Local failure mechanism of sand-blocking fence in latticed dune along desert roads

The latticed dunes in the Tengger Desert are widely distributed, and the sand-blocking fence placed here are highly susceptible to local failure due to complex wind-sand activities, posing a serious threat to the safe operation of the highway. To explore the local failure mechanism of sand-blocking fence in the latticed dune area, the local failure of sand-blocking fence in the latticed dune areas along the Wuhai-Maqin Highway in China was observed. Taking the first main ridge of the latticed dune as the placement location, the structure of the wind-sand flow field of sand-blocking fence placed at top, the bottom and the middle of windward slope was analyzed by Computational Fluid Dynamics (CFD). The results show that when placed at top of the first main ridge, the wind speed near the sand-blocking fence is the highest, up to 15.23 m/s. Therefore, the wind load strength on the sand barrier is correspondingly larger, up to 232.61 N·m−2. As the strength of material continues to decrease, the nylon net is prone to breakage. The roots of the angle steel posts are susceptible to hollowing by vortex action, which can cause sand-blocking fence to fall over in strong wind conditions. When placed at the bottom of windward slope, wind speed drop near sand-blocking fence is greatest, with the decrease of 12.48–14.32 m/s compared to the original wind speed. This is highly likely to lead to large-scale deposition of sand particles and burial of the sand-blocking fence. When placed in the middle of windward slope, sand-blocking fence is subjected to less wind load strength (168.61N·m−2) and sand particles are mostly deposited at the bottom of windward slope, with only a small amount of sand accumulating at the root of sand-blocking fence. Based on field observations and numerical modelling results, when the sand-blocking fence is placed in latticed dune area, it should be placed in the middle of the windward slope of the first main ridge as a matter of priority. Besides the sand-blocking fence should be placed at the top of the first main ridge, and sand fixing measures should be added.