Analysis And Research On Settlement Mechanism Of DX Group Piles

Multi-section Rotary excavation and squeezing and expanding cast-in-place piles have achieved good results in providing pressure resistance and controlled settlement.However,the research and analysis of settlement displacement of multi-section Rotary excavation and squeezing and expanding cast-in-place piles are still relatively small.Due to the particularity of DX piles,the formula for calculating the settlement displacement of a straight bored pile is not suitable for the calculation of the settlement of the DX pile.The calculation of the settlement of the rotary pile is relatively vague in the code,and does not consider the various factors affecting the settlement of the DX pile,so it seriously affects the application and development of this type of pile in engineering.Based on the research status at home and abroad,this paper discusses different codes and different theories,and applies the combination of numerical simulation and theoretical analysis to analyze the settlement mechanism,force characteristics and settlement displacement calculation of multi-section rotary excavation and squeezing and expanding cast-in-place piles.In order to provide a reasonable basis for the settlement calculation of pile foundation,it also provides some ideas and suggestions for the application of pile type in engineering.This paper mainly draws the following conclusions through research:(1)Under the same load conditions,the ratio of the settlement of the DX pile and the straight hole pile under the same conditions gradually decreases with the increase of the external vertical load and finally stabilizes.The curve of the change is roughly divided into three stages.First,the settlement ratio decreases sharply with the increase of external load.The external load at this time is mainly between the proportional limit of the settlement curve of the straight hole pile and the proportional limit of the settlement curve of the DX pile.Subsequent settlement ratio decreases slowly with the increase of external load,at which time the external load is located after the proportional limit of the DX pile settlement curve and before the curved sinking section.Finally,the settlement ratio gradually becomes smooth with the increase of external load.At this time,the external load is located at the curved sinking section of the DX pile settlement curve.At this stage,the settlement rate of the rotary-excavation and grouting pile is basically kept constant.(2)In general,the influence of various factors on the settlement ratio is relatively large,and the settlement ratio is negatively correlated with the variation of pile spacing,disc spacing,disk position and disk diameter ratio;the settlement ratio is positively correlated with the length to diameter ratios and the number of piles.(3)When the load reaches the proportional limit of the settlement of the straight hole pile,the settlement ratio under the influence of factors such as disk position,disk diameter ratio and disk spacing increases with the increase of the proportion of the resistance of the DX pile end,and the settlement ratio under the same load condition is smaller than the pile end resistance ratio.Mainly because of the existence of the bearing plate,the additional stress of the surrounding soil of the pile is diffused to the surrounding,thus reducing the diffusion of axial stress.It can be seen that the DX pile has strong sedimentation ability.When the load reaches the proportional limit of the settlement of the straight hole pile,the settlement ratio under the influence of the length to diameter ratio and the pile spacing increases gradually as the ratio of the pile end resistance increases.At this time,the capacity of the bearing plate to reduce the axial force is weakened,that is,The ability of the DX pile to control settlement is weakened.(4)By analyzing the settlement ratio under the influence of different factors,when the DX pile bearing plate can play a good role,the settlement ratio at this time varies from 0.3 to 0.5.