Research On The Safety Risk Of Existing Tunnel Adjacent To Deep Excavation

With th e d evelop ment o f the t imes and the actual demand,p eople b egan to s eek space underground.Thus,the underg round engineering is b eco ming mo re and mo re co mmon.Deep foundat ion pits and tunnel p ro jects are also beco ming mo re and mo re frequent during th e pro cess o f city const ruct ion.At p resent,the d eep foundat ion p it project ad jacent to the tunnel gradually p resents the characteristics of “large,tight,and deep”.Since such two structures are both deformation-sensitive,serious damage will b e caus ed if th e ad jacent tunnel st ructu re is damaged during the deep-foundation-p it construct ion.Therefore,th e systemat ic study of th e in flu ence o f safety ris k o f deep excavat ion near the e xist ing tunnel att ract ed mo re and mo re att ention.At p res ent,the research on the deep foundation pit eng ineering near the tunnel st ructu re main ly uses theo ret ical res earch,actual measurement an alysis,and numerical s imu lat ion methods.In thes e stud ies,th ere are few studies on the ris k o f adjacent p its in foundat ion pits.Regard ing the ris k res earch in the field of pits,domest ic and foreign res earch focus es on the t echnical ris ks during the constru ct ion of pits,and there is few ris k ass ess ments on th e surrounding environ ment.In o rder to scient ifically and accu rat ely ass ess the s afety ris ks o f d eep e xcavat ion near the exist ing tunnel st ru cture,th is p aper carries out the fo llo wing wo rk bas ed on the th eory of ris k man agement :(1)Count the d eep foundation pit p ro jects n ear th e do mest ic and fo reign 34 tunnel st ructu res,and use d at a stat ist ics to su m up th e facto rs,in cluding the overall situat ion o f the foundation pits,th e relat iv e posit ions o f the e xist ing tunnels and foundation p its,the soil condit ions where th e tunnels are lo cat ed,and the st ru ctures o f the enclosures,the condit ions o f reinfo rcement and const ruct ion pro cess.Co mb ined with the tunnel’s defo rmat ion and converg ence,th e influ encing facto rs of d eep tunnel excavat ion ad jacent tunnels were systemat ically analy zed and su mmed up,and they were su mmed up as the effect o f deep foundation pit const ruct ion and the vulnerab ility of tunnels in cluding eight majo r factors;(2)Based on the co mp rehens ive ris k inde x mat rix method,est ablish a ris k assess men t model fo r deep foundation p its adjacent to exist ing t unnels.To imp rove the reliability o f th e evalu at ion system,int roduce ent ropy weight method to imp rove the ev aluat ion p rocess of ev aluat ion index weights.By the su mmary of the lit eratu re,put fo rward the ev aluat ion crit eria and evalu at ion criteria for ea ch inde x lev el.Finally,the evalu at ion syst em is v erified th rough engin eering e xa mp les.Th e verificat ion results sho w that the evalu at ion system can p rovid e an effect iv e reference fo r engineering d ecis ion-making.(3)Est ab lish a ris k mon ito ring and early warning mech an is m fo r high-ris k deep foundation p its : a dynamic mon ito ring part,wh ich will b e des cribed in three parts : monitoring content,measuring point arrangemen t,and monito ring frequen cy;early warn ing part,with reference to exist ing normat ive st andards,co mb ined with the actual s itu at ion o f the p ro ject to d et ermin e th e depth.The foundat ion p it is close to the monito ring and alarming standards o f th e tunnel pro ject.On th is bas is,a three-level early warn ing man agement syste m is estab lished.