Abstract:

The drain pipes, which were applied to treat the dredger fill by vacuum preloading, were always plugged by fine particles. It is essential to keep out of construction period for delay to improve the efficiency of the dredger fill consolidation. The test of dead-weight sludging drainage plus a combination of vacuum method of drainage in the laboratory was carried out. As vertical drainage channels，the drain pipes were experimentally used during the first-stage called dead-weight sludging drainage. Then the drain pipes were filled with medium-coarse sand to consolidate the dredger fill by vacuum method. The pore water pressure of varied depths and ranges were continuously observed especially to approach the primary-stage consolidation law. On account for the balance equation of water in the soil seepage, the major changes of pore water pressure were dominated. The mechanism of the pore water pressure changes during the first stage was explained accordingly. In order to fine consolidation the equivalence circle diametric was determined by sand drain theory and the pore water pressure curves. So drainpipe spacing to achieve the same desired effect of consolidation was determined under different circumstances whether the soil is near or far from the drain for the actual project design parameters.

Key words: dead-weight sludging drainage, mechanism of pore water pressure changes, seepage force, drainpipe spacing