Deep mining near faults may easily cause rock bursts, which seriously threaten mining safety. Based on the engineering background of deep mining near fault in Yima coalfield, by collecting the rock burst events that happened near fault during deep mining, the correlation between fault structure and time-space features of rock burst was analyzed. The results show that the deep rock burst accounts for 84% in Yima coalfield at 600 m and 93% in the mining area within 1000 m from F16 fault. The risk of rock burst is positively correlated with mining depth and negatively correlated with the distance between mining area and F16 fault, and the frequency and intensity of rock burst near F16 fault increase significantly. Rock burst occurs in high stress concentration area, mainly in roadway, releasing energy level of 1.1 × 104 J–3.5 × 108 J, with impact damage range of 60–500 m. The mechanism of rock burst was explained from the view of the distribution of mining stress in surrounding rock. The stress of coal seam in deep mining near fault increases, and the disturbance effect of fault is obvious. Rock burst is easy to be induced under static and dynamic loads. The occurrence and mechanical characteristics of fault have different effects on rock burst and should be considered when evaluating the risk of rock burst.
The mechanism of crack expansion in conventional Brazilian discs is clearly obtained with the help of numerical simulations, and the direction of crack expansion is related to the loading speed. Then the relationship between the stress field and the platform angle was given quantitatively based on the theoretical analysis. To obtain the accurate tensile strength of self-compacting concrete under the premise of numerical simulation and theoretical analysis, flattened Brazilian disc (BD) splitting tests with six loading angles were carried out by using the split Hopkinson pressure bar (SHPB) loading system. The crack initiation mode and fracture propagation mode of specimens under different loading angles and loading rates were analyzed through digital image correlation (DIC) and strain gauges. When the loading angle lies between 28° and 30°, the specimens easily meet the requirement of central cracking under high loading rates. The experimental results were well explained with theoretical analysis from a view of dimensionless Griffith’s equivalent stress. The dynamic tensile strength measured from the non-central crack mode in flattened BD splitting tests underestimates the inherent dynamic tensile strength.
The effects of water content, compaction, and strain rate on the dynamic mechanics of clay soils are key issues in underground blasting excavation. Dynamic compressive stress-strain curves of clay with the interaction of water content, strain rate and compaction were obtained using a split Hopkinson pressure bar (SHPB). The results showed that the kinetic properties (uniaxial compressive strength and DIF) of clay with high water content were more sensitive to the strain rate, and increasing the water content weakened the uniaxial compressive strength of clay, while increasing the compaction usually increased the uniaxial compressive strength of clay. SAE increases exponentially with increasing strain rate, and water content variation has a greater effect on SAE than compaction. Based on the measured test data, the empirical equations between the dimensionless lateral limit uniaxial compressive strength and the strain rate, water content and compaction were obtained by the dimensional analysis.
At present, the analysis of monitoring data for the stress of dam is mostly based on statistical models. However, the monitoring data of the stress on some arch dams have considerably large error, it is hard to build a reasonable statistic model based on the monitoring data. In order to solve the practical application problem of the project, this paper calculates the elastic modulus of the dam by using finite element analysis based on the displacement of the hydraulic component separated from the statistical model of horizontal displacement. Then according to the reversed elastic modulus, this paper has calculated the dam stress under different water levels and temperature conditions. Finally, it has built a stress-deterministic model of the dam.
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