Abstract
"Shirasu" is a local term for volcanic deposits. The allowable unit bearing power of "Shirasu" in natural ground is 10〜20 t/m^2 before this. Loading tests didn't be given on this occation. Supposing that this value is irational, loading tests were carried out on natural "Shirasu". The purpose of this paper is to study the strength and the deformation of "Shirasu". Compressive and shearing strength tests were carried out. The results of the tests are summarized as followings. 1) The results of shearing strength test is shown as followings. τ=0.2+σtan40°(kg/cm^2) The compressive strength is 1.0〜2.0kg/cm^2. The compressive strength of weathered "Shirasu" is under 1.0kg/cm^2. 2) Comparing vertical with horizontal strength of loading tests on the tip of cliff or compressive strength tests, "Shirasu" is a unisotropic materials. 3) The allowable unit bearing power of "Shirasu" which exist generally in natural ground is 30〜35t/m^2 for practical use. However this can't apply to weathered "Shirasu".
