MEASUREMENT OF SHEAR WAVE VELOCITIES IN DILUVIAL GRAVEL SAMPLES UNDER TRIAXIAL CONDITIONS

概要

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A method of measuring the shear wave velocity in a triaxial test specimen (300 mm in diameter, 600 mm in height) has been proposed. The validity of the measurement method and the characteristics of the detected waves were confirmed by conducting preliminary tests on a steel cylinder and Toyoura sand specimens. By applying this method, the velocities of the shear waves propagating in the 'undisturbed' samples which were obtained from diluvial gravel deposits by means of an in-situ freezing method were measured under various confining pressures. The results of these measurements indicated that the effect of confining pressure on shear wave velocity was more significant for diluvial gravel samples than for clean sand, and that the shear wave velocities in reconstituted gravel specimens at in-situ overburden pressure were 20 to 30 percent below those in diluvial gravel samples. The shear moduli at a strain amplitude of l0^<-5> in cyclic triaxial tests were about 5 percent less than those determined from measurement of shear wave velocities. Moreover, it was verified that laboratory shear wave velocities in diluvial gravel samples were nearly equal to in-situ shear wave velocities measured at the sampling site, in the range of K_0 equal to 1.0 to 2.O. From this fact, it was concluded that the disturbance of the diluvial gravel samples was very slight during the entire sampling procedure.
社団法人地盤工学会の論文
1988-06-15