Dynamic Force Analysis Of Composite Soil-nailing Under Seismic Reaction

As a supporting form of combined micro-pile,prestressed anchor rod and soil nail wall,the micro-pile composite soil nail wall combines the advantages of supporting structures such as soil nail,anchor rod and micro-pile,which can alleviate the land of the proposed project The contradiction between the occupied area and the construction of the red line reduces the project cost and improves the overall stability of the foundation pit.In recent years,micro-pile composite soil nailing walls have been widely used in foundation pit and slope support projects,and can also be used as permanent support structures.In earthquake-prone areas,the support structure is also likely to be affected by earthquakes.At present,the analysis of the dynamic response of composite soil nailed walls under earthquake action is limited to the study of prestressed anchor composite soil nailed walls.No one has yet made a response to the dynamic response of micropile composite soil nailed walls under earthquakes Systematic numerical simulation analysis,this article aims to fill the gaps in this area and conduct in-depth research.This paper first introduces the mechanical mechanism of the micropile composite soil nail wall support structure,as well as the theoretical basis of dynamic analysis,and tells the selection of seismic wave and damping ratio.Subsequently,the FLACID three-dimensional finite difference software and its built-in structural modules are briefly introduced.Relying on FLAC3D,a three-dimensional foundation pit model under micropile composite soil nail support is established to simulate the excavation and support process under different working conditions,and the dynamic module in FLAC3D An EL-Centro seismic wave with a duration of 8 s was applied to simulate the process of the foundation pit being subjected to earthquakes.The data was collected and compared to analyze the changes in the displacement and settlement of the foundation pit and the internal force of the support structure under different supporting structure parameters and seismic intensity.The main research contents and achievements of this article are as follows:(1)By comparing the ordinary soil nail wall with the micro-pile composite soil nail wall,it is found that compared with the ordinary soil nail wall,when the micro-pile composite soil nail wall is used for supporting,the soil nail axis under static excavation and earthquake The force,horizontal displacement of the foundation pit,and settlement after the pit all decreased significantly,the sliding surface of the foundation pit also showed an expanding trend,and the overall stability of the foundation pit was significantly improved.(2)EL Centro seismic waves with peak accelerations of 0.1g,0.15g,0.2g,and 0.3g were applied to the foundation pit model supported by the micro-pile composite soil nail wall,and it was found that with the increase of seismic acceleration,the level of the foundation pit Displacement,settlement,axial force of soil nails(anchor rods),and bending moments of micro-pile all increase significantly,and the increasing trend becomes more obvious as the intensity increases,and the potential slip surface of the foundation pit gradually moves away from the side of the foundation pit mobile.(3)By changing the supporting structural parameters(number of bolt rows,number of rows of miniature piles,length of miniature piles,diameter of miniature piles)in the model of micropile composite soil nail wall support,the comparison found that under the action of earthquake,The installation of micro piles can effectively suppress the deformation of the foundation pit,reduce the internal force of the supporting structure and improve the stability.However,increasing the number of rows of micro piles on the basis of the existing micro piles has little effect on the stability of the foundation pit.To a certain extent,increasing the number of anchor rods,the length and diameter of the mini-pile can reduce the axial force of soil nails,the bending moment of the micro-pile body,the horizontal displacement and settlement of the foundation pit to improve the stability of the foundation pit.