Abstract: The shallow burred and unsymmetrical pressured highway tunnels have more safety hazards than other tunnels during the construction. A two-lane high tunnel experienced a crest collapse and the cracking in the initial supporting structures towards the shallow buried exit. The geotechnical, hydrological investigations indicated that the loose gravelly and boulderlike soils, which are difficult in the forming of the arching effect, are deposited at the collapsed area. The heavy precipitation was a majoring triggering factor to the crest collapse and the cracking in the tunnel supporting structure. The remediation measures included: backfilling of the collapsed area, ground backfill and improvement; installation of the perforated grouting steel pipes; installation of the pilot radial grouting pipes, installation of the pipe roof, installation of first immediately followed by the  secondary lining as well as construction monitoring.

Key words: two-lane highway tunnel, shallow buried tunnel under unsymmetrical pressure, collapse, cracking, remediation measures