青藏铁路涵洞周围沙害形成机理的数值分析

Numerical Analysis on Formation Mechanism of Sand Damage Around Culvert of Qinghai Tibet Railway

针对青藏铁路涵洞沙害形成情况,采用数值模拟和现场测试相结合的手段,对涵洞周围风沙流场特征进行分析,探究了沙害形成机理,并对风沙地区涵洞的设计提出了建议。结果表明:风沙流途经涵洞时,气流速度发生了变化使得风速重新分布,在涵洞背风侧形成相对弱风区,在迎风侧涵洞口形成相对强风区;洞口气流速度衰减是涵洞产生沙害的直接原因,积沙从洞口逐渐向内延伸长,最终堵塞涵洞;涵洞宽度一定时,高度越高洞口气流速度衰减幅度越小,越不容易引起积沙;在风沙地区设计涵洞,条件允许时建议提高涵洞高度。

In view of the formation of sand damage in the culverts of Qinghai-Tibet railway,the characteristics of wind sand flow field around the culvert were analyzed by means of indoor numerical simulation and field test,the formation mechanism of sand damage was explored,and some suggestions on the design of culvert in wind sand area were put forward.The results show that when the wind sand flows through the culvert,the air velocity changes,resulting in the redistribution of wind speed,forming a relatively weak wind area on the leeward side of the culvert and a relatively strong wind area at the culvert opening on the windward side.The attenuation of airflow velocity at the culvert entrance is the direct cause of sand damage to the culvert.The accumulated sand gradually extends inward from the culvert entrance and eventually blocks the culvert.When the culvert width is constant,the higher the height,the smaller the air velocity attenuation at the entrance of the culvert,and the less likely it is to cause sand accumulation.When designing culverts in windy and sandy areas,it is recommended to increase the culvert height when conditions permit.