Abstract: The crystallization blockage often occurs in the central drainage pipe of the tunnel. Hence, a cleaning technology for the central drainage pipe of the Guangxi expressway tunnel is tested. First, the blockage degree of the central drainage pipe of the tunnel is preliminarily judged by reconnaissance of the outlet and drainage ditch of the tunnel. Second, the positions of the central drainage pipe and the central inspection well are determined according to the tunnel design drawings and ground penetration radar scanning. Third, an inspection hole above the central drain pipe is drilled to check the internal conditions of the drain pipe using an industrial endoscope. Fourth, the pavement is cut to clean the working well. Fifth, the crystalline substance in the central drainage pipe of the tunnel is cleared using a highpressure cleaning vehicle and rechecked by a pipeline robot. Finally, the pavement is restored. By using this suite of cleaning technology, the blocked section of the central drainage pipe has been completely dredged, the crystalline substances in the pipe have been cleaned up, the drainage function has been restored, various risks caused by poor drainage have been reduced, the tunnel traffic safety and structural safety have been ensured, and the tunnel maintenance cost has been reduced, providing reference for similar projects.

Key words: highway tunnel, central drainage pipe, crystallization blockage, pipe inspection, highpressure cleaning