Research On Portal Double-row Piles-anchor Combination Supporting Structure Applied In Deep Excavation

In recent years, with the rapid development of urbanization and limitation of land resources, urban underground space has been fully utilized. The area and depth of foundation pit generated by the high-rise building structure are increasing gradually. And these are generally located in the buildings, roads, underground pipelines, subway and other relatively dense urban centers. Excavation the complexity of the surrounding environment increases the difficulty of engineers on the design of deep excavation. So, due to the structure itself limitations and applicable conditions of traditional support structures, a new supporting structure of portal double-row pile has developed rapidly in the last decade. Because the lateral stiffness of portal framed structure is relatively larger, it relatively better control the deformation, and the construction is simple.With the advantages of its own structure, the portal double-row piles supporting structure is more and more widely in deep foundation pit. With the continuous development of foundation pit engineering, in order to further meet their security and control excavation pit deformation of the surrounding environment requirements, setting prestressed anchor in the portal double row piles to increase resistance overturning safety factor of structure and control the deformation of its structure and surrounding environment. Therefore, portal double-row piles-anchor combination supporting structure is applied in deep foundation pit.Currently, the theoretical and experimental analysis of portal double-row piles-anchor combination supporting structure is still relatively lacking. Its theoretical study is far lagging behind the practice.It is need for further study of its theoretical analysis and improvement in order to make a guidance for the practical engineering.Through research and study the status quo and application in the engineering instance of portal double-row piles-anchor combination supporting structure, this paper in view of the portal double double-row piles-anchor combination supporting structure properties and its influencing factors, the theoretical analysis and numerical simulation method was adopted to study and analysis the structure. The main research contents and conclusions are the following several aspects:(1) Summarizing and analyzing the soil pressure, single-row pile-anchor retaining structure and the computational theory of portal double-row piles, and combination of the above theoreties, a improved theory based on classical soil pressure and calculating method of portal double-row piles-anchor combination supporting structure are proposed to analyze the distribution of earth pressure and internal force of supporting structure. The Bending moment of the supporting structure was similar to the distribution of "S" type. And the anchor suppresses the deformation of supporting structure and the development trend of bending moment(2) The supporting structure of the internal force are analyzed when the coupling beam is connected to front and back row pile rigidly, articulated, rigidly to front and articulated to back three situations. The rigidly situation structure of the internal force distribution is the best, rigidly to front and articulated to back is better and articulated is the worst.(3) For an engineering example, using ABAQUS finite element software numerical simulate portal double-row piles-anchor combination supporting structure. Analyzed the variation of internal forces and deformation of the supporting structure, and compared with the actual monitoring data analysis. Calculated and measured values are more consistent variation, both the maximum deformation error of about7%.(4) Respectively research the factors including portal double-row piles after pile spacing, the length of supporting piles, the stiffness of coupling beam, soil strengthening inside pit area, and the soil strengthening between the front and back row pile to affet the supporting structure force and deformation.Analysis found that in these factors, the row spacing between piles, soil strengthening between the front and back row pile, and soil strengthening in passive zone bottom have greater influence on the supporting structure.