| This article description five types of supporting forms of pile-nail-anchor composite reinforcement technology,mainly studying soil-nail wall and pile-anchor combined supporting structure and pile-anchor and soil nailing composite supporting structure.These two supporting types are pile-Nail-anchor composite reinforcement technology.Based on an engineering example of a soil-nailed wall and pile-anchor combined support structure in Xi’an,the traditional stability checking method of the soil-nailed wall and pile-anchor combined support structure is compared and analyzed,and the LiZheng Deep Foundation Pit software and MIDAS GTS NX are used.The software checks the overall stability of the soil-nailed wall and pile-anchor combined support structure,and verifies the reliability of the MIDAS GTS NX software;using MIDAS GTS NX software as research tool to explore the advantages of pile-anchor and soil-nail composite support structures the working mechanism of soil nails,anchor rods,rows of piles and surface layer;selection of the method of checking the overall stability of pile-anchor and soil-nail composite supporting structures and the scope of foundation pit engineering applicable to pile-anchor and soil nail composite supporting structures;application MIDAS GTS NX software explores the influence of rainfall on the deformation of pile-anchor and soil-nail composite supporting structures.According to an engineering example of a soil-nailed wall and pile-anchor combined supporting structure in Xi’an.Using Midas GTS NX software,the 3D model of the whole foundation pit project is established(Part AB foundation pit engineering adopts soil nailing wall and pile anchor combined support structure).According to the working characteristics of pile,soil nail and anchor rod in AB section of foundation pit excavation,one of the construction parameters of pile,soil nails and anchor rods are changed,and the other unchanged methods.The influence of the construction parameters of the anchor rod,soil-nailed and piles on the soil-nail wall and pile-anchor combined supporting structure contributes to the popularization and application of the pile-nail-anchor composite reinforcement technology.The main conclusions are as follows:(1)Most architectural design institutes in China adopt LiZheng series software(including LiZheng Deep Foundation Pit software)for foundation pit engineering design,which shows that LiZheng series software can withstand the test of time and practice.According to traditional calculation results,a deep foundation for the overall stability of the well with LiZheng and a comparison with the general stability calculation results with MIDAS GTS NX software,It not only verifies the reliability of the MIDAS GTS NX software,but also shows that the traditional checking calculation method of the soil-nailed wall and pile-anchor combined supporting structure is more safe.(2)Only the slider body of the surface layer supporting structure is larger than the natural slider,the surface layer limit the lateral deformation of the soil.The slider body of soil nailing+surface layer support structure is larger than that of only surface layer support structure,and soil nailing support has a strengthening effect on a small range of soil,The slider body of prestressed anchor cable composite soil nailing wall is larger than that of soil nailing+surface layer support structure.Anchor bolt can effectively control the horizontal and vertical displacement of soil.Pile row can effectively control the horizontal and vertical displacement of soil and further expand the reinforcement range of prestressed anchor cable composite soil nailing wall.(3)The check calculation of the overall stability of the pile-anchor and soil nailing combined supporting structure is more reasonable in accordance with the "Technical Regulations for Building Foundation Pit Supporting"(JGJ120-2012),in which soil nails are used as non-prestressed anchors to participate in the overall stability check.The pile-anchor and soil-nail composite supporting structure is suitable for foundation pit engineering where the soil strength is not very good and the excavation depth is 30 m.On the basis of the analysis,the concept of equivalent number of soil nails is put forward for the first time.The engineering cost of the pile anchor and soil nail composite supporting structure in the same foundation pit project is lower than that of the pile anchor supporting structure.Rainfall will significantly increase the horizontal and vertical displacement of the composite structure.Rainfall has a great influence on the horizontal displacement of the middle slope and the vertical displacement of the middle and lower part of the excavation and pile row.(4)With the excavation of the foundation pit,the soil nailing axial force of the soil nailing wall combined with pile and anchor structure is larger in the middle and smaller at both ends.The horizontal displacement of the pile is small at both ends and large uplift in the middle.Increasing the diameter of soil nailing and decreasing the horizontal spacing of soil nailing can effectively control the horizontal and vertical displacements of the slope roof of soil nailing wall and pile-anchor combined supporting structure,but it is not necessary to increase the diameter of soil nailing and decreasing the horizontal spacing of soil nailing blindly,which will increase the project cost.Therefore,when choosing the diameter and horizontal spacing of soil nailing support,the safety and economy of foundation pit engineering should be considered.The increase of pile diameter and concrete strength has little effect on controlling the horizontal displacement of the top of pile.The diameter of the anchor section and the prestress of the anchor can effectively control the horizontal displacement of the pile top of the composite structure of soil nailing wall and pile anchor.The prestress applied by anchor will reduce the axial force of surrounding soil nailing.The greater the prestress applied by the anchor,the greater the reduction of the axial force of the surrounding soil nailing. |
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