Model test on deformation and acceleration response of anchorage tunnels’ arch vaults under top explosion

If the deformation or acceleration of arch vault is too large,the surrounding rock of underground cavern will be damaged or unstable. In order to investigate the response regularities of arch vault’s deformation and ac-celeration to the explosion loads,the indoor top explosion model tests have been carried out. According to the principle of Froude similarity,the model tests are designed,and the surrounding rock of the excavation cavern has been strengthened by rockbolts with different anchorage parameters. The differences of deformation,acceleration and final damage morpho- logical characteristics of arch vaults of the caverns with different anchorage parameters are compared through the meas- ured wave curves and peak values of the deformation and acceleration of arch vaults. The results show that when the hoop strain and acceleration waveform curves of arch vaults are at the positive peak under explosive loads,the curva- ture decreases and the surrounding rocks of arch vaults are subjected to tensile deformation. The intervals between rockbolts have a greater effect on the deformation of arch vaults than their lengths. When the lengths of rockbolts increase to a certain extent,the deformation and acceleration of arch vaults are not obviously reduced,but increased con- trarily. When the lengths of rockbolts are the same,the arch vaults of the sparse anchorage caverns shows sink,longitu- dinal and transverse cracks and falling blocks. When the intervals of rockbolts are the same,cracks only appear on the arch vaults of the short and dense anchorage caverns,but deviate from the longitudinal direction,while the deforma- tions are relatively small and only produces longitudinal straight cracks of the arch vaults of the long and dense anchor- age caverns. The deformation of the arch vault of the cavern which elongates arch foot’s rockbolts is one order of mag- nitude smaller than that of a sparse anchorage cavern,and its arch vault’s acceleration is relatively small. Therefore, this reinforcement method is helpful to maintain the stability of arch vault. By comprehensive comparing the influences of deformation and acceleration on the stability of arch vaults of the anchorage caverns,it is found that the former can be regarded as the key index to assess the stability of arch vaults to some extent,but the latter can only be regarded as auxiliary index.