Experiment And Numerical Simulation Study Of Post-grouting Reinforcement Mechanism Of Pile Foundation Based On Slurry Control

Bored piles are widely used in high-rise buildings,bridges and other projects because of their high bearing capacity and wide application range.The construction technology of Bored pile leads to the generation of mud skin on the side of the pile and sediment at the bottom of the pile,which greatly weakens the bearing capacity of the pile,which will seriously weaken the bearing capacity of the pile.Through high pressure grouting,the negative effects caused by the mud skin and the sediment can be effectively improved,the bearing capacity of pile can be greatly improved and the settlement of pile top can be reduced.The slurry diffusion is related to the permeability,strength,slurry type and grouting pressure of the grouting stratum,etc.The weak position or large pore of the injected stratum is the slurry diffusion area,forming an irregular slurry pulse,which may deviate from the pile foundation and cannot realize the effective reinforcement of the pile foundation.At present,the grouting reinforcement mechanism is not clear,the grouting diffusion is not controllable,the construction technology is not mature,and relevant research needs to be carried out.In order to improve the effective utilization rate of slurry and control the retention of slurry within the required range,the "slurry controllable" grouting reinforcement of pile foundation is proposed.Based on the reconstruction and expansion project of Dezhou(Hebei province borders Shandong Province)to Qihe of Beijing-Taiwan Expressway,this paper deeply studies the improvement effect of different grouting schemes on pile foundation bearing capacity by means of theoretical analysis,field test and numerical simulation.The main research contents and results are as follows:(1)Through literature review and theoretical analysis,clarify the relationship between grouting parameters and solid form size,establish the "slurry controllable" grouting reinforcement and solid form calculation formula,based on the slurry return calculation formula,considering the rotating slurry head injection disturbance and curing the soil on the pile side,the calculation formula of "slurry controllable" grouting reinforcement pile foundation is established.(2)The self-developed self-rotating grouting device has carried out the field test of the slurry diffusion law of the self-rotating grouting device,explored the influence of different disturbance pressure,static grouting pressure,disturbance time and water-ash ratio on the slurry diffusion form and the solid compressive strength,and revealed the influence law of the grouting parameters on the slurry diffusion.Based on the relationship of grouting parameters on slurry diffusion and reinforcement effect,the grouting parameters are optimized,and the design and calculation method of "slurry controllable" grouting parameters is proposed to provide the basis of the selection of grouting parameters in the field construction.(3)Mat DEM discrete element software is used to simulate the cutting of high pressure injection cement slurry,which reveals the influence of different soil depth on the disturbance of high pressure cement slurry.The width and depth of the disturbance area increase with the injection pressure,and the edge splitting degree increases with the increase of the injection pressure;the quantitative relationship between the injection pressure and the disturbance area form is established.The Mat DEM discrete element software establishes the calculation model of pile foundation bearing capacity with different grouting layers and grouting depth,which reveals the distribution rules of pile side friction resistance,pile shaft force,load and load-settlement.The results show that during single layer grouting,the ultimate bearing performance of pile foundation decreases with the grouting depth,and the adjacent layer grouting spacing affects the bearing performance of pile foundation,with the best adjacent grouting spacing,and the sharing proportion of multilayer consolidation body decreases from top to bottom.