泥石流冲击作用下隧道明洞结构变形及损伤规律研究

Deformation and Damage Patterns of Opencut Tunnel Structures under Impact of Debris Flow

摘要:

西部山区交通线路上，山岭隧道容易遭受泥石流的冲击，进出口处的明洞结构损毁尤为严重。然而，泥石流对隧道明洞结构的灾害作用机理尚不清晰，其难点在于协调描述泥石流的流体力学响应与明洞的固体损伤响应。为此， 发展了耦合欧拉-拉格朗日数值方法，采用宾汉姆模型描述泥石流的流体力学性质，采用混凝土塑性损伤模型描述明洞结构的应力应变关系，通过模拟福堂隧道明洞受灾的真实案例，阐明了泥石流冲击作用下明洞结构的变形及损伤规律。仿真结果显示，迎流面冲击合力与冲击速度的平方成正比，明洞结构的损伤主要形成于冲击合力达到峰值的过程中。位移最大位置出现在迎流侧的边墙上，衬砌内表面出现沿轴向的张拉裂缝，外表面出现成片的剥落损伤。随着泥石流冲击速度和泥石流屈服应力的提高，明洞损伤加剧，裂缝斜向延伸到过流断面以外的区域，并可导致衬砌的失稳破坏。相较于侧面冲击，压顶冲击能够大幅降低明洞损伤程度及其对冲击速度的敏感性。上述结果表明，为提高我国隧道工程的泥石流灾害防治能力，需要对泥石流发育位置及成分进行现场勘查，建立相应措施降低泥石流冲击速度， 同时可通过隧道-山体空间关系的设置导向冲击发生位置，以降低泥石流的损伤作用。

Abstract:

Along the transportation routes in mountainous areas of western China, mountain tunnels are susceptible to debris flow impacts, with the open-cut tunnel structures at tunnel entrances and exits being particularly prone to severe damage. However, the disaster mechanism of debris flow acting on open-cut tunnel structures remains unclear. The primary challenge lies in the coordinated description of the hydrodynamic response of debris flow and the solid damage response of open-cut tunnel structures. To address this, a coupled Eulerian-Lagrangian numerical method was developed. The Bingham model was used to describe the hydrodynamic properties of debris flow, and the concrete damage plastic model was employed to characterize the stress-strain relationship of open-cut tunnel structures. By simulating a real disaster case at the Futang Tunnel, the deformation and damage patterns of the structure under the impact of debris flow were elucidated. The simulation results showed that the total impact force on the upstream side was proportional to the square of the impact velocity, and the damage to the open-cut tunnel structure primarily occurred during the process when the total impact force reached its peak. The maximum displacement was observed on the sidewall of the upstream face, with axial tensile cracks developing on the inner surface of the lining and extensive spalling damage on the outer surface. As the debris flow impact velocity and yield stress increased, the damage to the open-cut tunnel intensified, with the cracks extending obliquely beyond the flow cross-section and potentially leading to the instability failure of the lining. Compared with the side impacts, crown impacts could significantly reduce the damage level of the open-cut tunnel and its sensitivity to impact velocity. The above findings indicate that to enhance the debris flow disaster prevention and control capacity of tunnel engineering in China, it is necessary to conduct field investigations to determine the development locations and composition of debris flow. Corresponding measures should be established to reduce debris flow impact velocity. Moreover, the spatial relationship between tunnels and mountains can be utilized to guide the impact location, thereby mitigating the impact damage of debris flow.