In order to address the limitations in forecasting the maximum scour depth of conventional river bends, this study amalgamated the methodologies of isolated forest (IF) and gene expression programming (GEP). An IF-GEP model for predicting the maximum scour depth of river bends was established. The validation results demonstrate that the IFGEP prediction model surpasses existing formulations in terms of its accuracy on the test set. Moreover, it exhibits enhanced predictive performance compared to the traditional GS-SVR and RF models. Application of the prediction model to various rivers yielded remarkably close results to the actual measured values, affirming its strong predictive capability and robust generalization performance.

During the excavation of the construction adit, the Jiangmen Neutrino Underground Laboratory revealed three long and water rich cracks, and high-pressure jet water gushing appeared in local water exploration holes, which may have adverse effects on the stability of the surrounding rock of the tunnel. The influence of L1, L2, L3 on the deformation of surrounding rock of the experimental hall under different water pressures of the excavation face was systematically analyzed by using the discrete element method. The results show that the influence of water rich long cracks on the overall stability of the arch surrounding rock is small. The arch surrounding rock at L1 and L2 is not sensitive to the change of the drainage conditions of the excavation face. With the increase of the water pressure of the excavation face, the deformation of L3 arch shoulder increases sharply and the trend is not convergent. L2 has little effect on the deformation of the lower pool, and the shallow surrounding rock near L1 and L3 is obviously unloaded. Based on comprehensive analysis, 0.5 MPa is recommended as the control standard for shallow surrounding rock drainage at the excavation face of this project.

Simulation and prediction of runoff under climate change and land use scenarios are of great significance for the study of water balance and water resources planning and management. Taking the Qingshui River Basin in Zhangjiakou City as the research area, the global climate model GFDL-ESM2M and CA-Markov model were used to analyze and predict the meteorological data and land use in the Qingshui River basin, and the SWAT hydrological model was constructed to quantify the changes of water balance factors in the basin in 2025 under the joint influence of climate change and land use. The results show that under the three GHG emission scenarios, the rainfall in Qingshui River Basin increased significantly in 2025, the maximum temperature and average temperature under the RCP2.6 emission scenario decreased compared with 2015; The maximum temperature and average temperature under the RCP4.5 and RCP8.5 emission scenario increased, and the minimum temperature under the three scenarios decreased. From 2015 to 2025, arable land, woodland, grassland, water area and construction land changed by -6.24 %, -0.86%, 6.32%, 0.20% and 0.59%, respectively. Compared with 2014-2015, the water balance distribution of the watershed changed in 2025, and the peak monthly runoff occurred from July to September. The average annual runoff under the three discharge scenarios were 4.40 m³/s, 5.84 m³/s and 9.94 m³/s, respectively.

The flood discharge tunnel of large pumped storage power stations will be subject to high speed water flow, sand transport erosion and external water pressure during operation period, and the tunnel may suffer from local damage such as lining cracking, spalling and falling blocks, which will have a negative impact on its long-term use. Taking the flood discharge and sand drainage tunnel of the Fengning Pumped Storage Power Station as the research object, this paper firstly carried out robot-based real-time video, high-definition image and multi-parameter gas collection to realize the inspection of nearly 2 km cavern section. The defects of the tunnel were classified into structural and functional defects and graded. Then, the stability of the tunnel envelope was initially evaluated by combining the monitoring data within the tunnel for the past 6 years. Finally, numerical analysis methods were used to analyze and evaluate the forces on the tunnel envelope and lining structure under different operating conditions. The results show that the flood discharge and sand drainage tunnel has good service performance in the current state. The results of the study are of reference value for the operation and maintenance management of existing power stations and for the inspection of similar tunnels.

The selection of instability criterion is particularly important when the finite element strength reduction method is used to analyze slope stability, but a consensus has not yet been reached. Based on ABAQUS finite element software, the method of total displacement mode combined with cusp catastrophe theory was proposed to judge the safety coefficient of slope. For a classical slope case, the safety coefficient was calculated by using calculation non-convergence, abrupt change of displacement of characteristic point, plastic zone penetration and abrupt change of total displacement mode as the instability criterion, and compared with Spencer method. The results show that the new criterion has a clear meaning, is less subject to human interference, has a wide range of application, and has certain advantages over the traditional three criteria.

In order to solve the frequency safety problem caused by the large-scale access of renewable energy, adjustable-speed pumped storage unit (ASPSU) was involved in frequency regulation of new power system. Firstly, the AGC frequency regulation stability of ASPSU was analyzed through the root locus method. Then, the evaluation scheme of unit power command response performance was designed to measure the rapidity and accuracy of output of ASPSU. And on this basis, the active power dynamic optimization allocation strategy based on the rate of change of frequency (ROCOF) was proposed. The new energy disturbance was simulated in the LFC model of a two-area interconnected power system to verify the effectiveness of proposed strategy. The results show that the proposed active power dynamic optimization allocation strategy can give full play to the frequency regulation advantage of ASPSU, effectively prevent frequency exceedance and maintain the frequency stability of power system.

The weir-gate structure has larger discharge capacity. To accurately and efficiently check the discharge of weir-gate, three intelligent algorithms including BP neural network, SVM and GRNN were used to predict the discharge coefficient of cylindrical weir-gate. The correlation analysis and variation law between dimensionless parameters and discharge coefficient were discussed. The results show that the GRNN and the BP can accurately predict the discharge coefficient of the cylindrical weir-gate. The determination coefficient of the BP in the test stage is 0.997, the root mean square error is 0.009, the average absolute percentage is 0.801 %, and the Nash efficiency coefficient is 0.997, which is superior to the GRNN, and it can be used as an efficient and high-precision prediction model for the discharge coefficient of the weir-gate. There is a stronger correlation between the ratio of gate opening to cylinder diameter (a/D), the ratio of weir head to cylinder diameter (H_w/D) and C_d. The C_d increased with the increase of upstream Froude number (Fr) and H_w/D, and the greater the a/D is, the greater the increase of C_d is. The search results provide theoretical reference and technical support for the popularization and application of cylindrical weir gate in practical engineering.

Bidding is the main way for a hydraulic engineering contractor to obtain a project, and the level of the bid price directly affects whether the contractor can obtain its construction right. Before bidding, predicting the distribution of the bid price of the proposed hydraulic engineering can optimize the formulation of its own quotation. A global optimization Bayesian-MCMC algorithm was used to predict the Beta distribution parameters. Bidding behavior of contractor was simulated by numeric analysis. The algorithm does not need to consider the conjugate of the prior distribution and likelihood function in Bayesian estimation. The numerical simulation results show that the Bayesian-MCMC algorithm requires less data for simulation and has better prediction effect than the traditional moment estimation method.

In view of the problem of rapid durability deterioration and the service reliability reduction of concrete structure caused by saline ions erosion and freeze-thaw coupling in cold and drought irrigation area in northwest China, based on the rapid indoor freeze-thaw test, mechanical property change of clean water, 3%NaCl solution, 5%Na₂SO₄ solution was studied in the process of freeze-thaw. The freeze-thaw damage model was established to analyze the damage degree of relative dynamic elastic modulus of concrete block for three kinds of freeze-thaw mediums. The Weibull life prediction model was used to predict the life of test specimen. The results show that the mass loss, compressive strength and dynamic elastic modulus of the concrete mass damage sizes are 3%NaCl> 5%Na₂SO₄ > clean water; According to Weibull life prediction model, the fitting parameters b and C were obtained, and the correlation coefficient R₂ is above 0.9; The prediction results of model life are consistent with the mechanical performance test results at different operating conditions; The mass loss, compressive strength and dynamic elastic modulus life prediction of concrete under three freeze-thaw mediums are clear water> 5% Na₂SO₄>₃% NaCl. It can be seen that in the environment of freezing-melting and thawing erosion, $\text{SO}^{2-}_4$ erosion degree is greater than Cl^- erosion, and the clean water erosion degree is minimal. The research results can provide a theoretical basis for the mechanical performance characteristics research and later maintenance of concrete in cold and drought irrigation areas.

The selection of a suitable, efficient and accurate numerical model for groundwater flow is an important basis for numerical simulation work. The analytical solution of water level of seepage calculations of fully penetrating well in a phreatic aquifer was compared with the numerical solution of water level of structured conventional model, structured encrypted model and two unstructured encrypted models to analyze the degree of fit and error. The results show that the accuracy of the numerical simulation of all four models is quite good, and the average absolute error is less than 0.1, R² is greater than 0.98. Compared with the structured traditional model, the accuracy of the structured encryption model is the best, the unstructured 4-level encryption model is the second and the 3-level encryption model is the worst; The accuracy of the unstructured four-level encryption model is slightly worse than that of the structured encryption model, but the number of mesh is reduced by 90%. It is a highly applicable, efficient and accurate numerical model for groundwater flow, which improves the computational efficiency and makes up for the poor applicability of multi-point encryption of the structured encryption model.