A combined DJM-PVD method for soft ground improvement

摘要

Dry jet mixing (DJM) and prefabricated vertical drains (PVDs) have beennsuccessfully used for soft ground improvement worldwide. They both have advantages andnlimitations, and have been used independently so far. In this study, DJM and PVDs were used inncombination to enhance the performance of soft ground improvement. In the combined method,nPVDs are first installed and then DJM columns are installed between the PVDs at larger spacing.nThis combined method improves the effectiveness of ground improvement and creates a moreneconomical solution. This paper presents the concept, mechanisms, construction procedures, andnfield validation of this new method. In situ standard penetration tests were performed in dry mixedncolumns and cone penetration tests and field vane shear tests were performed in soils between thencolumns. Plate load tests were subsequently conducted on the treated ground. Excess porewaternpressures were monitored during and after the installation of DJM columns with and withoutnPVDs. Field validation was conducted through a pilot highway embankment on very soft clay innJiangsu, China. Long-term settlement monitoring was carried out for the construction of thisnhighway embankment. Field tests and monitoring clearly showed that the DJM-PVD methodnperformed well in enlarged spacing as compared with the conventional DJM method with closenspacing.