Study On Design Method And Application Of Soil Nailing Wall And Pile-anchor Composite Support Structure Based On Deformation Control

At present,the land resources are becoming more and more tense,the construction of foundation pit can have a bad influence on existing buildings due to the small spacing between adjacent buildings,public facilities such as water pipes and communication cables are often embedded near the existing buildings.Once the foundation pit deformation is too large,it will endanger people's lives and property safety.In the sensitive environment,the design controlled by strength can not meet the requirements of the surrounding environment for deformation.soil nailing wall and pile-anchor composite support structure is wildly used in foundation pit engineering.The study on the working mechanism of soil nailing and pile anchor is still to be deepened.This paper is supported by the National Development and Reform Commission scientific research project“Study on low carbon residential area planning and design technology in mountainous cities in southern China”(1010403820130116).Based on the foundation pit of Hanbin District Third People's Hospital,Combining FLAC3 D software and orthogonal test,through model test and long-term monitoring,the study on design method and application of soil nailing wall and pile-anchor composite support structure based on deformation control is carried out.The main work of this paper is as follows:(1)Based on the FLAC3 D and the orthogonal design,The maximum horizontal displacement of the soil nailing wall and pile-anchor composite support structure is taken as the research object,the orthogonal tests are designed with the support parameters as the experimental factors.By means of range analysis and variance analysis,the primary and secondary factors affecting the maximum horizontal displacement of the soil nailing wall and pile-anchor composite support structure are researched.(2)By using FLAC3 D software,the excavation and supporting process of soil nailing wall and pile-anchor composite support structure is simulated.The horizontal displacement distribution characteristics under different construction sequence(excavation height and tensioning opportunities of anchor cable)are analyzed,and the reasonable construction sequence of soil nailing wall and pile-anchor composite support structure is put forward.(3)According to the two kinds of commonly used simplified soil nailing wall and pile-anchor composite support structure analysis theory,"overload model" and "slope model",the FLAC3 D models are established,The law of deformation distribution and size of simplified analysis model is analyzed.Compared with the deformation of actual support structure,the conclusion that the deformation calculation result of the slope model is more in line with the actual situation is obtained.(4)In combination with the foundation pit of Third People's Hospital in Hanbin District and the reference to other model tests,the model test of soil nailing wall and pile-anchor composite support structure is designed.Through the installation of the model box,the selection of the soil nail material,the strain measurement,the application and the measurement of prestress,the deformation characteristics of retaining structure during excavation are studied and the applicability of "slope model" is analyzed according to the force of the supporting structure.(5)The characteristics of the foundation pit of Third People's Hospital in Hanbin District is analyzed and the theory of deformation control is applied.Some design measures are put forward,such as adopting "slope model" for design,reducing slope angle,increasing prestress.Besides,construction measure like construction according to reasonable construction sequence is also put forward.Through the long-term monitoring of foundation pit deformation,the rationality of deformation control measures and the safety of foundation pit are verified.