Mitigation of lateral slope movement and soil improvement using the vacuum-PVD scheme

Abstract

This paper interprets the results from field monitoring which was carried out during vacuum-PVD improvement in a site located near an actively moving slope. Interestingly, the monitoring results showed, among other things, mitigation in the outward lateral movements during and after the preloading process indicating relative stability in the slope and the efficiency of vacuum to mitigate lateral movements during the preloading period. Analyses were made on other field parameters such as pore pressure and settlement, as well as back-calculation of flow parameters to be considered during vacuum preloading design, such as permeability ratio (kh/ks) and horizontal consolidation coefficient (Ch) due to vacuum-PVD, were carried out. Post improvement, appropriate geotechnical properties were obtained from laboratory tests of clay specimens from borehole samples and undrained shear strengths were measured from unconfined compression and field vane shear test. The obtained properties indicated improvement in soft soil properties with a reduction in water content and an increase in maximum past pressure, OCR and undrained shear strengths. The prediction made for final shear strength using past literature, where applied additional incremental stress was reduced with depth, matched well with the shear strengths recorded from field testing.