| This paper is study the impact of blasting construction on the shotcreting that based on Wanxing Road tunnel in Jiangbei District of Chongqing Municipality.Through theoretical analysis,field experiment,data analysis and numerical simulation study on attenuation rate of vibration velocity,the relationship between age and shotcreting layer destruction,the relationship of different excavation and in different rock mass under different excavation methods,shotcreting layer under the footage the age and the damage range.The main contents of the work are as follows:(1)The basic situation,engineering geological conditions and blasting construction scheme of Wanxing road tunnel are briefly described.Ten measuring points are arranged on the arch waist of the Preliminary Bracing to obtain the vibration velocity of the measuring point under blasting vibration.Then,Sadowski’s formula is pushed out through data fitting to study the attenuation law of blasting vibration velocity,which ensure the safe construction of the tunnel blasting.(2)Using MIDAS/GTS NX to establish the finite element model of Wanxing Road Tunnel,and to study the effect of blasting construction on shotcerting,By extracting the vibration velocity of arch waist position of the Preliminary Bracing in the model and then fitting the data,the Sadovski formula is obtained to compare the vibration attenuation law of the measured data in actual engineering to verify the reliability of the numerical simulation.(3)Through numerical simulation,the damage scope of blasting to different age’ Preliminary Bracing was studied,Using the age of the primary spray layer as a variable(0.5d、1d、3d、7d、14d、28d),the vibration velocity of the primary spray layer at different ages is extracted.When the safe vibration velocity is exceeded,the distance in this range is taken as the damage distance.Finishing the data of fitting shotcreting age and failure distance,we get a logarithmic relationship,which can be used to determine the damage distance corresponding to the Preliminary Bracing of different ages,to take reinforcement measures in advance or to replace the initial support form and guide construction.(4)The influence of blasting on the shotcerting in different ages under different rock grades,different excavation methods and different excavation footage.Similarly,the data of the age and damage distance of the primary jet were extracted and the data were fitted to obtain the corresponding relationship.Then,the influence of blasting on the primary jet grouting under different operating conditions was analyzed.When the construction cycle is speeded up,the age of the shotcerting is low and can not reach the expected strength.The damage scope of the Preliminary Bracing can be judged by the research in this paper,so that measures can be taken to guide construction. |
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