Analysis And Discuss For Large Excavation Retaining And Protecting Structure Computational Model

In deep excavation constructions, the choice and design of retaining and protecting structure are very important. With the development of the urban construction, more and more large scale and deep excavations appear. In order to increase its total stiffness, the bracing of the retaining and protecting structure is usually designed as a frame structure. Traditional computing model such as plane frame computing model, uncompatible space computing model etc. can not exactly reflect the general situation of displacement and internal force of the pit. In this dissertation, on the basis of the searches and studies so far available, 3D analyzing model is proposed and established for deep excavations. A practical engineering project is taked as example, both pieces of software "Qi-Ming Xing" and "3D3S" are adopted to carry out the numerical studies for planar and space frame models respectively, and finally some meaningful conclusions are obtained.The main contents of this dissertation are as follows:1. The traditional plane computing method and traditional elastic footing beam method are modified. One-way soil spring is adopted to carry out 3D anlysis for the retaining and protecting structure. Spatial beam element a instead of planar truss element is adopted to model theretaining and struting structure. Sub-structure mothed is used to simplify the pill wall.2. Specifically for typical deep excavation shoring project, numerical analyses are carried out in software based on plane frame computing model and compatible space computing model respectively. The displacements and forces of the retaining and protecting structure for every condition of the construction process from planar and space models are compared and investigated.3. Compatible space computing model is established in which neither the plane bracing equivalent stiffness, nor the plane additional restrict shall be defined. The compatibility of the deformations of pill wall and bracing system is realized, which accords with the actual situation more than the traditional computing model.Finality, the problems requiring further studies are discussed.