块石通风性能实验研究

青藏铁路广泛采用的块石护坡和块石路基是通过空气对流降低路基的温度起到保护冻土的作用。块石的粒径、孔隙率、通风能力直接影响块石路基的空气对流作用。孔隙率试验测试结果表明:孔隙率与粒径大小有关,随粒径增大而增大。粒径0.10～0.25m的块石,孔隙率大致在38%～48%。通过风洞试验发现,块石层内风压梯度与风速存在非线性关系,与速度的平方成正比;阻力系数随块石粒径增大而减小。通过青藏高原天然风速条件下块石通风基础通风能力分析,块石层起到很好的通风作用。因此,对于温度场的计算,建议考虑块石路基中风的强迫对流作用。

Researches on ventilation properties of block stones layer

Block stones were used to protect permafrost from thawing by air convection effect in the embankment of Qinghai-Tibet Railway.The diameter,porosity and ventilating ability of the block stones pile had important influences on air convection effects.It was shown that the porosity increased with the block stone size.It was about 38%～48% for the block stones in the sizes of 0.10～0.25 m.And it was seen from the wind tunnel tests that the wind pressure gradient had a nonlinear relationship with the wind velocity.The resistance coefficient decreased with the increasing of block stone size.Based on the ventilation ability analysis of the block stone embankment in Qinghai-Tibet Plateau,the block stones layer had stronger ventilated effect.It was suggested to consider the effect of natural wind on thermal field under embankment with block stones layer.