Abstract
For the accurate design of structures subjected to both static and dynamic loadings, elastic wave velocity and small strain stiffness are essential parameters. Numerous techniques have been developed to estimate wave velocities of geomaterials. Bender elements which are widely adopted for wave velocity measurements are invasive in nature and are not suitable for coarse-grained materials. In the present study, new design configuration of disk transducer has been introduced to measure both vertical and horizontal wave velocities for coarse granular soils considering multidirectional oscillation of propagating waves. An innovative arrangement of both compression and shear type elements has been installed in a large-sized triaxial apparatus having rectangular specimens of size 236×236×500 mm to assess the wave velocities. The materials described are Toyoura sand (D50 = 0.24 mm) and Oiso gravel (D50 = 11.8 mm). This arrangement enables measurements of nine types of wave velocities, and thus the stiffness anisotropy to be quantified. For Oiso gravel, horizontal wave velocities are greater than vertical wave velocities for both shear and compression waves. For Toyoura sand, shear wave velocities are higher in horizontal direction of propagation, whereas similar compression wave velocities are observed from both horizontal and vertical directions.
Highlights
The precise analysis and design of geotechnical structures subjected to both static and dynamic loadings require accurate estimation of small strain stiffness, often quantified using elastic wave velocities
The time domain responses of P- and S-waves propagating in x, y and z directions of Oiso gravel and Toyoura sand are depicted in Figures 8 and 9, respectively
Due to smaller D50 of Toyoura sand as compared to Oiso gravel, higher frequency components can be spotted in the time domain responses of P- and Swaves [12]
Summary
The precise analysis and design of geotechnical structures subjected to both static and dynamic loadings require accurate estimation of small strain stiffness, often quantified using elastic wave velocities. Due to the simplicity of use, piezoelectric transducers have gained immense popularity for the estimation of small strain stiffness by performing wave measurements. In this regard, bender and extender elements are extensively used to obtain the shear wave (Vs) and compression wave velocities (Vp), respectively [2,3,4,5]. There has been a limited research conducted on the development and use of planar piezo-ceramic transducers to estimate wave velocities of coarse granular materials (gravels) [11]. There is a research gap present on the development and use of planar piezo-ceramic transducers to estimate horizontal wave velocities in soils. Due to the large specimen size (236×236×500 mm), this device is capable of measuring wave velocities (Vs and Vp) of soils having a wide range of mean particle sizes (D50) (from fine sands of 0.2 mm to gravels of 12 mm)
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