Experimental Study On The Model Of Pile-soil Displacement Shear Failure In Micro Uplift Pile

With the rapid development of urbanization in our country,the development and application of underground space are more and more widely,especially in the underground space,more and more attention has been paid to the problem of anti uplift.As a main form of the resistant drawing foundation,we urgently need to use a general theory to ensure the safe use of uplift pile.Under this background,this paper reviews the relevant uplift pile on the basis of research achievements at home and abroad,by the field test and theoretical analysis,the bearing capacity of tension piles with uniform cross section has been studied in depth and great achievements have been obtained.In this paper,the following research content:(1)Expounding the research significance and the development history of the uplift pile,summarizing the domestic and foreign related research results of uplift piles,including theoretical analysis,field test and numerical simulation analysis,etc,then on the basis putting forward problems and resolved.(2)Through the field full-scale test,comparing and analyzing of the uplift bearing characteristics of the prefabricated piles and the cast-in-place pile,and then calculating and finishing the test data,we obtain the load-displacement curve,pile axial force distribution curve and the situation of pile-soil failure,etc.The results show that the pull-out performance of cast-in-place piles is much larger than that of precast piles,and this can be widely used in practical engineering.(3)Analyzing and studying the variation of load-displacement at different pile lengths and pile diameters,and the distribution law of axial stress of loading.The static load test is carried out after the soil-water immersion test or the horizontal load of the pile is applied to the pile end.The bearing capacity of the test pile is compared with piles that are unloaded,and the reason of the changes of bearing capacity is analyzed.Through the experimental study of the pile,a reasonable design and construction method of the uplift pile is put forward.(4)According to the destruction state between pile and soil in the field test we found that: the relative displacement between the pile and soil did not happen,but the soil shear failure occurred in the soil around the pile.And with the increase of drawing load,the stress caused by the force transfer to the soil causes the shear strain of the soil,forming the shear limit equilibrium system in the soil around pile.Based on the shear failure mechanism and the limit equilibrium system,the displacement shear failure model of pile-soil is established,and also deriving the uplift ultimate bearing capacity equation under the displacement shear failure model of pile-soil.(5)Comparing with the traditional calculation method and calculation method of the pile-soil displacement shear failure,considering more factors,such as pile length,pile diameter and soil physical parameters(unit weight,cohesion,internal friction angle)and ground load etc,making the calculation more suitable to the practical situation.The calculated results are more close to the measured values in the field,proving the correctness of the theoretical analysis and the equation of capacity carrying.(6)Using finite element analysis software ADINA to establish the pile-soil displacement shear failure model,determining and solving the constitutive model of pile,the constitutive model of soil,the contact model of pile and soil,the treatment method of initial stress and the boundary conditions and so on;By comparing the finite element simulation with the experimental results,it is found that the ultimate bearing capacity and the load displacement curve of the single pile are approximately the same,and the mechanism of pile-soil displacement nephogram is similar to the shear failure mechanism;It is shown that the simulation results well reflect the bearing capacity of uplift piles,and further proving the correctness of the pile soil displacement shear failure model.(7)The result of field test,theoretical analysis and numerical simulation are compared to further verify the correctness of the pile-soil displacement failure mode.At the same time,according to the uplift performance of pile and the distribution of piles axial force,the design and construction resources of anti uplift piles are optimized.Under the premise of ensuring the quality,safety and the needs of practical engineering,making it more reasonable and economic.