New Reinforcement Measure For Expansive Soil Slags Of Nanjing-Baise Railway

With the rapid development of high-speed railway in Southwest China,the reinforcement of expansive soil slope is becoming more and more prominent.Special properties of expansive soil such as fracture,swelling characteristics which are different from other rock and soil mass,cause adverse effects to engineering constructions in expansive soil,and they are difficult to control with strong repeatability.Therefore,the research of the new supporting measures of expansive soil slope is always the key and difficult point in the field of railway construction.In practical engineering,large volume reinforced concrete retaining wall is often used to reinforce expansive soil slope,which leads to waste of engineering and is difficult to implement when space is limited;traditional flexible support measures are difficult to avoid large deformation under expansion force.This thesis relies on an expansive soil slag supporting engineering along the section NBSG-5 of Nanning-Baise railway line,and steel pipe geogrid retaining wall,a new specifically designed reinforcement measure of expansive soil slope is proposed.The retaining wall adopts reinforced expansive soil as the main body of the retaining wall and reinforces its rigidity with vertical steel pipe.This new supporting measure combined with rigidity and flexibility.In this thesis we use indoor model experiment and numerical simulation to research the effectiveness of the new type retaining wall under different moisture content.FLAC 3D is used to research the slope stability and deformation characteristics of the expansive slope with traditional geogrid retaining wall and steel pipe geogrid retaining wall in the same size in both wet and dry states.Firstly,comparing the reinforcement effect of these two kinds of retaining wall,to prove the validity of the new reinforcement.Furthermore,the reinforcement mechanism of this new kind of retaining wall is analyzed by simulating the slope deformation and steel pipe stress under different steel pipe spacing,putting forward the reasonable steel pipe spacing.Model tests are conducted to compare the slope reinforcement effects of traditional geogrid retaining wall and steel tube geogrid expansive soil retaining wall both in natural and rainstorm conditions.In this thesis we focus on the comparison of deformation of these two kinds of retaining wall in rainstorm conditions.Analyze strengthening effect of different supporting measures to verify the validity of the new reinforcement measures.According to the analysis of model experiment and numerical simulation of steel pipe geogrid retaining wall,it can be summarized with no doubt that steel pipe geogrid retaining wall can effectively support the expansive soil slope,especially when the expansive soil slope is under high water content.The research results will provide a reference for the supporting of expansive soil slags of the Nanning-Baise railway,also provide theoretical basis for the design of similar projects in the future.