Abstract:There are some shortcomings with present settlement velocity method to decide unloading time. Relation between settlement velocity and post-construction settlement is deduced. It is testified that the settlement velocity method is suitable for multi-layer ground. A new method to determine unloading criterion of settlement velocity is advanced. This method can take overload,undercharge,secondary consolidation into account and is suitable for composite foundation. Experiments and engineering practices show that the method is right.