Study on the Response Characteristics of Tunnel Crossing Active Faults of the Yellow River to Xining Water Diversion Project

The Yellow River to Xining water diversion project tunnel in Qinghai province has a total length of 74.4km and cross four regional active faults. Ensuring the safety when tunnel crossing active faults is one of the key issues faced by the Yellow River to Xining water diversion project. Aiming at the above issues, firstly, a thematic research method was adopted to propose the basic parameters of each active fault, providing a basis for targeted design. Secondly, taking the northern edge fault (F₂) of the Nanshan Mountains in Qinghai Province as an example, an elastic-plastic analysis model for tunnel crossing active faults was established using numerical simulation methods to study the response characteristics of the integral and hinged lining under different displacement. The results showed that under the condition of integral lining, the deformation, lining stress, and internal force of the tunnel increase with the increase of displacement. The deformation of the left and right side walls, the maximum tensile stress of the lining, and the maximum shear force appear at the center of the fault zone, while the deformation of the arch top and bottom plate, and the maximum bending moment of the lining appear at the intersection of the fault zone; Under the condition of hinged lining, the longitudinal stress, equivalent axial force, bending moment, and shear force in different parts of the tunnel do not show a significant increase in the maximum stress and internal force with the increase of displacement after reaching 30cm. The deformation mainly occurs at the hinge joint, effectively improving the stress state of the lining under displacement conditions. Finally, the next research direction for the Yellow River to Xining water diversion project tunnel crossing active faults is proposed.