Comparative experimental study on hook dynamic compaction and unhook dynamic compaction
The dynamic compaction method is one of the economically efficient and widely used soil improvement methods.The conventional dynamic compaction method involves lifting the hammer to a predetermined height,detaching the hammer from the hook,and then freely falling to compact the foundation to achieve the purpose of strengthening the foundation,which is the unhook-hammer dynamic compaction process.In recent years,in the construction of low energy level dynamic compaction,especially in the construction of dynamic compaction with energy levels not exceeding 4000 kN·m,there has been a phenomenon of non unhooking dynamic compaction construction with a single steel wire rope falling together,which is the hook-hammer dynamic compaction process.Due to the non unhooking,continuous construction,and high efficiency during the construction process of hook-hammer dynamic compaction,there is a trend towards low energy level hook-hammer dynamic compaction.During the construction process of hook-hammer dynamic compaction,due to the falling of the hammer with steel wire rope,internal resistance of the winch,and safety reasons,the acceleration of the hammer is less than the free falling acceleration,resulting in a certain amount of energy loss.This article conducts a comparative study on the effects of hook-hammer dynamic compaction and unhook-hammer dynamic compaction through engineering measurement.From the perspectives of the hammer landing speed and the depth of different energy levels of dynamic compaction pits,it is analyzed that the energy loss of hook-hammer dynamic compaction is about 25％higher than that of unhook-hammer dynamic compaction;The pit depth of hook-hammer dynamic compaction is 20％-23％less than that of unhook-hammer dynamic compaction.According to different energy levels,in order to achieve the same reinforcement effect as unhook-hammer dynamic compaction,a hook-hammer dynamic compaction hammer needs to increase the lifting height by 3-7m or increase the number of compaction blows by 40％.The research results of this article can provide scientific guidance for the standardized application of hook-hammer dynamic compaction method in dynamic compaction design and construction.
unhook-hammer dynamic compactionhook-hammer dynamic compactionenergy losslanding speeddepth of compaction pitdynamic compaction development
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