The undersea mining coal mines with the abundant valuable reserves in offshore area have been limited to working in the range of several kilometers for reason of the limited distance of ventilation. The paper presents the feasible guidelines that the possibility of sinking ventilation shaft through the offshore manmade island construction to extend the offshore mining area will be given to us from the safe and economical points of view.

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The present paper describes an improved practical method for the calculation of airtemperature and humidity along a roadway under complicated conditions.
Firstly working equations are introduced to evaluate heat flow from the surrounding rocks and sensible heat ratio of a roadway, either partially or totally wet, using the concept of modified air temperature which was proposed in the 2nd report of the present serial studies.
Secondly it is shown that the heterogeneous surrounding medium which cnsists of coal and sand stone or shale can be treated as an apparently homogeneous rock by introducing an equivalent thermal conductivity.
Finally discussions are made on the temperature variation of ventilation air when the air temperature at the reference point changes with time, and working equations are introduced by which air temperature can be calculated accurately enough in both cases that the temperature at the starting point changes suddenly and sinusoidally.

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In order to evaluate the applicability of high-speed waterjets technology to slot cutting in rocks from economic point of view, it is necessary to predict the depth of cut of an objective rock for various cutting conditions. The depth of cut is influenced by the cutting parameters such as driving pressure, traverse rate, standoff distance and nozzle diameter in addition to the mechanical properties of the rock.
In this paper systematic experiments were carried out both in air and in water for five rocks including mortar to know the effects of both driving pressure up to 98.1 MPa and traverse rate up to 198mm/min.
Main results obtained in this study are summarized as follows:
1) There exists a critical-driving pressure below which no cutting occurrs for both in air and in water.
2) The depth of cut in water is often greater than that in air when driving pressure is sufficiently large and traverse rate is small enough except granite. This is due to the cavitation errosion in water.
3) The depth of cut h can be expressed by the following equation as a function of driving pressure p and traverse rate V for both in air and in water.
h=A₁V^-n (p-p_c)
where P_c is a critical pressure, A₁ and n are coefficients.
4) The critical pressure is less dependent on the traverse rate in the range of this study and increases almost linearly with tensile strength of rocks.
5) The coefficient n is almost independent of the mechanical properties of rocks but depends mainly on the environmental medium.

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The pressure loss in solid-liquid two-phase flows is considered to be closely related to the motion of particles flowing in a pipe. In this paper, collisions among particles in solid-liquid flows in a horizontal pipe was observed with a high speed video camera. The frequency of collisions was obtained as a function of height. It reached a maximum in the vicinity of the surface of a moving bed, and decreased with an increase of height. The averaged value of impact and lift-off angle were approximately zero, and the shapes of frequency profile of both angles were almost symmetrical.
A simulation model of solid-liquid flows with taking into account the collisions among particles was established based on the experiments, and a numerical simulation was carried out to determine the motion of particles. The simulator gave almost the same particle trajectories, profiles of the particle velocity, and solid concentration as the experiments. Therefore, the present simulation model was confirmed to be reasonable.

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Fatigue on component wire for steel wire ropes under tension and bending has been studied. This paper describes the result of fatigue test of a steel wire which bears a natural curling and discusses the result of observation of the fracture face on specimen. Relation between S-N diagram and the fracture face is also discussed.
The following items show the conclusion.
(1) The degree of symmetry of fracture faces depend on both the residual stress and the curvature which the specimen beared before installed.
(2) Degree of flatness on the fatigue fracture face and the shape of S-N diagram are considerably influenced by the number of crack initiation spots.
(3) In the case installed convexly upwards with single spot initiation, the greater tensile load permit larger areas of the rapid fracture regions.

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Experiments are made to determine the condition of accumulator of oil hydraulic breaker. The influence of the accumulator behavior on the oil hydraulic breaker performance against variation of the volume and gas pressure of the accumulator is considered.
The results are as follows:
(1) The oil hydraulic breaker fitted with the accumulator can have higher percussion speed of the piston and more improved efficiency than the one with no accumulator.
(2) The percussion speed of the piston is increased against each accumulator volume with increase of supply oil flow rate, but it is saturated as increasing the accumulator volume over 0.2 or 0.3 Q. For the gas pressure of the accumulator over 3.43 MPa, it is also saturated.
(3) Relation between the percussion speed and the mean pressure of the rear chamber at the forward stroke of the piston is strong.

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Flotation behavior of calcite and dickite, alone and 1: 1 mixture, was investigated by a laboratory Denver type flotator at a pH 10.5 using sodium oleate as a collector and sodium silicate as a depressant with the intention of separating calcite from dickite.
Both calcite and dickite were negatively charged and therefore neither heterocoagulation nor slime coating took place at an alkaline pH.
The following results were obtained.
1) In the case of coarse particles system of both calcite and dickite fairly good floatability of calcite was obtained, but for fine particles no satisfactory results were obtained.
2) Selective flotation of calcite from dickite at an alkaline pH 10.5 might be explained by the following reasons, hydrophobic flocs of calcite were formed as the result of the increased adsorption of oleate ions on calcite surface and the addition of sodium silicate prevented slime coating.
3) Adsorption isotherm of sodium oleate on the surface of calcite and dickite was expressed by the Freundlich type isotherm and the oleate adsorbed on calcite surface forming a multimolecular layer at a high concentration.

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The authors have studied the reactions between ions of various collectors and the constituent ions of salttype minerals such as bastnaesite, apatite, fluorite, barite, rhodochrosite. The collectors used were sodium oleate (NaOl), n-oleoylsarcosine (OLSA), sodium octadecylsulfosuccinamate (SOSS), n-tallow-1, 3-diaminopropane dioleate (TDO), sodium dodecylsulfate (SDS) and dodecylammonium acetate (DAA).
Precipitate formation was monitored using a nephelometer. The solubility products of the precipitates of metal ions with SDS, NaOl and OLSA were determined by utilizing the Debye-Huckel law. The minimum concentrations of metal ions and anions needed to form precipitates with SOSS, TDO and DAA were measured. SOSS, OLSA, TDO and SDS preferentially reacted with Ce, La and Ba ions compared with Ca and Mn ions. Selective flotation of salt-type minerals with non-fatty acid type collector was discussed on the basis of the precipitate formation test results.
DAA and TDO formed precipitate of tungstate, sulfate, phosphate and carbonate but did not form with fluoride ions even at a high concentration. The adsorption mechanisms of SDS and DAA on typical salt-type minerals were interpreted in terms of the stability of the precipitates.

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