Design Principles and Frost Damage Characteristics of Frozen Soil Roadbed along the Heihe-Bei'an Highway
MENG Fan-song 1 , LIU Jian-ping 1 , LIU Yong-zhi 2 (1. Expressway Construction Bureau of Heilongjiang Province,Harbin Heilongjiang 150036, China; 2. State Key Laboratory of Frozen Soil Engineering, CAREERI, CAS, Lanzhou Gansu 730000, Ch
The Heihe-Beian Highway is located in sporadic permafrost regions, where 17 sections of permafrost, 3.165 km in length, appear. The mean annual ground temperature is high and the thermal stability is poor. Sporadic permafrost presents in swale swampy wetland with peat and surface water. Permafrost distribution and development has an obviously difference in different topographic units under the effect of conversing-temperature, vegetation, soil, aspect, surface water and ground water. Generally, permafrost mainly appears in ditch valley. No permafrost appears in high slopes and mountains. Seasonally frozen and thawed depth is about 1.5 to 2.0 m, with the maximum up to 2.5 m. Thickness of permafrost is about 3 to 6 m, with the maximum about 9 m. Ground ice takes place in massive, micro-layered, layered cryostructures near the permafrost table. Problems of frost heaving and thaw settlement, i.e., frost heaving in seasonal frozen areas and thaw settlement in permafrost areas, always occur. Frost heaving is extremely strong in swampy sections, strong in slope sections, and slight in hill sections. Permafrost conditions, its type and ground ice should be considered in the design principles of roadbed in order to ensure stability and reliability of roadbed in the regions of sporadic permafrost. Maintaining original design principle can ensure stable of a road with icy soil, because icy soil thawing is unable to result in settlement. Prethawing design principle may be applied to ice-rich and saturated-ice soil, but monitoring the roadbed deformation is necessary. Temporary road surface is used for saturated-ice soil and ice with soil, because the permafrost is too thick for thawing during the construction. It is possible to use a temporary road surface, and then add a concrete pavement after the permafrost under the roadbed thawing. Protecting principle may apply in thick and cold permafrost, because the permafrost cannot be thawed chronically. Cold permafrost must be protected to ensure roadbed stable.
【CateGory Index】： U416.168