Studies On Analysis And Optimization Design Of Soil Nailing Bracing In Deep Foundation Pit

With the utilization and development of high-rise or multi-rise building and underground space, there are more and more deep foundation pit projects in practical engineering. The difficulty tends to be more serious and the scale tends to be larger. Conventional design methods of foundation pit bracing cannot meet the need of today's development, especially for deep foundation pit located in poor and complicated geological condition. Soil nailing bracing techniques is a new technique with simple technology, low cost and short duration of construction. Compared with conventional bracing technology, not only soil nailing will actively support soil masses, but also interaction effect of soil nailing and soil masses will be mobilized leading to utilize in-site strength of soils to a maximum degree. The disturbed soil masses that originally induce loading effect on bracing structures are transformed into a part of bracing structures. Accordingly, the composite soil nailing bracing technique begins to be applied to reinforcement of soft soils or foundations. However, the working mechanism and design methods of the composite soil nailing bracing technique are not well known and further studies need to be made. Therefore, this thesis focuses on this special topic and the following fundamental studies on the related issues are performed.Firstly, an overall evaluation on design method and computational theory of soil nailing wall that is widely applied in the deep foundation pit bracing are made. The related issues are examined. Three-dimensional nonlinear numerical computation based on finite element method is conducted to analyze internal forces and deformation of soil nailing as well as working mechanism. At the same time, stability analysis is made. Furthermore, the optimization design of composite soil nailing bracing is performed for a case study. The results and conclusions are helpful and valuable for the soil nailing bracing.In the case study of deep foundation pit of Dalian Zhongyin Mansion, the discussions are emphasized on how to analyze and modify the previous design according to practical engineering geological conditions, periphery surroundings and the construction organization process and others. Furthermore, optimization of bracing design for the project is done considering construction technology and urgent measures. The practical significance of dynamic control and informationized construction in deep pit bracing is shown.