Study of Tunnel Damage Caused by Underground Mining Deformation: Calculation, Analysis, and Reinforcement

Abstract

Bayueshan tunnel (BYS) is an important construction crossing over coal mine goaf. The underground mining subsidence has ledthetunnelcrackedseriouslyinthreeyearsafteritwasbuilt.Inordertoevaluatethecoalmineinfluenceandfuturestability ofthetunnels,probabilityintegralmethod(PIM)wasusedtocalculatethetunneldeformation.PIMisanexperiencefunction methodbasedonrandommediumtheorywhichisusedwidelyinChina.Withtheparametersanalyzed,thetunnels’subsidence wascalculated.Theresultsshowthatitcaninterpretthetunneldamagewell,andthemaximumnormalstrainpositionsfitthe damaged tunnel positions well. It proved that PIM can be used to evaluate the tunnel’s radial deformation caused by undergroundcoalexcavation.Inordertomaintaintunnelstokeepalong-termstability,thefuturedeformationwascalculatedin casethecoalexcavationcontinues.Itshowsthatthetunnelwouldbecrackedagainiftheexcavationcontinued.Otherreasons suchastheoldgoafdeformationandwaterandvehicledynamicloadarealsoimportantreasonsforthetunnels’deformation. In order to keep traffic safety, it needs to reinforce the cracked foundation under the tunnel. Then, grouting injection was proposedtoreducetheoldgoafdeformationunderthetunnels.Ifthefracturezoneunderthetunnelsdisturbedbythedynamic trafficload,theoldgoafwillfaceariskofsuddencollapse.So,toensurethegroutingeffect,thegroutingdepthshouldbedeeper thanthesumoftrafficloadinfluencedepthandheightofcoalminecavedfissurezone.Thegroutingscopeshouldkeepallthe crackrockareaunderthetunnelfrombeingdisturbedbythedynamictrafficload.Thisdesigncanreducethesuddencollapse risk of the goaf and reduces the vehicles’ load disturbance on the cracked rock. The researched technology provides an engineering guidance to tunnel subsidence calculation, stability evaluation, and maintenance in complex geological and engineering situations.