摘要:
隧道开挖循环爆破不可避免会地对围岩造成累积损伤，针对目前数值模拟研究中几乎均是将炸药爆炸荷载简化为冲击荷载的不足，首先针对Bandaki微型爆破试验基于LS-DYNA软件对其进行了数值重现，验证了该数值模型所采用的RHT本构模型、ALE耦合算法及材料参数的合理性。其次，采用该软件真实模拟了某隧道断面88个炮孔的真实爆炸过程，克服目前方法未能考虑爆生气体作用及简化误差的不足，提高了计算精度；同时采用完全重启动技术和初始地应力施加方法很好地模拟了循环爆破与初始地应力耦合作用下隧道围岩的累积损伤机理。最后，基于上述数值模型研究了不同地应力条件下循环爆破对隧道围岩的累积损伤机制，发现随着循环爆破次数的增加，围岩损伤范围逐步扩大，累积损伤效应明显。初始地应力对隧道围岩损伤具有显著的抑制作用，损伤范围随地应力增大而减小。以第三次循环爆破为例，当初始地应力由0MPa逐渐增加到10MPa、20MPa和30MPa时，围岩平均损伤范围则由64.05cm逐渐降低到20.99cm、13.34cm和7.01cm，降低幅度分别为67.2%、36.4%和47.45%，即降低幅度总体上呈逐渐减缓的趋势。研究成果可为隧道爆破开挖工程提供有益参考。
Abstract:
The cyclic blasting in tunnel excavation inevitably causes cumulative damage to the surrounding rock. In view of the deficiency that the explosive load is almost simplified as an impact load in the current numerical simulation studies, the Bandaki micro-blasting test was first numerically reproduced based on the LS-DYNA software, which verified the rationality of the RHT constitutive model, ALE coupling algorithm and material parameters adopted in the numerical model. Secondly, the real explosion process of 88 blast holes in a certain tunnel section was truly simulated by this software, which overcame the shortcomings of the current methods that failed to consider the effect of blast gas and simplification errors, and improved the calculation accuracy. At the same time, the complete restart technology and the initial in-situ stress application method were adopted to well simulate the cumulative damage mechanism of the surrounding rock of the tunnel under the coupling effect of cyclic blasting and initial in-situ stress. Finally, based on the above numerical model, the cumulative damage mechanism of the surrounding rock of the tunnel under different in-situ stress conditions caused by cyclic blasting was studied. It was found that with the increase of the number of cyclic blasting, the damage range of the surrounding rock gradually expanded, and the cumulative damage effect was obvious. The initial in-situ stress had a significant inhibitory effect on the damage of the surrounding rock of the tunnel, and the damage range decreased with the increase of in-situ stress. Taking the third cyclic blasting as an example, when the initial in-situ stress gradually increased from 0 MPa to 10 MPa, 20 MPa and 30 MPa, the average damage range of the surrounding rock gradually decreased from 64.05 cm to 20.99 cm, 13.34 cm and 7.01 cm, with the reduction rates of 67.2%, 36.4% and 47.45% respectively, that is, the reduction rate generally showed a gradually slowing trend. The research results can provide useful references for tunnel blasting excavation engineering.
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