| In Hokkaido’s environment of heavy snowfall、 damages are caused by snow accumulation and snow accretion on various structures above ground. Snow falling from road signs located extensively along roads may cause damage to passing vehicles or create accidents as a result of blocked vision. The authors conducted a field test on countermeasures to reduce such damages in a region characterized by heavy snowfall、 and examined their effects in terms of amounts and grain types of accumulated snow. [*] The test was conducted in the Nakayama Pass near Sapporo between December 14、 2007 and February 29、 2008. Four types of countermeasure were applied - sloping roofs with gradients of 45 and 60 degrees (A-45、 A-60) and two types of pent roofs (B-45、 B-60). Cross-sectional observation was conducted three times for snow accumulating on these countermeasure roofs and on beam material with diameter of 21.63 cm. In the observation、 the volume of accumulated snow per unit width was obtained by measuring the cross-sectional shape and the snow density. [*] The mean temperature was -8.8 degrees Celsius and the maximum snow depth was 233 cm during the test period. The observation results revealed that snow accumulation of 50 cm or higher formed even on the countermeasure structures、 that the snow density was 150 kg msup-3 or lower、 and that the main grain types of accumulation were dry compacted snow and new snow. When the volume of accumulated snow was 0.1 msup3 or smaller、 the volumes on all countermeasures were larger than that on beam material. However、 since all accumulated snow had small amounts and low density、 the likelihood of damage caused by accumulated snow falling was considered low. Conversely、 the volumes of the accumulated snow on A-45、 A-60 and B-45 were similar to that on the beam material when the volume was 0.2 m3 or larger. Here、 the height of accumulated snow were 50 cm or higher - large enough to block a driver’s vision if they fell onto the windshield of a passing vehicle. Only the volume on the B-60 structure was as small as approximately 50% of that on the beam material、 and the height of accumulated snow was limited to around 30 cm. From the above results、 it was presumed that the pent-roof countermeasure structure with a gradient of 60 degrees (B-60) would be effective in reducing the volume of snow accumulation in regions with heavy snowfall. |
