Strength Property Assay Of Reconstituted Loess

As a special soil, loess widely exists in an unsaturated condition in nature, and is of complex mechanics characteristics. In china, the northwestern loess plateau is the main distribution area of loess. With the conduction and proceeding of western development strategy, loess is widely applied to actual project constructions, the mechanics characteristics of which influence the normal operation of various architectures and determine the reasonableness of project design proposal and foundation treatment strategy. Therefore, it is of great realistic significance and theory value to carry out deeper exploration and study of loess. Numerous assays and theory deductions of loess properties have been conducted, and many important achievements have been reached so far. However, study of unsaturated reconstituted loess is still immature and need to be improved by further study.In this study, with remolded loess as study object, quick direct shear tests were performed to study strength characteristics of remolded and normally consolidated specimens and remolded overconsolidated specimens. Furthermore, the deduction formula of measuring true strength index of remolded loess was reached by combination of related concepts of Hvorslev's true strength theory.Consolidation stability of loess samples were performed by controlling water content and mass of filled loess, and then the strength properties of remolded and normal consolidated loess were studies under different water content and dry densities. Influences of water content, unloading ratios and preconsolidation pressures on strength properties of remolded overconsolidated loess were also investigated by unloading and quick direct shear tests. Results of our study indicates that a strict function regularity exists between shear strength and water content, dry densities of remolded and normally consolidated loess; Water content, unloading ratios, and preconsolidation pressures are key factors influencing the shear strength of remolded overconsolidated loess; By comparison shear strength of remolded and normally consolidated samples and remolded overconsolidated samples, it is reached that the latter is larger than the former under the same preconsolidation pressure, and the gap between them gradually decrease with the increasing of water content. The shear strength envelope of remolded and normally consolidated loess is beneath that of remolded overconsolidated loess under the same condition, the gap between them decrease with the increasing of vertical pressures. By combination of concepts and traits of Hvorslev's true strength theory, the concept and significance of remolded cohesive strength—"cs"are presented here. cs is mainly influenced by soil compaction degree, and is the function relating with void ratio. Furthermore, shear strength formula of remolded loess after normal and stable consolidation is presented in this study, and it is demonstrated here that Hvorslev's true strength formula can equal to the deduction formula when we study and measure true strength characteristic and index of remolded loess after normal and stable consolidation in the condition of neglecting the influence of void water pressure. In addition, two assay methods for measuring true strength index of remolded loess after normal and stable consolidation are presented in this study. The results indicate: the assay method one shows that consolidated cohesive strength (cs) is the function of preconsolidation pressure (Pc) and water content (w), and that when Pc is a constant, it shows a power function relation of cs and w, that is, cs decreases with the increasing of w, and that when w is a constant, cs have a linearity increase with the increase of Pc; the assay method two more truly than method one presents the consolidation impact of preconsolidation pressure (Pc), and the value of consolidated cohesive strength (cs) are larger in method two than one under the same preconsolidation pressure (Pc). cs differences between the two methods reflect the degree of dilatation or rebound of samples after unloading. Intensity line of equal void level of the two methods at different void ratios were also presented by combination of true strength theory. Intensity lines of equal void level parallel with each other, which coincides with the inherent traits of Hvorslev's true strength line.