In the process of the rise and fall of the reservoir water level in the dry-hot valley reservoir area, the dry and hot conditions in dry and hot valley where the surface rock mass is located need to be considered, that is, the heat and wet cycle. Based on this, repeated shear tests of joint rock sample under heat and wet cycling were carried out. The results show that with the advance of the test period, the shear stress-shear displacement curve decreases as a whole, and the shear strength of the joint surface deteriorates obviously; The deterioration effect of shear strength under repeated shearing is particularly significant only in the initial state after the shear strength is modified; The deterioration effect of shear strength under heat and wet cycle is mainly concentrated in the first five cycles; After modification, the shear strength, cohesion and internal friction angle of the joint surface show a deterioration trend of “first fast and then slow” only under heat and wet cycle, which is consistent with the experimental results. The research results have guiding significance to the deterioration of rock mass and the stability analysis of bank slope in water-level-fluctuation zone of dry-hot valley.

In order to understand how the South-to-North Water Diversion Project has influenced the groundwater depth across the southern plains area of Beijing, this study collected the groundwater depth and water consumption measurements over the period of 2010-2020 in Daxing District. The geostatistical methods was carried out to analyze the spatial-temporal variability of the groundwater depth, and a principal component analysis (PCA) was used to evaluate the groundwater exploitation intensity over the period. The results show that the water diversion project has been putting the groundwater depth on a decline, reducing the average from 19.13 m over 2010-2014 to 17.67 m in 2015-2020, indicating a significantly constructive influence toward the groundwater depth recovery in the region. The nugget effect values of the groundwater depth, as calculated using the geostatistical semi-variogram model, dropped from 55.92% in 2010-2014 to 39.05% in 2015-2020. This decline indicates the weakening influence of human factors toward the groundwater depth. The PCA calculations show that the effect of regional water consumption on groundwater extraction intensity decreased from 2010 to 2020. Water consumption in industries, tertiary industries, and agriculture contributed to this tendency, while domestic water consumption stimulated groundwater extraction intensity. The findings turn out to be reliable theoretical and methodological references for groundwater resource management toward the regions along the water diversion routes.

Focusing on the influence of the project of water diversion from Yangtze River to Taihu Lake on the hydrodynamic characteristics of Gonghu Bay, the physical model of the wind-driven currents in Taihu Lake was used to analyze the influence on the hydrodynamic characteristics and the vertical flow velocity and planar circulation distribution in Gonghu Bay under the different wind speeds and different diversion flow of Wangyu River in the typical wind field in summer. The results indicate that the variation of Wangyu River diversion flow affects the hydrodynamic characteristics of Gonghu Bay mainly in the near and middle regions, but has little impact on Taihu Lake; The implementation of the water diversion project from Yangtze River to Taihu Lake significantly changes the vertical velocity distribution characteristics on the outlet axis of Wangyu River in the near and middle regions, but has no effect on the vertical velocity distribution characteristics at the junction section; The characteristics of the planar circulation in Gonghu Bay are affected by both wind speed and diversion flow, the changes of wind speed and diversion flow have a significant impact on the area, location and shape of the plane circulation. The research results can provide hydrodynamic theoretical support for evaluating the impact of the water diversion project from Yangtze River to Taihu Lake on the water environment of Gonghu Bay.

In order to investigate the non-stationary characteristics of runoff series in changing environments and to better predict the occurrence of flood events, taking Hutuo River in the Haihe River Basin as the research object, GAMLSS model was used to conduct a non-coherent frequency analysis of the runoff series during 1970 and 2012 by taking time, reservoir indicators and climate indicators as covariates. The results show that the runoff series of Hutuo River has obvious non-stationary characteristics with trend and abrupt changes. The GAMLSS model can better simulate the runoff series in changing environments and describe the flood regimes under the influence of climate change, thus outperforming the traditional model. Changes of the large-scale climate indicators NINO1+2 and NAO significantly affect the flood events in the Hutuo River, with increasing values of these two climate indicators indicating low flood risk and decreasing values indicating high flood risk.

In order to reduce the negative pressure of the steps, reduce the influence of cavitation erosion and improve the effect of step dissipation, the trapezoidal energy dissipation pier was added into the convex angle of the traditional steps to form trapezoidal energy dissipation pier and step combined energy dissipator. The method of combining hydraulic model tests and numerical simulations was used to study the hydraulic characteristics of trapezoidal energy dissipation pier and step combined energy dissipator. The results show that there is negative pressure on the horizontal and vertical surfaces of the trapezoidal energy dissipation pier and step combined energy dissipator near the convex angle, and there is a possibility of cavitation failure; However, the aeration concentration of the negative pressure area in the horizontal level and the vertical surface of the step is basically greater than 5%, which can effectively reduce the harm of cavitation erosion; Within the study range, the trapezoidal energy dissipation pier and step combined energy dissipator energy consumption rate can reach more than 70%, and the energy dissipation rate decreases with the increase of the flow rate. This combined energy dissipator is conducive to reducing the cavitation hazard of step and improving the effect of step energy consumption, which can provide a certain reference basis for the design of step energy dissipator and existing step spillway reinforcement.

Taking Dawen River Basin in Shandong Province as an example, Mann-Kendall method was used to analyze the consistency of the 6 h, 12 h, 24 h and 3 d annual extreme rainfall data. The regional linear moment method was used to infer the design value of the site rainstorm, and the regional design value was compared with the single-station linear moment method. The spatial distribution map of the design value of the 50-year rainstorm in Dawen River Basin was drawn. The results show that the Dawen River Basin can be divided into 3 hydrometeorological homogeneous regions, and the optimal distribution frequency linetype is dominated by the generalized extreme-value distribution (GEV). The difference (mean absolute relative error) between the results of single-station L-moment frequency analysis method and regional L-moments frequency analysis method decreases with the increase of the length of the sample series, and the larger the return period is, the greater the gap is; The spatial distribution of the designed rainstorm values in Dawen River Basin is not uniform, but the distribution trend of each period is basically similar.

In order to improve the accuracy of real-time flood forecasting in Jinhua River basin, the basin flood forecasting model coupled with Mike 11 Nam and Mike 11 HD and the real-time correction model based on Ensemble Kalman filter were established, and the real-time correction of flood forecasting in Jinhua River basin was realized. The simulation effect of the basin flood forecasting model on the main stations in the basin is good, and the simulation accuracy of flood discharge and flood level is high. When the real-time correction model is within 10h of the forecast period, the correction effect decreases with the increase of the forecast period, and the prediction error can be effectively reduced in the early stage of the forecast period. On the whole, the established basin flood forecasting model and the real-time correction model based on Ensemble Kalman filter can meet the application requirements of flood forecasting in Jinhua River basin.

The existence of fissures seriously affects the stability performance of rock structures, and how to reasonably describe the characteristic change law of nonlinear mechanics of rocks containing fissures has been an important research point in recent years. Based on this background, a smooth particle dynamics numerical simulation method (RSMPM) is proposed considering material point failure. The RSMPM was based on the basic calculation principle of the MPM algorithm, the Mohr-Coulomb damage criterion was adopted to traverse all material points in each calculation step, and the failure process was carried out for the material points that reach the damage condition. The dynamic fracture process of the rock was described by the failure process of the material points. The accuracy of the proposed numerical simulation method was verified by comparing the numerical simulation results (crack extension process, main stress cloud distribution) of single crack standard cube specimens and single crack Brazilian disc specimens with previous research results. The research results provide a certain reference for the application of smooth particle dynamics methods in rock mechanics engineering and the understanding of rock fracture mechanisms.

In order to reveal the influence of the gate opening on the hydraulic characteristics of hydraulic tunnels, a two-dimensional model of silt-releasing tunnel with different gate openings was established. The VOF method and standard κ-ε turbulence model were used for three-dimensional numerical simulation calculation of flow field in abrasive section of flood silt-releasing tunnel. The hydraulic characteristics such as flow state, velocity and pressure near the gate were obtained. The hydraulic characteristics under different gate opening degrees were analyzed to obtain the cavitation number from the gate to the threshold. The results show that when the gate operation opening is less than 1/2 maximum opening, the larger the gate opening is, the smoother the tunnel flow state is, the smoother the flow velocity near the bottom is, the lower the pressure difference between the upstream and downstream of the tunnel floor is. The smaller the gate opening is, the smaller the flow rate in the pressure cave is, and it is easy to cause sediment deposition; The greater the opening of the gate is, the more favorable the overall operation of the tunnel is. The research results have guiding significance for the optimization of the operating opening of the hydraulic tunnel gate and the anti-wear repair of the gate bottom sill.

In order to solve the problem of “seeing the sea in rainy season and having no water to use in drought” in cities in desert areas, taking Kuwait as an example, based on the concept of sponge city in conventional areas, combined with the actual climatic and geological conditions in desert area, the permeability coefficient of 5-50 m underground layer was calculated according to the experimental data obtained from the soil permeability test in N5-1 region. A number of seepage analysis schemes of rainwater storage tank were established, and different schemes were modeled and calculated. The results show that the combination of filling high permeability material around the rainwater storage tank and adding vertical recharge well at the bottom can solve the problem that rainwater cannot penetrate into the underground aquifer effectively.