抄録
In 4th report, the influences of moisture, ramming − energy, bentonite addition and grain size distribution upon green compressive strength in three kinds of base sands were studied and then these several combined factors having interaction were discussed. The outline of this experiment is as follows : 1) Provided that the compressive strength per unit content of bentonite is named as the bonding efficiency (η), then the value of η is mainly due to bentonite content and grain size distribution. Namely, the base sand Ⅲ is, in general, the largest in η and in the same sand, it takes a maximum value at a constant bentonite content.
Accordingly, the most effective bentonite content in practical use is due to the type of base sand. 2) η is generally related to deformability |b|. The larger η, the larger |b|. So η, compressive strength and surface hardness can be developed by increasing |b|.
