Study On Effective Reinforcement Depth Of Dynamic Compaction Of Backfilled Sand Foundation

The dynamic consolidation method has been widely used both in China and abroad since it invented in 1969.A series of advantages of the dynamic consolidation make it quickly become the popular ground treatment method.The dynamic consolidation is widely used due to their simplicity,high efficiency,and low cost.However,at present,there is no unified argument for the calculation of the effective reinforcement depth of thedynamic consolidation.There has been no authoritative definition and thecalculation method of the effective reinforcement depth of the dynamic consolidation.From the study on the mechanism of the dynamic compaction strengthening the foundation,it can be found thatthe main reason for this situation is due to the complexity and variability in the definition of the effective reinforcement depth.In this paper,the calculation of the effective reinforcement depth of the dynamic consolidation is determined in the construction project of the newly backfilled sand foundation.We use the MIDAS GTS/NX finite element analysis software to perform simulation test analysis on each major influence factor.Using dimensional analysis,we ensure that the calculated formula meets the requirements for equal dimensions and formula deduced.Get the following conclusions:(1)Research on the main influencing factors of dynamic consolidation method.In this paper,three-dimensional finite element simulations of the eight main influencing parameters affecting the construction of dynamic compaction are performed,and the stress and strain states under the influence of various parameters are obtained respectively.The conclusions are as follows: With increasing compaction energy,the depth of effective reinforcement of dynamic compaction gradually increases,and the compaction energy can be positively correlated with the effective reinforcement depth within a certain range.The larger the rammer size is within a certain range,the smaller the value of effective reinforcement depth for compaction,and the effective reinforcement depth will decrease with decreasing rammer bottom area.And there is a critical value in the size of the rammer.The number of dynamic compaction attacks increases within a certain limit,which is conducive to the increase of the effective reinforcement depth.There is a1/5th power positive correlation between the twoparameters.The main factors that affect the degree of effective reinforcement depth in the soil are analyzed as follows: dry density,Poisson’s ratio,compression modulus,and void ratio.Among them,soil dry density is inversely proportional to it,Poisson’s ratio is proportional to it.(2)Finally,this paper derives the empirical formula for effective reinforcement depth calculation:And the value of the correction coefficient was determined to be 0.66.(3)Compare the deduced formula with some sample data in a project.Select the test data of the backfill sand construction of an airport project in Nanchang and verify the applicability and accuracy of the formula.The maximum deviation between calculated and measured values is 6.4%,while the minimum deviation is only 0.4%.Therefore,this formula has certain applicability.