隧道爆破荷载作用下中隔壁动力响应与破坏机理研究

中隔壁结构作为隧道初期支护体系中重要的承载构件，在隧道爆破荷载作用下极易发生损伤开裂和破坏。首先依托双向八车道的港沟高速公路隧道工程，进行爆破荷载作用下中隔壁的动力损伤破坏试验，提出中隔壁支护结构的破坏形态及类型；然后利用ANSYS/LS-DYNA建立隧道爆破与中隔壁支护结构数值模型，采用流固耦合的方法模拟岩体爆破及中隔壁支护结构的动力响应，并考虑单段装药量、爆距等不同因素，研究其对中隔壁破坏模式及形态的影响。研究结果表明：隧道爆破荷载作用下中隔壁破坏形式分为背爆侧混凝土开裂剥落、中心区域混凝土震塌成洞、钢筋网及纵向连接钢筋震坏断裂、钢拱架发生扭曲变形4种类型；中隔壁支护结构在爆破应力波的作用下处于反复拉压状态，并在岩石破碎抛掷冲击的作用下发生破坏，且中隔壁支护结构中心、顶部和底部是结构最易发生损伤的部位；单段装药量和爆距的改变会对中隔壁支护结构的破坏范围和破坏程度产生影响，且结构呈现出不同的破坏形态，与现场试验结果一致；建议隧道爆破施工时爆距控制在40 cm以上，单段药量控制在7.2 kg以下，以减少对中隔壁支护结构的破坏。

Dynamic Response and Destruction Mechanism of Center Diaphragm Support Wall Under Tunnel Blasting

A center diaphragm support wall is an important part of a tunnel's initial support system. However, it is extremely susceptible to damage and developing cracks under tunnel blasting. In this Ganggou Tunnel of 8-lane dual highway project, field tests were performed within the framework of a blasting project for a highway tunnel to study the dynamic response of center diaphragm support walls, and different failure modes were obtained. The ANSYS/LS-DYNA software was used to simulate a model for center diaphragm support walls. A fluid-solid coupling algorithm was selected to simulate the process of rock blasting and the dynamic response of center diaphragm support walls. Different single period charges and distances were considered. The results indicate that the failure modes can be divided into four types, namely, concrete crack, concrete crush, rebar break, and steel arch distortion. Center diaphragm support walls endure repeated tension and pressure under blasting stress waves, and the impact of rock fragmentation and throw is the primary reason for their failure. Moreover, the center and four sides of center diaphragm support walls are extremely susceptible to damage. Changes in the single period charge and distance affect the scope and degree of failure, resulting in different failure modes. The results of numerical simulation are consistent with those obtained from the field test, and indicate that the optimum blasting distance is larger than 40 cm, while the single period charge should be limited to <7.2 kg.