Research On Vibration Rule Of Masonry Structure Under Tunnel Blasting

The harmful effects of blasting vibrations caused by blasting excavation of subway tunnels can easily lead to damage to surrounding buildings.Due to its own structural characteristics,masonry buildings are more likely to be destroyed under blasting vibration.In the construction of subway tunnels,it is necessary to strengthen the vibration safety monitoring of the masonry structures or to reinforce them.However,laying out vibration monitor and safety reinforcement on each floor of the masonry structure requires a lot of manpower and material resources.Therefore,to study the vibration velocity and stress variation law of each floor of a masonry structure under tunnel blasting can guide blasting vibration safety monitoring,dangerous house safety reinforcement,save manpower and material resources,and achieve the optimal state of economic security benefits.This paper takes the wind tunnel No.2 of Xizhen Station of Qingdao Metro Line 1 as the engineering background and leans through the residential building with 5 layers of masonry masonry structures.The vibration velocity is collected at the site and the drug-gap ratio coefficient is established using ANSYS/LS-DYNA software.The numerical models of 3.72,4.26,4.69,5.91,7.45,9.38,and 11.28 studied the variation law of the vibration velocity and stress with the floor,and analyzed the reason of the 6-layer magnification phenomenon from the energy point of view.The main conclusions were as follows:(1)The peak value of vibration velocity Vr shows a rapid attenuation of the vibration velocity in layers 1 to 2.The vibration velocity tends to be stable and steadily decreased in layers 2 to 5.The relative amplification phenomenon occurs in layer 6 and the relative amplification factor is 0.21 to 0.54(2)The peak velocity of vibration Vt shows the law of increasing first and then decreasing,and the peak value of vibration velocity appears in layer 2.The absolute amplification factor is 1.38～1.86.The specific manifestation is that the vibration velocity in the 1st to 3rd layers appears"hilly",the vibration velocity in the 3～6 layers is relatively stable,and the relative amplification phenomenon appears in the 6th layer,and the relative magnification factor is 0.80～1.15.(3)The peak values Vc、Vh of vibration velocity Vc and Vh decreased first and then increased.They showed a rapid decay in layers 1～2.They were basically stable in 2～6 layers,and they were stable and moderately decreased.The vibration speed did not change significantly.In the 6th layer,there is a relative amplification phenomenon,and the relative amplification factor is 0.14～0.60.(4)σ,τ,and v-M stress show a gradual increase in the stress in layers 1 to 2 or 1 to 3,a gradual decrease in stress in layers 2 to 5 or 3 to 5,and an enlargement in layer 6.(5)The minimum value of v-M stress,maximum principal stress σ,and maximum shear stress τ in layers 1 to 6 occurs in 4 or 5 layers,and the maximum value appears in 2 or 6 layers.(6)The drug-gap ratio coefficient has basically no effect on the vibration velocity and stress change law of each floor of the masonry structure.According to the research conclusion,in the blasting excavation construction,the vibration safety monitoring frequency of the 2nd,3rd,or 6th layer of the masonry structure should be improved,and the strength of the safety reinforcement measures should be strengthened.