Experimental Study On Thermal Conductivity Of Typical Soil In The Corridor Zone Of Qinghai-Tibet Plateau

With the advancement of infrastructure construction in western China,the lifeline engineering facilities connecting the mainland and Tibet are facing many new opportunities and challenges.In particular,the construction of wide-subgrade such as highways will bring huge heat,coupled with the increase in global warming temperature in recent years,in order to solve the thermal stability of wide-subgrade in permafrost regions,the exact thermal physics The parameter index is its indispensable prerequisite and foundation,and the thermal conductivity is the most important basic index.Therefore,it is necessary to further study the thermal conductivity of typical frozen and unfrozen soils in permafrost regions.This article mainly relies on the preliminary engineering geological survey project of Qinghai-Tibet highway(Geermu~Lhasa section).This paper aims to the frozen and unfrozen of disturbance soil in the Corridor of Qinghai-Tibet Plateau.According to the standard of geotechnical experiment,the paper analyzes the deficiency of paraffin contrast method in the test of thermal conductivity of permafrost.By selecting the transient plane method for testing,the rules and requirements of the experiment were set up,and a lot of indoor experiments were carried out on the thermal conductivity of the frozen and unfrozen of disturbance soil.This paper first analyzes the effect of soil type on the thermal conductivity.It is concluded that when the total water content and dry density of soil are within a certain range,the thermal conductivity of coarse-grained soil is greater than that of fine-grained soil.Frozen and unfrozen of disturbance soil thermal conductivity of coarse particles is greater than the fine particles,it is concluded that the soil pore size of?_f(frozen soil of thermal conductivity)and?_u(unfrozen soil of thermal conductivity)have great influence.Second,the columnar distribution of the thermal conductivity of typical frozen and unfrozen soils in silty clay,silty soil,fully weathered rock,sandy soil and gravel soil is plotted,and fitted the distribution curves separately,combined with the distribution range,puts forward the double factors(dry density?_d and water content?)of curved surface fitting formula.Finally,the effect of disturbance soil on the thermal conductivity under freeze-thaw was analyzed and studied.It is concluded that the difference between?_f and?_u is mainly due to the total water content.At the same time,the proportion of typical soils in different regions was analyzed,concluded that the silty clays in Kunlun Mountains,Chumaer River and Kaixinling District account for a relatively large proportion,the fully weathered rocks in the Beilu River area account for a relatively large proportion,the sandy soils in the Fenghuo Mountains and Tuotuo River areas account for a relatively large proportion,and the gravels soil in the Wenquan area account for a relatively large proportion.In addition,with the change of the different geomorphic units of Kunlun Mountain to Wenquan,the average value of the silty clay of?_u and?_f is the decrease trend,including the smallest in Wenquan area.With the change of different geomorphic units in the Kunlun Mountains to Wenquan,the average values of?_u and?_f of the silty clay as a whole showed a downward trend,and Wenquan area was the smallest.The average values of?_u and?_f of fully weathered rocks are first increased and then decreased,and they are the highest in Fenghuo Mountains and Tuotuo River respectively.The average values of?_u and?_f in sandy soils first increase and then decrease,respectively in Chumaer River.The rivers and the Beilu River area are the highest.The average value of?_u of gravelly soils increases first,then decreases,then increases,and the average value of?_f increases first and then decreases.The average value of?_u and?_f in the Chumaer River area is the largest.Based on the above research,the relevant laws of the thermal conductivity of typical frozen and unfrozen soil in the study area were proposed,and the thermal physical parameters were provided for the highway engineering design,construction and protection in the engineering corridor zone.At the same time,it also has important reference value for other projects in the area.