Application Of Foamed Light Soil In Soft Soil Subgrade Of High-speed Railway

Soft soil is widely distributed in China's coastal and inland areas.Subject to geographical constraints,many highway constructions have to be built on the thick soft clay foundation.The post-construction settlement of soft soil foundation is very large under the action of upper load,which seriously affects the safety and stability of high-speed railway operation.Research shows that,under the loading of trains?train track structure and self weight of subgrade,the post-construction settlement of the subgrade itself is limited.What's more,the post-construction settlement caused by soft clay foundation decides whether the post-construction settlement of subgrade can meet the standard requirements.At present,the approach of foundation reinforcement or improvement is usually adopted for soft soil subgrade to reduce the post-construction settlement.However,the treatment of deep soft clay foundation is of high cost and needs long construction period.In addition,the treatment effect also needs to be improved.Therefore,it is necessary to carry out the research on the new material and new technology of settlement control of soft soil foundation.The foamed light soil is of low apparent density,high strength and convenient for construction.Using foam lightweight soil filling to fill the roadbed can effectively reduce the subgrade load and the additional stress of soft soil foundation.This makes it possible to control the settlement of subgrade effectively without foundation treatment.Foamed lightweight soil roadbed is of good integrity and light weight.The engineering practice proved that selecting foam light soil as roadbed filling has obtained good results in reducing the differential settlement of subgrade and controlling soft soil roadbed settlement.This paper adopts the theoretical analysis,laboratory test and numerical simulation method to study the application of foamed lightweight soil in the soft soil subgrade of high speed railway.The main work is as follows:(1)This paper reveals the relationship between bulk density and compressive strength of foamed lightweight soil through compression strength test.Moreover,the development rule of the stress-strain curve of the foamed lightweight soil specimen is summarized in this paper.Also,the cause of formation of the development rule of stress-strain curve is deeply analyzed.The correlation between the bulk density and compressive strength of foamed light soil and the number of days of soaking were revealed by the immersion test of the foamed light soil samples.Furthermore,this paper provides effective guidance for the pouring construction of foam light soil under the water table.(2)This paper establishes a two-dimensional soil-filling surcharge model,respectively calculating the size of post-construction settlement of high-speed railway soft soil subgrade caused by the filling of the conventional filler and foamed lightweight soil.Therefore,the comparative analysis of consolidation settlement difference of soft soil subgrade caused by the foamed lightweight soil subgrade and conventional filling subgrade is completed.(3)This paper establishes a three-dimensional model of dynamic interaction of high speed train,ballastless track and foamed lightweight soil subgrade.In this model,the foamed lightweight soil subgrade is taken as the main research subject and the result of the dynamic action is analyzed in detail.Accordingly,the dynamic response law of foamed lightweight soil subgrade is revealed and the optimal design of the stiffness combination of the foamed lightweight soil subgrade bed is also carried out.