Abstract
It is the object of this paper to know the physical properties of extreme soft coal-measures rocks (i. e. such as compressive strength 100-200kg/cm2) under the tri-axial pressure.
The following results are obtained; elastic coefficients of the rocks are affected by the confining pressure, especially Poisson's number has a tendency to decrease as both the confining and the axial pressures increase. From this phenomenon it may be considered that Poisson's number of a rockl should be taken as a function of the external forces acting on it, and Poisson's number of the pressure zone surrounding a mine opening may be lower than those of the inner and the outer zones of it.
Further, it is noted that the rocks used in this investigation show the extremelyplastic behaviours even at the low confining pressure of 30kg/cm2.
