A Simplified Calculation Method For Row-piles With Bracing With Consideration Of Deformation Coordination

With the development of urban construction, foundation excavation become deeper and deeper, bigger and bigger and the surrounding construction conditions become more and more complex, so how to ensure the safety of deep excavation and surrounding buildings become the chief problem, and the design calculation method is the key of deep excavation. At present there are many design calculation methods for deep excavation, and the main method is the elastic subgrade reaction method, which is recommended by "Technical specification for Retaining and Protection of Building Foundation excavation" (JGJ120-99). But the elastic subgrade reaction method exist disadvantages of the deformation incoordination and artificial constraints. Therefore, this paper propose a new kind of more reasonable and accurate calculation method based on summing up the advantages and disadvantages of present methods and analyze the irrationality of the elastic subgrade reaction method.On the basis of equivalent transformation model, this paper establishes a new simplified method, which realizes the deformation coordination spontaneously. The equivalent transformation model suppose each support pile as the elastic support,which act on the internal bracing structure, and transform active earth pressure into the equivalent joint load, which act on the fulcrum. So through the equivalent transformation the spatial model consisting of the piles-bracing-soil is transformed into the plane model consisting of the equivalent springs-bracing system-equivalent joint load and the iterative algorithm is used to solve the spatial coupling problem of multi-internal bracing system in the new method. The main characteristics of this method are as follows:1. This method roundly considers the interaction and retaining effects of each component of the retaining and protecting structure.2. This method transform the spatial problem into the plane problem, while realizing the deformation coordination spontaneously, and the calculation principle of this method is consistent with the spatial model's, So compared with Spatial Finite Element Method, this method not only can reflect the spatial effects of retaining system, but also is simple and convenient. Compared with elastic subgrade reaction method, this method don't need to set additional artificial constraints, which often lead to distortion of the force and displacement in the elastic subgrade reaction method, so this method don't exist the problem of deformation incoordination,and the results is more in line with engineering practice.3. This method can conveniently provide the dynamic simulations for construction processes of excavation, internal bracing structure, prestress, so it can consider the influence of construction stage on the row piles with internal bracing system. 4. The calculation and programming is simple, so we can program the professional design software of row piles with internal bracing system, which can largely improve the accuracy and convenience of design of row piles with internal bracing system.5. Consider the influence of tangential foundation resistance on the row piles with internal bracing system.