HYDRAULIC CONDUCTIVITY OF COMPACTED WIDE GRADING GRAVEL SOILS UNDER FREEZE-THAW CYCLING

The design conception of composite liners is consisted of a geomembrane(GM),geosynthetic clay liners(GCls) and compacted gravel soils in landfills. This conception is presented on the basis of the climate characteristics, gravel soils material rich in nature, and GCls that have been exported all over the world for various applications. The artificially graded gravel soils are taken from natural sediment zone for flood alluvial at Yinchuan suburb in Ningxia. The gravel soil is figured out to meet the requirement of permeability coefficient through the compaction and penetration experiment. The frost-heaving ratio and hydraulic conductivity of gravel soil samples are tested under freeze-thaw cycling in this paper. The test results indicate that the frost-heaving ratio increases as the number of freeze-thaw increases. As the number of freeze-thaw increases, the permeability coefficient also increases. The permeability coefficient is increased by one to two orders of magnitude after 12 cycles of freezing-thawing. At the beginning of freeze-thaw cycle, it has an influence on the soil samples. The influence tends to be relatively stable state as the number of freeze-thaw cycles increases. The sensitivity of gravel soils under freeze-thaw cycling is less than that of the silt clay. It is acceptable to undertake the landfill composite liners which will be comprised of GCls/GM and compacted gravel soils together.