It is proved that the improvement effects cannot meet the use requirements for conventional vacuum preloading techniques improving new hydraulic reclamation mud foundation.To investigate the reasons,we analyze firstly the engineering properties of new hydraulic reclamation mud,and then carry out a full-scare single-well indoor model experiment considering different initial moisture contents.It is shown that:(1)the new hydraulic reclamation mud mainly consists of fine and very fine soil particles with high content of clay soil particles(clay & rubber) and strong hydrophilic minerals (illite & smectite);its pores mainly consist of isolated pores and intergranular pores;its moisture content is usually larger than 100% and more than 1.5 times greater than the liquid limit;its void ratio is larger than 2.5;its plasticity index is larger than 20;its liquid index is larger than 2.0.(2)when it is improved by no-sand vacumm preloading for new hydraulic reclamation mud,the vacuum degree loss can be up to 20% under the membrane,and the radial loss extent of vacuum degree is severe from vertical drains to soils;the radial range of vacuum degree is limited to the soil column with the diameter of around 40 cm;the unconfined compressive strength does not exceed 35 kPa in the range of soil column;it is small for the effective improvement depth and intensity of the soil strength growth.The above two reasons both result in the unsatisfied improvement effects.Therefore,it is very necessary to optimize the conventional vacuum preloading techniques or develop a new improvement technology for new hydraulic reclamation mud.