Measurement And Analysis On The Settlement Deformation Of Permafrost Foundation Along The Qianfeng-nenjiang Highway

The area of the permafrost is vast, which accounts for22.3%of the landmass ofChina. This percent is the third-highest of the world. A reliable transportation system isthe key factor in maintaining and improving the quality of life in the permafrostregions. The permafrost is a kind of ice-riched soil or rock and is very sensitive tochanges in thermal condition. Its instantaneous strength is much lower than long termstrength due to its rheological behavior. Hence, the temperature and deformation ofpermafrost foundation were studied for many years.A section on the highway from Qianfeng to Nenjiang was investigated as the testsection. The sensors were embedded in the permafrost foundation. The data oftemperature and deformation of permafrost foundation collected from December2011to February2012were analyzed. There were two parts in this research, which wereshown as followings.First of all, through analyses on the temperature data, the influence of the airtemperature and the depth of test spots on the temperature of permafrost foundationwere discussed. The results indicated that the temperature of permafrost foundationincreased as the increasing of air temperature. This trend was more obvious on the testspots which were closer to the surface of foundation. While the test spots were underthe surface of primary ground, the variations of temperature of permafrost foundationover air temperature and depth of test spots were tiny, which indicated that thepermafrost in the test section was protected well and its temperature was stable.Next, the influence of geology and method to process the permafrost ground onthe deformation of permafrost foundation were studied. The results revealed that thedeformation was affected by many factors, and the types of permafrost and themethods to process the permafrost ground were critical factors besides the airtemperature. First, the soil ice was much more sensitive to the disturbance and thevariation of air temperature than the other types of permafrost. The deformation of soilice was larger than other types while the conditions were similar. Second, among themethods to process the permafrost ground employed in the research, the deformationsof foundations with gravel pile were smallest, the deformations of foundationsbackfilled by sand gravel or weathered detritus were largest, and the deformations offoundations with cement stabilized sand gravel pile were in the middle. Third, if the thickness of backfilling layer was thicker than the thickness of the permafrost layer, theinfluence of permafrost on the settlement of foundation was removed. Hence, thedeformation of backfilling foundation was small. Fourth, the relative pile length wasdefined. The research results indicated that the deformation of foundation decreased asthe increasing of the relative pile length. While the pile length was longer than thelower limited of permafrost layer, the settlement of foundation can be restricted tosmall deformation by the use the gravel pile and cement stabilized sand gravel pile.