粘结式锚杆在爆炸动载下轴向应力分布研究

Axial stress distribution of grouted rockbolts subjected to blast loading

通过物理模型试验,研究在爆炸动载作用下临近工作面支护锚杆的应力状态。根据相似条件和简化假设,采用集中装药进行工程掏槽爆破模拟,利用粘贴在锚杆上的应变片测得近区端锚和全锚锚杆的轴向应变波。测试结果表明,爆破引起锚杆振动时间约为6 ms,经过9 ms的缓降期锚杆变形趋于稳定值;动载期间端锚锚杆在杆体中部锚固段测得峰值应力比杆体尾部自由段的值大,但相差不大,动载过后尾部的残余应力较大;全锚锚杆在杆体尾部测得的峰值应力和残余应力都远大于杆体中部测得值。利用无限体内一点受法向集中力作用的位移势函数,推导锚固体及周围岩体的轴向应力分布,并计算一定预应力在锚固区产生的附加轴向应力,结合动应力的作用分析锚杆的受力状态。

By model test,the stress distribution of anchored rockbolts close to working face is studied when subjected to blast loading.Based on similar condition,simplification and hypothesis,engineering cutting blasting was simulated in mass charge.Axial strain waves measured from strain gauges mounted on rockbolts were recorded considering both of end-anchored and full grouted rockbolts.Test results show that rockbolt vibration approximately ceases after duration of 6 ms and then bolt deformation keeps stable in 9 ms.For end-anchored bolts,peak stress on middle locations of bolts in anchor section is slightly greater than the value of tail location in smooth section when bolts are subjected to blast loading;but the latter presents a greater residual stress.For full grouted bolts,peak stress and residual stress measured on tail section exceed the values on central section.Utilizing displacement potential function of the infinite body under single force,distribution of axial stress on anchoring body and surrounding rock is theoretically deduced;and additive axial stress on anchored section is calculated under some prestress.Based on the state of additive axial stress and dynamic stress,stress condition of rockbolt is analyzed.