Blasting has been widely used for economical and rapid rock excavation in civil and mining engineering. In order to study the influence of relative horizontal distance and relative vertical distance between two tunnels on the dynamical response of the two tunnels, 10 numerical simulation cases are done by LS-DYNA 3D models under surface explosion by controlling the clear distance and height difference of double-line tunnel, and the ALE multimaterial fluid structure coupling algorithm is applied to analyze the dynamic response characteristics of double-line tunnel under different conditions. The numerical results show that the dynamic response characteristics of the tunnel lining are affected by the change of the clear distance and height difference of the tunnel. With the increase of the height difference between adjacent tunnels, the peak value of vibration velocity at the top of the lining on the blast face increases, which is due to the upward elevation of the right tunnel, which is more conducive to the reflection and superposition of stress waves. When the height difference of tunnel is 4–6 m, the vibration velocity and displacement of monitoring point C on the back blasting side will change abruptly, and the variation range of vibration velocity is about 25%, while the variation range of displacement is about 60%.
In this paper, the parallel-joint rock column model is established based on PFC software, and the effects of different joint positions on the mechanical properties, acoustic emission characteristics, and damage evolution characteristics of rock columns are analyzed. In the PFC models, the intact rock is simulated by parallel-bond model, and the joints are simulated by flat-joint contact model. The research result shows that on the whole, when the joint is outside the rock pillar, the UCS of the rock pillar is higher than that of the joint inside the rock pillar, while the elastic modulus is less than that of rock pillar with joint inside. The evolution characteristics of acoustic emission of rock pillars at different joint positions are basically the same. However, the maximum value of acoustic emission events and corresponding deformation of rock pillars at different joint positions are different. The damage of jointed rock mass can generally show three stages: no damage, slow damage increase, and sharp damage increase.
According to the geological conditions of the study area, the measured data of in situ stress was analyzed and the influence degree of buried depth was obtained. A numerical simulation research model with full consideration of fault structure and surface characteristics is established, and boundary condition functions with variables are used. The neural network optimized by genetic algorithm is used to establish the nonlinear relationship between the measured value and the simulated value of the variable boundary condition, and the optimal boundary condition function is obtained. Finally, the in situ stress in the study area was predicted. Through the analysis of the in situ stress field in the research target area, the stress boundary conditions are provided for the follow-up study, and the practical basis for the division of the dangerous area of the surrounding rock of the deep and long tunnel is provided.
The article undertakes the very important topic of the long-term durability of concrete in a natural draft concrete cooling tower with flue gas injection. The corrosive conditions, including temperature, relative humidity, and CO2 and SO2 gas concentrations, near the inner wall of a cooling tower with flue gas injection were monitored in real time to obtain the long-term durability performance of concrete. The pH and chemical compositions of the condensed liquid that adhered to the tower’s inner face and the macromorphology, compressive strength, and neutralization depth of in situ specimens were tested periodically. In addition, a finite element numerical simulation was conducted to simulate and verify the concentration distributions of CO2 and SO2 in the flue gas in the cooling tower. The results showed that the cleaned flue gas was enveloped, diluted, and uplifted by hot vapor in the cooling tower, and its concentration decreased. Meanwhile, the effective diffusion radius increased gradually as the flue gas rose. With the same elevation in the cooling tower, the concentration of flue gas decreased rapidly from the central point to the surrounding area. The air near the inner surface of the cooling tower was merely dampened air with a low concentration of acidic gas due to the gigantic diameter of the cooling tower. As a result, the injection of cleaned flue gas will not evidently increase the corrosion risk in a natural draft concrete cooling tower.
Through the simulation model test, coupling effect between single key strata and t overburden thick sandy soil layer is studied, failure character of thick sandy soil layer is obtained. Meanwhile, load transmitting law on the key strata(key block) is found. This discovery will make progress on dynamic roof structure theory.
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