasonic sensor continuously detects the distance between the sensor and the object by moving the robot manipulator.
Furthermore, it is proved that the allowable measurement-angle of the sensor is clearly extended as the roughness of surface of the object increases and as the slope angle of its surface decreases.
The measured values of rocks, moreover, are found to be considerably accurate within the error of 2.0mm. Therefore, the measurement system considered in this study could be satisfactorily available in measuring the inside surfaces of actual tunnels.

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This paper presents numerical modelling of powered supports for analysing the interaction of supports with the strata surrounding them. Finite element analyses were carried out for fourteen types of 2-leg shields, nine types of 4-leg chock shields and nine types of 4-leg shield, allowing us to compare their performances with one another. The main results obtained from the numerical analyses are as follows:
(1) The principal direction of the stiffness of powered support reflects its attitude, and provides a suitable indication of its performance of controlling strata.
(2) The inclination of hydraulic legs determines the principal direction of stiffness of 2-leg shield. Relatively weak roof strata are controlled by 2-leg shields better than by the others.
(3) The principal direction of stiffness of 4-leg chock shield is controlled by an algebraic sum of the inclination angles of the front and rear hydraulic legs. 4-leg chock shields whose front legs tilt forward and rear legs incline backward cope well with the condition of strata that both the roof and floor are moderately strong.
(4) The principal direction of stiffness depends solely on the inclination angle of the front hydraulic legs in 4-leg shields. Relatively weak floor condition is less harmed and better accommodated by 4-leg shields than by the others.

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In practice, rock mass is neither subjected to pure creep or pure relaxation but to a torce-cisplacement condition dictated by surrounding rock. But few are available in the literature about this problem.
Generalized relaxation test of Sanjoume-andesite and Kawazu-tuff was conducted under uniaxial condition. The generalized relaxation test investigates the property of time-dependent decrease (or increase) of stress under increasing (or decreasing) strain. Concretely, the increment of force-displacement relation was kept as follows;
ΔF_R-γ·K_R·ΔY_R=0
where ΔF_R is the increment of force, ΔY_R is that of displacement, K_R is the stiffness of rock sample in the elastic region and 7 is the direction factor of relaxation. Considering all possible boundary conditions (the relationship of the stress-strain), the direction factor of relaxation can be all real number.
By plotting all results on a stress-strain diagram, it can be said that the stress-strain curve shrinks as time goes by. In other words, rock characteristic line changes with the lapse of time.
A strain rate at an arbitrary time in the region where the strain rate is signified by a continuous increase is inversely propotional to the time up to final failure. If this law is applied to rock mass, the failure of underground constructions may be predicted.

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The two dimensional motion of the individual balls in a tumbling ball mill was analyzed numerically by a Distinct Element Method using the extended Kelvin model composed of nonlinear spring and nonlinear dashpot. A parameter related to the coefficient of viscosity is determined from the data of imperfect restitution between ball and mill shell. The simulation of the dynamic motion of the individual balls is based on the nonlinear perfect elasticity, nonlinear viscosity and Newton's law of motion. The dynamic motion of balls during milling calculated was compared with the actual three dimensional motion of balls observed in a mill. The effects of ball charge fraction and mill speed on the impact velocity of balls estimated were also discussed.
It can be concluded that the model simulation developed in the present study predicts approximately the actual motion of the balls in a tumbling mill. The motion reproduced from the simulation is strongly influenced by the ball charge fraction and mill speed. The impact frequency of the individual balls and their impact velocities at individual collisions can be estimated by the simulation technique proposed.

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A rock cutting rig has been designed and installed to investigate disc cutter performance in circular cutting mode as well as in linear one. A program of disc cutting experiment was performed in the circular cutting mode by using a single commercial disc cutter of diameter 150 mm and edge angle of 90° for seven different types of rock. The experiments resulted in determining semi-empirical formulae for thrust F_T, rolling force F_R and lateral force F_L acting on a disc cutter, written by F_T=K_TD^1/2P^1/2S^1/2F_R=K_RP_S^1/2F_L=K_LP^3/2
where D is a diameter of disc cutter, P is penetration of disc cutter and S is tool space. The coefficients of K_T and K_R correlate not only with strength property of rock such as fracture toughness and uniaxial compressive strength, but also with the stiffness property of rock. The coefficient K_L depends exclusively on the fracture toughness of rock These results do not conflict with those obtained from laboratory experiments using linear cutting rigs.

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