Study On The Performance Of Soft Soil Groung Improved By Vacuum-Heaped Load Combining Preloading Technique

With the development of high-speed railway and highway, it is more and more difficulty to meet requirements of the residual settlement. Thus, ground improvement techniques are facing many new challenges.Compared with conventional methods (i.e. DCM and equal-loading (or over-loading) pre-compression), vacuum-heaped load combining preloading technique has many advantages, such as improvement the stability of embankment during the construction periods, settlement and its rate, and other performance. Consequently, this technology is widely used in civil engineering. But much more researches are needed to master the control-technology of settlement and residual settlement of embankment.In order to study the performance of vacuum-heaped load, combining preloading technique on soft soil foundation systematically, a certain trial embankment with its soil foundation improved were constructed, and many testing items were carried out to research control-technology of settlement and residual settlement. Therefore, many valuable conclusions were drawn as following from designing, construction, testing and settlement estimating.1. The settlement and its rate of soft foundation improved by this technology is remarkable during construction, which is beneficial to control residual settlement.2. It is reasonable to select settlement as the design parameter, and verify the stability of embankment at any time during the construction periods.3. It is very important to control strictly construction quality and guarantee essential vacuum pressure.4. From in situ, analysis: The method of put more than one piezometer in one bore is practicable. And when surveying settlement of each layer, the waterlevel should be measured at the same time.The distribution law of vacuum pressure along with depth and the surface settlement's rate versus vacuum and heaped loads have been obtained. The relationship between soft soil layer's thickness and settlement, so as its rate were studied, the depth affected by vacuum-heaped loads is also researched.5. When calculating settlement, the result is influenced obviously by the way of selection loads. The sum of settlement values calculated separately through vacuum loads and heaped loads is bigger than the value caused by total loads. The common conclusion of two ways mentioned above is: The value calculated by e-p method is smallest, by e-lgp method is biggest, and by Es method is in the middle of the two methods above. Which method should be used is related to the thickness of soft soil layers.