Application Research On Bailey Beam Protecting Buried Pipeline-overpass During Blasting Excavation

In the process of speeding up our country's urbanization,making full use of underground space resources resolve the contradiction between engineering construction land and land resources effectively.However,municipal road construction will often encounter a variety of municipal pipeline protection problems in construction land.Ensuring the safety of these municipal pipelines is the premise of ensuring the normal operation of the city,otherwise their dilapidation could make potential danger such as power interruption,communication interruption,or water supply.So,the study on measures protecting buried pipelines during underground construction is significant.The open cutting ramp of the Tuojiang 4th Bridge and Connection line project in Luzhou,need to cross the buried high voltage transmission line,natural gas pipeline and communication cable.The way to ensure that the buried pipelines are not damaged during ramp excavation is a key issue.Based on the open cut ramp project,combined the safety quality,technical requirements and the characteristics of bailey beam,this paper puts forward measures on buried pipeline suspension protection of bailey beam.Then the static safety of bailey beam and the dynamic safety under the condition of ramp excavation blasting vibration load are analyzed.This paper analyses and checks the static safety of bailey truss beam under the external loads of self weight and pipeline and other components by ANSYS software.The results of calculation and analysis show that,bailey beam's maximum deformation is midspan displacement 17.6mm,that much less than required in the specification,1/400(56mm);The maximum compressive stress of bailey beam's single member is 86.9MPa,and the maximum tensile stress is 36.1MPa.Both are less than the yield strength 230 MPa of the material.It shows that there is enough safety reserve in this protection structure.Structural modal analysis of bailey truss beam shows that the first 10 order natural frequencies of the structure are much smaller than the blasting vibration frequencies.Therefore,the resonance phenomenon of Bailey beam structure will not occur under the dynamic action of excavation blasting.According to the way of blasting vibration load passing through the base to the structure,this paper uses ANSYS/ LS-DYNA software to simulate the dynamic response of bailey beam in the process of ramp excavation blasting,and the result shows the maximum vertical displacement of beam under blasting vibration is 19.9mm that the vertical displacement 17.6mm is increased by 13.1% under the static loading condition;the maximumcompressive stress of single member is 90.5MPa,the maximum tensile stress is 37.8MPa,and they added 4.1% and 4.7% to the static load,respectively.Even considering the action of static load at the same time,the deformation and internal force of the Bailey beam structure used for buried pipeline protection are still far less than the allowable values.