周边爆破中增设空孔，能够提升隧道轮廓质量，有效控制围岩损伤破坏，避免出现超欠挖和围岩稳定性差等问题。为了揭示空孔对周边爆破定向断裂及损伤控制的作用机理，更好地应用空孔周边爆破技术改善爆破效果，依据弹性力学、断裂力学、损伤力学及爆炸动力学等相关理论，系统阐述空孔对围岩损伤的控制作用，全面得出周边爆破中的空孔效应，进而给出空孔周边爆破参数的计算方法；采用实验室试验的方法，研究静载和冲击荷载作用下空孔孔径、孔间距等对岩石力学性能的影响，揭示空孔效应对岩石裂纹扩展的作用机理；设计、实施空孔周边爆破模型试验，分析空孔不同条件下周边爆破的损伤控制效应，完善空孔周边爆破的作用机理，丰富空孔周边爆破技术；建立苍龙山隧道工程的数值模型，开展空孔周边爆破技术的应用实践，验证空孔周边爆破损伤控制作用，优化苍龙山隧道周边爆破的参数设置，指导解决隧道建设的实际问题。研究得出以下主要成果：

    （1）空孔可有效控制周边爆破对围岩的损伤破坏：空孔能够对周边岩体产生初始损伤，促进爆破裂纹定向扩展，减少装药量，降低爆破振动对围岩的损伤破坏；空孔能够增加崩落孔爆破和周边爆破自由面的数量，隔断应力波的传播路径，应力波反射作用增强，削减爆炸载荷对围岩施加的应力；周边炮孔产生的爆炸应力波遇到空孔后，空孔迎爆侧首先出现初始裂纹，其切向应力释放，应力卸载波在围岩内传播，抑制围岩内随机裂纹的出现，诱导其它方向裂纹不断向两孔连心线方向偏转、靠拢，有效地控制周边爆破对围岩的损伤影响。

    （2）通过分析空孔孔径对应力波反射范围的影响，建立空孔孔径与应力波反射作用的影响关系式。空孔孔径越大，空孔的应力集中作用和对应力波的反射作用增强，岩石压密阶段变长，应变增大，峰值应力减小，损伤变量跳跃式增长，有利于贯通裂纹的形成和开挖区域内岩石破碎。同时，空孔孔径越大，能有效隔断应力波向背爆侧的传播，围岩内峰值振动速度降低，削减围岩所受应力，抑制随机裂纹扩展，基本保持岩石的原有强度，围岩的损伤破坏范围减小。

    （3）理论推导求得空孔效应对周边爆破炮孔间距的解析解。空孔与起爆孔间距较小时，无法发挥爆生气体和空孔效应对裂纹定向扩展的作用，爆炸能量利用率较低；间距过大时，爆炸应力波的衰减比较明显，空孔效应不足以使导向裂纹与爆生裂纹有效贯通，无法满足开挖要求。合理的炮孔间距设置可有效促进空孔效应的发挥，引导更多地爆炸能量作用于开挖区域的岩石破碎，裂纹沿轮廓线定向扩展、贯通，减少凹凸度，改善周边爆破成形质量，围岩内有效应力值较小，爆破对围岩的振动强度降低，有利于控制围岩的损伤破坏。模型试验与理论分析结果一致表明空孔效应能够将炮孔间距扩大30%。

    （4）空孔周边爆破对岩石断裂损伤破坏的机理是周边炮孔起爆后，在空孔方向产生最长径向裂隙，空孔周边的应力集中和反射拉伸波在空孔与起爆孔连线之间形成最大拉应力，空孔迎爆侧出现初始导向裂纹，引导和界定后续裂纹的扩展方向，最终在爆炸载荷和空孔效应的共同作用下，空孔定向裂纹与爆生裂纹沿开挖轮廓线相互贯通；空孔增大周边爆破的炮孔间距，减少装药孔数量，爆破自由面增加，隔断应力波的传播路径，加速应力波衰减，促使裂纹在两孔连心线方向扩展，切向应力释放，抑制随机裂纹的出现，围岩内微裂纹密度降低，损伤范围减小，有效地控制周边爆破对围岩的损伤破坏。

    （5）空孔周边爆破技术是将空孔设置于开挖轮廓线的周边起爆孔中间，利用空孔效应，引导裂纹定向扩展，形成良好开挖轮廓，减少装药量，削减围岩所受应力，抑制随机裂纹的出现，有效保护围岩。建立苍龙山隧道工程的仿真模型，将空孔周边爆破技术应用于工程实际，验证空孔效应对周边爆破断裂损伤的影响，优化苍龙山隧道的空孔周边爆破参数设置，指导解决现场实际问题。

    The quality of tunnel profile can be improved, the damage and destruction of surrounding rock can be effectively controlled, and the problems of over-excavation or under-excavation and poor stability of surrounding rock can be avoided by adding empty holes in perimeter blasting. In order to reveal the action mechanism of the empty hole on directional fracture and damage control of perimeter blasting, and better apply the empty-hole perimeter blasting technology to improve the blasting effect, according to the relevant theories of elasticity mechanics, fracture mechanics, damage mechanics and explosion dynamics, the control effect of empty hole on surrounding rock damage is systematically expounded, the empty-hole effect in perimeter blasting is comprehensively obtained, and then the calculation method of blasting parameters around empty hole is given. The effects of pore size and hole spacing on mechanical properties of rock  under static load and impact load were studied by laboratory tests, and the mechanism of empty-hole effect on rock crack propagation was revealed. Design and implement the model test of empty-hole perimeter blasting, analyze the damage control effect of the perimeter blasting under different settings of empty hole, improve the action mechanism of empty-hole perimeter blasting, and enrich the technology of empty-hole perimeter blasting. The numerical model of Canglongshan Tunnel project is established, the application practice of empty-hole perimeter blasting technology is carried out, the damage control effect of empty-hole perimeter blasting is verified, the parameter setting of Canglongshan tunnel perimeter blasting is optimized, and guide to solve the practical problems of tunnel construction. The main results of the study are as follows:

    (1) Empty hole can effectively control the damage and destruction of surrounding rock caused by perimeter blasting: empty hole can produce initial damage to surrounding rock, promote the directional propagation of blasting cracks, cut down the charge, and reduce the damage and destruction of surrounding rock caused by blasting vibration. The empty hole increases the number of free surface for caving hole blasting and perimeter blasting, the propagation path of stress wave is cut off, the reflection effect of stress wave is enhanced, and the stress imposed by explosion load on surrounding rock is reduced. When the explosion stress wave generated by the perimeter hole encounters the empty hole, the initial crack is first appeared on the blasting side of the empty hole, the tangential stress is released and the stress unloading wave propagates in the surrounding rock, which can restrain the random crack occurrence in the surrounding rock, and induces cracks in other directions to deflect and converge to the connecting line of the two holes, effectively control the damage and failure of the surrounding rock.

    (2) By analyzing the influence of empty hole aperture on stress wave reflection range, the relationship between empty hole aperture and stress wave reflection is established. The larger the empty hole diameter, the greater the stress concentration and the stress wave reflection, the longer the compaction stage, the larger the strain, the lower the peak stress, and the jump growth of the damage variable,which are conducive to the formation of penetrating cracks and rock fragmentation in the excavation area. The larger the aperture of the empty hole, the propagation of the stress wave to the backburst side can be effectively cut off, the peak vibration velocity in the surrounding rock is reduced, the stress on the surrounding rock is cut down, the random crack propagation is restrained, the original strength of the rock is basically maintained, and the damage range of the surrounding rock is reduced.

    (3) The analytical solution of empty-hole effect on the spacing between the perimeter blasting holes is derived theoretically. When the spacing between the empty hole and the detonating hole is small, the effect of explosive gas and the empty-hole effect on the directional crack propagation cannot be exerted, and the utilization rate of explosive energy is low. When the spacing is too large, the attenuation of the explosion stress wave is obvious, and the empty-hole effect is insufficient to effectively connect the guiding crack with the explosive crack, which cannot meet the requirements of excavation. The reasonable spacing can effectively promote the play of the empty-hole effect, guide more explosive energy to act on the rock fragmentation in the excavation area, and the cracks are directionally extended and penetrated along the contour line, reduce the concavity and convexity, improves the perimeter blasting forming quality, reduces the effective stress in the surrounding rock, decreases of strength of blasting vibration, smaller values of the effective stress, lower the blasting vibration intensity on surrounding rock, and beneficial to control the damage and destruction  of surrounding rock. The model test results are consistent with the theoretical analysis results, indicating that the empty-hole effect can enlarge the blasting hole spacing by 30%.

    (4) The mechanism of rock fracture damage caused by empty-hole perimeter blasting is that the longest radial cracks is generated in the direction of empty hole after perimeter hole blasting, the maximum tensile stress is formed between the line of the empty hole and the detonation hole by the stress concentration and the reflected tensile wave around the empty hole, and the initial guided crack is appeared on the blast-facing side of the empty hole, which leading and defining the propagation direction of the subsequent crack. Finally, under the combined action of the explosion load and the empty-hole effect, the directional crack of the empty hole and the blasting crack are connected with each other along the excavation contour line. The empty hole increases the blasting hole spacing of perimeter blasting, reduces the amount of charge hole, increases the blasting free surface, cuts off the propagation path of stress wave, accelerates stress wave attenuation, promotes the crack to expand in the two holes defiled line direction, releases the tangential stress, restrains the occurrence of random cracks, reduces the density of microcracks in the surrounding rock, narrowes the damage range, and effectively controls the damage and destruction of the surrounding rock caused by the perimeter blasting.

    (5) The empty-hole perimeter blasting technology is to set the empty hole in the middle of the perimeter blasting hole of the excavation contour, use the empty-hole effect to guide the directional expansion of the crack, form a good excavation contour, cut down the charge, reduce the stress on surrounding rock, restrain the appearance of random cracks, and effectively protect the stability of the surrounding rock. The simulation model of Canglongshan Tunnel Project is established, the empty-hole perimeter technology is applied to the engineering practice, the influence of empty-hole effect on the perimeter blasting fracture damage is verified, the parameters of empty-hole perimeter blasting of Canglongshan tunnel are optimized to guide the solution of practical problems in the field.