Rockburst is a sudden disaster that occurs during the underground excavation. It is still challenging to predict the rockburst quantitatively. In the underground excavation, the complex geological structures, the mechanical properties of rock mass, the shape of the excavation and the construction process have an important influence on the occurrence and extent of the rockburst. Nonlinear finite element analysis can model these influencing factors comprehensively and efficiently. However, it is very difficult to analyze the overall stability of the system based on the nonlinear finite element method, and the quantitative indicators for rockburst prediction based on the nonlinear finite element analysis are rare. According to the deformation reinforcement theory, the distribution of unbalanced force during the structural deformation indicates the potential damage zone and its distance from the unbalanced state to the equilibrium. It can also be considered as the driving force of the non-equilibrium evolution of rock mass. In this paper, the physical mechanism and prediction of rockburst are both explored based on the nonlinear finite element analysis using the concept of the unbalanced force. The distribution of unbalanced force during tunnel excavation is modeled considering the geological structures and in-situ stress field. The sensitivity analysis of case studies with changing ratio between horizontal and vertical in-situ stress, inner and outer layer stiffness, and fault dip angle is conducted. Unbalanced force distribution accords with the conclusion of strength theory and stiffness theory and can be used to explore strain rockburst and strain-structure slip rockburst. The unbalanced force can reflect the driving mechanism of rockburst and can be employed as the driving force of rockburst.
3D printed concrete (3DPC) is a rapid construction technology that uses concrete as an ink material to build three-dimensional structures layer by layer, with the advantages in free formwork, complex buildings printing and cost savings. In this paper, the printability and mechanical properties of 3D printed manufactured sand concrete (3DPMSC) were tested with different binder-to-sand ratios. The optimal dosage of manufactured sand was clarified, and the effect of manufactured sand dosage on pore characteristics was studied using CT scanning technology. The test results indicate that as the binder-to-sand ratio increases, the flowability, open time and extrudability of 3DPMSC gradually decrease. Improved buildability is obtained within the binder-to-sand ratio range of 1:1.1 ~ 1:1.3. In addition, the compressive and flexural strengths of the 3DPMSC increase as the binder-to-sand ratio decreases, and the mechanical strengths are optimal in the Z direction. The pore distribution in 3DPMSC significantly varies in directionality, with an increase in both pore volume and number. This research lays a foundation on the engineering application and science exploration of 3DPMSC.
Due to good mechanical properties, biocompatibility and corrosion resistance, zirconia ceramic has been widely used in dental repairing.However, the present technologies for zirconia ceramic fabrication based on stereolithography have some drawbacks, such as low fabrication accuracy, low debinding efficiency, high shrinkage, and shrinkage anisotropy.In order to solve these problems, a kind of hybrid resin was prepared by using different monomers with different functionalities, and then zirconia ceramic slurry with solid content of 55% (volume percentage) was prepared by using this hybrid resin, which dispersed organic matter pyrolysis interva, promoting debinding efficiency and avoiding crack.Besides, effect of laser power and scanning speed to the curing unit shape were studied, the optimum laser power of 670 mW and scanning speed of 2500 mm/s were selected to meet
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