Mechanical Behavior Analysis And Engineering Application Of Double-Row Piles Of Deep Foundation Pit

Double-row piles is a new kind of supporting structure that was developed on the basis of single row piles in recent years, The double-row piles has a much higher lateral stiffness compared to the single row soldier pile,This makes the lateral deformation of retaining structure is much smaller.compared with the pile pile brace type,it can be designed in a cantilever manner without any struts,which makes it cost lower,excavate more conveniently and shorten the construction duration.Especially in the coastal soft soil and soft clay area, the depth of double-row piles supporting is very deep,because the synergy of coupling beam, the double-row piles can be made to form a kind of similar to the door frame system of the spatial structure,which make the whole stability is good,at the same time,the soil between the double row piles can form a kind of "soil arching effect",that the earth pressure when the thickness reaches a certain value of deep soil reaches the maximum value and remain unchanged,which make the space effect of retaining structure with double-row piles is very strong,that can satisfy the deformation control of most of the environment.However,until now double-row piles have no unified calculation model, and there is no mature design method,also the mechanism is not entirely clear,most of the existing double row pile design on the basis of experience.The study of double row piles is lagging behind the engineering practice, the experimental data were few,the mechanical properties and working mechanism of double row piles is also a lack of system of further research,especially the factors affecting the mechanical properties of double-row piles such as different pile spacing and row spacing, different pile length, different excavation depth,pile stifess,the passive zone between reinforcement,pile reinforcement of soil,construction loads, the pit in pit,how these factors effect the deformation and stress distribution of double-row piles.At the same time the crown cantilever beams of double row piles and how the stress coordination is not clear,In addition the spatial effect of double row piles is also lack of deep study.In this paper, the numerical simulation and engineering example of double row piles is studied respectively,the main work and conclusions are as follows:(1) In order to get the research status of double row piles, this paper refer to and organize a large amount of associated with double row pile research papers,mainly from the theoretical research, experimental study, numerical simulation model, combined with the actual engineering and monitoring from four aspects of the study are summarized the research status of double row piles,The existing computational models are introduced in this paper.(2) Finite element software abaqus is adopted to establish the plane finite element model of double-row piles,the Drucker-Prager soil model was used,form different excavation depth when conditions are simulated,the moved under different working conditions and the pile bending moment were analyzed.(3) On the basis of the basic model, by changing the parameters of pile is studied different pile spacing and row spacing, pile length and pile body stiffness, different stiffness of coupling beam and passive zone between pile reinforcement, reinforcement of soil and construction load cases, pit pit and other characters of bearing force and deformation of double row piles, the influence of the optimal parameters for optimal design of parameters of double-row piles.(4) Take Jingzhou Wanda plaza project of deep foundation pit as an example, the design idea and the supporting schemes was introduced,finite element software abaqus was used to establish a three-dimensional finite element model of the excavation, the stress and deformation of the double-row piles were analyzed in the process of excavation.The simulation results and the site monitoring results are compared and analyzed, and compared with the theoretical calculation results,the results show that the numerical simulation results closed to monitoring results, but smaller than the theoretical value,that established by using abaqus finite element model of basic credible, partial conservative traditional theory calculation.(5) the force and deformation characteristics of the double row piles and anchor composite supporting structure were studied.abaqus was used to establish the finite element model of two two adjacent foundation pit excavation in Wanda plaza,double-row pile stress and deformation, settlement rules, the tensile stress of the anchor cable were analyzed of two two adjacent foundation pit excavation under the conditions of symmetric and asymmetric conditions between adjacent foundation pit excavation.the conclusions provide practical reference for the similar symmetric and asymmetric excavation adjacent foundation pit.