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Development of Dynamic Simple Shear Apparatus for Small Strain Dynamic Tests on Unsaturated Granular Soils by Bender Element and ultrasonic Sensors

Karimzadeh, Ali Akbar | 2016

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 48613 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Jafarzadeh, Fardin
  7. Abstract:
  8. Shear modulus and confined modulus are important parameters for static and dynamic analysis in geotechnical applications. Elastoplastic and nonlinear constitutive models has been formulized by these parameters. Cyclic simple shear apparatus had been developed by mounting bender element and ultrasonic sensor to measure continuous shear wave and pressure wave velocities for determination of G_max and M.For this purpose two new pedestals have been fabricated on which HAE ceramic disc and sensors were mounted. A pressure control panel and a hanging column system have been designed to apply high and low matric suction with high accuracy.At first two small strain tests were conducted for determination of the maximum shear modulus and confined modulus by approaching to hydraulic hysteresis at various suctions (0,1,2,2.4,3.7,5.1,7.5,26,50) on drying and wetting branch.In the following five tests was conducted on five distinct samples of Babolsar sand at 50kPa axial pressure and relative density of 60% by bender element and large strain cyclic simple shear tests for determination of G_max and G and calculation of the 〖G/G〗_max ratio afterward. Test results show that changing of maximum shear modulus and confined modulus are identical to changing of the soil water characteristic curve. Shear modulus G increases with increasing of suction at drying branch of soil water characteristic curve.〖G/G〗_max Increases till to suction of 3.7 kPa at the first section of SWCC then it decreases at the higher suctions of drying branch.Material damping acquired by analyzing pressure wave. The Material damping ratio at drying branch of SWCC before air entry decreases, however, increases at transition zone and decreases in residual zone as well as at wetting branch at first increase then decrease until 0 kPa suction
  9. Keywords:
  10. Unsaturated Soil ; Shear Modulus ; Bender Element Test ; Ultrasonic Waves ; Hydraulic Hystersis ; Blending Elements ; Compressive Modulus ; Dynamic Simple Shear Apparatus

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