Analysis On The Driving Process Of Open-ended Pipe Pile Considering Plugging Effects

The prestressed high-strength concrete pipe pile has been widely used in highways,large span bridges,high-rise buildings,ports,residential buildings,terminals and other projects because of its high bearing capacity,high cotrollability,low cost,good construction speed,good adaptability and good seismic performance.As the pile is part of the squeeze pile,in the process of piling will produce squeezing effect,the soil around the pile will produce horizontal displacement or vertical uplift,which may lead to adjacent building(structure)of the surface cracking and structural damage,road uplift,underground pipeline fracture and other engineering accidents.Which may have a negative impact on the surrounding environment,so the analysis of the pile pile pile process has important theoretical and engineering significance.In this paper,considering the effect of the plug on the open pipe pile,the stress deformation mechanism,the squeezing effect and its influencing factors in the pile pile of the open-ended pipe pile are further studied.Firstly,both domestic and foreign research status are summarized and analyzed.The mechanism of stress deformation in the process of pile piling is analyzed.The paper discusses the mechanism of pile sinking,the estimation of pile resistance,the determination of end pressure and the calculation method of ultimate bearing capacity of pile.On the basis of this,the relationship between the ultimate bearing capacity of the pipe pile and the pile force is described.Secondly,According to the formation process and mechanism of soil plug,the forced state of soil plug is analyzed,and the balance equation of unit plug is established,the expression of the total load in vertical is also obtained;the plug would be regarded as a "pile in the pile",then the formula of pile end bearing capacity limit of it is reduced,which is based on the ultimate bearing capacity model theory that is put forward by Terzaghi K,accordingly,the expression of he soil critical height in the process of driving is derived.Furthermore,the theory of hole expansion is briefly introduced,and it is applied to elastic-plastic analysis of the soil of pipe pile.At the same time,considering the soil plug effect of pipe pile,the expressions of radius of plastic zone and soil displacement are deduced.Finally,through the project example one,the conclusion is drawn that these expressions are appropriate by comparing and analyzing the results of theoretical calculation and engineering examples,and the influence of the factors such as radius-thickness ratio,the cohesion of soil and roughness of the surface between piles and soil are also discussed.It is concluded that the height of the soil is increased with the increase of the radius-thickness ratio,and decreases with the increase of the surface roughness between piles and soil,but the cohesion of the soil has little effect on the height of the soil.