For laboratory use, the authors constructed a "High Speed Annuler Shear Device KS-1" which could vary the annulus speed with respect to soil from 3 to 150 cm/sec and tried to see the effect of the speed and annulus materials on the soil-to-annulus friction, finding that the existing method of determining shear strength was unsuitable, principally because of no consideration of the speed. Besides, transient phenomenon of shear head was also analyzed theoretically. The most important conclusions of this investigation are as follows: 1. The relation between external frictional stress F and normal stress σ, so called F-σ curve, was found non-linear unlike Coulomb's theory. So, the authors deduced the reason as follows: The condition of frictional plane might change as σ increased, then internal friction began to be seen, whereas real external friction was seen when σ was small. 2. The relation between internal frictional stress S and normal stress σ, so called S-σ curve, was found non-linear unlike Coulomb's theory. So, the authors deduced that some shear failure around annulus rim due to vertical loading might occur in the soil prior to shear test. 3. In case of determining cohesion c and coefficient of internal friction tanϕ, therefore, it must be fully noted that the loading will be subjected to restriction. For the soil used, the upper limit of σ was around 0.7 Kg/cm^2. 4. For high fidelity measuring by strain gauge method, it is required to design shear head so as to get its natural frequency high. 5. At high speed friction, damped oscillations were seen on the chart. Therefore, the mean value of the oscillations must be read up for the data. 6. The shear stress was described by the equation S = c+K_vV^n + σtanϕ in which K_v, and n are the new soil values. 7. Effect of annulus materials on the internal frictional stress was quite observed.
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