Developemtnal Investigation of True Trizaial Testing Apparatus for Fynamic Soil Test

1985年，利用箱式三轴试验机研制了用于循环试验的轴向应变自动测量系统。利用电容式波高计测量滴管内水位的变化，可测量出三个垂直方向的轴向应变。结果表明，在循环加载试验中，该系统可以准确地测量应变。利用微型计算机开发了自动数据处理系统，可自动绘制应力应变、超孔隙水压力与循环次数、应变与循环次数的关系。为了建立液化试验体系，对Toyoua砂土进行了不排水条件下的循环加载试验。1986年，在恒定的总主应力条件下，对具有三种不同应力路径的Toyoua砂土进行了连续的循环加载试验。结果表明，循环加载过程中应力路径的不同会影响疲劳抗力。为了获得准确的试验数据，对试验程序和数据处理系统进行了改进，并将其应用于鹿儿岛石部湾的循环加载试验。通过筛分，将石拉苏分为三种不同的材料，即第一种材料是由直径小于2 mm的土壤颗粒组成，第二种材料是74-420微米和420-2000微米，第三种材料是420-2000微米和420-2000微米，第二种材料的粒度分布与东有砂相似，具有与东有砂相同的液化阻力。比第二粗的材料具有比第二粗的更大的抗液化能力。这一事实在通常的沙质土壤中是众所周知的。另一方面，第一种材料含有比74微米和74微米更细的颗粒，其液化阻力比第二种材料小。这意味着石拉苏的细小颗粒使石拉苏的抗液化能力较小。

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.