Liquefaction and Pore Water Pressure Generation in Sand: Cyclic Strain Controlled Triaxial Tests

Cyclic strain controlled laboratory triaxial undrained tests were performed on sand samples collected from earthquake affected Ahmedabad City of Gujarat (India). To study the factors controlling the liquefaction potential and pore pressure generation, cyclic strain controlled triaxial tests were carried out on (a) base sand, (b) pure sand, and (c) pure sand and non plastic silt mixture. All the tests were conducted on reconstituted soil samples and consolidated isotropically to different effective confining pressures. Base sand, clean sand and sand with non-plastic fines were tested using cyclic strain controlled triaxial undrained tests for different combination of shear strain amplitudes, initial effective confining pressure, and relative density (RD). In case of base sand and pure sand both have qualitatively the same liquefaction and pore pressure generation behaviors. For sand with non plastic fines, basic concept of limiting fines content (LFC) is justified and shown that how the behavior of mixture undergoes transition before and after LFC. This transitional behavior is observed both in the liquefaction strength and pore pressure generation. To obtain a mean relationship between liquefaction strength, pore pressure generation on relative density, confining pressure and shear strain amplitude, approaches previously adopted by Talaganov (1996) are used.