| The subway tunnel is generally in the city center,around a variety of buildings,underground pipeline cross intensive,complex distribution,subway tunnel construction will produce a threat to its security If the control is not good will result in pipeline gas leakage and explosion,water pipe burst forming flood,broken cable communications interruption and other accidents.For areas with relatively complex geological conditions,it is very easy to cause more serious consequences.The geological features of the Dalian area are characterized by "rock hard" and "loose soil","high ground water level" and so on,and the construction of drilling and blasting method is the main construction method of this kind of geological condition metro tunnel.When drilling and blasting method is employed,seismic waves generated by tunnel blasting excavation will affect the surrounding ground of buried pipelines adversely and cause the deterioration of surrounding reservoir conditions and increase the difficulty and risk of subway construction.Taking Dalian subway tunnel as background,based on the investigation of the joint type,planting age and geological conditions of the buried pipeline along the project,combined with similarity model test and in-situ test method,the effect of blasting excavation on adjacent buried pipeline is studied.At last,combined with the Dalian subway tunnel project,safety precautions for surrounding buried pipelines are put forward in the progress of tunnel subway excavation blasting.The main content of this paper is as follows:(1)Based on similarity theory,a similar model test was designed to study the influence of the tunnel excavation on the surrounding strata and the deformation and internal force of the pipe.The results show that the 2.5D from the top of pipe(D pipe diameter),due to the boycott of the pipeline,the ground settlement amount no longer with the stratum depth increases,on the contrary,slowly become smaller.The settlement curve of the pipeline and the settlement curve of the strata have the similar settlement rule,and all obey the Gauss curve.(2)Through the similar model experiment,the vibration response analysis of the pipeline under blasting load is studied.According to the monitoring data,the Sa Rodolfo J Ki prediction formula of particle vibration is established by regression analysis method,and the simulation results are compared with the field blasting monitoring results.The results show that the attenuation law of the maximum velocity of the particle with the distance from the explosion center about experimental is consistent with the measured results.According to the law of particle velocity attenuation,the formula for calculating the maximum charge quantity is established.By means of point strain wave time history curves,the relationship between the peak value of dynamic stress and the distance of explosion,as well as the explosive quantity is studied.The tunnel model test has a number of parameters,through the control variable method,the blasting vibration response of the pipeline under blasting load is studied.(3)Based on in situ monitoring and similarity,combined with Dalian subway tunnel blasting excavation engineering practice,from the explosion of source control and blasting seismic wave propagation process control point of view,safety protection measures of adjacent underground pipelines in the process of blasting excavation of urban subway tunnel was put forward,which provides reference for blasting excavation construction methods and the safety of underground pipelines in similar areas. |
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