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In the literature, the effect of different factors on the liquefaction resistance of sand has been widely investigated using the cyclic simple shear test or cyclic triaxial test. In which, the effect of CSR on liquefaction resistance significantly depends on the type of sand. In Vietnam, the sandy soils are widely distributed in coastal areas where many wind power farms are built and planned to build. Thus, the liquefaction resistance of sandy soil in these areas should be evaluated. In this study, the effect of cyclic stress ratio (CSR) on the liquefaction resistance of sand distributed in the coastal area of Soc Trang province, Vietnam will be evaluated for the first time using cyclic triaxial apparatus (Wykeham Farrance). The sand samples were prepared using the dry pluviation method with a relative density of about 56%. The stress-controlled method with CSR from approximately 0.1 to 0.35, the effective confining stress of 50 kPa, and the frequency of 1 Hz were applied. The research results showed that the axial strain and build-up of pore water pressure significantly depended on the range of CSR. In particular, this research has indicated the threshold of CSR for the liquefaction of sandy soil in this study area. Accordingly, under the testing conditions, sand samples were not liquefied with a CSR of less than 0.25. [ABSTRACT FROM AUTHOR]

In this study, direct shear tests and cyclic triaxial tests were conducted to investigate the effectiveness of using municipal solid waste bottom ash (MSWIBA) material as fill material or base/sub-base in Vietnam. A square of large -- scale (300 x 300 x 140 mm) and a small scale (60 mm in diameter) direct shear test were carried out on MSWIBA samples to study the effect of specimen size on shear strength of the samples. The results show that the MSWIBA sample at R95 has a very high CBR value of 115%, which is much higher than the CBR value of crushed stone for subgrade applications. The cohesion and friction angle in the case of R95 are higher than those in the case of R90. The value of cohesion and friction angle in the large direct shear test are significantly higher than those obtained in the small direct shear test. The shear strength of MSWIBA is like natural sand. The resilient modulus decreased with the increase of deviator stress in the case of R90 sample and increased with the increase of deviator stress in the case of R95. The numerical method results also show that MSWIBA material can be used as construction material such as roadbed and foundation layers. [ABSTRACT FROM AUTHOR]