In this paper, characteristics that the overlying strata movement is controlled by solid backfill materials are illustrated in the coal mining with solid backfilling method. In addition, the mineral and chemical composition, density and moisture content of waste rock and fly ash are tested and analysed by physical-chemical treatment. By investigating the compaction deformation and timedependence characteristics under different ratios of waste rock to fly ash, the optimal ratio of the mixture is obtained to achieve the smallest deformation, and results show that deformation mainly occurs in the initial period of loading. Combining the results of density test on site backfill materials, it indicates that the mass ratio of backfill materials to coal mining is 0?83 in order to ensure the effective of controlling the overlying strata in the coal mining with solid backfill method. The findings of the research provide references for the selection of solid backfill materials in coal mining.
Authors investigate the compaction properties of five materials that are commonly used in the solid backfill mining technique, obtaining stress-strain, bulk-ratio-stress and strain-time relationships for each of them. The results indicate that all five materials undergo three stages during the compaction process: fast compaction, slow compaction and steady compaction. Although the stress reached 20 MPa in the experiments, for all five materials, most of the deformation occurred below 2?5 MPa. Deformation under constant stress generally accounted for only 2?62-8?5% of the total deformation. The authors conclude that a tamping force of 1?5-2?5 MPa should provide sufficiently dense backfill of the gob. The results of these experiments could provide the basis for selection of solid backfill mining materials and for control of the bulk ratio and of late-stage surface subsidence, thereby ensuring secure mining under buildings, railways or water bodies.
In this paper, the strength of brittle bulk metallic glasses (BMGs) was investigated, and a corresponding theoretical model was proposed by modification of Griffith theory using fractal geometry. It was shown that the fracture energy and strength of brittle BMGs not only are related to the plastic zone size, the length scales of atomic order range and the surface energy but also has significant relationship with the fractal dimension in fracture surface. The strength of typical BMGs was also calculated by our improved model, which is in excellent agreement with the experimental data. This study provides a compelling approach for investigating and understanding the high strength of BMGs.
ABSTRACT:The Vakhsh River is one of the major rivers in Tajikistan. The quantitative analysis of watershed topography and developmental characteristics in Vakhsh River catchment can reflect the morphological characteristics of the region, which is of great significance for revealing the quantitative relationship between the hydrological and the geomorphological process. In this paper, the D8 algorithm and the spatial analysis method were used to extract the river networks, the catchment boundary profile lines and the longitudinal valley profile lines of the four major tributaries in the Vakhsh River from the ZY3-DSM of 10 meters resolution. On this basis, five quantitative indices including the frequency of wave, amplitude of wave, gully density, the longitudinal slope and roundness rate were used to analyze the watershed landform and its development degree. According to the experimental results, the catchment have a high surface complexity and a mature landform. Yovonsu river catchment which is in the downstream of Vakhsh River is oval and has low terrain complexity with large frequency and small amplitude. Among the midstream and upstream, the Mukson River has developed into geriatric terrain that is the most mature and has the highest surface complex, while the Obikhingon River and the Kizilsu River have developed into a stable maternal terrain. In terms of topography, the boundary elevation of the Obikhingon is basically in accordance with the normal distribution, while the Kizilsu and the Muksu show a peak state with elevations of 4,000-5,000m and 5,000-5,500m, respectively.
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