爆炸动载与预紧力静载下全长锚固玻璃钢锚杆受力特征研究

Mechanical behaviour analysis of fully grouted GFRP rock bolts subjected to pre-tension load and blast dynamic load

针对爆破动载下全长锚固玻璃钢锚杆力学响应特征及破坏问题,建立动-静载联合作用下全长锚固玻璃钢锚杆受力分析模型,分析爆破动载下玻璃钢锚杆轴向应力和剪切应力分布特征,研究最大单段起爆炸药量、爆心距、岩体弹性模量对玻璃钢锚杆力学响应特征的影响。结果表明:在爆破动载作用下,全长锚固玻璃钢锚杆轴向应力和剪切应力均集中出现在锚杆尾部锚固段与自由段交界面附近较小范围内,且最大单段起爆药量对锚杆受力影响显著;锚杆轴向应力和剪切应力随着爆心距的增加快速降低,在爆心距10～15 m范围内锚杆受爆破动载影响最大,易发生尾部杆体断裂破坏;随着岩体弹性模量增大,锚杆轴向应力逐渐降低,但剪切应力先逐渐升高后再缓慢降低。研究结果与现有实验室相似试验结论及现场试验现象相吻合,可以为爆破动载下全长锚固玻璃钢锚杆的支护设计及爆破控制提供依据。

In order to analyze the mechanical behavior of glass-fiber-reinforced plastic(GFRP) rock bolt under the blast dynamic load, a new approach was proposed to describe the mechanical behaviour of fully grouted GFRP rock bolts under combined action of dynamic and static loads, the approach was applied to analyze the axial and shear stresses distribution characteristics of GFRP rock bolt under blast dynamic load, the paper analyzed the influence of the quantity of explosives, the distance between the point of interest and the blasting source and the Young’s modulus of rock on the mechanical behaviour of GFRP bolts. It was found that large axial and shear stresses of fully grouted GFRP rock bolt are mainly distributed in a small region near the bolt collar, and the influence of the quantity of explosives on rock bolt is significant. The axial and shear stresses decreased quickly with the distance between the point of interest and the blasting source increased, for the case examined where the bolt is within the range of 10-15 meters from the blasting point, the influence of blast load on rock bolt is significant and the installed GFRP rock bolt is easy to break in the region near the bolt collar. With the increase of the Young’s modulus of rock, the axial stress of rock bolt is decreased and the shear stress of rock bolt is increased firstly and then decreased. The predicted distributions of axial and shear stresses in the rock bolt under blast load s are consistent with published laboratory results and the field test results of GFRP rock bolts. The proposed model provides a method to quantitatively evaluate the effect of blasting on the mechanical behavior of GFRP rock bolts so that a better ground support system can be designed in practical mining applications.