Abstract:

At present, the primary measure Is clearing foundation in patchy permafrost regions, which slove the permafrost issues under the highway subgrade in Heilongjiang province. The influences induced by clearing foundation or not are analyzed by the method of field investigations and numerical simulation calculation. The study indicates that the project of clearing foundation or not is feasible. But it is disadvantage to the heat stability of subgrade by clearing foundation. The significant influence takes place in the 1－3 years after the highway constructed; during which artificial permafrost table increased obviously, but not resulted in a large area of subgrade thawing settlement. The long-term influence by clearing foundation made the annual average ground temperature increase and artificial permafrost table in middle of subgrade reduce in permafrost regions. It also developed thawing core in soil profile ahead of almost four month in subgrade; and the thickness of thawing core in soil profile would increase about 0.3 to 0.6m than without clearing foundation. Through above analysis, the main influence factors that caused greater effect on thermal field of roadbed by clearing foundation are the season constructed and initial temperature of soil after backfilling.

Key words: patchy permafrost regions, highway subgrade, foundation clearing, field test, numerical simulation calculation