风沙地区铁路路堑挡沙墙设计参数优化与防护效果

为探究风沙地区铁路路堑流场中的湍流-沙颗粒运动特性，针对性地优化设计防护措施的结构参数，对某铁路路堑流场进行了数值模拟分析。基于欧拉-拉格朗日框架建立了LES-DPM三维湍流流场模型，研究路堑在风沙地貌下的风沙流特性及沙颗粒运动规律，并根据其风沙运动特点设计单排挡沙墙和双排挡沙墙两种类型的风沙防护措施，同时通过对不同距离、不同排列方式的流场特征和防沙效果进行对比获取最优的风沙防护措施设计参数。研究结果表明：路堑结构因下凹结构导致堑内出现大量小尺度马蹄涡，钢轨附近多为破碎的低速涡团，湍流结构复杂；钢轨附近风速均小于3.6 m/s,移动沙粒易受逆压梯度影响及紊流作用向路堑内沉降；由于路堑流场的沙埋风险大大增加，对比发现，将高度2 m的挡沙墙布置在迎风侧距路堑20 m可获得最佳的防护效果，大部分颗粒被阻隔在挡沙墙前，越过挡沙墙的颗粒大多沉降在其后回流区内，且粒径均小于0.125 mm;同时发现，当采用前低后高的双排挡沙墙(2 m/3 m)可以进一步增加低速回流区范围并减少运动至路堑内的颗粒数量，提高防护效果。

Design parameters optimization and protection effect of the retaining wall for railway cutting in wind-blown sand region

To investigate the turbulence-sand particle movement characteristics of the flow fields of a railway cutting in wind-blown sand areas and to optimize structural parameters for the protective measures, the numerical simulation analysis of the flow field with a railway cutting was carried out. Based on the Euler-Lagrange framework, the three-dimensional turbulent flow model of LES-DPM was established, and the characteristics of wind-sand flow and the movement of sand particles in the aeolian landform were studied. Two types of the protective measures were designed according to the characteristics of wind-sand movement, At the same time, the optimal design parameters of sand protection measures are obtained by comparing the flow field characteristics and sand prevention effects at different distances and different arrangements. The results show that a large number of small-scale horseshoe vortices appear in the cutting due to the concave structure, and most of the low broken velocity vortices near the rail, the turbulence structure is complex. The wind-velocity near the rail is less than 3.6 m/s, the moving particles is easily affected by the reverse pressure gradient and turbulence to settle into the cutting. The risk of sand burial is significantly increased. Therefore, it has been determined that the most effective protection can be achieved by placing a 2 m high retaining wall on the windward side at a distance of 20 m from the cutting. Most of the particles are trapped in front of the retaining wall, while those that manage to pass through settle in the backflow area behind it, with a particle size less than 0.125 mm. It has been observed that the utilization of a double-row sand retaining wall (2 m/3 m) can further expand the range of low-velocity reflux area and decrease the number of particles entering into the excavation, thereby enhancing its protective efficacy.