LAUSR

Abstract Opencut tunnels are linear arch constructions that are being used as new structures to prevent sand encroachment on railway lines. The large size and shape of the contained structure affect the wind field around the structure in a manner different to how traditional constructions prevent sand accumulation. The present study identified the characteristics of wind velocity and flow fields in opencut tunnels in a wind-tunnel simulation. Results show that airflow having different wind angles (15°–90°) had different effects on the sand-accumulation-prevention characteristics of the opencut tunnel. The inflection point of a rapid change in wind speed was 6H (where H is the vertical height of the model) from the windward side of the opencut tunnel, and the position of an area of strong wind on the upper part of the opencut tunnel gradually moved to the windward side with an increase in the wind angle. This trend was not affected by a change in the indicated wind speed. The reattachment distance on the leeward side decreased with an increase in the wind angle, being 1H at 75°–90°, 2H at 30°–60° and 6H at 15° or less. The protection effect was best for a large angle of the main wind direction (exceeding 75°). Observed characteristics of the wind field show that the opencut tunnel is effective at all wind angles in preventing and controlling railway sand flow hazards and can thus ensure smooth railway operation.