The compaction of road embankment soils by ensuring their long-term strength

Abstract

The thesis is devoted to improving the optimal compaction criteria of road embankment soils, which provide their long-term strength. The first unit contains the analysis of modern soil compaction methods, subgrade deformation causes in the embankment, finite element method (FEM) solves of soil compaction tasks, regulatory framework of quality control disadvantages, and others. The second unit is stated a new author's method and the laboratory tests results of water migration in compacted silty loam embankment, including the stabilized (or final) clay soil moisture values, depending on their type (number plasticity), soil skeleton density, embankment height and time «rest» of the subgrade before it’s operation are presented. Water migration patterns in clay soil, placed in plastic tubes (it is simulated the soil multilayer consolidation of road embankment) through time is researched. In the third unit as a result of statistical processing by least squares method the research laboratory and field data, the empirical dependence of compacted clay soil stabilized moisture for their multilayer consolidation in relation to soil skeleton density and plasticity number values is obtained. Empirical dependence parameter corresponds to maximum molecular moisture capacity at what it is advisable to do the subgrade clay soils multilayer consolidation for their long-term strength ensuring. The embankment thickness of multilayer consolidation and subgrade «rest» time after 2 months did not significantly affect the stabilized soil moisture. In the fourth unit the field observation of clay soils compaction with multilayer rolling at five objects is performed. Full-scale experiment found that multilayer loams moisture consolidation by plastic limit of these soils during the «rest» time after subgrade erection and before its operation is reduced to a maximum molecular moisture capacity. General form of receiving from laboratory tests dependence of compacted loams stabilized moisture for their multilayer consolidation in relation to soil skeleton density in road embankment and plasticity number is approved. The fifth unit contains the FEM modeling correct conditions of clay soils compaction process being a part of road embankments; suggestions for the optimal compaction criteria of road embankment soils; thesis results implementation. With high statistical indicators values the empirical equation of the relationship between clay soil skeleton density in each compacted layer and the initial clay soil skeleton density within the layer after its dumping and leveling, initial thickness of filled and planned to horizontal level subgrade by grader or bulldozer layer, reduction of each clay soil layer surface under the smooth roller is obtained.