An attempt is made to assess the internal instability of granular soils based on analysis of variation of the secant slope of the soil particle size distribution (PSD) curve according to three commonly used semi-empirical criteria: the Kezdi criterion, the Sherard criterion and the Kenney and Lau criterion. A computer code ASISGS is developed to first obtain the secant slope curves of soil PSD curves and then the potential for internal instability in 34 soil specimens is analysed. Comparison with experimental results indicates that the Kenney and Lau criterion successfully distinguishes between stable and unstable soil particle distributions for a majority of soil specimens. The Kezdi and the Sherard criteria are not always reliable, however, and are barely applicable when the finer fraction is less than a specific threshold value, especially for internally stable soil specimens which would be deemed as internally unstable. The intersections of the secant slope curves and the limited slope lines demonstrate that the threshold values can be taken as 15% and 12·95% for the Kezdi criterion and the Sherard criterion, respectively. Finally, a new synthetical chart is proposed for assessing internal instability of granular soils; the results derived are in good agreement with experimental results.

In this paper the distribution of shear stress along the anchoring section of prestressed bolt was presented. The distribution of shear stress along the anchoring section of prestressed bolt was analyzed with the plane elastic theory. The analytical solution of shear stress along the anchoring section was deduced. Several cases of shear stresses were analyzed with the analytical solution. The results show that shear stress of prestressed bolt are not uniform distribution along the anchoring section; it is has no relations with the prestress value where the shear stress peak value is; the shear stress is at a certain range along the anchoring section; the shear stress peak value increases with the increase of prestress value;the larger the diameter of the anchoring section is, the less of shear stress peak value is.

In this study an attempt is made to develop an optimal parametric model to represent the particle size distribution (PSD) curves of granular soils based on experimental data. Four unimodal models and one bimodal model are studied to determine which model performs best. As it is very difficult to determine the model parameter values without the assistance of a computer, because of the equations’ complexity, a software package has been developed based on the Matlab platform. A database of 21 soil specimens with pre-fitted PSD curves and 13 soil specimens with a number of experimental data are studied to evaluate the performance of these models. The results indicate that most of the gap-graded soil PSD curves can be correctly represented using the Fredlund bimodal parametric (FBP) model, while all the well-graded soil PSD curves can be represented using both the FBP and Fredlund 4 parametric (F4P) models.

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Under the action of compressive load, the growth and coalescence containing flaws in brittle materials (rock and rocklike materials e.g.) will result in the local buckling and global fracture of rockmass. But, the mechanisms on propagation and coalescence of 3-dimensional internal flaws are not clear till now. We examine brittle fractures of manmade specimens using frozen casting resin and rocklike material to observe 3D internal flaws growth process at about -30° C. A team of specimens containing three internal flaws is measured; flaws are made of three parallel oblong aluminum films. The propagation and coalescence pattern of three internal flaws is observed under compressive stress. An interesting phenomenon is that the crack initiated from the second flaw quickly turns to the one induced from the third flaw and forms a bigger fracture plane, then splits the specimen. It shows that the flaw distribution pattern will greatly affect the flaws growth and coalescence process. The mechanisms that lead to the wing and anti-wing crack initiation and coalescence are described.