硅藻土护坡在多年冻土地区高填土路基中的应用研究

Application of Diatomite Slope-Protection to Higher Embankment in Permafrost Regions

边坡防护是提高多年冻土地区高路堤稳定性的重要措施之一．通过室内实验给出了硅藻土在不同含水条件下冻融态的导热系数及同一含水条件下的冻融导热系数比，证实硅藻土在100％的稳定含水条件下就可以实现较大的冻融导热系数比．根据硅藻土的这种特性，2003年底在214国道红土坡北侧K391＋000-K391＋120的范围内布设了长度120m的硅藻土护坡试验段和无护坡措施的对比路段．3个周期的观测资料表明，由于硅藻土施工季节不当，在最初的3个周期，硅藻土表现出了较大的热阻作用，硅藻土护坡试验段的坡面温度高于对比断面，左坡脚位置的上限也高于对比断面．但是在这3个周期中，硅藻土护坡试验段正向着有利于冻土发育的趋势发展，而对比断面却趋于恶化．

Preservation of permafrost is one of the two principles adopted by permafrost engineering. Adjusting thermal conductivity is one of the three guiding ideas which can make it become true. Thermal conductivity of frozen saturated diatomite is higher than that of thawed saturated diatomite. Under the condition of water content 100%, the thermal conductivity ratio between frozen and unfrozen diatomite is about 1.5. With the consideration of thermal transfer characteristics, adopting aquiferous diatomite in cold regions is beneficial to the preservation of permafrost. In order to prove the effect, a 120-m long experimental section was arranged at Hongtupo between K391 ＋000 and K391＋120 along the National Highway 214. Both of the side slopes were coated with saturated diatomite. The three-cycle data observed in the field show that the slope with diatomite layer did not cool down to the underlying frozen earth in winter, and served as a thermal insulation layer in summer. Furthermore, owing to the construction season, a large quantity of heat absorbed in the summer can not be released in the winter when the slope surface was coated a layer of dry diatomite. Therefore, in the following three years, slope surface temperature of the test section is higher than the neighboring comparing section without measures. The permafrost table in the left foot is also deeper. The invalidation of the diatomite layer is connected with its weak water retention ability, the arid climate in the test area and the unapt construction season. However, it is a good tendency that ground temperature of test section and the permafrost table is climbing. On the contrary, the comparing section is getting worse.