This paper presents a review on the effect of saturation and back pressure application and discusses the practical aspects of back pressure application. Previous studies suggested use of back pressure during saturation phase; however there is no clear guideline for the level of back pressure that is appropriate to use in triaxial testing. Some researchers even suggested that circulation of carbon dioxide (CO2) should be used to expedite the saturation process instead of using back pressure to enhance the degree of saturation of tested sands in liquefaction tests. Nonetheless, different levels of back pressure 100, 200, 300 and even higher are typically used in sample preparation to achieve better degree of saturation (higher levels of Skempton’s pore pressure coefficient). The level of saturation influences the cyclic behaviour and strength. Therefore, there is a need to assess the proper level of back pressure to simulate real field condition. Examples of testing results on non-cohesive soil are presented to demonstrate how the saturation and back pressure levels affect the behaviour of tested specimen. The importance of realistic representation of field conditions in laboratory testing is demonstrated through examples of soils that are buried under impounded water such as marine sands. In cases where marine sands are buried under high water depths, the level of impounded water can be modelled in triaxial testing by applying different levels of back pressure. Finally, suggestion for the level of back pressure to properly simulate field condition is presented.
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