The Research On The Controlling The Crack Of The Push-extend Multi-under-reamed Pile Under Action Of Vertical Tensile Force

In recent years with the increasing of the national economy, the development of cityconstruction and the development and utilization of underground space, it is gettingmore and more that different functions and types of construction projects and theconditions about bearing of vertical force of foundations of building or structure sothat the application of Push-extend multi-under-reamed concrete pour pile increasingcontinuously.It is in a certain condition of the early study stage seeing from the currentdevelopment situation.The Push-extend multi-under-reamed concrete pour pile can bea effective way to resolve the vertical uplift because of its special structure of pile.Not only the uplift bearing capacity is higher compared with other forms of pile,butalso it has some advantages that it can shorten the pile length, reducing the pilenumber, avoiding through some complex formation and saving working time andmaterials with the same uplift bearing capacity. Meanwhile the tensile bearingcapacity of concrete is low so it is a key problem that how to solve Crack-controllingunder the action of vertical force of Push-extend multi-under-reamed concrete pourpile.The crack can be controlled effectivity by means of setting prestressed steel andcontrolling of prestressing at the same time of improving the tensile ability of pile.According to the study of the aspects of setting principles, methods and specificationsof prestressing force confirmed a effective program to control the crack.And itprovides reliable basis for the uplift bearing capacity study of Push-extend multi-under-reamed concrete pour pile.In the paper it analyzes the influence of the prestressed reinforcement on pile bymeans of ANSYS software simulation and extrapolates the computational formula ofsetting prestressed reinforcement principles.The paper studies the features and benefits of Push-extend multi-under-reamedconcrete pour pile as a kind of uplift pile sufficiently and pile-forming methods of thepile which based on the development of the domestic and foreign and features andadvantages of Push-extend multi-under-reamed concrete pour pile; It analyzes theaffects on pile when setting prestressed reinforcement under the factors of disc diameter size and the plate location of single plate pile and disc slope angle and platespacing of double disk pile by software of finite element analysis of ANSYS. Itanalyzes the changing rule of the pile and the difference with other kinds of pile onthe basis of displacement of pile and pile soil, the change rules of stress and damagephenomenon.Combined with the result of software simulation analysis, it extrapolates thecomputational formula of setting prestressed reinforcement principles based on thechange rules of prestressed reinforcement of Push-extend multi-under-reamedconcrete pour pile.