Numerical Simulation Analysis Of Pile-Anchor Support System In Deep Foundation Pit

The construction land has become tighter with the development of cities andtowns in our country, which makes Foundation Pit Support increasingly constrainedby the ambient conditions, and the requirements of controlling the deformation ofexcavation has become stricter. Anchor pile bracing has been widely used for it hasstrong adaptability to the ambient conditions, and be able to better control pitdeformation, and the requirement of space for construction is small. It has been usedfrequently in the pile-anchor supporting design as an optimization design tools toexert pre-stress. However it may cause anchor overload or pile fracture by exertingexcessive pre-stress. The accident of the deep excavation has occurred because of theimproper design. Therefore, it is necessary to strengthen the research of pre-stressedcomputational theory and three-dimensional numerical simulation analysis, in order toguide practice better.With an example of pit supporting design of Paris square underground parkinggarage in Maanshan City, this paper researches the theoretical calculation and thestability analysis of the foundation pit, based on the detailed introduction to the theoryof the pit pile-anchor support design and calculation of earth pressure. In this paper,gives a detailed analysis of the deformation of the pit and pile, and makes a compareanalysis with the pile force and anchor axial force in the next three pre-stress, byusing ABAQUS finite element software to simulate and analysis the middle of theHuashan road in the east side of the pit.(1) The maximum horizontal displacement of pile body occurs at the top of thepile, along the depth decreases, it is basically the same for vertical displacement;however the bottom is slightly larger. The sphere of influence of horizontaldisplacement and settlement is about4times the distance of pile top within pit depth.(2) With the increase of pre-stress, the axial force of anchor cable is increased;the axial force is evenly distributed in the free section, and increases rapidly and thendecreases by the anchor point in the anchorage section. The first row Anchor plays amajor role in limit pit deformation, and the second row anchor able to share the axialforce of first row.(3) Increase the anchor pre-stress can effectively control the deformation of thepile body and excavation, but with pre-stress increases, this effect becomes obvious.Excessive pre-stress will increase the axial force of the anchor and make the pile tosustain too much negative moment, which may cause the anchor to overload and pulloff or pull out from the soil, and also lead to fracture failure occurs pile. Therefore itis unreasonable and unreliable to ensure the stability of the pit by increasing the pre-stress.(4) The sphere of influence of the soil deformation induced by excavation cannot be reduced effectively through improving the anchor pre-stress.This study points out the reasonable and unreasonable places in the design ofParis square underground parking garage in Maanshan City by the simulation analysis:This study suggests that the pre-stress value of this project is appropriate, but thesecond row anchor design slightly longer. The conclusions and laws from this papermay help to forecast the deformation of the pit and determinate the anchor pre-stress,and also accumulate some experience for construction of the foundation pitengineering.