Evaluation of Dynamic Properties of Partially Saturated Sands Using Cyclic Triaxial Tests
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ORIGINAL PAPER
Evaluation of Dynamic Properties of Partially Saturated Sands Using Cyclic Triaxial Tests Pradipta Chakrabortty1
•
Aaditaya Raj Roshan2 • Angshuman Das1
Received: 15 November 2019 / Accepted: 27 April 2020 Ó Indian Geotechnical Society 2020
Abstract A series of strain-controlled cyclic triaxial tests were conducted to estimate the dynamic properties and the cyclic behaviour of partially saturated synthetic fine- and medium-grained sand. The soil samples were prepared for the cyclic triaxial test at low (RD B 20%) and high relative density (RD C 60%). The test results of fine- and mediumgrained sand revealed that both shear modulus and damping ratio reduces with the increase in the initial degree of saturation (expressed in terms of Skempton’s coefficient B). The maximum excess pore water pressure (EPWP) ratio development at initial cycles follows an increasing trend with the increase in the B coefficient. The studied fine sand is found to be affected more by the initial degree of saturation due to more voids present in it. Another novel aspect documented here is the effect of initial soil saturation on the Dobry’s EPWP model parameter F. The model parameter F has been modified depending on the initial degree of saturation, relative density and grain size of the soil sample.
& Pradipta Chakrabortty [email protected] Aaditaya Raj Roshan [email protected] Angshuman Das [email protected] 1
Department of Civil and Environmental Engineering, Indian Institute of Technology Patna, Bihta, Bihar 801106, India
2
Department of Civil Engineering, Birla Institute of Technology and Science Pilani, Pilani, Rajasthan 333031, India
Keywords Partially saturated Dynamic properties Strain-controlled cyclic triaxial tests Skempton’s coefficient B EPWP model List of Symbols AD Area of the triangle Arect Area of the rectangle AL Loop area ASRpeak Peak average stress ratio B Skempton’s coefficient for pore water pressure parameter Ba Pore air pressure coefficient Bw Pore water pressure coefficient Cc Coefficient of curvature Cu Coefficient of uniformity D Damping ratio D50 Mean diameter of soil Esec Secant Young’s modulus Esec,initial Initial secant Young’s modulus Ginitial Initial shear modulus Gmax Maximum shear modulus Ks Bulk modulus of sand Kw Bulk modulus of water N Number of cycles NL Number of cycles required for liquefaction n Porosity p0 Mean effective stress patm Atmospheric pressure q0 Deviatoric stress ru Excess pore water pressure ratio Sr Initial degree of saturation ua Pore air pressure uw Pore water pressure r03 Effective confining pressure rd Deviatoric stress
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Indian Geotech J
r0 sc l e c cc ctvc cd;min cd;max w
Confining stress Cyclic shear stress Poisson’s ratio Axial strain Shear strain Cyclic shear strain Threshold cyclic shear strain Minimum dry density Maximum dry density Matric suction
Abbreviations ASHL Asymmetric hysteresis loop comp Compression CRD Constant relative density EPWP Excess pore water pressure ext Extension FS Fine sand MS Medium sand
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