Developemtnal Investigation of True Trizaial Testing Apparatus for Fynamic Soil Test

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In 1985 the automatic measuring system of axial strains was developed for cyclic test vy the box type's treu triaxial testing apparatus. The capacitance type's wave heighr meter was made use of to measure the change of water level in the burette from which three axial strains in the orthogonal directions can be mesaured. It was found out that the strains couls be accurately measured by this system in the cyclic loading test. The automated data processing system also developed by using a microcoputer and the relations between stress and strain, excess pore water pressure and cyclic number, strains and cyclic number could be automatically drawn. The cyclic loading test on Toyoura sand was carried out under undrained condition in order to establish the system for the liquefaction test.In 1986 the cyclic loading rest on Toyoura sand with three different stress paths on II-plane were continuously carried out under the constant mnean total principal stress condition. It was found out that the difference of stress path in the cyclic loading peocess infulences the liwuefaction resistance. The test procedure and data processing system were modified to obtain the accurate test data.Shibushi Bay in Kagoshima and used for the cyclic loading test. Shirasu was divided into three different material by sieving, i.e., the first was composed of the soil particles whose diamter was smalleer than 2 mm, the second was 74-420 <micrn>m, and the third was 420-2000 <micrn>m. The second material whose grain size distribution is similar to one of Toyoura sand has the same liquegaction resistance as Toyoura sand. The thied material which is coarser than the second has lager liquefaction resistance than teh second. This fact is well-known for usaual sandy soil. On the other hand the first material which includes the finer grain than 74 <micrn>m has smaller liquercation resistance than teh second. This means that the fine grains in Shirasu make the liquefaction resistance of Shirasu small.