It is obligatory to verify the performance of high-energy-absorbing pocket-type rockfall protection nets by full-scale experiments. While the performance verification by full-scale experiments can provide a practical evaluation, it requires a lot of cost and time because it is necessary to conduct the experiments under several conditions depending on the structure of the rockfall protection net. Therefore, the performance verification by combining full-scale experiments and numerical analysis may be a useful tool. In this study, a full-scale experiment of a high-energy-absorbing pocket-type rockfall protection net was conducted to evaluate the net performance with respect to the required capability, and reusability and repairability of the components by understanding the behavior of the net under the action of heavy weights. Throughout the experiment, the deformation of the net, the change of the wire rope tension with time, and the displacement of the top of the net and the top of the pillar were measured in detail. Moreover, it was confirmed that it is possible to evaluate the performance verification based on the performance requirements. Then, the full-scale experiment was replicated by numerical simulations to examine the effects of the rock shape on the behavior and performance of the simulated net. Through the thorough investigations on the deformation of the net, the relation between the maximum tension of the wire rope and the slip length of the shock absorber, the temporal change of the tension of each wire rope, and the absorbed energy of each structural member, it was judged that the reproducibility of the model predictions is adequately high. Specifically, when the impact energy is constant, the effect of the rock shape on the behavior and performance is considered to be small.
The purpose of this study is to expand the application of wastepaper sludge ash (WPSA) as a construction material. The strength and thermal conductivity of WPSA solidified by hydration reaction were investigated for use as a ground improvement solidifier and civil engineering material. The mixture of fly ash, silica fume, gypsum, and ordinary Portland cement was also investigated. The effect of the mix proportion and the amount of the powder mixture on the strength was investigated, and the strength development was discussed based on the XRD and SEM-EDX results. The experimental results showed that the uniaxial compressive strength of mortar specimens with a water-powder ratio of 1.0 was 5 MPa to 9 MPa at 28 days of age. The strength of the mortar specimens decreased with the addition of fly ash but increased with the addition of by-products such as silica fume. The strength of the solidified material using WPSA was lower than that of the existing solidified materials. The strength of the solidified material made of WPSA was developed due to the formation of albite by hydration reaction, recrystallization of WPSA, and pozzolanic reaction with fly ash and silica fume. Then, the reflectance and thermal conductivity of the solidified material were measured, and the thermal conductivity was examined by the heat transfer experiments. The thermal diffusivity of the solidified material was also estimated by analyzing the experimental results. It was confirmed that the reflectance of WPSA was higher than that of ordinary Portland cement. In addition, the re-incineration of WPSA showed higher reflectivity. The thermal conductivity of the WPSA paste specimens was smaller than that of cement mortar and larger than that of gypsum. The results of the heat transfer experiments suggest that the thermal insulation property of the re-incinerated WPSA is improved.
The high-pressure grinding roll (HPGR) has been known to achieve a high mineral liberation with relatively low energy consumption. However, quantitative methods for evaluating the effect of HPGR grinding on the promotion of the mineral liberation of copper ores have not been fully established. This study aims to establish a quantitative evaluation of promoting the liberation ratio of copper minerals by HPGR grinding. We performed clack observation using the combination of the paint penetration method and the mineral liberation analyzer (MLA). Direct clack observation reveals that HPGR grinding can promote the formation of cracks in the product particles. The liberation ratio of copper minerals is related to the percentage of cracks in the product particles. Besides, the grinding tests using a laboratory ultra-small scale showed that the liberation ratio of copper minerals became larger than that of the ball milling alone. In all conditions where HPGR grinding was conducted before ball milling, the ball milling time became almost half that of the ball milling alone. The grinding kinetic constant of the HPGR milling product in ball milling is also determined. The grinding kinetic constants for 80% passing particle size in HPGR grinding products are larger than that in feed ores, and they are consistent with the trend of ball milling time. This might be because the HPGR milling causes cracks in the particles, which are more easily ground in the subsequent ball milling. Consequently, this study demonstrates that the ratio of clacks and the grinding kinetic constant in the ball milling process after HPGR milling can be used as an index to quantitatively evaluate the effect of HPGR milling on promoting the liberation of copper minerals.