Model Test Study On The Improved Filling Embankment In Permafrost Regions

In the paper, a new embankment structure is studied that is the improved graded structured embankment. In this embankment, the filling soil is improved on particle grade and laid horizontal drain board. An in situ model testing was designed on Beiluhe testing field in the Qinghai-Tibetan railway, and its mechanism is analyzed to heat exchange and moisture migration. The results showed that improved graded structured embankment is a kind of effective structure forms to protect permafrost.1. It is studied about the styles and causes of damage of roadbed, effective measures to protect roadbed in the permafrost regions. It is thought that the key is the actions of soil, temperature and water to control the damages of roadbed, if one of the three factors is mended, the damages will be controlled and the measure can protect the permafrost.2. The influencing factors are moisture content, porosity, dry density and particle graded of soil to the thermal conductivity, and the value of the thermal conductivity is related the moisture content and dry density of soil.3. The engineering geology condition is surveyed in Beiluhe testing field in the Qinghai-Tibetan railway, the design principle is confirmed to the embankment, and on the basis of the results about the physics and mechanical examination of the filling soil in the room, it was built to the test model of improved graded structured embankment for testing in the suit of Beiluhe testing field in the Qinghai-Tibetan railway.4. The application is succeeded to the fiber grating strain sensor for monitoring the deformation in the model embankment, and the fiber grating strain sensor would be used the long-term monitoring the deformation in the permafrost. The results of the monitoring deformations indicated that the frost heave deformations and the frost heave area is reduce, and the time of freezing phases during the frost heave is shorten, to compare with the ventilation duct in the roadbed. At the same time, the results of the temperature monitoring confirmed that the gravel coarse granule graded layer has the heat exchange form of the convection, in the diversity conditions to the cold and hot season, and the layer manifests the effect of the on-off to thermal. But to the macadam medium granule graded layer, the thermal conductivity difference doesn't be in evidence in the cold and hot season, because the porosity in this layer is less than and the dry density is more than the gravel coarse granule graded layer, in this layer, the heat exchange form is conduction.5. In the improved graded structured embankment, the pathway of the precipitation seep downward is changed toward the horizontal lateral seep, due to the together effect to the fine granule soil graded layer, the amortize layer can be formed to the precipitation seep downward,...