At ash hill in Kitami City, Hokkaido, where some concrete pile driven in as end-bearing Pile for a reinforced concrete buildings. By doing so several concrete pile (HSA, σc=92kg/cm2, φ=30cm) broke in the middle of the basement site. I was asked to investigate the cause of the damage of the piles, so I did many mechanical testings and geological examinations in the ash. The compression strength test indicated some pumices and hard clay layer in the ash, but their strength were weaker than the concrete piles allowable strengths. Therefore was done a seismic refraction investigation at this ash hill basement (diabase). First was comfirmed the position of the basement site by boring, and after the basement was beaten by heavy weights (63.5kg), so that seismic refraction waves were recorded in detectors at the ground surface. By analysis of the travel time-distance cauve, under the ground surface was found an unregularity in rise and fall topgraph, may be the concrete piles broke at a rise position in basement. This seismic refraction method may be usefull in other field of basement investigation.
The relations between many kinds of physical and mechanical properties of rocks, such as density, water absorption, compressive strength, tensile strength, shear strength and Young's Modulus were investigated using many test data in author's laboratory. Each relation between particular two properties as listed above, has wide variety according to the kind of rocks. So, it is difficult to establish simple relation through all kinds of rocks. The properties of particular kind of rocks, such as granite, andesite, tuff, sandstone and mudstone, have fairly good relations with each other properties, so, these relations on main kinds of rocks were illustrated systematically in figure-20, with common parameter of uniaxial compressive strength (in dry condition). Using these relation, a kind of physical property may be estimated from other properties Through above investigations, and other information on weathring test and ultrasonic velocity measurement of rocks, anther proposed an attempt to classify rocks with these physical properties. The compressive strength is selected to be common index of classification. Most of other physical properties seems to show some remarkable change at 1500kg/cm2 and 300kg/cm2 of compressive strength, so these values may be useful to classify rocks, such as compressive strength>1500kg/cm2 ……very hard-Hard Rocks compressive strength=300-1500kg/cm2……Moderately hard-Moderately soft Rocks compressive strength<300kg/cm2……Soft-Very soft Rocks.