Factors Affecting the Relation of Fracture Toughness V_(GC) with Critical Void Growth Ratio R_C/R_O

The relationship between fracture toughness VGC and critical void growth RC/RO was studied for ten kinds of Steel. The macroscopic fracture toughness VGC was determined by using notched tensile specimens. and the microscopic parameters of critical void growth ratio RC/RO were quantitatively measured under SEM. Then, the coefhcient C in the relation VGC = C In(RC/RO) proposed in author's past work was specifically explored. The correlation of C with tensile proderty parameter φ=σyδ/(Eφn) was presented for the Steel investigated, and the effects of low temperature on C were also discussed. Results show that the coefficient C is linearly related to the parameter and insensitive to low temperature.

Modeling for critical state line of granular soil with evolution of grain size distribution due to particle breakage

Determination of the critical state line(CSL)is important to characterize engineering properties of granular soils.Grain size distribution(GSD)has a significant influence on the location of CSL.The influence of particle breakage on the CSL is mainly attributed to the change in GSD due to particle breakage.However,GSD has not been properly considered in modeling the CSL with influence of particle breakage.This study aims to propose a quantitative model to determine the CSL considering the effect of GSD.We hypothesize that the change of critical state void ratio with respect to GSD is caused by the same mechanism that influences of the change of minimum void ratio with respect to GSD.Consequently,the particle packing model for minimum void ratio proposed by Chang et al.(2017)is extended to predict critical state void ratio.The developed model is validated by experimental results of CSLs for several types of granular materials.Then the evolution of GSD due to particle breakage is incorporated into the model.The model is further evaluated using the experimental results on rockfill material,which illustrates the applicability of the model in predicting CSL for granular material with particle breakage.

The effect of confining boundary on soil deformation in one dimensional frost heave tests and the theoretical volume correction

Frost heave is one of the major complications in highway construction in cold regions. Laboratory experiments are im- portant in the study frost heave behavior of soils, and one-dimensional frost heave experiments are the easiest way to evaluate the soil frost heave potential. In a one dimensional frost heave test, the deformation in axial direction is non-uniform because of the confining effect of the cutting ring＇s sidewall. If the effect of confining boundary on soil de- formation is ignored, the deformation will be over-estimated. In this paper, the effect of confining boundary on soil de- formation is theoretically studied and a volume correction method is developed and applied to the frost heave test of a sulfite saline soil. Test results demonstrate that the sulfite saline soil will expand to a loose, low-density state after several freezing-thawing cycles under the condition of zero axial stress.