地铁保护区内爆破施工对既有地铁隧道结构的振动影响

Influence of Blasting Construction in Subway Protection Zone on Tunnel Structure Vibration

目的:为探究地铁保护区内爆破振动对既有地铁隧道结构的影响,总结爆破振动响应规律,需研究既有地铁隧道衬砌结构对爆破地震波的动态响应规律。方法:基于青岛市某地铁保护区基坑工程的爆破施工具体案例,运用ANSYS/LS-DYNA软件建立了显动力数值计算模型,设定了模型的计算参数和炸药参数。根据基坑爆破中心与隧道衬砌结构的径向距离、爆破角度2个参数的不同取值,设置了四种工况,分别对各工况下隧道衬砌结构的振动速度(以下简称“振速”)与频率响应特征、应力响应进行了环向和纵向分布规律分析,并通过与现场实测值进行对比来验证模拟数值结果的合理性。结果及结论:振速峰值出现在距离爆心最近的衬砌结构部位;振速最大值和最小值总体呈对角线分布;隧道迎爆面的振速最大,背爆面的振速最小;爆破药量越大,振速从迎爆面到背爆面的衰减幅度越大;隧道衬砌结构应力场呈动态变化,背爆面结构拉应力值约为迎爆面的40%~50%,且呈现由爆距最小处向两侧衰减的规律;爆破振动监测点宜布置在距爆心最近处,并随着爆心方位的变化及时更换布设位置;爆破振速控制指标(1.0 cm/s)下,爆破产生的附加应力对衬砌结构带来损伤的可能性较低。

Objective:In order to explore the effect of blasting vibration in subway protection zone on the existing tunnel structure,and summarize the response law of blasting vibration,it is necessary to study the dynamic response law of existing subway tunnel lining structure to blasting seismic wave.Method:Based on a specific case of blasting construction in the protection zone of a subway excavation project in Qingdao,ANSYS/LS-DYNA software is used to establish a dynamic numerical calculation model.The calculation parameters and explosive parameters of the model are set,together with four different working conditions based on different values of the radial distance between the blast center and the tunnel lining structure,and the angles of blasting.The vibration speed,frequency response characteristics,and stress response of the tunnel lining structure under each working condition are analyzed for circumferential and longitudinal distribution patterns.The validity of the simulation numerical results is verified by comparing them with on-site measured data.Result&Conclusion:The peak vibration velocity occurs in the lining structure closest to the blasting center.The maximum and minimum vibration velocities are generally distributed diagonally.The vibration velocity is highest on the blasting face of the tunnel and lowest on the back blasting face.The larger number of explosives,the greater the attenuation of vibration velocity from the blasting face to the back blasting face.The stress field of the tunnel lining structure undergoes dynamic changes,with the tensile stress value of the back blasting face being approximately 40%to 50%that of the blasting face and exhibiting a pattern of decreasing towards both sides from the point of minimum blast distance.Blast vibration monitoring points should be arranged closest to the blasting center and their locations should be altered promptly with changes in the blasting direction.Under the blast vibration control index of 1.0 cm/s,the possibility of additional stress generated by blasting causing damage to the lining structure is low.