The Influence Of Underground Tunnel Excavation By Drilling And Blasting Method On Urban Buried Pipeline System

As an efficient and widely used way of energy transmission,buried pipeline is of great significance to people's production and life.With the development of subway construction in China,drilling and blasting method is the first way to develop underground space on the basis of considering efficiency and economy.The blasting vibration produced in the construction process will inevitably have a certain impact on the urban underground pipeline system,and even cause disasters.Therefore,it is significant to analyze the dynamic interaction mechanism of pipeline and soil under blasting load and to study the seismic characteristics of adjacent buried pipeline during blasting.This paper discusses the generation process of blasting seismic effect.The peak velocity of pipeline vibration is the main reference index of engineering safety control.The frequency of pipeline vibration,duration of blasting vibration,frequency of blasting vibration and other factors should also be considered in the safety evaluation of buried pipeline.Through dimensional analysis,the modification form of Sadovsky vibration velocity empirical formula considering time-frequency effect is given.Considering the pipeline as a thin cylindrical shell,the plastic failure criterion of pipeline under dynamic load is defined,the dynamic interaction analysis method of pipeline soil is summarized,and the settlement of pipeline is predicted according to the peck formula.According to different layout states(parallel and vertical)of pipeline and tunnel to establish the numerical model by ANSYS / LS-DYNA dynamic finite element software,the seismic characteristics of buried pipeline are studied,and the weak links of pipeline under blasting load are summarized.The results show that the top and bottom of adjacent buried pipelines are easy to be damaged by blasting,while the farthest end of both sides is easy to produce large vibration velocity.Therefore,in the actual project,monitoring points should be set at the top,bottom and far end of the pipeline,and key protection measures should be taken.At the same time,according to the established numerical model,the dynamic influence process of underground blasting on pipe soil structure can be understood intuitively.Finally,the causes of the accidents caused by the excessive blasting vibration of the buried pipeline are summarized,and the fault tree is established for analysis,so as to put forward reasonable suggestions for the safe construction of the project.