Stability Analysis of Shield Excavation Face Based on Particle Flow in Different Depths of Sandy Gravel Stratum

Abstract

Theobjectiveofthisworkwastostudytheminimumsupportforceoftheshieldexcavationfaceofsand-gravelstratum.Basedon the geological conditions obtained from the exploration of the 18th line of the Chengdu Rail Transit and the shield excavation parametersobtainedfromexcavation,particleflowDEMPFC3DandFLAC3Dwereusedastools;thedigitaltriaxialcompression testwasperformedtocalibratethemesoscopicparametersofthesoil;numericalexcavationmodelswerebuiltfordeep-buriedand shallow-buriedsandandgravelstratumshieldtunnels;surfacesettlementandminimumsupportforceunderdifferentdepthsand different supporting forces were obtained in the end. The stability of the excavation face under the condition of 10kPa∼60kPa support force was analyzed; the excavation surface gradually tended to stabilize, and the surface subsidence decreased with the increaseofsupportforce.Whenthesupportingforcewasgreaterthanorequalto3kPa,theexcavationsurfacewasstableandthe surface settlement speedgradually decreasedtozero with time.While analyzingthe stabilityof theexcavationface of 5m, 10m, and15mburieddeepgraveltunnelsandtheinfluenceofthesupportforceonthesurfacesettlement,theminimumsupportforce that did not consider the surface settlement was reduced and the minimum support force required to control the surface settlementwasincreasedasthetunneldepthdecreased.Usingthismethod,thedepthoftheexcavationsand-graveltunnelandthe supportoftheexcavationfacecouldbeobtainedtomeettherequirementsofsurfacesubsidencecontrolandtheeconomicbenefits of the project could be improved.