Stability Evaluation Of Surrounding Rock Of The Mingyazi Tunnel And Its Rapid Excavation Technology

It is important to carry out surrounding rock stability evaluation and rapid excavationtechnology research of the extra-long highway tunnel in complicated geologicalcondition.Taking Mingyazi tunnel of Shitian highway as an example in this artcle.Completionof a long highway tunnel surrounding rock stability evaluation and quick excavationtechnology use the method of field investigation, theoretical analysis, FLAC numericalsimulation and on-site monitoring.The main work and conclusions are:(1) Completed the surrounding rock’s stability influencing factors of the tunnel.Thestudy showed that the main factors are rock hardness,quality designation,wave velocityclassification,intactness of the rock velocity of rock and basic quality designation of rock.Usethe maximum membership degree law grading on the surrounding rock.It is consistent withsurrounding rock grade of the test section after excavation.It is proved that the classificationmethod is feasible.(2) Researched on the deformation characteristics of surrounding rock in soft rocktunnel.The results show that the failure mode of grade Ⅴsurrounding rock is usually presentedas partial collapse,plastic invade and sliding.Use the elastic-plastic theory analysis, assumingthat the volume of the plastic ring unchanged,find the radial displacement of the wall.Thedisplacement as a theoretical limit.The result of numerical simulation and on-site monitoringis less than the theoretical limit of displacement.So the surrounding rock is stable after theinitial support.(3) Carried out rapid excavation technology research of the Mingyazi tunnel. The resultsshow that the main factors to influence the construction speed are the speed of drillingblast-hole and anchor-hole.designed scheme of grade Ⅴ surrounding rock blasting.Use thetracked four-arm jumbo to improve the speed of drilling blast-hole drill.Because Site- surrounding rock is crushing,complex geologic structure and difficulty of blastholecomletion,it is proposed to use automatic anchor pole in the fracture to solve the problem ofdrilling slow.