Abstract:To address the challenge of achieving high accuracy in tidal level forecasting along the tidal reach of the Yongjiang River Estuary, this study introduces a hybrid model (VMD-LSTM hybrid model) that integrates classical harmonic analysis (T_TIDE), variational mode decomposition (VMD), and long short-term memory network (LSTM). The VMD-LSTM hybrid model utilizes the T_TIDE package to obtain the hourly water level data of the estuary. The tide-simulated water levels are calculated, and the corresponding residual water levels are derived by subtracting tidal levels from the measured data at each station. The VMD model is employed to decompose the residual water levels into 13 Intrinsic Mode Functions (IMFs), specifically IMF₀ through IMF₁₂, which correspond to the D0 to D12 tidal species in sequence. LSTM-based regression is performed on each IMF component and tide level of the residual water levels for step-by-step prediction over a forecast horizon ranging from 12 to 48 hours. The sum of the predicted values of each IMF component and tide level is the predicted value of the estuarine water level. The results showed that: the VMD model can completely separate the D0 to D12 tidal constituent fluctuations in the residual water level for the Yongjiang River Estuary; the root mean square error (RMSE) of the VMD-LSTM hybrid model for short-term water level forecasting at 12 hours, 24 hours, 36 hours, and 48 hours was reduced by at most 0.15, 0.13, 0.16, and 0.16 m, respectively, compared to the LSTM model. In addition, the hybrid model of VMD-LSTM demonstrates the most significant capability for error correction in the D0 and D2 tidal bands. Compared to the LSTM model, this approach can reduce the spectral peak prediction errors of these tidal bands by up to 0.05, 0.04 m·d0.5, respectively.

Abstract:To more accurately simulate flood propagation in the Qinhuai River Basin, a loose coupling approach was employed to integrate hydrological processes with one-dimensional (1D) and two-dimensional (2D) hydrodynamic processes. A coupled distributed hydrological-hydrodynamic model was developed by combining the grid-Xin’anjiang model for upstream hydrological simulation with 1D and 2D hydrodynamic models to simulate downstream flow dynamics. Specifically, a 1D model was applied to river channels, while a 2D model was utilized to simulate flood inundation in complex urban environments. This study proposes a comprehensive distributed hydrological-hydrodynamic coupling model that effectively represents the entire basin’s behavior. The results demonstrate that the model effectively simulates five flood events from 2015 to 2020, achieving an average Nash-Sutcliffe Efficiency Coefficient of 0.932, indicating high accuracy and reliability. As a case study, the 20200713 flood event was analyzed, revealing critical flood risks in areas such as Zhenghuai Road, Fenghuang East Street, and the Wudingmen Sluice area with maximum inundation depths exceeding 0.5 meters.

Abstract:In order to improve the spatial and temporal resolution of the global climate model, we selected the water conservation region of the Yellow River Basin as the study area. Based on NCEP reanalysis data, this study identified factors and corresponding grids with strong correlations to temperature and precipitation. These were used to construct a Statistical DownScaling Model (SDSM). The accuracy of SDSM was evaluated by using daily precipitation and temperature data from 21 meteorological stations in the water conservation area of the Yellow River between 1971 and 2014. The reliability of the downscaling data was verified by comparing the daily precipitation and temperature data of the downscaling data, MRI-ESM2-0 and EC-Earth3-Veg climate modes with the measured data. The results show that the atmospheric circulation factors affecting the temperature and precipitation in the water conservation region of the Yellow River Basin are mainly downward shortwave radiation flux and precipitable water. The model’s performance showed a better simulation of daily temperatures, with the correlation coefficient and Nash efficiency coefficient above 0.95. The correlation coefficient is about 0.70, Nash efficiency coefficient is about 0.50, for daily precipitation. In the entire basin, the daily temperature and precipitation based on SDSM simulations outperformed those of both EC-Earth3-Veg and MRI-ESM2-0 climate models.

Abstract:To overcome the limitations of traditional investigations on the temporal-spatial distributions of precipitation isotopic compositions based on single-source data in the Qaidam Basin, this study synthesized data from multiple sources, including TNIP, previous literatures, C-Isoscape, and GCMs, to establish the local meteoric water line (LMWL) and analyze intra-annual and interannual variations of precipitation isotopic compositions as well as temperature and precipitation quantity effects. The findings indicated that the slope and interception of the LMWL were lower than those of the Global Meteoric Water Line (GMWL), with the slope showing a gradual rising eastward spatially, attributed to the difference in below-cloud secondary evaporation. On intra-annual scale, precipitation δ 18O shows a seasonal variation with high values in summer and low values in winter, in which trend over time is influenced by temperature fluctuations. A significant temperature effect was observed for precipitation isotopes across the basin, whereas no obvious precipitation quantity effect was identified.

Abstract:Taking an asphalt concrete face rockfill dam (CFRD) on the 100 m-level deep soft overburden of the upper reservoir of a pumped storage power station as an example, the deepest overburden section of the dam is selected, and the stress and deformation behavior of the dam body during the filling period and the water storage operation period are calculated and analyzed by Biot’s consolidation theory, with emphasis on the distribution law of consolidation deformation of the dam foundation and the dissipation of excess pore water pressure. Meanwhile, for the dam foundation with saturated soft clay overburden, the total stress method of “ φ =0” is used to analyze the deep anti-sliding stability of the dam foundation during construction. The results show that during the dam filling process, the excess pore water pressure in the overburden keeps increasing, diffusing and dissipating simultaneously. The complicated changing process is closely related to the permeability of the stratum. When the dam body is filled to about 1/3 of the dam height, the excess pore water pressure in the overburden reaches its peak. The relatively large permeability of the upper gravel clay overburden makes most of the excess pore water pressure in the overburden dissipate when the dam construction is completed, and the overburden is basically consolidated five years after the construction. Due to the rapid dissipation of pore pressure in the gravel clay overburden during dam filling and after dam impoundment, and the additional stress of deep saturated clay is small, the settlement increment after dam construction is only -7.35 cm (excluding rheology), accounting for about 2.18% of the final stable settlement of -337.58 cm. The safety factors of anti-sliding stability of dam slope and deep overburden calculated by total stress method, and effective stress method with corresponding parameters under the conditions of completion period, storage period and reservoir water level change are all greater than the corresponding allowable values according to specified design codes, thus the possibility of dam slope instability is small.

Abstract:A numerical simulation of the characteristics of flushing during the venting process for a hydraulic self-cleaning system in a storage tank was conducted using computational fluid dynamics (CFD) method. An analysis was conducted to analyze how the opening time of the gate and changes in water level within a storage tank influence the flow characteristics during venting flushing processes and the flush effect of sediment at the bottom of the system. The nonlinear regression fitting formula between the scour rate and the water storage height was constructed. The results show that the maximum average flow velocity of venting flushing decreases with the increase of gate opening time and increases with the increase of water storage height. The velocity attenuation of venting flushing flow mainly occurs in the front half of the corridor, and the flushing shape of the corridor sediment after venting flushing is V-shaped distribution. The scouring rate of the venting flushing decreases with the increase of the gate opening time. At 1.5 m water storage height, when the gate opening time increases from 10 s to 20 s, the scour rate decreases from 46.27% to 35.23%. The scour rate of venting flushing increases with the increase of the water storage height. With the gate open for 10 seconds, the scour rate increased from 4.83% to 58.67% as the water storage height rises from 0.5 m to 2 m.

Abstract:One type of hole-type wave dissipation structure, capable of reducing wave impact while maintaining water flow connections, is proposed in this study to reduce the impact of ship wave on the revetments of inland water ecological channels. The wave dissipation behavior of this type of breakwater is investigated through physical model tests in wave flumes. Also, the effects of holes, wave height and water depth on the wave transmission, reflection, and wave forces are analyzed. The experimental results indicated that the interaction between waves and the hole-type wave dissipation structures results in significant wave transmission, reflection, and turbulence induced by the holes, leading to substantial alterations in the characteristics of wave propagation. The wave height of transmissive waves is large in the vicinity of the dissipation structures and decreases apparently and stabilizes when away from the structures. The wave transmission coefficient gradually decreases with a reduction in hole diameter and an increase in wave height. The wave reflection coefficient remains almost unchanged with a decrease in hole diameter and increases gradually with an increase in wave height. Transmission/reflection coefficients as a function of water depth are in relation to water level-relative position of the holes and degree of wave transmission. Both wave pressure and suction increase rapidly with an increase in wave height and then remain stable. As the hole diameter increases, the wave pressure gradually decreases, while the wave suction remains similar. And the porosity has a greater effect on the reduction in wave pressure than in wave suction.

Abstract:In order to explore the engineering properties and parameter distribution characteristics of lakebed sedimentary soft soils of Taihu, a large amount of experimental data of lakebed soft soils along the Taihu tunnel was collected. The value range, variability, probability distribution model, and spatial distribution pattern of physical and mechanical parameters were systematically analyzed. Then, the correlations between soil property indexes of various soil layers were explored. The results show that the physical and mechanical parameters of lakebed soft soils have high variation coefficients and no obvious functional variation pattern in spatial distribution. The plastic limit and liquid limit satisfy a normal distribution, the density and dry density approximately follow a normal distribution, while other parameters do not conform to a normal distribution. The most significant physical indexes related to the intensity parameter of soft soil are natural water content, natural void ratio and dry density, respectively, which have exponential or power functions in relation to those mechanical indexes. Compared to compression modulus, the coefficient of compression has a better correlation with natural water content, natural void ratio, and dry density. The correlation coefficients between intensity parameters and deformation parameters of clay are the largest, followed by mucky soils and silty clay, and silt has the smallest correlation coefficients.

Abstract:In view of the limitations in detecting the bearing capacity of gravel piles using the stacking method, a prefabricated intelligent leveling anchor pile static load test equipment suitable for detecting the bearing capacity of gravel piles has been developed by integrating an intelligent leveling system. The equipment capable of burying the anchor cable in the anchor pile around the test pile can provide pull-out force during the static load testing process. The intelligent leveling system is capable of automatically adjusting the angle of the reaction beam, effectively preventing it from tilting. The results of the field test demonstrate that the static load testing performed by the equipment for the anchor pile method aligns with the settlement change law determined from the static load test using the traditional stacking method. The error identified is reasonable, and the bearing capacity obtained meets the engineering design requirements. The compactness of the anchor pile after the anchor cable is pulled out does not significantly decrease, and its bearing capacity still meets the engineering design requirements. The use of this equipment for static load testing can effectively shorten the time required for equipment erection, reduce the site area needed for testing, and improve both the safety and stability of the test.

Abstract:Given the fact that computational effort and memory requirements are considerable when applying the quasi-bond method (QBM) to structural analyses, this paper introduces a hybrid numerical method combining QBM and the classical finite element method for modeling and simulating deformation and crack evolution in quasi-brittle materials. The proposed approach, referred to as QBFEM, utilizes linear elements for spatial discretization of structures. Cracked material regions and potential damage zones are designated as quasi-bond analysis domains where continuous-discontinuous solutions are performed, while non-damaged zones are solved using the finite element method without involving any coupling regions along the QBM-FEM transition zones. Subsequently, several tests of stiffness matrix assembling by both QBM and QBFEM for different meshes were conducted to demonstrate the efficiency of QBFEM. Finally, three numerical examples-plate with a single hole under tension, single crack plate under shear, and undamaged gravity dam under hydrostatic pressure-are provided for validation, which demonstrate that QBFEM can effectively capture the initiation and propagation of Mode I fracture in solid materials.

Abstract:This paper presents a finite element numerical model of GFRP post anchored concrete slabs (GFRP-PACS) using ANSYS/LS-DYNA software and the Arbitrary Lagrange-Euler (ALE) algorithm’s effectiveness is validated through physics experiment results. A comparative analysis of bond-slip behavior simulations among the share node, CONSTRAIN_BEAM_IN_SOLID and CONTACT_1D methods reveals distinct failure mechanisms under different models while maintaining similarity in the overall simulation process. The study investigates the effects of GFRP reinforcement ratio, concrete slab thickness, and TNT weights on the failure mode, failure volume rate, energy sharing rate, and blast resistance bearing capacity of GFRP-PACS. A damage grading prediction curve for GFRP-PACS is established to assess the impact of material parameters on structural performance. The results indicate that the ALE algorithm can effectively simulate the explosion process of GFRP-PACS. While simulations using different bond-slip models exhibit similar failure processes, they yield distinct final failure modes. Increasing the reinforcement ratio and the thickness of the concrete slab can effectively reduce the axial force in the GFRP bar, and the failure volume rate of the concrete slab, and improve the energy sharing rate and overall blast resistance bearing capacity of the concrete slab. The damage grading prediction curve can assess the impact of changes in TNT weight and slab thickness on the damage.

Abstract:In view of the issue that current research on gravity caisson wharf only considers the separate effects of seismic or wave actions, which does not reflect actual conditions, a finite element model of the gravity caisson wharf is established based on the open-source numerical computation platform OpenSees. Dynamic response analysis is conducted under the joint action of earthquake and wave, and the impact of the earthquake and phase difference on the wharf’s displacement is discussed. The results demonstrate that the wharf experiences significant horizontal and vertical displacements under seismic action alone. The combined effect of earthquakes and waves significantly influences the magnitude of the wharf’s displacement, with specific conditions depending on the phase-difference between the earthquake and the wave. In the cases of the most unfavorable versus favorable phase-difference conditions, the maximum horizontal displacement of the wharf increases by 37.1% and decreases by 26.9%, respectively, compared to the case of only seismic action. Therefore, in the dynamic response analysis and seismic design of caisson wharf, it is necessary to consider the unfavorable conditions under the joint action of earthquakes and waves.

Abstract:To study the influence of the principal stress rotation on the relaxed soil pressure of tunnels, based on the trajectory of the major principal stress arches, the lateral pressure coefficients under the tower-shaped (triangular) and basin-shaped sliding failure surfaces were analyzed for common project scenarios in actual engineering projects. The lateral pressure coefficient calculation formulas considering the principal stress rotation angle were proposed. According to the force balance of the soil micro-element in the limit equilibrium state, the calculation formula of the relaxed soil pressure at the tunnel crown was derived. Compared with the relaxed soil pressure calculation formula of Terzaghi, the proposed formula for calculating relaxed soil pressure does not contain the soil lateral pressure coefficient, which has multiple influencing factors and tends to be challenging to accurately calculate, and instead substitutes it with the principal stress rotation angle which has a significant impact on the relaxed soil pressure and is closely related to the engineering construction and soil properties. This is especially true for cohesive soils when compared to existing formulas. For relaxed soil pressure, the proposed formula does not require using iterative methods and coordinate translation to calculate the lateral pressure coefficient, thereby improving computational efficiency and accuracy. The case study results demonstrate that the algorithm presented in this paper is significantly superior to Terzaghi’s approach, with estimated values aligning well with experimental measurements.

Abstract:A standard physical model of beach profiles was established based on the morphological features of the erosion section of Benin beach. The wave propagation and evolution laws, along with pore water pressure response characteristics, were investigated through physical tests of wave shoaling and breaking on a slope. Wave shoaling, breaking, and liquefaction during wave propagation were analyzed. The findings indicate a substantial increase in wave height as it propagates near the sandbar; wave propagation deformation increases with rising incident wave height. Nonlinear parameters of the wave continually increase during onshore propagation and attain critical values close to the sandbar, resulting in breaking. With increasing heights and periods of the incident wave, the wave-breaking zone shifts seaward progressively, with long-period swell more prone to breaking than short-period storms. As the proportion of swell increases, the breaking wave occurs earlier, characterized by spilling breakers. Additionally, abrupt changes in waveform result in a sharp increase in vertical pore pressure gradient near the sandbar, affecting soil effective weight. The higher the incident wave height, the larger the horizontal pore pressure gradient, increasing susceptibility to liquefaction. Furthermore, bimodal spectrum waves with 50% wind wave proportion cause the largest horizontal pore pressure gradients and most significant liquefaction, followed by swollen waves; wind waves alone result in the smallest liquefaction.

Abstract:To enhance the efficiency of container transfers between trains and ships under the direct transfer mode and to reduce operational costs, this paper proposes an optimized strategy for crane and tractor scheduling that fully utilizes the overlapping time windows of both modes. A multi-objective optimization model is constructed to minimize the operation time and cost per container, and an intelligent algorithm is designed for its resolution. An empirical analysis at the WuXue Port multimodal transport hub tests the optimization effects of different terminal layouts and advanced railway utilization scenarios. The results show that, for a specific direct transfer ratio (50%), the proposed optimization model effectively improves the coordination between cranes and tractors, enhancing container transfer efficiency and reducing operational costs across various scenarios, with a maximum comprehensive benefit increase of 11.7%. The optimization extent of generalized direct transfer in terms of time and overall efficiency is higher than that of the narrow sense. Moreover, the segregated yard layout achieves more significant optimization benefits than the shared yard layout for generalized direct transfer. Additionally, for different direct transfer ratios, the proposed strategy yields optimization benefits overall. In the medium to low direct transfer ratio range (＜70%), the generalized mode shows a more significant improvement after optimization than the narrow sense. Conversely, at high ratio conditions (≥70%), the narrow sense mode and shared yard layout achieve better optimization performance, indicating that adopting a suitable direct transfer layout mode is an effective way to improve the comprehensive efficiency of terminal operations in different scenarios.