Research On Deep Pit Foundation Support Related Problems For Lanzhou Center

Deep pit foundation engineering encompasses a wide range of applications, namely in: st ructural engineering, geotechnical engineering, environmental engineering and other multi—d isciplinary facets, coming together to form a comprehensive research, to consider the strength,stability and deformation, but also consider the problems with soil structure interaction. Beca use of the complexity of deep pit foundation, the excavation and supports, the theoretical rese arch, design and construction of deep pit foundation engineering are challenged. While under ground engineering scale continues to expand, the development and construction of the under ground engineering cost is getting higher and higher. The area of excavation surrounding inte nsive buildings, underground municipal pipelines and complex environmental geology have i ncreasing difficulty with traditional excavation getting larger and larger, thus the technology with traditional excavation has been unable to meet the needs of modernization. Therefore, th e problem need more in-depth research.Because of its superior mechanical properties and high cost performance,pile-anchor supporting structure has been used in a growing number of domestic and foreign excavation project. Anchor and piles are two different structures, the combined system of the two groups accepting the situation is more complicated with not only the interaction between structure and soil being taken into account, but also the rational allocation of anchor piles and the force. Under normal circumstances, the axial deformation modulus is greater than the axial bolt deformation modulus of rock and soil. Limit equilibrium method, elastic foundation beam method and the finite element method are three methods to calculate the internal force of anchor piles supporting structure, in which the finite element method is an effective and widely adopted method of simulating the excavation problems in foundation engineering. Lanzhou center deep excavation belong to large, ultra-deep excavation, and the project implementation process is influenced by various uncertain factors, including the foundation pit excavation, rainfall and dynamic load, therefore it is significant to make an in-depth study of the project.Combining with the project of Lanzhou center deep foundation pit, the deep foundation pit engineering under complex geological conditions supporting the problem carried on a research into the methods of theoretical analysis, computation and numerical simulation of the comprehensive use and also researching the control deformations, due to the deep foundation pit construction and excavation. The dissertation summarizes the current research status, the application of deep foundation pit bracings for the deep foundation pits, in terms of their advantages and disadvantages, and then researches the supporting forms of the pile anchor for the retaining mechanism. The computational methods used were established by the aid of the finite element analysis software, Midas/Gts for the model analysis incorporated within the reasonable excavation of prestressed anchor cable, embedded depth of supporting pile, retaining pile stiffness and other factors on the influence of internal forces for the supporting structure of the foundation pit and the deformation pattern of the foundation pit.After the excavation of deep foundation pit, displacement of soil settlement around deep excavation constantly increasing.The increasing trend consistent, pit deformation has obvious temporal effect, as the internal structure of the internal structure of support system construction completion of pit deformation gradually stabilized. The horizontal displacement of deep pit engineered foundations for the Lanzhou Center project meets the standard requirements for the settling deformation of the anchor position and reasonable settling depth which contribute to the advantages of the pile anchor supporting system. The use of pile as a retaining structure can be seen that, the stress and deformation performance by the pile body becomes far less than the pile anchor retaining structure and the anchor can greatly reduce the stress properties of the horizontal displacement of the foundation pit and pile. The role of the size of the prestressed anchor affects the deformation of the foundation pit and the supporting pile bearing performance for within a certain range, the deformation of the foundation pit decreases with the increase of prestress, whereas the bending moment of bored pile increases with the increase of prestress, thus, the design of the pile supporting anchor and the selection of a reasonable prestress all give full play to the advantages of this form of support which can in return yield good economic benefits. The deformation of the foundation pit with bored pile stiffness increases as the deformation increases the drilling pile stiffness to some extent that can control the foundation pit. The same trend was observed in the results of the finite element simulation and measured values; the analysis of the model can predict the horizontal displacement of the top of the pile and the foundation settlement which can be used to guide the field construction.