A Study Of The Thermal Physical Properties Of Unsaturated Net-Like Red Soil

Net-like red soil is a kind of clay widely distributed in south of China.In the past,the formation age,composition,physical and mechanical properties of net-like red soil were mainly studied,but there is little research on its thermophysical properties.Soil from Xuancheng,Anhui Province was used to study the effects of temperature,compaction work and water content on its thermophysical properties,meanwhile,the relationship between microstructure and thermophysical properties was quantitatively analyzed by SEM and IPP.The conclusions are as follows:(1)The thermal conductivity of unsaturated net-like red soil was measured by heat flux method.The results show that the experimental data of samples with different heights under the same temperature environment are almost the same,which shows that there is no linear relationship between the height of samples and the thermal conductivity.The thermal conductivity under negative temperature environment is slightly larger than that under normal temperature environment In the range of 14%~18%water content.With the increase of water content,the growth rate of thermal conductivity is roughly the same.In the range of 18%~20%water content,the thermal conductivity decreases by 0.095 W/(m·K)for every 1%increase of water content in normal temperature,while in negative temperature,the thermal conductivity increases by 0.084 W/(m·K)for every 1%increase of water content due to ice formation.In the range of 20%~22%water content,the thermal conductivity continues to increase,but the thermal conductivity and growth rate under negative temperature environment are obviously higher than that under normal temperature environment.The thermal conductivity of heavy impact specimens is slightly higher than that of light impact specimens in both normal and negative temperature environments,and the change trend of both is consistent.(2)The specific heat capacity of unsaturated net-like red soil was measured by cooling method.The results show that the specific heat capacity increases first and then decreases with the increase of water content,and the water content corresponding to the peak specific heat capacity is about 18%;the specific heat capacity of lightly impacted specimens is larger than heavily impacted under the same water content.(3)Quantitative analysis of the micro porosity character on the failure surface of the sample shows that the pore area less than 1?m~2 is more than 50%,about 40%of the pore diameter is less than 1?m,and more than 60%of the pore circumference is 1-5?m.The average pore diameter and perimeter of failure surface under heavy impact condition are smaller than that under light impact condition.Under the action of larger compaction work,soil particles are more closely combined,which makes the pore smaller and the contact between soil particles increased,thus making the soil under heavy impact condition have better thermal conductivity.