Abstract:To explore the physical meaning of model parameters in Xin’anjiang-Haihe model and improve the simulation accuracy, by taking a part of Haihe River Basin above the Huangbizhuang reservoir as an example, the Xin’anjiang-Haihe model was established. The physical meaning of model parameters was qualitatively analyzed based on factors such as land surface characteristics, groundwater extraction, and water management facilities to clarify their roles in the runoff generation and flow concentration processes. Formulas for calculating the basin leakage based on the infiltration equation and water balance method were proposed to determine related model parameters. Subsequently, the model with calibrated parameters was used to conduct the flood simulation. The analysis revealed that the surface storage capacity of reservoirs could be considered as the storage capacity for surface runoff, while the subsurface storage capacity, influenced by factors such as groundwater over-extraction, represented the average water deficit in the basin after a storm event. The leakage coefficient represented the ratio between the leakage and the basin runoff during the flow concentration process. The simulation results of the model showed that compared with the original Xin’anjiang model, the proposed method improved the qualification rate of flood runoff depth increased by 42.9% and the qualification rate of peak discharge increased by 28.6% in Weishui basin, and by 33.4% for flood runoff depth and 33.3% for peak discharge in Pingshan basin.

Abstract:To study the changes of drought characteristics in the propagation from meteorological drought to hydrological drought in the Yellow River Basin in the future, it is urgent to study the characteristics and transmission process of drought, so as to provide guidance for drought early warning. In this paper, the variable infiltration capacity (VIC) model was used to simulate the hydrological process of the Yellow River Basin in the historical period (1961-2014) and the future period (2015-2100), and the drought intensity propagation index and the drought duration propagation index were constructed based on the matching of drought events, and the changes of the drought characteristics propagation in the Yellow River Basin in the future compared with the historical period were analyzed. The conclusion shows that climate change has shortened the drought propagation time in the Yellow River Basin and in the future scenario, meteorological drought translation rate and hydrological drought sensitivity are higher than those in the historical period; thus, meteorological drought is more likely to spread to hydrological drought. The intensity of drought intensity propagation in the future period will remain basically unchanged, while the intensity of drought duration propagation will decrease significantly in the future.

Abstract:To improve the capability of water disaster prevention and control in Zhejiang Province, the spatial distributions and variations of the peak discharge of different frequencies and its statistical parameters in different river basins were analyzed, and the correlations between different peak discharge frequencies and its statistical parameters and catchment areas were established. The results show that calculated results of peak discharge frequencies are in good agreement with design values in relevant planning, verifying the reasonability of the calculated results. For all the discharge stations, the peak discharge of different frequencies and the average value of the peak discharge are positively correlated with the catchment area. For the positive correlation between peak discharge frequencies and the catchment area, it could be expressed by a power exponent equation and fitted by a double logarithmic line. The coefficient of variation and the peak modulus are negtively correlated with the catchment area. In the figure of the double logarithmic line, the fitted line for the typhoon runoff region is located at the top, below which is the fitted line for the Meiyu runoff region.

Abstract:To comprehensively understand the response of climate change and human activities impact of the river hydrological health, the precipitation-runoff double accumulation curve method and Pettitt method were used to analyze the abrupt change of runoff of Yong’an River, and the long short-term memory (LSTM) neural network model was developed to reconstruct the natural flow series based on meteorological and runoff datasets. Various optimal ecological flow calculation methods were compared and filtered to reveal the change trend in the river hydrological health degree ( R HD), and contribution of each driving factor was quantitatively evaluated. The results show the mutation in the runoff series of Yong’an River occurred in 2003, which is consistent with the operating time of the Xia’an reservoir. Compared with the five probability density function methods, the Q50 flow is recognized as the optimal ecological flow calculation metho for the Yong’an River Basin. Compared to the contribution of human activity (approximately by 34.74%), climate change is the main factor (approximately by 65.26%) contributing to the decline in the hydrological health of Yong’an River. The R HD of the measured runoff after the operation of the Xia’an reservoir showed a significant increase compared with the R HD of the restored natural runoff, especially in March, April, and October.

Abstract:Based on precipitation data from 58 rainfall stations in Wenzhou City from 1970 to 2020, the spatio-temporal evolution of nine extreme precipitation indices at different altitudes was analyzed by using the methods of moving averages, Mann-Kendall trend test, inverse distance weight, and Spearman’s rank correlation test, and attribution analysis of changes in the indices was carried out. The results show that there is a positive correlation between extreme precipitation indices and altitude,which is that the extreme precipitation indices increase with altitude. The extreme precipitation indices, such as annual precipitation, extreme precipitation and 1-day maximum precipitation, all showed different degrees of increasing trends with time. The indices of extreme precipitation, frequency of extreme precipitation and number of days of precipitation decrease from west to east in the spatial distribution of Wenzhou City. Extreme precipitation thresholds vary significantly in space.

Abstract:To clarify the rainfall-runoff response patterns in karst catchments and the mechanisms by which they are influenced by dry and wet conditions, a semi-distributed rainfall-runoff model was developed based on the V2Karst model. The developed model provides methods for calculating the consumption of epikarst water by vegetation transpiration and the convergence of groundwater flow through underground conduits. The model was applied to the Yangchang River catchment, a typical karst catchment in southwestern China, to verify its accuracy. The results show that the developed hydrological model for the karst catchment can effectively characterize the dynamic processes of discharge at the Yangchang River catchment outlet, evapotranspiration, and terrestrial water storage. During the dry season, runoff primarily comes from small fractures and dispersed infiltration in the matrix (82.1%). In the wet season, the hydrological connectivity of large fractures increases, significantly contributing to runoff. During the wet season, vegetation roots tend to consume shallow soil water (82.8% of total transpiration), whereas in the dry season, the epikarst water contributes more to vegetation transpiration, with its proportion increasing to 35.9%. Dry and wet conditions have a significant controlling effect on the hydrological connectivity of the karst catchment and the storage in different medium layers, thus affecting the flow paths and the water source for vegetation transpiration.

Abstract:To evaluate the applicability of reanalysis and satellite-derived precipitation data in the Yangtze River Basin, ground-based meteorological station observations were used as a reference. This study employed evaluation metrics such as correlation coefficient, root mean square error, relative bias, probability of detection, false alarm rate, and critical success index to compare the daily-scale applicability of ERA5-Land reanalysis precipitation data and IMERG-Final satellite-derived precipitation data in the region. The results indicate that compared to IMERG-Final, ERA5-Land performs poorly in the upstream plateau areas of the Yangtze River Basin, primarily due to significant overestimation of precipitation intensity and a higher false alarm rate. In the middle and lower reaches of the Yangtze River Basin, both ERA5-Land and IMERG-Final have their respective strengths and weaknesses. While ERA5-Land generally exhibits superior overall capability in capturing precipitation events, its ability to simulate precipitation intensity is weaker than that of IMERG-Final. During winter, ERA5-Land significantly outperforms IMERG-Final in detecting precipitation events and shows stronger correlation with ground-based meteorological observations. Conversely, IMERG-Final demonstrates much higher accuracy than ERA5-Land in summer, indicating that satellite-derived methods are more reliable than reanalysis-based methods for estimating precipitation during seasons with higher precipitation intensity.

Abstract:To study the structural behaviors of the paraffin-based phase-change material (PPCM)-mixed clay core wall, including the stress, deformation, seepage and hydraulic fracturing, this work constructed a seepage-stress coupled analysis model for a core-wall dam filled with PPCM-mixed clay (PPCM-Clay) based on finite difference method. Then, the distributions of stress, deformation, seepage fields and hydraulic fracturing behaviors are analyzed for the core wall filled with PPCM-Clay and conventional clay under two conditions (right after construction completed and after impoundment), following with analyzing the feasibility of mixed filling with PPCM-Clay and conventional clay. Results under both conditions show that: the distributions of stress and deformation for PPCM-Clay core wall are basically consistent with conventional clay core wall, with a slightly higher maximum vertical displacement than conventional clay core wall; the distributions of permeability coefficient for the PPCM-Clay core wall is similar to conventional clay core wall, but with a higher level; the minimum safety coefficients meet the requirement of specifications, but most of which are lower than conventional clay core wall; the hydraulic fracturing will not occur in both PPCM-Clay core wall and conventional clay core wall. It’s feasible to fill core wall with PPCM-Clay below 0 ℃ and fill core wall with conventional clay above 0 ℃, which can reduce the total PPCM content and address the issue that the core wall filled with PPCM-Clay would perform a higher maximum vertical displacement.

Abstract:To reveal the distribution characteristics and intrinsic law of the flow field near the bridge pier in water under the action of ice cover flow, the spatial distribution and transient change characteristics of the flow field around the combined bridge pier under the conditions of clear water and ice cover scouring were investigated by applying indoor high-precision three-dimensional measurement techniques. The test results show that the distribution of longitudinal flow velocity along the vertical line at the section away from the bridge pier was parabolic under the ice cover flow condition, and the flow velocity in the middle and lower part was larger than that in the upper part, indicating that the ice cover roughness will change the vertical distribution of flow velocity and reduce the original thalweg position of the water flow section. The existence of ice-cover will weaken the frequency of the first and third quadrant burst events, while the second and fourth quadrant burst events will be strengthened. The vertical distribution of sudden events in all four quadrants shows a wandering pattern and the turbulence intensity of the water body was strengthened after the ice layer was covered, which is the key factor to promote the saltation of sediment particles.

Abstract:Using a stress-controlled dynamic permeability deformation test system, experiments were conducted on gap-graded cohesionless soil to investigate the suffusion behavior under confining pressures of 30, 60, and 90 kPa. The study explored the suffusion behavior of the soil and analyzed the variation characteristics of fine particle loss, volume change, and critical hydraulic gradient under different confining pressures. The results show that, at lower confining pressures, fine particles are more prone to being lost, leading to increased pore connectivity and a significant rise in seepage velocity. In contrast, higher confining pressures compress soil pores, reducing the continuity of flow paths and causing a significant decrease in the permeability coefficient. At low hydraulic gradients, seepage velocity exhibits nonlinear variations; however, as the hydraulic gradient increases, it gradually becomes linear, generally conforming to Darcy’s law. Increasing confining pressure raises the critical hydraulic gradient required to initiate suffusion, demonstrating a positive correlation between the confining pressure and critical hydraulic gradient. The effect of confining pressure on fine particle loss differs at various stages, but its overall impact on the total amount of fine particle loss is not significant. Under higher confining pressures, the soil particles bond more tightly, resulting in less deformation of the specimens. Under the confining pressure of 30 kPa, the volume change curve exhibits a distinct step-like pattern.

Abstract:To investigate the impact of the anisotropy of BFRP corrugated plates on the performance of corrugated plate linings, experimental studies on the biaxial tensile, bending, and shear properties of BFRP corrugated plates were conducted. Additionally, a finite element model was used to simulate and analyze the effects of parameters such as wave height, wave spacing, thickness, and material on the deflection and stress peaks of the corrugated plate lining under both normal and extreme conditions. The results show that the fiber orientation significantly influences the tensile, bending, and shear strength and modulus of BFRP corrugated plates. The bending strength perpendicular to the fiber direction is more than 90% lower than the bending strength parallel to the fiber direction, and the deformation capacity is reduced by 68%. Under similar deflection conditions, the BFRP corrugated plate lining is more than 40%-60% lighter than the corrugated steel plate lining, resulting in 1.7-1.9 times increase in structural safety factor and a significant improvement in the elastic deformation capacity of the structure.

Abstract:Stepwise landslide warning surface model is presented based on moving least squares. Based on the monitoring data of the Wangjiapo landslide in Three Gorges Reservoir area, the proposed model is set up, and its ability to provide early warning of the stepwise deformation is validated. The cumulative displacement-monitoring period curve is fitted via moving least squares, and its derivative is used to determine the range of the stepwise deformation during the landslide. The maximum point of its second derivative within the deformation range is taken as the “quasi-failure point” to obtain the current rainfall, previous rainfall, and displacement rate thresholds of each stepwise deformation. The threshold surface of the stepwise deformation is constructed with the monitoring information of the “quasi-failure point” by using moving least squares. A four-level warning threshold surface model is established with the displacement rate as the classification standard for early warning analysis. The validation results of the Wangjiapo landslide show that the warning level is consistent with the actual displacement of the landslide. The model has good early warning effect and enables warning of landslide stepwise deformation.

Abstract:This paper sorts out the effects of the individual and combined effects of wind and wave loads on the pitch of floating wind turbines. The anti-pitching effect of floating wind turbines with external stabilization devices such as tuned mass dampers, wave energy converters, and ship anti-rolling equipment are also explored. The mechanism of different anti-pitching measures is analyzed. Finally, this study indicates some problems that still need to be solved in future research of control strategy, arrangement form and application object.

Abstract:In response to the limitations of two types of site selection methods based on port evaluation and operations research optimization, from the perspective of Chinese port and shipping enterprises, a model for selecting container hub ports in overseas port clusters was established, considering both the lowest total cost of logistics network and the optimal supply conditions of hub ports. The model was solved using the second-generation non-dominated sorting genetic algorithm (NSGA-Ⅱ). Taking the port cluster on the West Coast of Africa as a case study, the constructed model was applied to conduct a simulation analysis of the container hub port selection schemes under different scenarios, and the priority sequence for the construction of container hub ports within the port cluster was determined based on the hub port weighted selection probability. The results demonstrate that the model can integrate the advantages of the two site selection methods and can be solved efficiently based on the NSGA-Ⅱ algorithm, making the obtained site selection results more in line with the interests of Chinese operators. Moreover, from the perspective of China, some ports led by the Port of Tangier and the Port of Durban possess hub value among the port cluster on the West Coast of Africa.

Abstract:Taking the large-diameter rock-socketed monopile as for offshore wind turbine the research object, the nonlinear viscoelastic constitutive model of the soil and the damage model of the rock mass are introduced into the finite element model to describe the stiffness attenuation of the soil and the rock with strain. The specific conclusions are as follows: when considering the nonlinear dynamic interaction of pile-soil-rock under the action of dynamic loading from the pile top, the rock embedded at the bottom of the pile can effectively improve the deformation resistance of the pile, and the deformation of the pile increases with the degree of weathering of the rock, and decreases with the increase in the embedded rock depth. The relative magnitude of the dynamic load (the ratio of the magnitude of the dynamic load to the static load-bearing capacity) has the greatest influence on the dynamic stiffness of monopile, followed by the degree of weathering of the rock and the rock-socketed depth. Maximum damage to the rock often occurs in the vicinity of the soil-rock interface, and minor damage near the bottom of the pile can occur for the strong weathered rock case; the inertial effect of the dynamic load increases the amount of damage to the rock compared to the static load case.