Analysis On Vibration Characteristics Of Tunnel Lining Concrete And Secondary Lining

In the process of blasting excavation,the vibration and shock wave generated by explosion will cause certain damage to the lining concrete.Under multiple blasting vibration,the damage will continue to accumulate,and ultimately reduce the performance index of the structure,which will affect the safety and practicability of the lining structure.Based on the strength damage theory of yunlongshan tunnel in Beijing,this paper studies the vibration damage characteristics of lining concrete under blasting vibration by means of field monitoring,indoor simulation test and numerical analysis.Firstly,the attenuation law of vibration velocity and main vibration frequency under the action of blasting vibration is analyzed by means of on-site monitoring,and the strength damage characteristics of concrete blocks are analyzed by blasting vibration simulation test according to on-site monitoring data.In order to further study the stress and displacement variation characteristics of each position on the lining concrete structure,the numerical simulation method is used to study and analyze it,The main research work and achievements are as follows(1)After fitting the vibration velocity and the main vibration frequency with the Savart formula,the prediction formula of the blasting vibration attenuation law is obtained;at the same time,the similar standard number equation is established by using the principle of dimensional analysis,and the prediction formula of the main vibration frequency with respect to the vibration velocity is obtained,and its effectiveness is verified by the field observation data.(2)After short age concrete is disturbed by blasting vibration,its uniaxial compressive strength will first increase and then decrease according to different ages;under multiple blasting vibration,the strength damage of concrete will accumulate under multiple blasting vibration.The linear regression method is used to fit the relationship between blasting damage accumulation and vibration times,and the relationship between concrete strength damage accumulation and vibration times is obtained The relationship of the number of vibration can be used to predict the strength damage of concrete.(3)The maximum tensile stress on the lining concrete of the same section appears at the arch bottom,and the tensile stress of lining concrete gradually decreases with the increase of blasting center distance.The results show that the maximum tensile stress at the distance of 20 m is greater than the tensile strength of C25 concrete at the age of 28 h;the maximum tensile stress at the distance of 60 m is less than the tensile strength of C25 concrete at the age of 12 h,which indicates that the maximum tensile stress will not cause tensile damage at the distance of 60 m,which can be called safe distance.Through the research on the damage characteristics of lining concrete under blasting vibration,the precondition and research foundation for the prediction and control of blasting vibration based on lining concrete damage are provided.