新生代碎屑岩(clastic rock)の比重と孔隙率について
1953 年 18 巻 3 号 p. 109-112
詳細
1953 年 18 巻 3 号 p. 109-112
Recently bulk density of clastic rocks has been measured in core-analysis or at gravity survey by some geologists. As the value of bulk density are varied by porosity and water content in the same sample, it is necessary to exchange the value into the unit weight in water saturated state.
The ralation between unit weight in weter saturated state (ρ3), average unit weight of mineral constituents of the aggregate (ρ0) and porosity (n) is expressed by the equation ρ3=ρ0(1-n)+n (1) (where specific gravity of sutarated water ρω=1)
So that the eguation to exchange the unit weight in dry state (ρ1) into ρ3 is as follows: ρ3=ρ1(1-1/ρ0)+1 (2)
On replacing the dry state (ρ1) by the natural state (ρ2), the equation (2) will be transformed as follows: ρ3=ρ2(1-W0)(1-1/ρ0)+1 (3) Where W0 is water content in natural state.
The more the porosity decreases according as the geclogic time passes, the thinner the bed of clastic rocks becomes. The relation between these thickness and porosity is expressed by the equation d1/d1=1-n1/1-ni (4)
in which d1=original thickness of the stratum n1=original porosity of the stratum di=the thickness of the stratum when the porosity (ni) varies from n1 to ni, (ni<n1)
