微差段间重复扰动导致深埋隧洞围岩损伤机制

 爆破荷载和地应力的瞬态卸载是深埋隧洞开挖损伤区孕育及演化的重要影响因素。根据深埋圆形隧洞爆破开挖过程，采用理论模型和数值模拟相结合的方法分析开挖面上各段爆破引起的爆炸荷载和地应力瞬态卸载应力场的变化规律，并比较各段爆破开挖对隧洞保留岩体的损伤程度。计算结果表明，爆炸荷载对围岩岩体造成的破坏主要是张拉破坏或张剪破坏，地应力瞬态卸载造成的破坏主要是压剪破坏；各段开挖爆炸荷载和地应力瞬态卸载对最终的开挖损伤区均有贡献，体现了重复扰动损伤效应，其中以MS7和MS9段的影响最大，表明各段开挖对最终损伤程度的影响不仅与荷载值的大小有关，与各段的开挖半径同样关系密切；当地应力水平不断提高时，地应力瞬态卸载对损伤区的贡献也会越来越明显；当深埋隧洞开挖的爆破参数相同时，地应力水平将成为围岩损伤的决定性因素。

Damage mechanism of surrounding rocks due to repeated disturbance between blasting delays in deep tunnels

Blasting load and geostress transient unloading are important factors influencing the development of excavation damage zone(EDZ) in deep tunnels. The blasting load and geostress transient unloading of every blasting delays were analysed，and the damage extents of surrounding rocks induced by blasting excavation were compared based on the results from the theoretical model and numerical simulation. The damage mechanism of the blasting load was found to be mainly tension or tension-shear failure and the geostress transient unloading was mainly the compression-shear failure. On the excavation face，every blasting delays had an contribution to the final EDZ which reflected the repeated disturbance and the MS7 and MS9 were the main contributors to the EDZ. The EDZ induced by every delays is not only related to the load value，but also associated with the excavation radius. In addition，the higher the geostress level，the higher influence on the EDZ that caused by geo stress transient unloading. Under the same condition of blasting parameters，the geostress level is the decisive factor to the development of EDZ during deep tunnel excavation.