鋳物砂の粒度配合による通気度計算法の一考察

抄録

  To clarify the correlation between grain distribution and permeability, an analysis was made assuming that the sand grains of various size are alternately arranged by the layers of thin thickness in the specimen as shown by Fig.1. For the mixtures of coarse grains and fine grains, a calculating equation is expressed by
  [Written in non-displayable characters.]
for the mixtures of coarse, medium and fine grains
  [Written in non-displayable characters.]
where K : permeability calculated, K_a, K_b and K_c : experimental permeability of various grains respectively, H_a, H_b and H_e : heights of layers of various grains in the specimen respectively, α : ratio of a experimental value to a calculated value. In order to obtain. value α, silica sands of 70, 100, 140 and 200 mesh were used after washing with water, drying and screening by a standard sieves, and a content of binder(bentnite)and moisture were added in prorortion to specific surface of the sand grains. The combinated sample were prepared 70 kinds : The mixtures of coarse grains and fine grains were 42 kinds and the mixtures of coarse, medium and fine grains were 28 kinds. The results obtained were as follows :
      arithmetic average value ?? =1.09
      coefficient of variation ν=σ/??×100=9.4%
where σ : standard deviation.
  It may be suggested, therefore, that the permeability of the mixture of sand grian can be determined by the calculation from the above equation under the consideration of the grain distribution.