No abstract

Using coal gangue as subgrade filler can not only solve the environmental problems of coal mine waste accumulation but also decrease the subgrade cost, which has important theoretical and practical significance. A series of cyclic triaxial tests was carried out using the large-scale dynamic and static triaxial apparatus (LSDSTA) to investigate the permanent deformation (ε) of coal gangue subgrade filler (CGSF) under cyclic loading. Experimental grading was designed by using the fractal model grading equation (FMGE), and then well-grading limits of CGSF were captured. The relationship curve between ε and the numbers of cyclic loading (N) can be divided into three stages, i.e., the rapid growth phase, the deceleration growth phase, and the approaching stability phase. N = 1000 can be used as the criterion for reaching the stable stage of CGSF. The effect of confining pressure (σ3′) on ε is related to the level of σ3′. The effect of σ3′ on ε is significant when σ3′ is smaller, whereas the influence of σ3′ on ε is smaller when σ3′ is larger. Furthermore, the influence of grading (Df) on ε of coal gangue samples is significant. With the increase of Df, ε first increases and then decreases, reflecting that there is an obvious optimal grading for coal gangue samples under cyclic loading. Moreover, the effect of compaction degree (Dc) on ε of CGSF depends on the level of Dc. ε is hardly affected when Dc is smaller, whereas increasing Dc has a significant effect on restraining ε when Dc is bigger. In addition, according to the analysis of the permanent deformation curve for CGSF, the unified calculation model of permanent deformation for CGSF under cyclic loading is established. Compared with the existing permanent deformation models, the proposed model in this paper can better describe the permanent deformation of CGSF under cyclic loading. Finally, the model parameters are analyzed, and the model is verified.

The disintegration of soft rock in water is an important cause of engineering disasters, and the research on the disintegration characteristics is also of great significance for the design and production practice of major projects. Considering this, a series of slake durability experiments were conducted to explore the disintegration behaviours of red sandstone under cyclic drying-wetting cycles, and the Soil Mechanics' theory was introduced to investigate these artificial weathering of red sandstone. Then, based on the analyzing of the grain size distribution, the predicting model of the disintegration breakage of red sandstone through Weibull distribution was established. In addition, the proposed model was compared with the widely used fractal model to illustrate the advantage of established model. The physical significance of the parameters was captured. Moreover, the disintegration behaviours of red sandstone were quantified by the newly derived and traditional disintegration ratio. The updated expressions of gradation indicators (i.e., C u and C c Þ of unified soil classification were acquired based on the proposed model.

A simple experimental equipment and test scheme is designed to estimate the swelling deformation under the lateral unconfined condition with coupling effect of uniaxial load and water-rock interaction. This paper carried out the swelling test under the lateral unconfined condition and analyzed the qualities of lateral unconfined swelling of weak swelling rock by applying simple self-designed saturated equipment to the swelling test on the platform of microcomputer-controlled rock shear rheological tester RYL-600. As a result of this study, the following conclusions were derived: (1) considering the coupling effect of load and water, the stress level is considerably lower than the mudstone-saturated uniaxial compressive strength, and it is discovered that the coupling effect is striking. (2) The swelling reveals the demonstrable time effect, which increases rapidly at the beginning of the swelling deformation, and after that, the deformation tends to maintain a certain value. (3) Both the rate and the scale of swelling deformation are restrained by the axial load.