Experimental Study On Thermal Conductivity For Warm Frozen Soils In Permafrost Regions

Along with advance of china`s western development, the frozen soil engineering construction in cold region also boosts steadily and systematically. With the global climate warming, the annual average temperature is rising in Qinghai-Tibet. There are numerous engineering problems and challenges for lifeline systems built in permafrost region, including roads, railways, pipelines and etc. especially those in warm permafrost which physical and mechanical properties are extremely easy to change on the influence of external environment and are uncertain and instability have to guarantee heat stability of subgrade under permafrost, and keep long-time dynamic stability of it. While, reasonable thermal conductivity of warm frozen soil is the premise and basis to evaluate the thermal stability of warm frozen permafrost region. It is important for optimizing the engineering design and to ensure the project security to study thermal conductivity of warm frozen soil.We took the undisturbed warm frozen soils from Qinghai-Tibet Engineering Corridor as the research object. Based on the physical properties of warm frozen soil is sensitive to temperature, we put forward the deficiency of traditional testing method in measuring thermal conductivity of warm frozen soil. We proposed the testing method of thermal conductivity of warm frozen soil in terms of the theory of one dimension steady heal conduction and introduced the test procedures and requirements detailedly. Finally experiments have been carried out to measure thermal conductivity of undisturbed and remoulded warm frozen soil.We studied the correlation between thermal conductivity of warm frozen silty clay and temperature, dry density, water content. The results showed that the thermal conductivity of warm frozen soil decreased linearly with temperature increasing and the thermal conductivity of warm frozen soil increased gradually with dry density, water content increasing. While the temperature of warm frozen soil was higher, the rate of increase of thermal conductivity was smaller with water content increasing.Regarding the dry density, water content for undisturbed frozen soil as the standard, we employed silt clay, silt to sample preparation and measured the thermal conductivity of two kinds of warm frozen soil. According to mathematical statistics method, we established the empirical equation of therml conductivity between undisturbed soil and remoulded soil.We provided important data basis for Qinghai-Tibet Engineering Corridor project design, construction. Meanwhile, it had important reference values to study the thermal properties of the warm frozen soil.