Characteristics of 3D swelling pressure of GMZ001 bentonite

An experimental research on characteristics of 3D swelling pressure of GMZ001 bentonite is reported.Samples are prepared using the static uniaxial compaction.Tests are preformed by use of 3D swelling-shrinkage apparatus,of which some modification has been made to enlarge the measuring range of swelling pressure.For the specimens investigated in this study,both the vertical(parallel to the direction of compaction) and horizontal(perpendicular to the direction of compaction) swelling pressures show exponential functions against their dry density,however,the swelling pressures are independent of the initial suction of samples.The increase of the dry density results in the decrease of the ratio of horizontal and vertical swelling pressures.When the dry density is lower than 1.45 g/cm3,the vertical and horizontal swelling pressures are almost identical,while an invariable ratio of horizontal and vertical swelling pressures of 0.78 is obtained when the dry density is larger than 1.6 g/cm3.Evolution of the swelling pressure is affected by both the dry density and the initial suction of the specimens.For specimens with higher dry density and higher initial suction,the development of swelling pressure ceases for a while in the course of hydration before it reaches its final maximum.The increase of the dry density leads to the increase of the development speed of swelling pressure,however,the speed difference between the higher and lower dry density specimens becomes insignificant with time.Compared with the higher suction specimens,the development rate of swelling pressure of specimens with the lower suction is inferior at early stage,but it becomes superior after a period of time.The equilibrium time of the maximum swelling pressure relates to the dry density,while the initial suction does not play an important role in it.