| At present,the research on the joint support of multiple support methods in ultra-deep foundation pits is in-depth,and the deformation control of the joint support structure is particularly important in the foundation pit with large excavation depth.Taking a deep foundation pit project in Beijing as an example,the deformation characteristics of the deep foundation pit retaining structure are studied.The deep foundation pit project adopts composite soil nailing wall + pile anchor combined support system.The deep foundation pit with deep excavation,complicated geological conditions and no similar construction can be used.It is the deepest deep foundation pit in Beijing.Through the collection of monitoring data,the factors such as pipeline settlement,surrounding surface settlement,horizontal displacement and settlement of pile top are analyzed and discussed.Midas simulation software combined with monitoring data is used to analyze the construction process of foundation pit,and the anchor in the process of foundation pit excavation The simulation values and monitoring values of the force,foundation settlement and deformation law are analyzed and discussed to verify the reliability of the model.The spatial depth effect of the internal force and deformation of the super deep foundation pit combined support structure is discussed,and the parameters affecting the supporting structure are discussed.Conduct analytical discussions.Research indicates:(1)The midas pit engineering was simulated by midas software,and the monitoring data of the horizontal displacement of the pile body,the ground settlement value around the foundation pit and the axial force value of the anchor rod and the corresponding simulation values were collected,and the graph was drawn.Through the analysis and comparison,the correctness of the model is proved.Through the simulation analysis,the rationality of the design is further confirmed.(2)In the foundation pit engineering of sand and silty clay soil,with the increasing depth of excavation,the bending moment of the retaining pile,the horizontal displacement of the pile body and the horizontal displacement of the pile top are obvious,and the extreme points are all open.Near the excavation surface,when excavating to the design elevation,the maximum value is reached;the inflection point position in each bending moment curve is consistent and coincides with the position where the prestressed anchor is installed,and the displacement curves of each pile body are “large in the middle and small in the ends”.(3)The trend of deformation control of the enclosure structure parameters within a certain range is very obvious,but after the out of range,the deformation control ability is obviously weakened;through the correlation analysis,the fitting equation and the fitting curve are obtained,for the project example The selection of the parameters of the enclosure structure was quantitatively analyzed.The research results can provide theoretical basis and practical experience for the design of composite support structure of the same type of ultra-deep foundation pit. |
