The ZM Fishway is the rare vertical slot fishway with high altitude and the long length at the domestic and foreign. The effect of fishway is particularly vital for the gene exchange and population reproduction of the upstream and downstream fish. To investigate the effectiveness of the fishway, we monitored the species, quantity and environmental factors of fish by trap and video observation method from March to July in 2021. In total, 9 species of 143 680 fish belonging to 2 orders, 4 families and 7 genera were captured. The species and quantity of fish passing through were mainly Schizothorax oconnori, Schizothorax macropogon and Racoma waltoni, which were the main objects of fishway designed. The number and species of fish showed obvious seasonal and circadian rhythms. The number and species of fish in May and June were significantly higher than those in other months, and the number of fish during the day was significantly higher than that at night. The canonical correspondence analysis (CCA) results of fishway environmental factors show that the main environmental factors affecting the effect of fishway were the water stage and water temperature. The research results could provide reference data for the optimization and effective operation of the ZM fishway, and it was of great significance to the protection of fishery resources in the middle and lower reaches of the Brahmaputra River.

In order to investigate the impact of typical ecological revetment fish-nest brick on the hydrodynamic characteristics of straight water conveyance channels, a 3-D numerical model (LES) incorporating fish-nest brick was developed using large-eddy simulation technology. Periodic boundaries were employed in the longitudinal direction to allow for the repeated development of water flow within the computational domain. The reliability of the numerical model was extensively validated through experimental data from flume tests. Subsequently, the LES model was used to simulate the hydrodynamic characteristics of channels containing fish-nest brick. The results indicate that the fish-nest brick divide the channel into a high-speed main flow region and a low-speed fish-nest cavity. The time-averaged flow velocity in the main flow region is approximately 1.8 times the cross-sectional average flow velocity (U₀), and a continuous distribution of vortices exists throughout the entire water depth range. Conversely, the time-averaged flow velocity and turbulence within the fish-nest cavity are at relatively low levels, making it suitable for fish habitat and the hatching of adhesive eggs. The mixing layer at the mouth of the fish-nest cavity exhibits relatively strong vortex structures, which significantly enhances turbulence intensity and services as the primary driving force for momentum exchange between the interior and exterior of the fish-nest cavity.

In order to investigate the influence of the vegetation in beach and river bottom on the water flow characteristics at different time periods, under the condition of changing the vegetation diameter (6-10 mm) only, the numerical simulation was used to study the variation of vertical velocity distribution, contoured velocity, water level and intensity of turbulence along the way at different vegetation diameter. The results show that the vertical velocity distribution shows an "S" distribution in the vegetation zone and a "J" distribution outside the vegetation zone; In general, the larger the diameter is, the lower the overall velocity is, the more obvious the upstream congestion of the water level is, and the larger the water surface slope ratio is; The turbulence intensity is proportional to the vegetation diameter; The turbulence intensity of water flowing through the vegetation is greater than that of the vegetation channel when the vegetation diameter is the same.

Geotechnical engineering generally involves three-dimensional steady seepage problem with free surface. Traditional numerical methods for solving free surface are based on the assumption of continuum, and the pore flow is averaged over the whole area containing solid particles. In fact, water flow can only occur along the pores of porous media. Based on the equivalent principle of head and flow, the equivalent seepage velocity, continuity equation and boundary conditions of the pipe network model were derived by simplifying the pore structure of porous media into a three-dimensional orthogonal pipe network. Based on the local coordinate system, continuous penalty Heaviside function and variational principle, a three-dimensional steady seepage analysis method with free surface was established for equivalent pipe network model. Thus, the three-dimensional seepage problem was simplified to a one-dimensional form, which greatly reduces the difficulty of solving the three-dimensional steady seepage problem with free surface. The effectiveness of the equivalent pipe network model was verified by the three-dimensional free surface seepage analysis of homogeneous right-angle trapezoidal dam. The three-dimensional steady seepage analysis of the left abutment slope of Kajiwa Hydropower Station was carried out. By comparing with the variational inequality method, the equivalent pipe network model can well reflect the seepage field characteristics of the left abutment slope of Kajiwa Hydropower Station, and has strong applicability and high computational efficiency for the seepage problem of 3D complex engineering.

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.

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.

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.

In order to study the viscoelastic properties of hydraulic asphalt concrete, bending creep tests under different temperatures and stress conditions were carried out. The Burgers model was used as a constitution model for the viscoelastic mechanical behavior of hydraulic asphalt concrete, and a nonlinear fitting of the test data was carried out by the most rapid descent iteration method to obtain the fitting curves and Burgers model parameters under different test conditions. By analyzing the variation law of the parameters, the function equation of the parameters with temperature and stress was established by using Origin polynomial fitting function. The creep behavior of hydraulic asphalt concrete was predicted. The test results show that the Burgers model optimized by the most rapid descent method can better fit the test curve, and the fitted correlation coefficients are all greater than 0.996, especially in the isokinetic creep stage, the fitted curve is closest to the test curve; Under the condition of constant stress, the parameters of the Burgers model decrease with the increase of temperature; Under the condition of constant temperature, the parameters E₁ and E₂ increase with increasing stress, and the parameters η₁ and η₂ decrease with increasing stress.

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.

Aiming at the Dakuaitian landslide in the Three Gorges reservoir area, which appeared cracks in July 2021 and intensified deformation in August, causing serious safety hazards to local villagers and infrastructure, 9-view Sentinel-1A uplift SAR image data from March 2021 to August 2021 were used as data sources to obtain the time-series deformation characteristics of the landslide in this time period by using SBAS-InSAR technology, and compared with the concurrent GNSS monitoring and geological exploration data. The results show that the deformation of the middle and rear part of the landslide is obvious and is in the state of creeping deformation; The signs of landslide deformation are in good agreement with the InSAR results, which verifies the effectiveness of SBAS-InSAR technology in landslide monitoring; The accumulated rainfall in the previous period and the short-time intense rainfall are the main factors that induce the current deformation of Dakuaitian landslide. This study shows that the SBAS-InSAR technology has a broader application prospect in the field of geological disaster monitoring and early warning in the Three Gorges reservoir area, and provides a reference for similar reservoir area landslide deformation monitoring and early warning.