Prevention and Remediation of Rockslide at Left Portal of North Tunnel of Da Nang – Qu Ang Ngai Expressway in Quang Nam, Vietnam

Da Nang - Quang Ngai Expressway is one part of the North - South Expressway of Vietnam being 130km in length, 24.5m in width. The Tunnel is a section of 4 construction packages with station of 22+500km – 23+000km. The tunnel is designed to go through a small hill, altitude of about 120m above sea level and 500m long and has two bounds – called North and South Tunnel. The North Tunnel has two portals – left and right. Bedrock is sedimentary rock (alternation of sandstone and conglomerate). Authors have investigated the field, detected inaccuracy in geotechnical investigation report, applied discontinuity model and failure criterion for anisotropic rock, analyzed stability of rock slope and proposed a solution to prevent rockslide at the Left Portal of the North Tunnel of the Expressway.