Analysis On Force-deformation Of The Double-row Piles Retaining Structure Under Earth Pressure At Nonlimit State

With the rapid development of social economy, the accelerated pace of urbanization, tall buildings, high-rise buildings are emerging and underground space is used, which come deep foundation pit engineering on larger scale. The traditional forms of retaining structure are unable to meet the requirements of the construction. Double-row piles retaining structure, which is developed and applied widely in recent years as a new form of retaining structure, has stronger anti-bending and greater lateral stiffness. Besides, it is greater in bracing depth than common bracing structures. It also has advantages such as simplifying the construction, shortening the construction period, low environmental requirements, high space utilization rate and good overall stability etc. So it has gradually become a preferred embodiment of the deep foundation pit engineering, and widely applied in various types of deep foundation pit engineering, especially in soft soil area. Although the double-row piles retaining structure has many advantages, there are still some issues worthy of further study, especially the problem relating to the earth pressure acting on the front and back piles, and that involving the influence of pile-soil interaction on stability of the retaining structure. The foundation pit engineering, which is often temporary, is out of work after foundation construction accomplished. Therefore, it is a great theoretical and practical significance to investigate the distr ibution mechanism of the earth pressure, and conduct all possible optimal design considering the satisfaction of the safety and stability of the deep foundation pit engineering, in the calculation process of designing double-row piles retaining structure.First of all, this paper discusses the features and mechanism of force-deformation of the double-row piles retaining structure based on the research state quo deep foundation pit engineering at home and abroad feature of main retaining structures. Besides, based on the existing research findings, it summaries several typical calculating models of double-row piles retaining structure as well as analyzes advantages, disadvantages and applicability of the models.The second, though assuming a basic calculatio n example, using finite element method of rod system to simulate the force-deformation of the double-row piles retaining structure, which is obtained in the discipline of deep foundation pit retaining engineering, under the Rankine earth pressure. And comparing to single cantilever pile, it also studies the mechanism of force-deformation of the double-row piles retaining structure. By comparative analysis of parameters, it discusses the rules on how elements like the spring stiffness at the bottom of the front and back piles, compressibility of soil between the double-row piles, row distance, pile stiffness and joint stiffness inflict an impact on the force-deformation the double-row piles retaining structure.The last, this paper analyses the deformation of the double-row piles retaining structure, and combining the relevant theory and calculation formula of earth pressure considering the influence of displacement, it is put forward that using the earth pressure under nonlimit state to calculate soil pressure behind the back row pile. And comparing the two kind of earth pressure, it is studied that the law of fore-deformation of the double-row piles retaining structure under the active earth pressure at nonlimit state.