Although the preloading method with vacuum and surcharge has many advantages
but it also has some negative effects. Firstly
it may lead to instability of embankment especially when fill is constructed in a short period and vacuum is unloaded immediately after finishing of surcharge because the undrained shear strength will decline with the unloading of vacuum. Secondly
it may lead to more settlement after construction especially when pavement is constructed immediately after unloading of vacuum for the value of compression modulus will decline with the unloading of vacuum. Other negative effects such as cracking and settlement of ground near the improvement zone have been reported in other papers already.