<p>The Luding-Shimian Highway is located in the west of Sichuan, China. The geological movement is active in this area, and the dikes are widely distributed. During tunnel excavation, dike intrusion frequently leads to significant deformation and falling blocks of the surrounding rock. After the construction of the secondary lining, severe cracking was observed in the dike-intruded area of the Chuni Tunnel. XRD analysis, thin-section identification, and uniaxial compression testing revealed alterations in the intrusive dike area, including the formation of clay minerals and reduced uniaxial compressive strength. The parameters of FEM were determined by Hoek–Brown criterion. The force of the structure was asymmetrical due to the differing properties of the bedrock and intrusive dike. The position of dike intrusion can help identify the vulnerable areas of the tunnel lining. When the dike approaches the tunnel face, steep lateral deformation changes may lead to circumferential cracking at the side wall. If the dike intrudes from the arch waist position, excessive deformation increases the likelihood of longitudinal cracking at the arch waist and side wall. At the same time, the inverted arch also has the risk of uplift. When the dike intrudes from the vault position, damage to both the vault and the inverted arch becomes more probable. To address these challenges, the proposed measures included increasing the thickness of the secondary lining, reinforcing the surrounding rock through grouting, closing the inverted arch. The measures enhances tunnel stability and safety, addressing a critical research gap in dike-intrusive strata and providing theoretical and practical support for similar conditions.</p>