Water contents play an important role in study of liquefaction of loess.Saturation of undisturbed loess samples is an inevitable step in the liquefaction study.Taking WF12440 hollow cylinder apparatus as a testing platform

the back pressure method is used to saturate loess fully.The apparatus provides 3 ways to increase confining pressure and back pressure

i.e.manual stepping

automatic stepping

and continuous ramping.The pore water pressure parameter B is automatically checked to see whether the loess is fully saturated.Testing results show that even for undisturbed loess samples with low initial saturation degree

the back pressure method can be used to make B reach 0.95 and fully saturate the samples.The continuous ramping is the most efficient and convenient way

where the initial pressure difference of 10 kPa and initial confining pressure of 10 kPa should be kept.Otherwise

the samples could be damaged.If the change of pore pressure in one minute is less than the 5% of difference between the cell pressure and the back pressure

the pore pressure is considered stable and B value can be checked.