Model Experimental Research On New Embankment Structure Of Lateral-constraint And Seepage Control In Collapsible Loess Ground

Collapsible loess is widely distributed in China, but the nature of collapsible loess isobviously different from place to place. The key technologies of subgrade engineering incollapsible loess region include how to meet the settlement requirements during and after theconstruction of subgrade in collapsible loess region, improving the seepage property offoundation and subgrade structure at the same time and studying the new subgrade structurewhich has lateral-constraint and seepage control. In this thesis, on the basis of the subgradestructure with lateral-constraint and seepage control, theoretical analysis and model test arecombined to study the effects of lateral-constraint and seepage structure in high speed railwaysubgrade on restraining the lateral deformation of foundation and improving the seepageproperty of foundation soil in collapsible loess area. The main content of this thesis include:Firstly,a theoretical study is made on the effects of compaction pile on improving thebearing capacity of foundation, restraining the lateral deformation of foundation andimproving the ability of seepage control of foundation. The strengthening mechanism ofcompaction pile is analyzed to provide a theoretical reference for the subsequent model testscheme.Secondly, lime-soil compaction pile and cement-soil compaction pile with different pilespace are adopted as lateral seepage control structure for indoor model test. According todifferent fillings of compaction piles and pile spaces, the change of moisture content of thefoundation soil in different position and depth is measured. It is concluded by comparativeanalysis that setting compaction piles has a significant effect on the lateral seepage controlcompared with foundations without compaction piles. And with the space decreasing, thechanging rate of moisture content of the foundation soil decreases gradually with the time,which means the slower the flowing speed, the better the seepage control effect. In terms ofthe two kinds of compaction piles mentioned above, cement-soil compaction pile has a bettereffect on seepage control.Finally, model test is carried out by simulating that the underground continuous wall isused as the lateral-Constraint structure for foundation, deformation of foundation in differentdepth is measured and it is concluded by analysis that: with the foundation depth increases, the vertical and lateral deformation of each point in soil decreases gradually, and the side withlateral-constraint has a smaller lateral deformation than the side without lateral-constraint,which indicates that lateral plastic deformation is not likely or cannot happen in the soil incases with lateral-constraint, as a result, lateral deformation is not likely to happen. Therefore,using underground continuous wall as the lateral-constraint of the foundation can effectivelylimit the lateral deformation of foundation soil, and reduce the foundation settlement.