隧道进口岩堆斜坡爆破振动动力响应研究

Dynamic response of talus slope at entrance of tunnel under blasting vibration

隧道钻爆法施工影响进口段岩堆斜坡稳定性,因此有必要开展爆破振动作用下岩堆斜坡动力响应规律研究。以大前石岭隧道爆破掘进为例,通过现场监测分析爆破振动作用下加速度、速度响应规律;对萨道夫斯基经验式及其衍生式进行改进并进行适用性评价。结果表明:爆破振动作用下斜坡振动加速度、速度随爆心距增加而逐渐减小,在洞口1~2倍隧道建筑限界长度段存在放大效应;改进式整体上能较好地拟合岩堆斜坡峰值振速,但在边界处适用性较差;不同条件下不同经验式拟合效果不同,采取单一经验式预测爆破振动速度会受限于拟合优度;何理经验式各方向速度拟合效果最好;基于坡面位置几何关系变换萨族经验式形式,改进式能更好地解释坡面峰值速度分布规律,并预测出最大速度及其具体位置;基于改进式提出了最大爆破振动速度和具体位置的简单算法,以此优化药量并进行安全判断;现场隧道掘进至130 m处采用80 kg药量进行爆破时,洞口岩堆斜坡振动速度峰值(4.37 cm/s)小于安全振动速度(8 cm/s),该药量下爆破施工对岩堆斜坡稳定性影响较小,斜坡基本处于安全状态。

Due to the influence of tunnel drilling and blasting construction on the slope stability of the talus slope in the entrance section,there is a lack of research on the response law of blasting vibration of loose talus slopes and theoretical tools to guide field blasting.Therefore,it is necessary to research the dynamic response law and velocity prediction of rock heap slope under blasting vibration to avoid accidents caused by excessive vibration velocity.We carried out a talus slope blasting excavation test in a certain place and obtained the test data to analyze its response characteristics.Then we used the Sadovsky’s empirical formulas to fit the velocity and obtained the maximum vibration velocity and position of the talus slope to guide the blasting operation,monitoring,and safety protection.(1)Through field monitoring,it is found that the acceleration and velocity of slope vibration under blasting vibration decrease gradually with the increase of blasting center distance,and there is an amplification effect in the hole section of 1-2 times the length of the limit height of tunnel building.It is suggested that this be used as the length of vibration protection for the tunnel entrance.(2)As many scholars have improved the Sadovsky formula,it is not clear how the applicability and accuracy of these formulas in predicting the blasting vibration velocity of rock slope are.Besides,we found that there is a self-correlation problem between these formulas and the amount related to the spatial position,which cannot well reflect the influence of parameters on velocity.Therefore,we established the slope spatial coordinate system,and transformed the formulas according to the spatial geometric relationship of blast center distance,horizontal distance,and elevation,so that the independent variables are not self-related.Then we carried out the applicability evaluation.The study found that,on the one hand,the improved formulas can explain the relationship between peak velocity and related variables,and show the distribution law on the slope better.On the other hand,the improved formulas can better fit the peak vibration velocity of the talus slope on the whole;But the applicability of the boundary is poor.The fitting effect of different formulas is different under different conditions.Finally,As one of derivative formulas,Heli’s formula has the best fitting effect on velocity in all directions.Therefore,based on data fitting,we obtained a complete prediction formula of blasting vibration velocity and obtained the maximum velocity and its specific position.In this process,we studied the blasting vibration law of rock pile slope,improved and evaluated the accuracy of Sadovsky formulas in the prediction of talus slope velocity,and proposed a simple algorithm for the maximum blasting vibration velocity and specific location.