With increasing depth of working place, the abnormal phenomena due to rock pressure such as rock burst and gas outburst are becoming liable to occur in our coal mines. Then, today, it is most important to take measures against rock pressure for predicting and preventing such accidents in deeper mines. As one of the measures, the in-situ stress measurements are of great importance.
The Yubari new colliery started its development at the depth of 800-850 m below surface. The assessment of rock pressure of working place, therefore, is especially inevitable for this colliery to undertake a further develnpment of coal in safety.
The authoms carried out in-situ stress measurements in thisc olliebryy thes tresrse liemef thodo f Door stopper, and made estimations about the primary and secondary earth pressure around the galleries of various depth.
The following results cbuld be obtained:
(1) The measurements conducted at the gallery of SL 600, showed that the maximum original principal stress was nearly equal to the calculated overburden pressure and its direction approached the direction of the normal to bedding plane.
(2) The intermediate original principal stress of the point had east-west direction and its value was approximately three-fourths of the overbumden pressure.This dimection coincided with that of the tectonic stress which have played an important role on the fommation of the geological structure in this district.
(3) The distribution of the measured secondary stress around the gallery, was corresponding fairly well to the fracture and elastic zone assessed by RQD measurements of the surrounding rocks.
(4) As to the relationship between depth and stress, it was found that the vertical pressure was almost equal to the overburden while the horizontal stress was a little less than the overburden varying linearly with depth.

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One of the authors, Murakado, has reported that changes of delay time, incomplete blastings, and misfires seen in M.S. delay detonators set in charge holes, which accompany so often combustion of explosives, are caused due to detonation of explosives in nearby holes. In this work, to obtain some information about mechanisms of such phenomena, we attempted to examine the effects of compressive deformation on M.S. delay detonators.
An M.S. delay detonator was set in a steel-container, which was filled with imitation explosives, and then compressed by an external pressure before blasting. It was found that the delay time of the detonators came to change at the external pressures of 60 and 204kg/cm²in powdery explosives and gelative dynamite, respectively. It was also found that the detonators started to be deformed at these pressures, above which the degree of deformation increased nearly linearly with increasing the pressure. The lead plate tests showed that the incomplete blasting occured at pressures of 330 and 280kg/cm²in powdery explosives and gelative dynamite, respectively, and above these pressures, the curves of the degree of deformation vs. pressure leveled off.
The results in this work clearly indicated that M.S. delay detonators were considerably deteriorated by compressive deformation., Our unpublished work showed that in fact, considerable deformation by adjacent blasting was seen in M.S. delay detonators, which was detected with a strain gauge attached directly to M.S. delay detonators.

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In this paper the authors studied on laminar flow of paper slurry in connection with the hydraulic transportation of wastes.
Applying the thin layer model of water near the inner wall of pipe in laminar flow, the relation between coefficient of friction λ_p and moddyfied Reynolds number R_ep was investigated theoretically and experimentally.
As the results the following relations were ascertained, _??_
and also, the following values were obtained,
_??_
where, D=inner diameter of pipe, L=length of test section, ΔP=pressure loss, V_m=mean velocity, l=fibre length of paper, γ_p=specific weight of paper slurry
δ=thickness of thin layer of water, ρ_p, ρ_w= density of paper slurry and water, μ_w=viscosity of water, χ_w= shear stress, α n₁= constants.

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At the field test of H.D.S.-C.L.B. mining system (Hydro Dynamic Separation-Continuous Line Bucket mining system) by oblique attachment system of buckets to the rope line, which was carried out in March 1975, the behavior of a bucket was measured with Bucket Behavior Recorder which had been developed by the authors and other devices.
The results obtained from the analysis of the above experimental data are described as follows;
(1) The dredging path of the bucket on the sea bottom could be estimated as shown in Fig. 11, and it almost agreed with the empirical eauation which had been obtained from the model experiments in the indoor test tank.
(2) The shape of the dredging rope line on the bottom could be also estimated as Fig. 13, and consequently the distance between the descending and ascending rope lines could be inferred. The rope line distance on the bottom increased by about nine times compared to that on the test vessel. However, it could not be definitely concluded whether the effect of oblique attachment system was shown in water or on bottom.
(3) The sum of buckets, both waiting and dredging buckets, could be counted up.
(4) The recovery form on the bottom of the buckets attached obliquely to the rope line could be checked by the observation of sampling results with specific bucket.
According to the model experiments in the indoor test tank, it was scarcely possible to recognize the effect to widen the rope line distance except heavier buckets and the buckets did not. take steady recovery form on the sediments in case of oblique attachment system. Accordingly, H.D.S.-C.L.B. mining system by oblique attachment system involves many problems to be solved for raining manganese nodules.

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From the analysis of the gravity stratification in air pulsated jig, it was possible to calculate the horizontal velocity of the particles and I have examined the relation between the horizontal velocity and the falling velocity of the particles.
In the same particle size, the horizontal velocity is closely related to the falling velocity.
However, the smaller the size of particle the slower is the horizontal velocity and it can not be increased in proportion to the reduction ratio of the falling velocity due to the effect of hindrance.
The distribution form of the horizontal velocity for each particle is changed depending on the operational conditions of the jig.
It was conjectured that this distribution form give a great influence on the capacity and the separating accuracy of the jig.

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This invention is undertaken to ayply the rotary kiln for the selective reduction of lateritic nickel ores by city gas at the temperature range of 600°C to 800°C.
First, the cooling conditions of reduced ores were observed.industrially by means of X-ray analysis with the aid of chemical analysis.
Then, according to the decomposition 4FeO→Fe₃O₄+Fe, it was considered that the process had to undercool the wustite in the reduced ores, prevent the eutectoid decomposition of the wustite and precipitate the pre-eutectoid Fe₃O₄. This effective controlling step was the rapid and slow cooling method based on the precipitation of pre-eutectoid magnetite from wustite.This results were applied to the rotary kiln of laboratory scale. The reducing power of city gas was insufficient. Therefore, the addition of 5% coal was desirable for the supplimentary reducing agent. Moreover, the reduction temperature was higher 100°C to 200°C, than preliminary experiment. At the temperature range 800°C to 900°C, nickel was reduced to metal, and iron was reduced to the magnetic oxide. Some metallic iron was unavoidably produced. The extraction percentage of nickel by solution of ammonia and ammonium carbonate was 85% to 90%.

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