Study On The Effect Of Tunnel Blasting Construction On The Vibration Of Adjacent Buildings（Structures）

At present,the rapid development of traffic engineering has led to a significant increase in the utilization rate of underground space.Considering the density of buildings,new tunnels will inevitably be close to the existing buildings.Beacase of the limitation of topography,environment and engineering geological conditions,in many cases,the process of tunnel blasting vibration may damage the adjacent buildings and endanger the safety of the construction site.In order to effectively control the impact of blasting vibration,the form of blasting load,modeling method and the impact on adjacent buildings（structures）are studied and analyzed.Among them,the conduction law of blasting stress wave in different rock and soil medium structure and peak particle vibration velocity of road are difficult to determine.Therefore,it is necessary to study the conduction law and peak velocity of blasting stress wave in different medium.In this paper,Based on the excavation project of a new tunnel under the national highway.By combining with theoretical analysis,numerical simulation and field tests,the vibration effect of tunnel blasting construction on adjacent structures are studied.The main research details and results are shown as follows:（1）Based on the stress wave theory,the propagation law of blasting vibration in geotechnical medium is analyzed theoretically.When the blasting vibration is transmitted to the interface of different medium,combined with the propagation theory of wave in elastic solid,the reflection coefficient Cr and transmission coefficient Ci determined by wave impedance h.The displacement wave equation of the stress wave incident and the calculation formula of pavement vibration velocity is derived.By substituting the ultimate tensile stress criterion of road concrete material into the relationship between stress and vibration,the safety criterion of blasting vibration velocity of existing road pavement can be obtained as 7.85 cm/s.（2）ANSYS LS-DYNA finite element software is used to simulate and analyze the measured conditions of the tunnel blasting engineering.According to the actual situation of blasting excavation and the characteristics of adjacent environment,a numerical model considering the influence of different medium interface on stress wave attenuation is established to simulate the response of tunnel blasting to adjacent roads.The results show that:the influence range of blasting stress wave is centered on the explosion source and propagates in a circular shape in the rock mass;with the increase of the distance from the explosion source,the principal stress gradually weakens;in the whole process of stress wave attenuation,the maximum tensile stress mostly appears above the tunnel excavation section.When t=10 ms,the maximum principal stress is 0.78 MPa at the pavement,which is within the tensile strength of concrete and meets the limit value of the standard.（3）Through the analysis of the numerical simulation results,the blasting vibration velocity variation law of different horizontal distances from the road surface to the tunnel face is studied.The particle vibration velocity presents the phenomenon of "cavity effect" in front and behind the tunnel blasting section;the particle vibration velocity presents the phenomenon of"amplification effect" in the interface between the geotechnical medium and the road surface.（4）The existing engineering blasting technology is compared and introduced.According to the design scheme of field blasting,the vibration monitoring and measurement of the road section underpass the tunnel is carried out.The analysis of the measured data shows that the peak particle vibration velocity of the pavement decreases with the increase of the distance,and the maximum vibration velocity of the particle in Z direction is 2.35 cm/s.（5）By comparing and analyzing the predicted results of the formula with the measured values and the numerical simulation results,it is found that the vibration velocity gradually decreases with the increase of the distance from the explosion source.The average relative error between the predicted value of the theoretical formula and the measured value is 9.17%,and the average relative error between the numerical simulation and the measured value is 10.47%The feasibility of the theoretical prediction formula for the reflection and transmission of stress wave at the interface of different medium is verified.