Dynamic characteristics of machine foundation under harmonic loading on gypseous soil with various degrees of saturation

Most previous studies on collapsible soils have demonstrated considerable variability in reliability, primarily due to variations in testing procedures and sampling methods. Additionally, it has often employed static testing as its primary method of validation. However, as development continues, a gap remains in our understanding of how collapsible soil reacts to various dynamic stresses, including mechanical equipment, power stations, trains, roadways, and other dynamic loads. Conventional studies often fail to adequately represent real dynamic loading conditions. Accordingly, it is essential to investigate the response of gypseous soils to vibration and varying moisture content. This research aims to characterize the dynamic behavior of gypseous soil under different saturation states (unsaturated and saturated), subjected to harmonic loading at a relative density of 35%, with additional consideration of foundation depth and eccentric mass. The experimental program aims to establish a database that enables reliable correlations between wave attenuation and soil damping in gypseous soils. Results showed that the dynamic characteristics of gypseous soil increased by 50−52% with settlement, 3−6% with sorption stress, 47−68% with total stresses, 42−46% with acceleration, and 44−48% with vertical displacement as frequency increased. However, they decreased by 6−7% for settlement and total loads, 2−5% for acceleration, and 6−9% for vertical displacement when gypseous soil saturation rose to 60%. Saturation levels also influenced these increases, which ranged from 60% to 100% (149−150%) for settlement, 139−173% for total stresses, 50−51% for acceleration, and 52−54% for vertical displacement. Meanwhile, suction stress increased between 45% and 457% as the gypsum soil's saturation level reached 60%, then decreased between 100% and 104% as saturation increased above 60% but before reaching 100%.