Study On Stress-strain Relationship Of Sand As Porous Material By Confined Compression Test

Considering soil’s porousness, its confined compressive deformation is distributed into two parts:one caused by mass exchange and the other by skeleton deformation, and a definite physical meaning is given to mass strain by mass exchange. Porous material’s constitutive relation formulas under confined compressive condition are deduced, which consider the effect of mass exchange on strain. The conception of visual skeleton mass axial strain and visual skeleton mass volume strain are put forward, so is the decomposed expression of visual strain based on mass exchange.Using ideal porous material’s constitutive relation formulas under confined pressed condition and assuming no mass exchange occurs while sands’unloading,this article studies stress-deformation characteristics of sands’confined compression test under cyclic loading.Firstly,the normal confined compression tests involves the following4aspects: sands may reach the first ultimate void ratio if press is enough high with no obvious soil structure change; the unloading curves under different main pressure classes are parallel to each other; sands own the only characteristic unloading curve regardless of density; the loading way (or cyclic way) affects mass exchange and a power function relationship is found to exist between B and p. Then another power function relationship is found to exist between skeleton’s elastic module Es and visual pressure p by new confined compression tests, through which can also get skeleton’s Poisson ratio indirectly.The utilization of the two uniformization formulas can predict skeleton’s Poisson ratio of normal tests, then both the two kinds of skeleton’s Poisson ratio,one by indirect measurement and the other by prediction,are found to accord with the same rule. It preliminarily certificates rationality of the two uniformizable formulas.In addition, different computing methods are applied in this article, find that using Li to calculate strain seems to be more applicable and reasonable.