Study On Heat Preservation Strengthening Layer Of Subgrade In Seasonal Frost Regions

The railway roadbed freezing and thawing stability problem is very prominent in the seasonal frozen soil area.In this paper,the application of a wide range of foam insulation applications in the road insulation,the optimization of foam concrete can solve the polystyrene（EPS）insulation board,polyurethane（PU）insulation board poor durability and good insulation performance.First,the basic experiment parameters were determined by foam surplus coefficient test and water cement ratio test.Then CBR bearing ratio test as the roadbed fillers and foam concrete structures to test the performance of bridges.Finally,the optimal test dry density was obtained by combining the compressive strength and other properties.On the basis of the above,different types,different contents and different lengths of fibers were added into the foamed concrete to obtain the best performance of the fiber foamed concrete.Finally,in order to further improve the performance and economic aspects of the fiber foamed concrete,different types of cement and different content of fly ash were added.After the comprehensive test and performance test,the optimal ratio of the fiber foamed concrete was obtained.The main research contents and research achievements are included:（1）According to the basic experiment,it is found that the foam surplus coefficient is 1.1 and the water cement ratio is about 0.5.（2）Based on the CBR bearing experiment,the test bridge of the foundation of the railway subgrade bed and the foam concrete strength index was constructed.（3）Based on the analysis of compressive strength,thermal conductivity and microstructure,it is concluded that the optimal dry density of foam concrete is 1 200 kg·m^-3.（4）In the foam concrete,mixed with different lengths and different content of polypropylene fiber,glass fiber and basalt fiber,obtained content of 0.10%,length of 12 mm glass fiber foam concrete comprehensive performance best.（5）Through the cement type and fly ash content test,obtained P.O 52.5 cement,fly ash content of 20% of the glass fiber foam concrete comprehensive performance is the best.