Impact Experimental Study On Dynamic Response Characteristics Of Full-length Mortar-anchored GFRP Bolts

In order to solve the problem of blasting vibration destroying the full-length mortar-anchored glass-fiber-reinforced plastic?GFRP?bolts in tunnel support during mining,the dynamic response characteristics of the full-length mortar-anchored GFRP bolts were studied by establishing impact test physical model of the GFRP bolt and FLAC^3D numerical calculation software.Firstly,similarity criteria are established according to the similarity theorem.Similarity and feasibility of test are discussed in two aspects:model and dynamic loading similarity of blasting.Propagation and simulation method of blasting stress wave is analyzed,and size of similar physical model and loading mode of dynamic impact are determined.Then,based on the similar theory,a physical model of impact test for GFRP bolt is established to study the dynamic response characteristics of full-length mortar anchored GFRP bolt.The results show that under the impact load,the axial force of GFRP bolt presents an exponential decay trend from the end of the anchor to the depth of the anchor and decays within the range of 300-400 mm anchor.The maximum axial force is at the orifice position.The maximum axial force of bolt increases linearly with the increase of impact load,and the average maximum axial force of bolt under different impact load decreases with the increase of elastic modulus of test model.Finally,the force distribution characteristics of full-length anchor GFRP bolt under dynamic blasting load are studied by FLAC^3D numerical calculation software.The results show that the axial stress of GFRP bolt under impact load decreases exponentially from the anchoring depth of free section of anchor rod along the fitting curve of rod distribution,and the axial stress at orifice position is the largest,and then decreases rapidly along the direction of rod propagation.The axial tensile stress is symmetrical with the axial compressive stress curve,but the axial tensile stress is greater than the axial compressive stress.The axial tensile stress at the orifice is 1.2-1.5times of the axial compressive stress.With the increase of amplitude of vibration speed,the axial stress of GFRP bolt increases accordingly,and the maximum axial force increases exponentially;furthermore,the stronger the vibration is,the faster the axial stress of anchor increases.With the increase of elastic modulus of surrounding rocks,the maximum axial stress of GFRP bolt decreases continuously under dynamic blasting load,and the faster the stress wave attenuates in the GFRP bolt,that is,the shorter the attenuation distance.The conclusions of physical model test,numerical simulation and theoretical analysis in previous literatures are mutually validated in this paper.The research results provide theoretical support for the design of full-length mortar-anchored GFRP bolt support under dynamic blasting load.