A comprehensive evaluation model that combines an analytical hierarchy process (AHP) method and the improved version of the Criteria Importance Through Inter-criteria Correlation (CRITIC) method is proposed to solve integrated assessment problems related to the service status of groins in waterways. In view of the influencing factors and functional characteristics of damaged groins for waterway regulation, a waterway groin service status (WGSS) evaluation index system with a hierarchical structure was constructed using target-criteria elements. Additionally, based on the multi-attribute characteristics of the indicators, standards for rating and assigning values to elemental indicators were developed. Considering that traditional empowerment methods are rather one-sided and limited, an AHP-improved CRITIC method combination assigning optimization model was established based on the least squares principle, and the optimal combination weights were solved by the Lagrange multiplier method. The reliability and applicability of the model were tested by successfully applying the evaluation model to the comprehensive evaluation of the service status of spur dikes in the upper reaches of the Yangtze River. The results showed that the combined weights that were calculated by the AHP and the improved CRITIC optimization model were able to reflect both subjective and objective information, which makes up for the shortcomings of a single assignment method, and the weights assigned to the service status evaluation indexes for groins were reasonable. The comprehensive evaluation method to determine the service status of groins proposed in this paper was more accurate than the traditional evaluation method with subjective assignment and provided a scientific basis for decision making to maintain the sustainability of groin function.
The effective prevention and reduction of the hazardous impact of landslide-generated impulse waves on the moored ships are crucial for the sustainable operation of the reservoirs. Although the investigations of landslide-generated impulse waves have been widely studied in the past decades, few efforts involved their impacts on the moored ships. The authors in this paper specifically examine the hazardous impact of the impulse waves on the moored ships by applying the physical experiments. Considering that the impulse wave was an external force acting on the mooring line, the impulse wave generation, propagation, and its impact on the moored ships are hence explored in detail. The results indicate that the impact of impulse waves on the moored ships was mainly due to the first wave amplitude and height, and an exponential function relationship between the relative wave height and wave crest amplitude was revealed. Furthermore, the attenuation of the maximum wave crest amplitude was approximated by a power exponential function. On this basis, the mooring tension could be calculated based on the linear relationship between the mooring tension and wave height. Ultimately, the safety of the moored ships in the port can be evaluated.
The damage of roadbed retaining wall caused by mountain torrent is the most common disaster in geotechnical engineering. Based on the central point method, a reliability analysis model of the gravity retaining wall under mountain torrent load was established in this paper, and the performance functions of the anti-sliding and anti-overturning stability were derived. Finally, the reliability indexes of the anti-slip stability and overturning stability of the gravity retaining wall were obtained. We also analysed the sensitivity of stability reliability by changing the values of five variables which were the angle of mountain torrent load (ε), internal friction angle (ϕ), included angle between the retaining wall and the straight surface (θ ), friction angle (δ), friction coefficient f. For the anti-sliding reliability, f, ε and ϕ have the greatest influences on the stability of the retaining wall. The increases of the other two variables have positive impacts on the anti-sliding stability. For the anti-overturning stability, the index coefficient increases with the increases of θ and ε, and decreases with the increase of ϕ until stability. The calculation method proposed in this paper considered the influence of mountain torrent, therefore it has a good practical application value in engineering.
Bubble dissolution during the flood discharge creates high total dissolved gas (TDG) concentration zones downstream of the dams. The dissipation of supersaturated TDG is a very slow process. Thus, the elevated TDG may remain through the water body for hundreds of kilometers downstream and lead to gas bubble disease (GBD) and even mortality in fish. To improve the navigation conditions of waterways, dikes (i.e., a solid structure) of varied sizes and shapes are commonly constructed. However, this would affect the dissipation and transportation of the supersaturated TDG. It would significantly change the turbulence intensity and hydropressure of the flow, which dominates the dissipation of TDG. Therefore, TDG distribution in the waterway differs from that in the natural river. In this study, a numerical simulation of the TDG at the Yangtze River’s upper reaches (one of the inland waterways in China) was conducted with the establishment of a two-dimensional TDG dissipation model. The effect of the dikes’ size and shape was analyzed to assess the influence of the regulation structures on the dissipation and transportation of the supersaturated TDG. Meanwhile, simulation in the study area with the natural topography was also set as blank control. Based on that, impact evaluation of TDG supersaturation on fish under different simulation scenarios was made. This study can provide a scientific basis for reducing the adverse effect of supersaturated TDG in fish and the construction of ecological waterway therefore.
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