Study On Influence Of Different Blasting Excavation Methods On Dynamics Of Existing Tunnels With Small Distance

In recent years,with the increase of the demand for transportation capacity in China,the small tunnel has become a common structural form.For the construction of small tunnels,the difficulty of design and construction will be greatly increased,and the distance between the two tunnels will be smaller.The existing tunnels will be affected by the blasting construction of new tunnels.Therefore,the dynamic response generated by the small-space tunnels during the blasting construction is an important research topic.The purpose is to ensure the safety of existing tunnels with small.A feasible blasting excavation plan is developed under the condition of new tunnel construction progress.Based on the engineering background of the Wa-Gui section tunnel of Qingdao Metro Line 1,the theoretical research,numerical simulation calculation and on-site monitoring are carried out according to the relevant data and data of the project.The research aspects are as follows:(1)Combining indoor and outdoor test data,geological exploration report and design drawings,the physical and mechanical parameters of the rock mass of the project are determined by relevant empirical formulas.(2)Combining the actual project overview and blasting construction conditions,the finite element model is established by ANSYS software,and the three kinds of blasting excavation methods in the same level of surrounding rock are studied under the conditions of pilot hole method,upper and lower step excavation method and CD method.The deformation,stress development law,displacement field and vibration velocity of the surrounding rock and lining of existing tunnels with small are analyzed,and the relevant data of surrounding rock and existing tunnel structure under the same surrounding rock conditions are obtained.When controlling the existing tunnel structure and surrounding rock displacement and vibration speed,CD method blasting excavation method is preferred to protect the existing tunnel lining and surrounding rock safety,and ensure the safe and rapid advancement of the project.(3)When the surrounding rock grade is Ⅲ and Ⅳ surrounding rock,the vibration response of the same construction method of different surrounding rocks is compared under the condition of guiding hole method,and the vibration velocity of surrounding rock under the condition of class III surrounding rock is obtained.The self-vibration frequency is high,the period is short,and the free vibration decay speed is fast,from which the most reasonable blasting excavation method under the same blasting condition is judged.(4)According to the comparison between the calculation results of ANSYS/LS-DYNA finite element software and the measured vibration velocity data obtained by on-site monitoring,the accuracy of the finite element calculation results is verified,and the rationality of the construction design and the field engineering are demonstrated.Provide guiding significance;analyze the vibration monitoring results of existing tunnels on the site,and use the linear regression of the Sadowski formula to obtain the vibration attenuation law in the existing tunnel under a certain distance,and guide the tunnel blasting informationization.And construction,providing reference for similar projects.