| With the advantages of the high efficiency and mature technology,the drilling and blasting method is widely used in tunnel construction.However,the restriction of topography and geological conditions not only makes the line of new tunnel parallel to the existing tunnel in design,but also makes the distance of both tunnel smaller.Blasting of new tunnel construction is bound to cause vibration response of existing parallel tunnel and affect its operating safety,therefore,there is of great significance to analyze the effect of existing tunnel under blasting vibration.This paper is based on the Guanjing tunnel project,then combines numerical simulation,the study on influence of new tunnel blasting vibration on existing parallel tunnel is carried out.The main research contents and results are summarized as follows:(1)Summarizing the present research conclusions of blasting vibration,then according to the production and transmission principle of blasting seismic wave,the influence factors of blasting seismic wave’s transmission are analyzed.Expounding the difference between the blasting seismic wave and natural seismic wave.(2)Linear regression analysis is performed with field measured date by using the least squares.The equation of blasting seismic wave’s attenuation in tunnel face is obtained.Thes equation only apply to the IV lever of rock.(3)The three-dimensional model is established by using of finite element software MIDAS/GTS,then inversion analysis for transmission coefficient of blasting vibration is carried out.Numerical simulation analysis is carried out on the existing tunnel blasting vibration by optimizing parameters of surrounding rock,the pratical coefficients are got.On the basis of this,the formulas of blasting vibration velocity attenuation rule about the front of exsting tunnel face and the behind of existing tunnel face are deduced,the formulas can provide a reference for design and construction.(4)According to the formulas from rock parameters optimized,under the condition of maximum velocity,the permitted maximum charge quantity per one detonating period which the distance between new tunnel and exsting tunnel is 15 m and the permitted maximum charge quantity per one detonating period which under the building on the surface.(5)Some conclusions reached from above analysis.Along tunnel radial,the blasting velocity of existing tunnel lining which close to the blast is larger than the velocity far from blast,what’s more.Along tunnel axis,the velocity in behind of tunnel face is larger than the velocity in front of tunnel face,and the velocity attenuation rate in behind of tunnel face is greater than the front of tunnel face. |
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