Study On The Seismic Behavior Of Foamed Concrete Subgrade

China is a country with a high incidence of earthquakes.The roadbed is the most common and basic structure of highways.Once it is damaged by an earthquake,its breakage is universal,and the loss of life and property is also considerable.With the advancement of modern technology,roadbed fillers have gradually developed towards light materials.Foamed concrete has the advantages of light weight,good fluidity,short setting time and can be poured vertically to save space,and is increasingly used in highway engineering.This thesis aims to reveal the dynamic response characteristics of foamed concrete subgrade through shaking table test of foamed concrete subgrade and large-scale finite element analysis,and analyze the response characteristics of acceleration,displacement and stress of foamed concrete subgrade under the action of ground motion.This thesis summarizes the research status of foamed concrete and subgrade anti-seismic.Taking the test section of foamed concrete subgrade in the Cheng-Le Expressway expansion project as the engineering background,the research on the seismic performance of foamed concrete in highly seismic area is conducted.Samples were prepared on site,and tests were carried out on the bulk weight,flow value,and unconfined compressive strength of the foamed concrete,and their basic mechanical properties were analyzed,which provided index properties for the subsequent research on the dynamic response of the foamed concrete road base.Based on summarizing previous research results,the key issues such as model box selection and boundary condition treatment for shaking table test of foamed light soil subgrade were studied.Considering factors such as vibration table load-bearing,table size,etc.,using similar principles,and referring to the construction requirements at the construction site,the foamed concrete subgrade model was constructed in layers.Load Wolong wave,Kobe wave and EL wave to analyze the seismic acceleration and strain dynamic response characteristics of foamed concrete subgrade.The numerical analysis method of subgrade based on dynamic FEM analysis is introduced,and the finite element models of foamed concrete subgrade under the two conditions without foundation and foundation are established in Ansys.First,the transient dynamic analysis method was used to load seismic waves,and the dynamic response of the foamed concrete subgrade without numerical foundation calculated by numerical simulation was compared with the results of shaking table test data to verify the rationality of the numerical model.Secondly,the seismic response of displacement and stress of foamed concrete subgrade with foundation under the action of Wolong wave is analyzed.Finally,the influence of different soil parameters on the dynamic response of subgrade seismic is explored.The results show that the tops and joints of the new and old roadbeds are vulnerable parts.Properly increasing the elastic modulus and bulk density of the foamed concrete,or replacing and reinforcing the foundation can make the foamed concrete subgrade better seismic performance.The research in this thesis provides a reference for the use of foamed light soil subgrade in highly seismic area.