Vibratory roller compaction is a well-known method in improving the mechanical properties of field rockfills. However, the meso mechanism of rockfill densification under vibratory roller compaction has not been understood clearly. This paper presents a discrete numerical method to simulate the vibratory roller compaction of field rockfills. Firstly, rockfill particles were modeled by irregular and stochastic clusters, which can be breakable. In addition, the segregation of field rockfills was replicated in a practical manner. Then, a new model of the vibratory roller was presented, in which the frame inertia was considered. Finally, the developed method was applied to simulate the vibratory roller compaction of field rockfills in the Shui Buya Project. Results show that (1) the numerical simulations of vibratory roller compaction of field rockfills agree well with the field experiments; thus, the feasibility and rationality of the developed simulation method are verified; (2) the dynamic response of field rockfills under vibratory roller compaction can be predicted by the presented numerical method with calibrated model and parameters; (3) the new roller model with frame inertia considered is much more accurate than the roller models in early studies. Thus, the developed discrete numerical method can be further adopted to explore the meso mechanism of rockfill densification under vibratory roller compaction in the future.
The three-dimensional roughness characteristics of the tensile granite joint surfaces are studied. Firstly, the tensile granite joints are prepared by splitting cubic granite blocks, and the triangular networks of the joint surfaces are established based on the topographic data collected by laser scanner. Then, the roughness characteristics of the two-dimensional profiles in different positions and different directions are studied. It proves that the roughness of the tensile granite joint surface is position and direction depended, and the roughness parameters based on the profiles are inadequate to characterize the roughness of the three-dimensional joint surfaces. Some new roughness parameters to characterize the three-dimensional joint surfaces are finally calculated on the basis of the triangular networks, these parameters can reflect the spatial and anisotropic characteristics of the joint surfaces. The results in this paper will lay the foundation for further study of the roughness characteristics and mechanical properties of the tensile rock joints.
The creep property of cement grouted joint is studied based on creep test and theoretical analysis. Firstly, the multi-stage shear creep test under constant normal stress, joint roughness and cement filled thickness is carried out to obtain the creep deformation. Then the conventional linear Nishihara model is used to fit the test results. Due to the big deviation of the theoretical results from the test, the instantaneous elastic shear stiffnesses under different loading stages are calculated. It is found that they vary with the shear stress. The reasons for the nonlinearity are analyzed. Finally the parameters of the Nishihara model are modified to be nonlinear and fit with the test results showing good coincidence between them. These researches release the creep property of the cement grouted joint, and will provide a good basis for further research considering more influencing factors such as normal stress, joint roughness and cement filled thickness.
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