In order to improve the aerated concentration of the stepped energy dissipator, mitigate the damage of cavitation and cavitation erosion, and improve the energy dissipation rate, the stepped energy dissipator with segmented piers was proposed. The influence of the arrangement of the front pier and the reverse pier of the energy dissipator on the hydraulic characteristics of the stepped energy dissipator with segmented piers was studied by numerical simulation. The results show that the stepped energy dissipators with segmented piers generate hydraulic jump near the energy dissipators in the flat and straight section of the terrace. The arrangement of the main pier has better effect of hydraulic jump aeration, higher concentration of aeration along the way, and better effect of cavitation erosion mitigation; The flow velocity along each stage increases gradually, and the arrangement of the main pier has lower flow velocity and better energy dissipation effect; A large range of positive pressure is formed on the upstream area and the upstream area of the energy dissipation pier, and negative pressure is generated on the top and back surface of the energy dissipation pier. The arrangement of the positive pier has a high blocking effect on the water flow, and the arrangement of the reverse pier has a large negative pressure; Under each flow condition, the energy dissipation rate of the two arrangement forms is higher, and the energy dissipation rate of the positive pier arrangement form is higher when the flow is larger, which has better energy dissipation effect. The arrangement of the main pier has better effect in reducing the cavitation damage of the step and improving the energy dissipation rate, which can provide a reference for the structural design of the stepped energy dissipator with segmented piers.

Setting a panel outside the soilbags-constructed retaining wall may affect the behavior of the wall. Therefore, a full-scale test of the soilbags-constructed retaining wall with fixed panels and with unfixed panels were conducted to explore the influence of the panel on the deformation mode and lateral earth pressure of the wall. The results show the walls with fixed and unfixed panels deformed laterally in a cantilever-like manner, but the lateral earth pressure acting in the fixed-panel wall is greater than that in the unfixed-panel wall. A calculation formula for calculating the earth pressure acting on the soilbags-constructed retaining wall under limited displacement was established based on the linear elastic constitution theory, and then it was used to analyze the relationship between the lateral earth pressures and lateral strain. It is found that distribution of the lateral earth pressure of the soilbags-constructed retaining wall with unfixed panel is close to the calculated active earth pressure as a result of the poor deformation constraint of the unfixed-panel, which indicates that the flexible characteristics of the soilbags-constructed retaining wall can be fully utilized by the wall with unfixed panel, so as to effectively reduce the earth pressure behind the wall.

Since total organic carbon (TOC) is not a routine hydrological monitoring data, the monitoring frequency is much lower than that of flow data and it often has missing values, which makes it difficult to evaluate TOC flux. This study proposes an improved computational model based on functional data analysis (FDA) for the evaluation of riverine TOC fluxes. First, the discrete data set is functionalized, and all the indicators are transformed into s function curves in the same evaluation time domain. And then the TOC flux of the evaluation section during the study period is calculated by Riemann integral. The results of the TOC evaluation at the Zhutuo station on the Yangtze River show that, The average value of the annual TOC flux at Zhutuo Station from 2018 to 2020 is 702 000 t; The intra-annual distribution of TOC fluxes is extremely uneven, with a high concentration in the flood season, especially in summer; The annual average value of TOC flux during the flood season (June to September) is 438 200 t, equivalent to 62.43% of the total; The annual average TOC flux in summer is 349 000 t, equivalent to 49.72% of the total; While the annual average value of TOC flux during the dry season (October to May) is 263 700 t, equivalent to 37.57% of the total; The annual average TOC flux in winter is 71 300 t, equivalent to 10.15% of the total; Compared with the traditional method, the improved TOC flux model is also able to deal with missing values and inconsistencies in multi-indicator monitoring sequences more effectively, and to accurately assess the course of TOC fluxes over different seasons and periods of abundance and depletion.

In order to explore the energy evolution law of rock failure process in the excavation process of diversion tunnel, this paper selects magnetite ore and carries out conventional triaxial and triaxial pre-peak constant axial pressure unloading confining pressure tests. The results show that in the conventional triaxial test, the rock is dominated by elastic strain energy storage and dissipative strain energy consumption before the peak stress, and the elastic strain energy release and dissipative strain energy consumption after the peak stress. With the increase of confining pressure, pre-peak shear fracture energy is higher than post-peak shear fracture energy. In the unloading confining pressure test, the dissipated strain energy increases exponentially. The faster the unloading rate, the shorter the unloading period is, and the higher the rate of energy increment per unit time between the unloading point and the drop point. Based on the M-C criterion of rockburst dynamics, the loss of rock cohesion and the dissipated strain energy of rock under unloading path, the damage variable in the process of rock unloading is defined, and the damage degree of rock deformation and failure is revealed from the perspective of energy.

To further promote the construction of sponge cities, system dynamics and Morris, EFAST sensitivity analysis methods were used to analyze the regional differences in the benefits of sponge facilities in residential areas. The research conclusions are as follows: The comprehensive incremental cost benefit and economic, environmental, and incremental social benefits of Shenzhen, Beijing, Lanzhou sponge facilities in operation for 20 years accounted for 1 504.5 (69%, 23%, 8%), 352.4 (54%, 28%, 18%), and 2.0 (27%, 53%, 20%) ten thousand yuan, respectively. The sensitivity of the comprehensive benefit parameters of sponge facilities from high to low is sorted as average annual precipitation, rainwater recovery rate, economic loss caused by water shortage, etc. Among them, the rainfall and rainfall characteristics limit the benefit value of Beijing and Lanzhou. The low of water use in Lanzhou also affects the benefit value.

To study the internal flow characteristics of bulb tubular turbine with different blade opening structures under large medium and small flow conditions, and to make theoretical support for the optimization of the flow passage components structure and the coordinated relationship, the research indexes were taken as three-dimensional streamline distribution, central meridian plane streamline distribution and central meridian plane pressure distribution. The results indicated that the maximum flow velocity existed at the runner of the bulb tubular turbine in the flow pattern analysis, and the flow pattern was chaotic, which was the focus of efficiency optimization. The reason of vortex in the draft tube was analyzed, and it could be optimized by reducing the dead water area. The internal pressure showed an overall decline tendency from the inlet channel to the draft tube. The pressure value at the runner discharge cone was the smallest. The pressure in the draft tube gradually increased along the flow direction, and the highest pressure value was 82 464.15 Pa when the flow rate reached 124.92 m³/s. The calculation results can provide a reference basis for the modification and optimization of the bulb tubular turbine.

In order to study the influence of climate change on rainfall extreme value distribution in main flood season, based on the daily rainfall data from 1960 to 2017 in Jiangxi Province, a variety of test methods were used to detect and test the abrupt change points. Genetic algorithm and Fisher's optimal segmentation method were used to stage the flood season before and after the climate abrupt change, and the extreme distribution of staged rainfall and design rainfall before and after the climate abrupt change were discussed. The results show that 1991 was the abrupt change year of precipitation in Jiangxi Province from 1960 to 2017, and it was necessary to pay more attention to the occurrence of extreme heavy rainfall in Guangchang and Poyang Lake regions. Genetic algorithm is suitable for the division and staging of flood season. After the abrupt climate change (1991-2017), the designed rainfall value in the main flood season of Jiangxi Province was greater than that before the abrupt climate change (1960-1990), and also greater than that in the whole period (1960-2017). When calculating the designed flood based on the designed rainfall, the influence of climate change on the designed rainfall value should be considered, and strengthen protection against floods.

Based on the finite element method, this paper numerically analyzes the stress behavior and its adverse effects when diaphragm of dam foundation axis shifts downstream during operation, and proposes remedial measures and reference critical values. The results show that when the axis does not shift, diaphragm of dam foundation is only subjected to bending moment and produces local tensile stress, but its influence is not obvious. When the axis is shifted downstream and the offset is less than 30 cm, diaphragm of dam foundation is subjected to the combined action of pressure and bending moment, resulting in stress concentration and adverse effects. In the case of no other processing, when the axis does not shift and the offset is less than 15 cm, it can be temporarily not processed; If the axis offset to the downstream is more than 15 cm and not more than 27 cm (measured maximum offset), in the subsequent construction, the concrete base needs to be widened downstream at least 20 cm, which can reduce the tensile stress extreme of diaphragm of dam foundation and weaken the stress concentration, so as to improve the stress behavior of diaphragm of dam foundation. The finite element simulation provides a reference for the safety evaluation and treatment measures when diaphragm of dam foundation is eccentric.

The Gaoxin District and Jinshui District were selected as the representatives of the new and old urban areas of Zhengzhou to explore the evaluation indexes that affect the risk of rainstorm waterlogging in cities and the importance of each index, and a risk index evaluation system covering natural and social factors was established. The importance of each evaluation index in new and old urban areas was determined by using random forest model. The results show that for both new and old urban areas, the sensitivity of disaster-inducing environment is the most important first-level indicator. Among them, imperviousness and pipe density are the most important tertiary indicators for surface and subsurface disaster-preventing environments, respectively. The risk of disaster-causing factors is the least important for Jinshui District and Gaoxin District, and the importance of rainfall is much greater than that of rain type. The difference between the old and new urban areas is mainly reflected in the stability of disaster-bearing body, whose importance is 0.23 and 0.09 for Jinshui District and Gaoxin District. The conclusion can provide some reference for the prevention and control of rainstorm waterlogging disaster in Zhengzhou.

Influenced by terrain and construction costs, the water flow of the flood drainage ditch outside the surrounding wall of the construction project in hilly regions should be minimized as much as possible. However, the capacity of existing or planned small reservoir in the low-lying areas of mountain flood gully outside the walls of construction projects is usually small and difficult to expand, which cannot meet the normal requirements of reservoir flood control. Aiming at this kind of engineering technical problems, this paper proposes a technical scheme with the construction of a small empty reservoir for flood prevention and drainage in construction projects. Compared with the normal reservoir flood regulating system, the storage capacity in this system can be greatly reduced, and the downstream flow reduction requirements can be met. The function and design points of the empty storage capacity peak cutting and flood regulating system are elaborated in detail combined with the actual engineering cases, which aim to provide important technical support and experience for the flood prevention and drainage project of small watershed in mountain and hilly regions.