Study On Deformation And Stress Of Pile-anchor Retaining Structure In Excavation Of Deep Foundation

With the rapid development of China’s economy,a variety of high-rise buildings and underground engineering continue to emerge,various forms of deep foundation pit engineering is also applied more and more widely in major cities.Pile-anchor retaining structure system plays the leading role in the foundation pit support structure,due to the advantages of convenience in making measures,the need of small space,the strong ability to control the deformation of foundation pit and so on.However,because of the lack of design and knowledge in the support system,especially in the traditional design theory and most numerical analysis models,there are still some defects,which makes the construction can not give a more reasonable solution,leading to frequent accidents.In this paper,the pile-anchor retaining structure is studied,and some problems such as traditional support design method,defects of foundation pit numerical model,anchor anchoring performance and force characteristics,and application of engineering examples are discussed and studied.(1)The design and calculation scheme of the traditional pile-anchor support structure based on the elastic fulcrum method is introduced in details.The existing problems of this method are pointed out,that is,each working condition is independent of each other,the calculation result is distorted,and the complexity of the calculation process caused by the waste of resources and time.(2)Based on the ABAQUS finite element software,the finite element numerical model of the foundation pit is established,and the deformation of the foundation pit and the axial force distribution of the anchor are simulated under different working conditions.Then,the design parameters of the anchor,further analysis of the impact of deformation of the foundation pit.Finally,compared with the traditional design method of pile-anchor support structure,the numerical simulation has obvious advantages.(3)Through the simulation of the axial force of the anchor,the defects of the whole numerical model of the foundation pit are found,that is,the whole model of the foundation pit can not consider the contact between the anchor,the anchor solid and the soil.In order to study the mechanical properties of the bolt in depth,the numerical model of the anchorage resistance of the bolt is established by means of the uplift test of the bolt.Accordingly,the relationship curve between the pull load displacement is obtained,the transmission characteristic of the anchor force and the distribution of the side friction are also studied.Furthermore,the influence of different confining pressure and anchoring section length on the anti-uplift performance of the bolt is explored.In this paper,based on a deep foundation pit engineering of a commercial center in Xi’an the traditional design scheme,numerical simulation analysis,bolt tapping test and simulation are combined with each other to the,explore the deformation and stress pattern of the pile and anchor support structure in deep excavation.The conclusions may provide guidance for the construction of similar pit engineering in Xi’an area,and also provide reference for the predicting the deformation of the foundation pit and the performance of the bolt.