To mitigate frequent landslides at the Bolu Tunnel, designs for a micro-piled wall system and tunnel extension projects were developed and implemented. Within the scope of the (O4-25) KK Bolu Mountain Tunnel Portal Exit (Asarsuyu Area) Km: 3+800 Landslide Investigation and Engineering Service Procurement, planned by the T.C. Ministry of Transport and Infrastructure, General Directorate of Highways, 4th Regional Directorate, a SC-Special 62s multi-plated corrugated steel structure was designed to serve as the extension structure for the existing highway tunnel affected by the landslide.