Research On Application Of Foamed Cement Banking In Seasonal Frozen Soil Subgrade

Seasonal permafrost regions account for about 53.5% of China’s land area,and their research has a wide and important impact on the development of natural resources and social and economic development in China.The highway gene in the seasonal frozen soil region is subjected to periodic freeze-thaw cycle,and the roadbed is often damaged by frost heave and rolling,which has a serious impact on regional transportation and economic operation.In order to solve the problem of freezing damage of highway subgrade in seasonal frozen soil area,this paper proposes a design method of thermal insulation subgrade of FCB,which can meet the requirements of thermal insulation,mechanical bearing capacity,frost resistance and engineering economy.On the one hand,it can meet the bearing capacity of the subgrade and play the function of subgrade filling;on the other hand,it can play the function of heat preservation and insulation.It can effectively control the frost heaving and turning and other diseases of the subgrade and play the role of double functional layer.In this paper,the feasibility of FCB thermal insulation roadbed is studied and demonstrated by laboratory tests such as thermal conductivity measurement,unconfined compressive strength measurement,freeze-thaw cycle test and finite element theoretical analysis.The research is carried out layer by layer from three aspects: material properties of FCB,design theory of thermal insulation subgrade and design of typical subgrade in seasonal frozen soil area.The main research results are as follows:(1)As a thermal material,FCB has small thermal conductivity and large thermal resistance,so it is a good thermal insulation material.The thermal conductivity of W6～W10 bulk density grade of FCB is 0.140～0.284W/(m·℃).When the same thermal insulation effect is achieved,the necessary thickness of the thermal insulation layer of FCB is only 1/9～1/2 of the thickness of the other subgrade filling layer,which has a good thermal insulation effect.(2)When used as subgrade filler in seasonal frozen soil area,the compressive strength of FCB with bulk density W6～W10 is 1.38～4.62 MPa,which meets the requirements of subgrade filling strength and road performance.After the waterproof treatment,the strength loss rate is small after 15 freeze-thaw cycles,and the loss rate is24.4%～12.9%,which meets the frost resistance design.(3)At the same time,considering the bearing capacity of the roadbed,thermal insulation,frost resistance and engineering economy,the most severe frost heave area in the heavy frozen soil area(Greater Khingan),FCB thermal insulation layer with bulk density of W7 is selected,the optimal thickness is 140 cm,and the cost of effective treatment of one square meter of road surface is 327 yuan.In the area with the most severe frost heaving in the middle permafrost region(Urumqi),FCB heat insulation layer with bulk density of W6 is selected,and the optimal thickness is 100 cm.The cost of effectively treating one square meter of road surface is 206 yuan.(4)The use of FCB thermal insulation roadbed,in line with the design concept of environmental friendly,can effectively reduce the impact on the surrounding environment during the construction period,at the same time has a good value of promotion and application,can produce huge economic and social benefits.