Abstract:To clarify the main driving factors of runoff evolution in the Fuchunjiang Reservoir Basin, the trend and mutation of annual runoff depth, precipitation, and potential evapotranspiration from 1970 to 2022 in the basin were analyzed. The contributions of precipitation, potential evapotranspiration, and underlying surface conditions to runoff evolution were quantified by using the Budyko hypothesis attribution method. The results indicate that both precipitation and runoff depth exhibit a non-significant upward trend, while potential evapotranspiration shows a significant increase. The mutation year for runoff depth is identified as 2012. Increased runoff depth is mainly induced by rising precipitation and changing underlying surface parameters caused by the expansion of impermeable area and the reduction of forest land area, with contribution rates of 51.61% and 52.55%, respectively. The reduction in runoff depth is caused by the increase in potential evapotranspiration, with a contribution rate of 4.16%.

Abstract:Xin’anjiang model was used to simulate the flood process of Qujiang River watershed of Qiantang River. The effectiveness of six real-time correction methods for correcting flood forecasting results in the study area was evaluated based on indexes such as Nash efficiency coefficient (NSE), relative error of flood peak (RE), and peak time error (Δ T ). These methods included real-time correction method, real-time correction method by feedback simulation, autoregressive (AR) method, random forest (RF), k -nearest neighbor algorithm (KNN), and artificial neural network (ANN). The results show that all six correction methods can reduce RE, with RF being the best, followed by the real-time correction method and the method by feedback simulation. In terms of NSE, ANN and AR methods perform well, especially when the starting forecast time is far from the flood peak; ANN shows a better performance. In terms of peak time, RF has the best correction performance, followed by ANN. Overall, ANN shows the best performance, which can improve the accuracy of flood forecasting to a certain extent.

Abstract:Under the new inflow and outflow patterns of Hongze Lake, a two-dimensional hydrodynamic model was established to investigate the impact of elevated water control levels during flood season on water levels and operational scheduling of the lake. The variation characteristics of the water level at Jiangba in the lake area under the conditions of elevated water control levels and the lakeside projects were analyzed. According to the dispatching rules for flood detention areas in Hongze Lake, suggested values for the water control levels during flood season for different combinations of water inflows and lakeside projects were given. The results show that the second stage of the project on the sea-entering channel can significantly reduce the peak water level at Jiangba when the current water control level of Hongze Lake is 12.5 m. The Fengtieying River Diversion Project has almost no impact on the water level at Jiangba under the synergistic effect of the project on the sea-entering channel. For a flood event with the same magnitude in 2007, the water control level within 14.0 m does not increase the flood risk in the detention area around the lake. Therefore, the water control levels of Hongze Lake during flood season can be raised by 1.0-1.5 m. Under the condition of the once-in-a-century flood event, the peak water level at Jiangba will not change when the water control level remains within 14.0 m. However, the elevated water control level can cause the detention area to open ahead of time, and the water control level can be raised by 0.5-1.0 m without increasing the flood risk in the detention area.

Abstract:To further understand the mechanism of runoff evolution in cold alpine catchment under climate changes, the evolution characteristics of hydro-meteorological elements in the Yangbajain Catchment from 1982 to 2013 were systematically analyzed. By incorporating glacier mass balance and groundwater storage changes into the Budyko attribution analysis equation, the contributions made by changes in each factor to runoff evolution in the catchment were assessed.The results show that precipitation, average temperature, potential evapotranspiration, runoff amount,and groundwater storage in the Yangbajain Catchment show an upward trend from 1982 to 2013, with increasing rates of 3.0 mm/a, 0.02℃/a ( p ＜0.05), 0.53 mm/a, 1.99 mm/a ( p ＜0.05), and 2.18 mm/a ( p ＜0.05), respectively. As the climate gets warm and humid, the sensitivity of runoff evolution in the catchment to changes in the hydro-meteorological elements has increased. The contribution rates of precipitation, potential evapotranspiration, underlying surface of non-glacial areas, glacier mass balance, and groundwater storage changes to runoff changes are 189%, -2.99%, -78.3%, 20.9%, and -28.7%, respectively. Improvement in vegetation growth and degradation of frozen soil are important factors causing changes in the underlying surface in the catchment, with contribution rates to runoff changes of -27.9% and -50.4%, respectively.

Abstract:In order to evaluate the flood control and drainage capacities of different drainage schemes in the factory area of the offshore region, the MIKE21 model was used to simulate the overland flow drainage process in the factory area, and the MIKE11 model was coupled with the MIKE21 model to simulate the open channel drainage process in the factory area. The MIKE URBAN model was coupled with the MIKE21 model to simulate the pipeline drainage process in the factory area. The drainage processes in the factory area under the special combination scenarios of extreme rainstorms occurring inside the factory area, with the outside of the factory area encountering the backwater effect of floods were studied under the overland flow drainage, open channel drainage, and pipeline drainage schemes, and the water accumulation depth inside the factory area and the spatio-temporal changes of floods at different locations were obtained. The results show that under the overland flow drainage, open channel drainage, and pipeline drainage schemes, the maximum water accumulation depths in the factory area are 0.073, 0.125, and 0.087 m, respectively. The overland flow drainage scheme has the best effect, and the open channel drainage scheme has the worst effect; raising the height of the factory site can reduce the impact of the backwater effect of external floods during the flood peak period on the pipeline drainage and open channel drainage schemes.

Abstract:To comprehensively understand the water quality status and evolution trend in the water source area since the operation of the eastern route of the South-to-North Water Diversion Project (SNWDP-ER), the water quality index (WQI) assessment method, the Mann-Kendall trend test, and principal component analysis were employed to analyze the evolution trend of water quality and major pollutants in six monitoring sections of the water source area along SNWDP-ER from 2012 to 2023. Based on the stepwise multiple linear regression analysis method, the key indicators affecting the WQI values of the water source area were identified, and a minimum water quality index model was constructed. The application feasibility of this model was evaluated using the WQI data of 2023. The results indicate that the annual average value of WQI shows an overall increasing trend. From 2012 to 2017, the average value of WQI is 38.0, indicating a poor water quality assessment status. The average value of WQI from 2018 to 2023 is 67.4, and the water quality has significantly improved and remained at a good level continuously. The types of water pollutants in the water source area are mainly organic substances and nitrogen and phosphorus nutrients. Agricultural non-point source pollution generated by agricultural planting, industrial wastewater, and point source pollution caused by the direct discharge of untreated domestic sewage are the main sources of pollutants. Strengthening the prevention and control of point source and non-point source pollution is the fundamental way to improve water environment problems in water source areas. The minimum water quality index model has better performance in water quality assessment, which is helpful in saving monitoring costs and improving assessment efficiency.

Abstract:The generation and release patterns of total dissolved gas (TDG) supersaturation caused by the flood discharge of high dams and large-scale reservoirs were first analyzed, and the factors affecting the generation and release of TDG supersaturation were investigated. The challenges and shortcomings existing in the current research were summarized, and abatement measures for TDG supersaturation and their mechanism were sorted out from the perspective of engineering measures and non-engineering measures based on a large number of Chinese and foreign research cases. Moreover, an evaluation idea of hierarchical screening was proposed, and an abatement measure evaluation system for TDG supersaturation was established. The future research directions were pointed out, including the mechanism of TDG gas-liquid mass transfer, the development of the TDG supersaturation prediction model, the optimization of abatement measures for TDG supersaturation, and the improvement of the abatement measure evaluation system for TDG supersaturation.

Abstract:To explore the subsurface erosion characteristics of sand with varying particle morphologies under unsteady flow conditions, three types of coarse-grained sand with distinct particle morphologies, namely quartz sand from Fujian Province, river sand from the Yangtze River Delta, and weathered sand from Anhui Province, were selected for investigation. Three key particle morphology parameters were utilized, including aspect ratio, roundness, and roughness. An independently designed apparatus capable of applying diverse hydraulic loading methods for subsurface erosion tests was employed to assess the anti-subsurface erosion performance of sand with different particle morphologies. The results demonstrate that under various water head conditions, the anti-erosion coefficient of the samples is negatively correlated with both the void ratio and the particle morphology parameters. Specifically, as the void ratio increases, the sample’s density decreases, thereby reducing its anti-subsurface erosion performance. Moreover, as the morphology of the coarse-grained sand is closer to a standard sphere, the anti-subsurface erosion performance of the samples gets lower. Under identical void ratio, coarse-grained sand morphology, and gradation, the anti-erosion coefficient under the constant water head condition is greater than that under the cyclic water head condition. In other words, the anti-erosion coefficient of the samples will be reduced under the cyclic water head condition, and subsurface erosion is more likely to occur under the cyclic water head condition.

Abstract:To explore the influence of different stress states and angles of inclination of bonding surface on the mechanical properties of caesious sandstone-mortar composites during tunnel construction, triaxial compression tests on caesious sandstone-mortar composites under different angles of inclination and confining pressures were carried out. The evolution patterns of the strength, deformation characteristics, and damage modes of these composites were analyzed. Based on the crack closure effect, anaxial crack closure model of the composites was developed, and its rationality was verified. The results show that as the confining pressure increases, the yielding behavior of the caesious sandstone-mortar composites becomes less obvious. In addition, the confining pressure has the greatest effect on improving the strength of the composite with an angle of inclination of 60°. The peak strain and elastic modulus are positively correlated with the confining pressure. As the angle of inclination increases, the peak strength and cohesion change in an “N”-shaped manner. The composite with an angle of inclination of 60° has the lowest peak strength. Under high confining pressure, the composite with an angle of inclination of 60° experiences overall slip instability along the contact surface, but other composites with different angles of inclination undergo shear damage penetrated with a single main crack. The established axial crack closure model of the composites can effectively describe the relationship between the pre-peak axial stress and strain curves.

Abstract:To evaluate the effectiveness of locust bean gum (LBG)and sisal fiber (SF) for improving red clay, laboratory unconfined compressive strength tests and numerical simulation methods were employed. The unconfined compressive strength response characteristics and the microscopic structural damage mechanisms of the improved red clay were investigated. The results show that LBG and SF significantly promote the compressive strength of red clay. The compressive strength of the unimproved red clay is 75.5 kPa, and that of the improved red clay reaches 888.3 kPa when the mass fraction of LBG and SF is 4% and 0.6%, respectively. The microcracks of the red clay improved by the composite material are mainly diamond-shaped, and their number decreases with the increase in the mass fraction of LBG and SF, with shear microcracks dominated. LBG and SF can effectively improve the strength of the contact force chain between soil particles and enhance its resistance to damage and deformation. With the increase in the mass fraction of SF, the non-orientation of the contact force chain is stronger, and the transmission direction is richer. There is a synergistic effect between LBG and SF in improving the microcosmic mechanism of red clay, and the improvement effect of their composite material is better than that of a single material.

Abstract:To address the issues of low efficiency and strong subjectivity in traditional geometric morphology assessment of steel structures, an automated assessment method for geometric morphology of steel structures by incorporating laser point clouds was proposed. Grounded in classical algorithms including denoising and clustering techniques, the proposed method achieved automatic segmentation of target point cloud data. To overcome limitations in precise segmentation of point clouds data of complex steel structure, a manufacturing deviation calculation method based on local spatial relationships of point clouds was developed, which was then applied to detect point cloud data of complex steel structure while providing recommended parameter configuration ranges. Through local projection analysis and triangular mesh topological relationship evaluation, the method completed the automatic surface defect identification and quantitative analysis, resolving the long-standing challenge of quantitative metric deficiency in visual inspections. Laboratory results demonstrate that the proposed method effectively evaluates geometric morphologies of steel structures with complex configurations, verifying its reliability and practical utility.

Abstract:Based on the fatigue constitutive models of concrete and steel reinforcement, as well as the bond-slip constitutive model of the FRP-concrete interface under fatigue loading, a finite element model of reinforced concrete (RC) beams strengthened with externally bonded fiber reinforced polymer (FRP) under fatigue loading was established using ABAQUS. The model simulated the characteristics of the flexural fatigue life of FRP-strengthened RC beams influenced by the interfacial bond performance. A fatigue life prediction formula for FRP-strengthened RC beams that simultaneously considered the effects of steel reinforcement stress amplitude and FRP axial stiffness was proposed. The results indicat that the finite element model considering the interfacial bond performance can more accurately simulate the fatigue failure modes of FRP-strengthened RC beams. Reducing the stress amplitude and increasing the FRP axial stiffness can both enhance the flexural fatigue life of FRP-strengthened RC beams to varying extents. The results of the prediction formula are in good agreement with the experimental data, thereby verifying the accuracy of the formula and providing a valuable reference for practical engineering applications of FRP-strengthened RC beams.

Abstract:In order to improve the speed and accuracy of seismic response prediction of aqueduct structure, Jiehe aqueduct was studied, and Midas Civil-2021 was used to construct the finite element model. On the basis of verifying the reliability of the finite element model, the sample data were obtained, and the machine learning model was constructed by using the long short-term memory (LSTM) algorithm and the time series transformation (TSTF) algorithm to predict the nonlinear seismic response of the aqueduct, and the prediction results were optimized by adjusting the time window size and sampling period. The prediction results of the displacement response at the top of the pier show that the average accuracy of the LSTM model and the TSTF model is 76.22% and 88.30%, respectively. Compared with the prediction speed of the finite element model, that of the LSTM model and the TSTF model is improved by 128.54% and 47.90%, respectively. The analysis results of the vulnerability of the aqueduct structure show that the damage exceedance probability of the pier gradually increases with the rise of the water level.

Abstract:A typical bimodal spectrum in West Africa was obtained based on the measured wave data, and the transformation, deformation, and spectral evolution characteristics of irregular waves on typical beaches under the conditions of different energy proportions of wind waves and swells were studied through physical model experiments. The results demonstrate significant differences between bimodal spectral waves and unimodal spectral waves in terms of significant wave height variation, spectral peak energy evolution, and nonlinear interaction. The increase in the significant wave height for bimodal spectral waves is primarily governed by the shoaling process of low-frequency swell components, with higher swell proportion leading to larger maximum wave height before wave breaking. Compared to unimodal spectral swell, the swell spectral peak of bimodal spectral waves exhibits faster energy growth during transformation and slower energy dissipation after wave breaking. Nonlinear interaction between swell and wind wave spectral peaks induces energy transfer from high-frequency wind wave components to low-frequency swell components, resulting in relative energy growth of the swell spectral peak in bimodal wave spectrum.

Abstract:The measured data of the Bohai Sea No.18 ice coverage area was selected, and a wind turbine model was established based on the NREL 5 mW monopile offshore wind turbine (OWT) structure by ANSYS finite element software. The vibration reduction effects of tuned mass dampers (TMDs) and bidirectional tuned mass dampers (B-TMDs) on the bidirectional vibration response of monopile OWT structures under the combined action of wind, sea ice, and ocean current loads were analyzed. The results indicate that B-TMD can play a bidirectional control role for the tower and reduce the vibration responses of the wind turbine tower both outside and inside the plane, and it has a better control effect on the tower cylinder.The control effect of B-TMD on the out-of-plane and in-plane displacements at the top of the tower improves with the increase of the mass ratio and is not greatly affected by the wind-ice angle. The robustness of B-TMD is relatively poor, and the distribution of damper parameters inside and outside the plane can easily affect the control effects. When damper parameters inside and outside the plane are the same, the B-TMD could exert optimal control effects.