Shear behavior of overconsolidated Nakdong river sandy silt: Fid-Bau Portal

Shear behavior of overconsolidated Nakdong river sandy silt

Tint, Khin Swe / Kim, Young Su / Seo, In-Shik / Kim, Dae-Man

Abstract In this research, overconsolidated drained, undraned and unconsolidated undrained of Kakdong river sandy silt in triaxial compression tests were performed on specimens of silt with 26% sand content. In CIU and CID tests, the specimens were consolidated isotropically from 100 to 400 kPa and unloaded to 200 kPa for OCR-2, unloaded to 100 kPa for OCR=4 and unloaded to 50 kPa for OCR=8 before shear condition. In UU test, the samples were carried out under effective confining pressure 100 to 400 kPa during shear. In CIU-OC tests, the flowing characteristics were observed: the deviator stress decreased with higher OCRs and showed strain-softening behavior after failure. Pore water pressure decreased to negative; that the samples were higher dilative volume change tendency under unloading due to increasing OCRs. CID-OC tests indicated that the deviator stresses increased and presented strain-softening tendency after failure. Became negative due to dilatancy with higher OCRs under small strains. In UU tests, peak deviator stresses were different and displayed strain-softening tendency under higher effective confining pressure after peak value. The pore water pressures increased with small strains before failure and depended on saturation condition at failure. The undrained shear strength and the internal friction angle in UU test cannot be determined accurately due to dilative effect and low-cohesion of sandy silt. By using the concepts of critical state, the stress paths showed similar and all failure points followed to a unique slope line which forms a critical state line (CSL) in stress path diagram.