Theoretical Analysis And Numerical Calculation Of Retaining Structure With Double-row Pile

With the rapid development of three-dimensional urban space, as well as the rapid development of urban constructions in large numbers, the foundation pit appear, due to the demand for building the upper structure, the excavation is becoming deeper and deeper. For pit excavation, it is a greater challenge for civil engineers how to reasonably calculate, check and design the braced system.Compared with single-row pile retaining structure, the lateral stiffness of the double-pile retaining structure is more, and this kind of retaining structure can provide with less lateral displacement of the structure; And the ability of supporting deeper foundation pit. At the same time, this kind of retaining structure has the advantage of shorter construction duration, not to set up support, excellent mechanical behavior, facility and lower cost. So it has the priority considered form of the deep foundation pit engineering. In recent years,the double-row pile retaining structure is a new type structure, which is used in the deep foundation pit engineering. It is the crown by two parallel piles,and link the piles’ top with top ring beam and link beams. Which is formed similar to the structure of the portal frames system. Compared with the other supporting structures, this retaining structure has a lot of advantages: firstly it has greater lateral stiffness and better overall stability, and spatial effects, limit the deformation of retaining structure effectively, secondly the restraining depth of this structure is deeper than other restraining structure, finally it need not support, so do not need to dismantle, shorten the construction period, convenient construction and the cost of investment costs are not high, etc. Some of the previous project examples show that the double-pile application prospects are very promising, especially for soft soil layers, the better. At present, the experts and scholars did not study the pile-soil interaction mechanism clearly, there is not have unified computational models and methods, there is no specification to make appropriate provisions. Pile spacing, row spacing, pile diameter, the influence of force and deformation to supporting structure caused by different pile stiffness and different pile soil awaits further analysis and study.The thesis summarizes the following content:collect a large number of papers which are related on Double-row pile retaining structure, research and analysis various models and calculation theories, and further improve double-row pile theory. Based on the basic idea of elastic foundation beam method, a designing and calculating theoretical model has been put forward to. Internal force and deformation of double-piles in Taiyuan pit project are calculated using aforementioned procedure. Excavating and supporting process of double-row piles deep foundation was simulated, and the change law of soil displacement field on pit boundary during the process of excavation was analyzed by using finite difference method analysis software Flac3d. The calculation and analysis of the structure in the double pile bending moment and pile displacement distribution law to change a basic working conditions while maintaining the other conditions unchanged; According to the initial engineering condition, respectively, to change row spacing, pile spacing, and other parameters, calculation and analysis the distribution of the moment and displacement of the double-row piles, subject to the safe, economical and reasonable technical requirements of the engineering design is given a reasonable range, and ultimately achieve the purpose of optimization of the support structure design.