Research On Monitoring Of Deep Foundation Pit Support Based On Comprehensive Pipe Gallery

As a solution for centrally placing urban pipelines,the integrated pipe gallery can effectively reduce the negative impact of repeated pipeline construction on urban production and life,and has been widely promoted and applied in many cities in China.Deep foundation pits need to be excavated during the construction of the integrated pipe gallery.Different support methods should be adopted for different engineering geology situation and groundwater conditions to ensure the safety of the foundation pit.At present,there are many foundation pit support methods,among which pile anchor support is widely used due to its special advantages,while steel sheet pile support is widely promoted in China because of its characteristics of recyclability and convenient construction.Based on the collation of existing research results at home and abroad,this paper summarizes the application characteristics of these two foundation pit support schemes in the foundation pit of the integrated pipe gallery.Research focus and research methods were selected based on these knowledge.On this basis,this paper reviews the design and calculation methods of pile-anchor support and steel sheet pile support by consulting the foundation pit design specifications and related manuals,and summarizes that the main influencing factors of pile-anchor support are pile diameter,The performance of pile-anchor support system are influenced by the pile spacing,the horizontal spacing of the bolts and the bolt arrangement,while the main influencing factors of the steel sheet pile are the stiffness of the pile section,the surrounding soil stiffness and the internal support arrangement.This paper uses Midas GTS NX geotechnical numerical analysis software to analyze the influencing factors of pile anchor support and steel sheet pile support in the foundation pit of the integrated pipe gallery on these basis.Moreover,the design data of a comprehensive pipe gallery foundation pit were used to established corresponding numerical models.Numerical calculation results are compared with the monitoring data,and the foundation pit support scheme is optimized.The main conclusions are as follows:(1)For pile anchor support,increasing the pile spacing and properly adjusting the bolt arrangement can reduce the cost and speed up the construction progress to a certain extent,but the bolt arrangement has a significant impact on the bending moment and displacement of the pile body.Specific analysis is needed.For steel sheet pile support,adjusting the internal support arrangement can also significantly increase the construction work surface.In addition,the influence of soil layer stiffness on steel sheet pile support is significant.(2)The results obtained by the numerical calculation method in this paper are in good agreement with the measured data.For the pile anchor support,the method of increasing the horizontal spacing of the anchor and adjusting the vertical arrangement of the anchor in the project is to the top of the slope.The horizontal displacement and settlement have little effect,and the adjustment method can be used to adjust the foundation pit.For the steel sheet pile support,although the removal of the lower row support will increase the horizontal displacement and settlement of the slope top,the increase is still within the allowable range,so the adjustment method can be used to optimize the steel sheet pile support.