高寒区隧道洞口段覆雪波纹钢棚洞减载方法研究

Study on load reduction method of snow-covered corrugated steel shed hole at tunnel entrance in alpine region

高寒区隧道洞口段易受上方覆雪及落石影响,采用现有大跨径波纹钢棚洞会产生较大变形和失稳,影响边疆公路运行安全。为此,依托某线路隧道洞口段波纹钢防雪棚洞项目,从拱效应及加筋桥减载原理出发,运用有限元软件构建了EPS板、EPS板+加筋雪、EPS板+加筋冰等10种减载方案的三维波纹钢棚洞模型,研究不同减载方案对棚洞应力、棚洞变形和覆雪压力的影响,对比分析棚洞受力变形特征及减载效果,筛选出最优减载方案。结果表明:施加减载材料后,棚洞上方覆雪压力均不同程度分散到棚洞两侧,减小了棚洞结构的受力;随着覆雪高度增加,减载效果更显著,其中30 cmEPS板+加筋冰组合式方案的减载效果最佳,棚顶应力减少32.72%,棚顶位移减小22.63%;针对波纹钢棚洞的减载问题,建议隧道洞口30 m范围内采用30 cmEPS板+加筋雪方案,距隧道口30 m以外范围可采用30 cmEPS板+加筋冰方案。

The tunnel entrance section in alpine region is easily affected by snow load and rockfall.Using the existing long-span corrugated steel shed hole will cause large deformation and instability,which will affect the safety operation of the border highway.Therefore,based on the corrugated steel snow shed hole project at the entrance of a tunnel of a certain line,starting from the arch effect and load reduction mechanism of stiffened bridge,the three-dimensional corrugated steel shed hole models of 10 load reduction schemes were conducted by using finite element software,including EPS plate,EPS plate+reinforced snow,EPS plate+reinforced ice.The effect of each load reduction scheme on the stress of shed hole,shed hole deformation and snow cover pressure were studied.The stress deformation characteristics and load reduction effect of steel shed hole were compared and analyzed,and the optimal load reduction scheme was selected.The results show that after applying the load reduction material,the snow cover pressure above the shed hole is dispersed to different degrees on both sides of the shed hole,which reduce the force of the shed structure.With the increase of snow cover height,the effect of load reduction is more significant.Among them,the combined scheme of 30 cm EPS plate+reinforced ice has the best load reduction effect.The roof stress is reduced by 32.72%and the roof displacement is reduced by 22.63%.In view of the load reduction problem of corrugated steel shed hole,it is recommended to adopt 30 cm EPS plate+reinforced snow scheme within 30 m of the tunnel entrance,and 30 cm EPS plate+reinforced ice scheme can be used for 30 m distance away from the tunnel entrance.