Model Experimental Study On The Mechanical Behavior Effect Of Around Composite Foundation Under Dynamic Compaction Vibration

Accompanied by economic reform in China, and the rapid development of economy,the development of city space getting smaller, people have to built the larger buildings onthe bad foundation, so civil put increasingly higher requirements on foundation, it isinevitable to deal with the bad foundation. At present, some projects which stand inCaofeidian industrial zone are carrying on, but the area is located in the coastal zone,mostly surrounded by sea on filling the land, and the foundation has low bearing capacity,we must adopt some foundation treatment. As the dynamic compaction is one methodthat suitable for kinds of soil layer, construction shortcut, using simple construction tools;and the effect of the geotechnical which processed by the dynamic compaction, could fullplay, and the chemical composition of the geotechnical would not change; and thisconstruction method will not destroy its surrounding environment, so the dynamiccompaction is the first choice in the foundation treatment. However as the different ofconstruction sequence, the huge vibration which produced by the dynamic compactionmay destroy the existed underground buildings and structures, so the research of thepower transmission mechanism and the dynamic compaction produced the influencingfactors must be imperative, when the hydraulic fill foundation was strengthening bydynamic compaction.The subject uses a model test and theoretical analysis method to study the decaylaws of the dynamic compaction in vibration on filling foundation and the influence ofmechanical properties of the composite foundation on surrounding. The main researchcontents include: through the indoor model test, it researches the propagation law ofvibration wave in the vertical and horizontal transmission under the different tampingenergy；and it also researches the vibration of dynamic compaction effects to the piledirection of the tensile stress and the level of impact on the role of the pile； at the sametime, it researches the transferring law of the vibration of dynamic compaction in thecomposite foundation and the failure mechanism of the composite foundation. The mainconclusion: soil pressure in horizontal and vertical direction were relatively substantialattenuation and the vertical soil pressure far outweigh the level, and changes of thevertical soil pressure could be used to reflect the rammer strike effect to the soil which is produced by the dynamic compaction；because of the soil damping effect, with thedistance of the change, dynamic compaction vibration rapid decays,and it decays fast inthe near and slow in the distance； in composite foundation, the change of theacceleration in the horizontal has a significant attenuation trend. Although the distancebetween piles is short, the acceleration attenuation is bigger；this can explain that thepiles have a blocking function to vibration transmission of the dynamic compaction；the dynamic compaction would destroy the piles of those in the composite foundation,and the failure position will appear in the areas on the top of the piles, This is consistentwith damage of the field construction；the tamping energy and the ramming strikedistance are two crucial factors of the effects to changes of the composite foundation；The effect of level impact and the vertical tensile stress produced by the dynamiccompaction vibration is the main cause of the failure mechanism in the CFG pilescomposite foundation. The research result of this subject provides a theoretical basis forguiding reinforce coastal areas on filling the foundation design and construction.