Bearing Mechanism And Stability Evaluation For Dynamic Replacement Gravel Pier Composite Foundation

It also has the great advantage of dynamic replacement and drainage consolidation to reinforce soft foundation. Dynamic replacement method is based on dynamic compaction, but they are very different. However, the current research work is very scarce for dynamic replacement, references are extremely rare, and the mechanism is not clear. This article combined with Dalian SkyCity actual project, around basic characteristics and bearing mechanism of dynamic replacement gravel pier composite foundation, the following studies were carried out.In summary, on the basis of analysis of the basic characteristics of dynamic compaction gravel pier, it was discovered that the pier produced a significant swelling effect when subjected to hammering. Obviously, the ratio of pier gravel surface and the area of surrounding reinforced soil could not accurately reflect the actual engineering replacement rate of composite foundation. The concept of volume replacement rate was proposed, and it was expressed by the volume ratio of piers and surrounding reinforced soil. Meanwhile the conversion relationship of volume replacement rate and area replacement rate was obtained, that was over the original area replacement rate multiplying an increasing coefficient a (a= 1.25-1.6) to indicate the volume displacement rate. Taking into account the effect of pier swelling, reducing the design pier diameter appropriately was put forward. Using two simplified models of drum and funnel determined the improved pier value that could be used on the project, and by means of numerical simulation proved the rationality of this method.Meanwhile, by means of finite difference software FLAC3D, the impact on the ultimate bearing capacity of cushion thickness, pier forms, pier diameter, the replacement rate and other factors were considerd. Three-dimensional numerical models of composite foundation in different operating conditions had been established. It analogd and discussed the variation of ultimate bearing capacity with these factors. It showd sphere of influence and provided a reference for composite foundation.The parameters of the dynamic replacement method were systematically discussed. Construction technology and quality control indicators and requirements of dynamic compaction gravel pier composite foundation were proposed. These compaction parameters and these parameters of numerical analysis were applied to the actual project. After construction the bearing capacity foundation was detected to verify the reasonableness of the parameters. Adopting the proposed volume replacement rate calculated foundation bearing capacity, indicating the rationality of this method.