Research On Calculation Models And Numerical Simulation Of Deep Foundation Pit With Double-row Piles

Take part of the piles from the concentrated single-row piles backward, link the piles'top with top ring beam and link beams, then will get double-row piles retaining structure. Compared to single-row piles retaining structure, this kind of retaining structure can provide with more lateral stiffness, less lateral displacement of soil, as well as the ability of supporting deeper foundation pit. Furthermore, it works without brace and for it's excellent mechanical behavior, this kind of retaining structure has the advantage of shorter construction duration, facility and lower cost. It has gradually have the priority considered form of the deep foundation pit. Though there are several kinds of calculating model about the double-row piles retaining structure, but there is not a recognized model which can reflect the affect of distance of the two pile rows, the stiffness of the ring beams and the slenderness ratio of the piles, for the reason that the calculating theories about double-row piles aren't complete, and somehow, the practice develops faster than the theory. In addition, the national and the local technical specification just have a little advising and regulation about double-row piles retaining structure. This paper analysis the difference between double-row piles and single-row piles retaining structure, the working mechanism and affecting factors of double-roe piles retaining structure. The calculating and analysis are based on a deep foundation pit in the area of Hankou, which supposed to adopt single-row piles retaining structure, multi-braced piles retaining structure and double-row piles retaining structure respectively.Firstly, analyzed and summarized several calculating theories about the single row piles with mult-layer bracing system. On the base of elastical resistance and limit balance methods, discussed and analyzed the influence of different distance of piles, the height of slope, and the position of fulcurm to the moment, designed length of piles, the reaction of the bracing system and the stability of the deep foundation pit.Secondly, substituted the single-row piles retaining structure with double-row piles retaining structure on the similar engineering condition, calculated and analyzed the distribution of the moment and displacement of the double-row piles, based on the initial engineering condition. According to the initial engineering condition, change the sharing rate of earth pressure, the distance of the two rows and piles when in the same row respectively, calculate and discuss the diversification on the moment and displacement of double-row piles retaining structure. Furthermore, summarize and analyze the characteristic of double-row piles retaining structure.Lastly, use the finite-difference software to establish models and carry on the numerical simulation to simulate the excavation on the initial engineering condition of the same double-row piles retaining structure, compare the results with the conclusion based on elastic resistance method. Summarize the results when change the distance of the pile-rows and link beam stiffness respectively, analyze the results'differences and changing law.