The carbon sequestration and oxygen release function of wetlands plays an important role in regional atmospheric regulation and is one of the important ecosystem service functions of wetlands. To quantify the carbon sequestration and oxygen release capacity of the Yellow River Delta wetland ecosystem and analyze its driving mechanism， this paper used the CASA model to calculate the net primary productivity（NPP） of the Yellow River Delta Wetland from 2005 to 2020， and converted it into carbon sequestration and oxygen release through the photosynthesis equation， and used the geographical detector and contribution index to identify the main driving factors and contributions of the evolution of carbon sequestration and oxygen release function. The results showed that the multi-year average net primary productivity of the Yellow River Delta wetland from 2005 to 2020 was 321.5 g/m²， with a total of 907.9 Gg C/a， with an overall decreasing trend in NPP from 2005 to 2020； the multi-year average of carbon sequestration and oxygen release were 309.3 and 836.4 g/m²， respectively. The overall trend of carbon sequestration and oxygen release is decreasing. In terms of spatial distribution， the spatial distribution characteristics of oxygen sequestration were consistent with those of NPP， and the high value areas were mainly concentrated in forest land， followed by grassland and cropland； the results of the Geodetector indicated that the land use type and NDVI are the main controlling factors for the spatial distribution of carbon sequestration and oxygen release in the Yellow River Delta wetland； the analysis results of the contribution index show that forest， grassland， and cropland have positive contributions to carbon sequestration and oxygen release， while land use types such as aquaculture ponds， salt pans， and construction land have negative contributions to carbon sequestration and oxygen release， the contribution indices of culture ponds， salt pans and construction land showed an increasing trend from 2005 to 2020， indicating that the negative impacts of human activities such as the development of urbanization and reclamation culture on the carbon sequestration and oxygen release functions of the Yellow River Delta wetland have been gradually strengthened. The study results can provide the scientific basis for the stability and sustainable healthy development of the Yellow River Delta wetland ecosystem.

Green roof is an important infrastructure for the low impact development （LID） and sponge city construction. How to establish a simple and practical hydrologic model， taking the runoff coefficient as an important index， for green roof to evaluate the rainfall-runoff reduction effect is an important question. Based on the measured data of rainfall runoff of green roofs at different times， the calculation expression of runoff coefficient is developed on the basis of the calculation formula of rainfall runoff depth of SCS model. Also， the potential maximum retention is calculated when the measured initial loss is selected reasonably using event analysis method. The results showed that the initial loss and the potential maximum retention at that time are basically linearly related， with an average ratio coefficient of about 0.28. The potential maximum retention will be reduced due to the rainwater retention during the rainfall period， and then gradually recovered during the drought period， and the overall trend is that the initial recovery rate is fast， then gradually decreases， and finally approaches 0. Based on this， A calculation expression to describe the variation process of the potential maximum retention including the rainfall and drought periods is proposed. Based on the runoff depth and runoff coefficient formulas of the SCS model， combined with the calculation expression of the potential maximum retention variation process， the continuous variation processes of the runoff depth and runoff coefficient for green roof are simulated and then the model effect is evaluated using the certainty coefficient R ² and the Nash Sutcliffe efficiency coefficient NSE. The results showed that the calculated values of runoff depth and runoff coefficient are in good agreement with the measured values. The R ² values are 0.93， and 0.85， the NSE values are 0.94， and 0.85 respectively， which has a good simulation effect.

To effectively evaluate the quality of urban water distribution projects and fully consider the fuzziness and randomness of influencing factors in the evaluation process， thereby improving the stability and reliability of water distribution projects in urban water supply systems and comprehensively reflecting the actual quality status of these projects， this paper proposes a quality evaluation model for urban water distribution projects based on a combination weighting method and cloud model. The evaluation system is constructed， including five primary indicators： water quality condition， personnel factors， construction quality， government supervision， and equipment and materials， as well as 32 secondary indicators， further divided into different quality levels for each evaluation indicator. To ensure the scientific and rational weight distribution， the Lagrange multiplier method is used to optimize the combination of weights obtained from the Best-Worst Method （BWM） and the improved Criteria lmportance Though Intercrieria Correlation（Critic） method. Based on the cloud model theory， the evaluation parameters of each quality level are finally determined and applied to the quality and safety evaluation of the Qiandao Lake Water Diversion Project， the second water source of Hangzhou. The final project quality level is determined by calculating the cloud similarity， and the results are compared with those obtained using the fuzzy comprehensive evaluation method. The research results show that the constructed model can accurately reflect the actual quality status of the urban water distribution projects. The final quality level of the project is excellent （Level II）， consistent with the actual project evaluation results， with the main influencing factors being training effectiveness （X _2，4）， team collaboration ability （X _2，6）， and equipment calibration and inspection （X _5，4）. Moreover， a comparison of the evaluation results with those of the traditional fuzzy comprehensive evaluation method reveals that the established model has significant advantages in addressing the correlation， fuzziness， and randomness of indicators， thereby improving the stability and credibility of the evaluation results. This enhances the accuracy of the quality evaluation results for urban water distribution projects.

The ecological footprint of agricultural water use is of great significance for understanding the ecological status of water environment and measuring the ecological occupation of water resources by agricultural development. The dynamic evolution patterns and driving factors of China's agricultural water ecological footprint are analyzed using water ecological footprint models， visualization maps， Kernel density estimation， Moran index， and geographic detectors. The results show that： ①From 2005 to 2022， the total ecological footprint of agricultural water use in China increased from 19 million square meters to 21 million square meters， with a regional ranking of Northeast>Central>West>East. The ecological footprint of agricultural water use per 10000 yuan of GDP decreased from 2.13 to 0.49， with a regional ranking of West>Northeast>Central>East. ②The ecological footprint of agricultural water use per 10000 yuan of GDP shows a spatial change feature of decreasing “from north to south” and “from northwest to southeast”. High value areas are distributed in Xinjiang， Xizang and Ningxia， while low value areas are distributed in Sichuan and Chongqing in the southwest and Henan， Shandong and Hebei in North China； ③The Kernel density estimation shows a dynamic evolution pattern of “increasing peak height、 decreasing peak number、 curve moving to the left、shortening right tail、decreasing width”； ④ During the investigation period， the spatial Moran index was significantly positive and mainly distributed in the first、second、and third quadrants； ⑤The results of the geographic detector reveal that， the average explanatory power of driving factors is ranked as follows： fiscal support for agriculture （0.25）>economic development level （0.23）>proportion of primary industry （0.20）>water resource endowment （0.19）>agricultural water conservancy infrastructure （0.19）>proportion of animal husbandry （0.15）>agricultural disaster rate （0.11）>degree of agricultural mechanization （0.07）. The explanatory power of agricultural water conservancy infrastructure， fiscal support for agriculture， proportion of animal husbandry， and agricultural disaster rate shows a fluctuating upward trend. The research conclusion is that the ecological footprint of agricultural water use per 10，000 yuan of GDP in China shows a trend of decreasing convergence and agglomeration； In terms of space， it mainly presents a positively correlated agglomeration pattern， with "low-low agglomeration" areas accounting for 45.16%， which is the most important agglomeration mode； The financial support for agriculture and the infrastructure of agricultural water conservancy are the core factors that continue to promote spatial differentiation.

The meteorological drought-waterlogging abrupt alternation regulation displays a significant dependency on the spatiotemporal scales of data sources. The response of the regulation on the data resources is very important. This paper evaluated the drought-waterlogging abrupt alternation’s spatiotemporal distribution during the flood season， driving factors and its response to data sources based on the 59 weather stations， 302 rainfall stations， and 130 meteorological-climatical monitoring indexes， using drought-waterlogging abrupt alternation index （DFAI）， time series analysis， geostatistical and machine learning methods. The results show that the main types and intensity of drought-waterlogging abrupt alternation in the flood season are opposite under the two data sources. The drought-to-waterlogging incidents increased by 2.5 times as the main type for the meteorological data， followed by the intensity of abrupt alternation decreasing more than 10%. In comparison， the waterlogging-to-drought incidents increased by 2.6 times as the main type for the precipitation data， in addition to the intensity of abrupt alternation increasing more than 69%. Besides， the drought-to-waterlogging incidents presented a significantly spatial distribution difference under the two types of data resources. The drought-to-waterlogging and waterlogging-to-drought incidents on annual scale and typical annual scale were observed in the eastern and southern part of the study area for the meteorological data， respectively. In comparison， these two types of incidents on the annual scale and the typical annual scale were detected to appear in the northern and southern part of the study area for the precipitation data， respectively. The DFAI’s temporal changes’ driving factors were significantly different for the two types of the data sources. Based on the random forest and K-nearest neighbor algorithms， the Tibet Plateau Index and El Nino and Southern Oscillation indices were detected as the main driving factors under the weather station data source， indicated by the absolute values of correlation coefficient and partial correlation coefficient ranging from 0.32 to 0.35 and 0.33 to 0.36. Their contribution rates were greater than 45% on the temporal changes of the DFAI. Under the rainfall station data source， the Asian Meridional Circulation index was regarded as the main driving factor， indicated by the absolute values of correlation coefficient （0.32） and partial correlation coefficient （0.38）. Its contribution rate was estimated to be 79% on the DFAI’s temporal changes.

Soil moisture （θ） plays an important role in water cycle and climate change. However， due to the strong spatial and temporal heterogeneity of θ， it is still a challenge to effectively monitor and estimate soil moisture. In order to optimize the layout of soil moisture monitoring sites and predict soil moisture， this paper took the Shale Hills in Huntington， central Pennsylvania， USA as the study area. Based on the daily scale data of 33 sites in the study area for 3 years （from May 20， 2011 to May 19， 2014）， a time stability analysis was carried out. Then the sites of each soil layer are optimized by combining the analysis results with the division of landform units in the study area. Finally， the optimized sites were taken as the input values of the model， and linear （stepwise multiple linear regression-SMLR） and non-linear （back propagation neural network-BPNN） models were used to construct soil water relationship models between other sites （27 sites） and the optimized sites （6 sites）， so as to predict θ at sites other than the optimized sites. The results show that it is feasible to select sites based on time stability analysis， and the method of time stability analysis combined with the division of landform units can select 6 sites in each soil layer as the input values of the model. The nonlinear model is much more suitable for soil water prediction in the study area， and has good prediction effect for the whole study area， every landform unit and every site. In the validation datasets of different soil layers， 32， 29 and 30 sites in each soil layer have R2 values above 0.7. The RMSE values were all lower than the accuracy of the soil moisture content probe. The ratio of the average RMSE to the measured soil water is less than 6% in whole small watershed， and no more than 8% in each landform unit， and in more than 90% of the sites， the ratio does not exceed 10%. The research results provide a theoretical basis for optimizing soil moisture monitoring and solving the data loss at some sites.

The low spatial resolution of the time-varying gravity field model data provided by GRACE and its successor satellite GRACE Follow-On limits its application in high-resolution long-term drought monitoring. In order to solve this problem， the XGBoost machine learning method was used to carry out downscale reconstruction of the changes in terrestrial water storage in mainland China from 2002 to 2022， and the GRACE TWSA with a resolution of 0.1 ° was generated for nine major basins in China. The modeling effects of different basins were compared. Then， the GRACE-DSI drought index based on GRACE data was compared with the traditional drought index scPDSI and SPEI， and the spatial distribution characteristics of different grades of drought in nine major basins in China were analyzed. Finally， the drought events in nine major basins in China and the spatial distribution of drought in 2022 were monitored.The results show that except for the inland river， the performance of the other eight watershed downscaling reconstruction models is better， and the consistency between GRACE TWSA and NOAH TWSA is further improved after downscaling reconstruction. The correlation between GRACE-DSI after downscaling reconstruction and scPDSI and SPEI drought index was also significantly enhanced. The frequency of drought in the middle and lower reaches of the Yellow River Basin， the Haihe River Basin and the Pearl River Basin is high and mainly light drought. Similarly， the frequency of drought in the southern part of the Songliao River Basin is also high， but it is mainly characterized by moderate drought and light drought. In addition， the proportion of light drought and moderate drought in the nine major basins is close， and the proportion of heavy drought and extreme drought is different. The proportion of heavy drought in the Huaihe River Basin and the Songliao River Basin is the highest， which is 14 % and 13.4 % respectively. The proportion of extreme drought in the Yangtze River Basin is the highest， which is 16.5 %， while the proportion of extreme drought in the Haihe River Basin is the lowest， which is only 6.1 %. From 2002 to 2022， most of the severe drought events occurred in the northern basins， and 3 of the top 6 drought events occurred in the Songliao River Basin； compared with scPDSI and SPEI， the spatial variation of drought monitored by GRACE-DSI is more consistent with the actual situation. However， since GRACE data represent all water changes， glacier melt water may lead to underestimation of GRACE-DSI.

In view of the defects of traditional spatial interpolation model sample’s dependence on sample data and prediction uncertainty， this paper proposes a new digital mapping method for spatial distribution of precipitation， ensemble learning （EL） algorithm. Based on the relationship between precipitation and multiple geospatial factors（geographic location， vegetation cover， topographic features）， an EL-based precipitation spatial mapping model is established with the sample data of 618 meteorological station observations in 2019 in China. The EL model uses the generalized linear regression （GLM） model as a meta-learning machine to integrate the primary predictions generated by Anusplin， geographically weighted regression （GWR）， and Gaussian process regression （GPR） models， and then generates precipitation grid point data at 1 km resolution for the whole country. Results show that the EL model achieves the best prediction with an determination coefficient （R ²） of 0.96 and an Root mean square error （RMSE） of 55.17 mm， which is 10.95%， 16.54%， and 18.02% lower than the RMSEs of the single model of GPR， GWR， and Anusplin， respectively. The EL model proposed in this paper shows potential applications in large-scale site-based spatial distribution mapping of precipitation.

In order to improve the prediction accuracy of daily sediment concentration time series， and improve the predictive performance of deep hybrid kernel extreme learning machine （DHKELM）， this paper compares and verifies the optimization effects of ten fish swarm algorithms，namely electric eel foraging optimization algorithm （EEFO）/Genghis Khan shark optimization algorithm （GKSO） algorithm/beluga whale optimization （BWO） algorithm/white shark optimization （WSO） algorithm/whale optimization algorithm （WOA）/tuna optimization （TSO） algorithm/sailfish optimization （SFO） algorithm/marine predator algorithm （MPA）/remora optimization algorithm （ROA）/manta ray foraging optimization （MRFO） algorithm， on benchmark test functions and instance objective functions， and proposes TVFEMD^Ⅱ - Ten Fish swarm algorithms - DHKELM daily sediment concentration time series prediction model. Firstly，TVFEMD^Ⅱ is used to decompose the daily sediment concentration time series and obtain several decomposition components； Secondly， based on the training sets of each component， the DHKELM hyperparameter optimization instance objective function is constructed， and 8 benchmark test functions are selected as comparative verification functions. Ten fish swarm algorithms are used to perform extreme value optimization and comparative analysis on the benchmark test function and instance objective function. Finally， the TVFEMD^Ⅱ - Ten Fish Swarm Algorithm-DHKELM model is established， and each model is verified through an example of predicting daily sediment concentration during the flood season at Longtan Station in Yunnan Province. The results show that： ① The total ranking of the ten fish swarm algorithms for benchmark function optimization is only 10% the same as the total ranking for instance objective function optimization. Overall， EEFO and GKSO have better optimization effects， while ROA and WSO are poor. ② The overall ranking of the optimization of the instance objective function by the ten fish swarm algorithms is basically consistent with the overall ranking of the prediction accuracy of each model optimized by the ten fish swarm algorithms. This indicates that the stronger the extreme value optimization ability of the fish swarm algorithm， the better the DHKELM hyperparameters obtained through optimization. The better the performance of the prediction model constructed from this， the higher the accuracy of daily sediment concentration prediction. ③ The mean absolute percentage error （MAPE） of TVFEMD^Ⅱ - Ten Fish Swarm Algorithm-DHKELM model for predicting daily sediment concentration in instances ranges from 0.927% to 1.583%. The model has small computational scale， high prediction accuracy， and good robustness， which has good practical value and significance. ④ In the case of very limited decomposition components，TVFEMD^Ⅱcan decompose complex daily sediment concentration time series into more regular and easier to model and predict modal components， greatly improving the time series decomposition effect and significantly improving the accuracy of daily sediment concentration prediction.

In order to study the flow field and flow pattern inside the curved ramp outlet tank culvert and explore the optimization scheme of the undesirable flow pattern， the physical model test and numerical simulation were combined to study and analyze the internal flow pattern. Two different rectification schemes were designed to solve the undesirable flow pattern inside the pressure box culvert， and the flow pattern， velocity and pressure distribution of the characteristic section inside the box culvert were studied and compared. The results show that， under the original design， there are undesirable flow patterns such as flow in the box culvert and backflow at the inlet end. At the same time， the maximum flow distribution ratio in the culvert is 36.07%， the minimum is 8.73%， and the maximum pressure difference between the two sides of the barrier pier is 354.90 Pa. After adopting the combination scheme of “pier position + slope ratio optimization of flow bottom plate”， the flow phenomenon inside the culvert is eliminated， the return part of the inlet water in the box culvert is eliminated， and the flow distribution ratio of the culvert is reduced to 20.23% at the lowest， which is closest to the ideal flow distribution. The pressure difference between the two sides of the remaining piers is reduced to 35.15 Pa， and the rectification effect is remarkable， which provides a reference for the flow improvement of similar pump stations in the future.

This paper discusses the effectiveness and mechanism of local scour reduction around piers at an oblique angle to the water flow when the front piers are protected by the permeable collar in one-double and two-double piers layout. The methods used are laboratory model tests and numerical simulation. The model test results show that as the angle increases， the scour of the front piers change little， while the scour of the rear piers gradually increases. When the oblique angle is small， the protection of the front piers has a significant shielding effect on the rear piers. However， when the oblique angle is greater than 30°， the shielding effect of the first piers on the rear piers basically disappears. When the one-double piers layout are arranged， the maximum scour depth of the rear piers is greater than that of the front piers. When the two-double piers layout are arranged， the first pier has a sour-reduction effect on the second and third piers， and a scour-intensifying effect on the fourth pier. It is therefore recommended that the layout angle of multiple piers should not exceed 30°. Alternatively， the piers at the farthest downstream should be protected. The numerical simulation results show that when the front row piers are protected by the permeable collar， the flow velocity around both sides of the piers is obviously decreased， the shielding range of the downstream is obviously increased， and the shielding effect is significantly increased. With the increase of oblique angle， the superposition effect of the flow around the front and rear row piers leads to the increase of the pier side velocity and shear stress of the riverbed， resulting in the intensification of local erosion.

Water-gas-sand three-phase flow is the most complicated flow in intake system for hydraulic machinery， where the key difficulty is that the vortex takes both gas and sand into the system， which induces large erosive damage on pumps， resulting in unsafe and unstable operation of hydraulic machinery. This study focuses on the characteristics of three-phase vortex flow in sump with sand by experimental test to figure out the effects of water-gas vortex flow on the sand movement in the bottom， and further to analyze the critical submerged height. The results obtained show the physical process that the bed material load is possible to enter the system following FAGV， i.e.， during the formation to dissipation of the floor-attached gas vortices （FAGV）， the particle movement in the bottom is enhanced to spirally enter the pipe. Compared with the same situation in clean water， the frequency of vortex occurrence is higher and the duration is longer if the FAGV occurs， and the critical submerged height is also different， so it is necessary to make new design standards of sump with sediment flow.

Rivers carry water resources and are channels for material and energy transfer. The management of river-related construction projects is an important part of ensuring the flood control， drainage， and stable river conditions of rivers. The water resistance ratio is an important control indicator for river-related construction project management， and the study of its calculation method is of great significance for controlling the impact of river-related construction projects. The traditional water resistance ratio， also known as the structural water resistance ratio， refers to the proportion of the cross section area of the river occupied by a river-related construction project at a certain design flood level. The article reveals the inadequacy of the current structural water resistance ratio in reflecting the degree of obstruction of water flow dynamics propagation in river related construction projects. The structural water resistance ratio weakens the flood control impact of river-related construction projects near the main channel of the river， and over-reflects the flood control impact of river-related construction projects near the shallow shoals of the river. On the basis of the structural water resistance ratio， combined with the hydrological properties such as water depth and flow velocity of the river， the article proposes a hydraulic water resistance ratio. The hydraulic resistance ratio refers to the proportion of the flow of the cross section occupied by the river-related construction project to the total flow of the entire river section at a certain design flood level. Compared with the structural water resistance ratio， the hydraulic water resistance ratio more effectively reflects the degree of obstruction of water flow dynamics propagation in river related construction projects， and the calculation method is simple， which can compensate for the shortcomings of the structural water resistance ratio. This article suggests incorporating the hydraulic water resistance ratio into the control indicators of river related construction projects， effectively controlling the degree of impact of river related construction projects on river flood discharge.

Based on a high head and large discharge shaft spillway tunnel project， a new Dragon head shaft spillway tunnel is proposed. Numerical simulation is used to compare and analyze the original design of the platen-type shaft spillway and the optimized new-type dragon head shaft spillway. The latter has a smooth flow connection and a better flow pattern. The hydraulic characteristics of the new Dragon head shaft spillway are studied by numerical simulation and model test. The results show that the water cushion in the stilling well is deeper and the floor impact pressure and pulsation pressure are smaller， which improves the turbulent strength and energy dissipation rate and reduces the risk of cavitation and cavitation erosion. The water flow in the connecting section of the dragon head is stable， and the phenomenon of water rushing to the top is avoided. The results of hydraulic model test and numerical simulation on the water surface line， flow rate and pressure in the spillway tunnel of the new Longhead shaft are in good agreement. The optimized new Dragon head shaft spillway can effectively improve the energy dissipation of shaft and provide a new energy dissipation scheme for the project.

On the double-layer non-uniform sand riverbeds， under the condition of critical breakdown of topsoil layer， local scour pits on bridge piers will continue to develop downward. The changes of the riverbed composition affect the gradation characteristics of coarsened cover layer on the bottom of the local scouring pit around bridge pier. The coarsened cover layer at the bottom of the bridge pier local scour pit will affect the maximum local scour depth of the bridge pier. In this paper， using natural non-uniform sand to simulate single-layer and double-layer soil riverbeds， and through the flume test， four sets of flow and four sets of non-uniform sand were set to study the gradation characteristics of the cover layer on the bottom of the local scour hole around the bridge pier，on the double-layer sediment riverbed under the condition of critical breakdown of the topsoil. The results show that， the scouring process of the double-layer sediment bed is more complicated than that of the single-layer sediment bed， and that factors such as initial bed sand gradation of the top soil and initial bed sand gradation of the bottom soil affect the formation process of the coarsened overburden layer at the bottom of the scour pit. Under the condition of critical breakdown for topsoil layer of riverbed， the gradation curves of the coarsened cover layer on the bottom of the local scour pit around the bridge pier in the double-layer sediment riverbed is between the coarsened cover layer gradation curves obtained when the surface layer and the bottom layer sediment are used to simulate the single layer bed respectively. Under the condition of critical breakdown for topsoil layer of riverbed， the over-scour rate decreases with the increase of the thickness of topsoil layer， the relative coarseness of topsoil and the relative median diameter of the cover layer. On this basis， the gradation calculation formula of the coarsened cover layer on the bottom of local scour pit around bridge pier is proposed. The calculated value of the formula is compared with the measured value， which verifies that the formula is not only applicable to the calculation of the gradation of the coarsened cover layer at the bottom of the double-layer sediment bed scour pit under the critical breakdown condition of the topsoil， but also can better calculate the gradation of the sediment in the coarsened cover layer at the bottom of the single-layer sediment bed scour pit， and the error of the result is small.

The estuary coastline is dynamically changing under the combined effects of river sediment replenishment， fluvial-tidal dynamics， and human activities. Based on water-sediment monitoring data at the Jiaji station and remote sensing satellite imagery within the Wanquan River estuary from 1987 to 2022， the evolution trend of the water-sediment flux into the sea and the coastline was clarified. Combining the regression analysis， the impacts of water-sediment variation on coastline characteristics were further revealed. The results show that there is no significant trend change in the water discharge of the Wanquan River， the average flow stands at 145 m3/s， and the contrast between the flow in wet years and dry years is conspicuously significant. The concentration of suspended sediment has witnessed a significant decrease， amounting to 32% over the past five years.The sediment discharge also shows a decreasing trend and mutates around 2015， with a 70% decrease after the mutation. The total length of estuary coastline has shrunk by 6.19 kilometers， while the proportion of artificial coastline has been increased from 14% to 43%； the fractal dimension of the coastline decreases slightly， indicating a reduction in coastline complexity. However， the position of the coastline changes little. Regression analysis shows a good positive correlation between coastline length and fractal dimension and sediment discharge， indicating that the sediment replenishment directly affects the structure of the coastline， but the position of the coastline remains relatively stable under human intervention

Under the limitation of topographic and geological conditions， multi-stage stilling basin often leads to poor downstream flow pattern and energy dissipation ratio due to worse water flow connection. Based on the design of overflow crest outlet and bottom outlet of Qingshan Reservoir in Hebei Province， the combination of numerical simulation and model test is used to study the change rule of the characteristic hydraulic parameters under the different sizes of the first-stage stilling basin and the secondary-stage stilling basin. The results show that： when the length of the first-stage stilling basin meets the conditions of stable occurrence of the hydraulic jump， continuing increase the length of the pool has little effect on the energy dissipation rate； The decrease of the height of the end sill （that is， the depth of the pool） leads to the gradual increase of the Froude number of the contraction section， and the energy dissipation rate of the first-stage stilling basin at the surface and bottom outlet increases firstly and then decreases with the decrease of the sill height； The increase of the length of the linear section of the secondary-stage stilling basin leads to the location of the hydraulic jump moves towards downstream， and the moderate increase of the angle of the curved section axis is favorable to improving the energy dissipation rate， but the energy dissipation rate decreases when the angle is too large；On this basis， the combined energy dissipation type of the first and secondary-stage stilling basin is recommended， and the numerical simulation and model test are carried out. The result shows that： extending the guide wall in the first-stage pool improves the flow pattern of the secondary-stage pool， the Froude number of the section before the jump in the two stilling basins are more than 4.50， and form a stable hydraulic jump. The comprehensive energy dissipation rate reaches 70.12%， which is significantly improved compared with the initial scheme. The research results can be used as reference for similar engineering designs.

In order to investigate the mechanical mechanisms of compression failure in cohesive soil under varying initial moisture conditions and unveil the microscale mechanical effects of water on the macroscopic deformation properties， advanced particle flow software PFC^3d was employed in conjunction with indoor triaxial compression test results. The results show： the DEM simulation results established can effectively reflect the mechanical performance of soil under varying initial moisture content conditions； The peak strength， tangent modulus， cohesion and internal friction angle of the soil exhibit a decreasing trend with the moisture content increases； As the vertical strain increases， larger displacements occur at the specimen's ends， with smaller displacements in the central region. This leads to the formation of a shear zone in the central area， characterized by initial shear contraction followed by shear dilation of the soil. Upon applying confining pressure， the anisotropy of the particle contact normal is initially small. However， as the soil reaches its peak state， the contact normal of the particle system exhibits strong anisotropy； During the shear process， the development of microcracks in the specimen undergoes stages of zero development， rapid development， and slow development， with shear cracks dominating the process；In the model， shearing converts a significant portion of boundary energy into elastic strain energy and a smaller portion into damping energy. This study offers a novel approach to understand the compressive deformation and failure behavior of soil under varying initial moisture content.

In order to investigate the effect of opening and closing cracks of quasi-brittle materials on crack initiation under compressive-shear fracture failure， the press-shear fracture tests were carried out on the cubic gypsum samples with closed cracks and open cracks with a size of 150mm， and the effects of crack inclination angle and fracture morphology on the compressive strength， failure mode and crack initiation angle of the samples were studied. The pressure-shear tension-tensile fracture characteristics of quasi-brittle materials with different fracture morphologies are revealed. At the same time， based on the pressure-shear tensile cracking criterion considering T stress， the initiation angle of different fracture samples is predicted， and compared with the traditional theoretical prediction curve and the test results. It is found that the pressure-shear tensile cracking criterion considering T stress has more accurate prediction results. Moreover， the relative critical size α is introduced， and the critical size α of the quasi-brittle material in this paper is 0.1 through the comparison of the samples with two different fracture forms， which verifes the applicability of the criterion. Finally， the law of the dip angle of prefabricated fractures on the initiation angle and the differential fracture behavior of closed and open cracks under the two fracture types are explained.

In the increasingly complex and harsh geological environment of engineering， the quality requirements for grouting reinforcement are becoming higher and higher. A single grouting method and material can no longer meet the actual needs of engineering construction. This article proposes the concept of composite grouting for sandy tunnels through material composite and process composite， in order to meet the strict requirements for anti-seepage and reinforcement in high head and large flow loose gravel formations. That is， for low-permeability and dense sand layers， high-pressure fracturing method is used to generate a slurry vein skeleton， followed by infiltration grouting in locally weak and loose sand areas， ultimately forming a dense and solid composite structural system. This article analyzes the mechanical mechanism of slurry splitting and diffusion in composite grouting technology， derives the basic relationship between splitting width， slurry pressure， and ultimate diffusion distance. Then， based on the basic theories of elasticity and structural mechanics， the stability of the slurry vein skeleton and surrounding rock composite structure is analyzed， and the reinforcement effect of composite grouting is scientifically evaluated. Finally， the section tunnel of Chongqing Metro Line 10 is selected for on-site testing of the actual reinforcement effect of composite grouting.

In view of the application requirements of natural pozzolan in 17.1 million m³ RCC at 1 yr. design age in Basha Dam in Pakistan， the real long-term activity of natural pozzolan was researched by using strength activity index （SAI）， X-ray diffraction （XRD）method and selective dissolution method， and the feasibility of improving the activity of natural pozzolan was explored by using low temperature calcination and particle grading optimization. The results show that the SAI of natural pozzolan tends to decrease continuously with the increase of age， and the main mineral components are mainly inert crystals， whose reaction degree is only comparable to that of quartz powder. Although calcination can activate chlorite and kaolinite in pozzolan， it is difficult to effectively increase the long-term SAI because of its low content. Through the optimization of gradation， the compressive strength ratio of cementitious materials with 50% high pozzolan content can be increased by 6%， and the filling effect can be fully exerted.

Accurate discrimination of surrounding rock state after excavation is of great significance in guiding the excavation construction and improving the support scheme. Aiming at the problem that the plastic zone index in the traditional finite difference simulation method cannot accurately reflect the influence range of surrounding rock excavation， this paper proposes a kind of surrounding rock state discrimination index based on local elastic strain energy release， and elucidates the feasibility of this index based on FLAC^3D finite difference numerical simulation. At the same time， through the comparison of elastic strain energy release and plastic zone distribution， the excavation stability evaluation of Gongyi Pumped Storage Power Station′s underground cavern group was carried out. The results show that the range of elastic strain energy release is obviously lower than the depth of plastic zone， which can better reflect the loss of bearing capacity of surrounding rock， and the discrimination method of surrounding rock state based on elastic strain energy release has good applicability in the evaluation of stability of top arch excavation support of Gongyi Pumped Storage Power Station.

The rock-embedded pile foundation of power transmission lines is mostly made of reinforced concrete. The wet-dry cycle in the actual environment has a significant impact on the basic mechanical properties of the rock and concrete structural surface of the rock-embedded pile foundation. In this paper， samples of limestone concrete structures were subjected to different numbers of wet dry cycles， and indoor normal stress tests were conducted to obtain the shear mechanical properties of different normal stresses. A mathematical model was established for the relationship between the shear strength of the limestone concrete contact surface and the number of wet dry cycles. Results revealed significant differences in shear stress-strain curves between limestone concrete and single limestone samples. As the number of wet-dry cycles of the samples increased， the structural plane's cohesive force， shear strength， and residual strength decreased. Internal friction angle changes were less noticeable. The model accurately reflects peak stress changes under different wet-dry conditions， with a minimum error of 4% and a maximum of 12.8%. This provides a theoretical basis for studying pile-rock interface mechanics in karst foundations.

To comprehensively reveal the shape evolution of gap-graded coarse granular particles under cyclic shear， a series of simple shear tests were conducted using artificially dyed gypsum particles at different shear cycles， and the 3D shape of the particles was obtained using a laser scanner. The results show that within the gap-graded coarse materials， smaller particles exert a grinding and rounding effect on larger particles， manifested by lower elongation， greater sphericity， and roundness of the larger particles. With the increase of shear cycles， both larger and smaller diameter surviving particles （particles that remain within their original size range after breakage） successively undergo fracture damage， but eventually the final particle shapes tend towards regularity. Conversely， the shape of migrated particles （particles generated from breakage） gradually approach regularity with increasing shear cycles， yet still exhibit significant differences compared to surviving particles of the same size. This suggests that using generalized descriptions of particle breakage behavior based on whole gradation is inappropriate. The shape of larger particles tend towards spherical and flattened shapes， while smaller particles more readily assume spherical and columnar shapes. The shape parameter distribution of SH reconstructed particles closely resembles their real state， and strong linear correlations exist between some shape parameters. These research results can provide a reference for understanding the particle shape protection mechanism and constructing the shape evolution model.

The performance test of polyoxymethylene （POM） fiber self-compacting concrete（SCC） was carried out， and the influence law and mechanism of fiber geometric characteristics and fiber content on the working performance and mechanical properties of SCC were analyzed. The results show that when the fiber length is constant and the content is increased in the range of 0.8~2.4 kg/m³， the slump spread of SCC decreases， and the mechanical properties of SCC increase first and then decrease. When the fiber content is constant and the fiber length increases within the range of 6~20 mm， the slump spread of SCC does not change much， and the mechanical properties of SCC increase first and then decrease. The cylindrical fibers with a dosage of 1.6 kg/m³ and a length of 12 mm has the largest improvement on the compressive strength of SCC， which is 3.6% higher than that of plain SCC at 28 d. The 28 d splitting tensile strength of SCC is increased by 14.52% when the flat fiber with a length of 12 mm and the cylindrical fiber with a length of 6mm are mixed， and the dosage is 1.6 kg/m³. The addition of POM makes the microstructure of SCC more compact， and the close combination of fiber and gel can effectively absorb the energy generated by damage and improve the macro-mechanical properties. The research conclusion can provide a reference for the engineering application of POM fiber self-compacting concrete.

Flow measurement in irrigation districts is an essential means to achieve precise water distribution and charging based on water volume. In this paper， an irrigation flow distribution and measurement device was developed， which used a rectangular section eccentric Venturi tube as the throttling element， and is suitable for flow distribution and measurement at the head of tertiary canals and field canals in irrigation districts. Through physical model experiment and hydraulic simulation， the measurement feasibility was investigated， and the appropriate height reduction ratio for the rectangular section eccentric Venturi tube was determined. The results show that it is feasible to measure the flow of irrigation canal by use of the flow distribution and measurement device with eccentric Venturi tube with rectangular section， and the relative error of the outflow coefficient in the actual flow experiment is less than 5%； The suitable height reduction ratio ranges are 0.30~0.55、0.30~0.55、 0.30~0.55、0.30~0.50、0.30~0.50 and 0.30~0.50 respectively for the S500~S1000 rectangular section eccentric Venturi tubes. When higher flow measurement accuracy is required， the rectangular section eccentric Venturi tube with a smaller height reduction ratio should be selected； when lower head loss is required， the Venturi tube with a larger height reduction ratio should be adopted. This new flow distribution and measurement device has both flow distribution and measurement functions， and has the advantages of low construction cost， small head loss， and convenient management， and has an optimistic application prospect for the flow distribution and measurement of tertiary canals and field canals in irrigation districts.

In order to investigate the relationship between the changing law of phreatic evaporation of summer maize in sandy ginger black soil and yellow tidal soil of Huaibei Plain and the meteorological factors and burial depth， the meteorological observation and evapotranspiration meter data of Wudaogou Experimental Station from 2011 to 2022 were selected， and the correlation analysis between phreatic evaporation and meteorological factors during the growth period of summer maize was carried out， and multiple linear regression was performed by the stepping method， and the independent variables of the model were analyzed by the pass-through analysis to reveal the main influencing elements of maize phreatic evaporation， and a regression model was established. We also proposed a nonlinear fitting function between phreatic evaporation coefficient and 0.2-5.0 m burial depth. The results show that： ①in the sandy ginger black soil， the phreatic evaporation coefficient was significantly correlated with the water vapor pressure difference at the burial depths of 0.2 m and 0.4 m； with water vapor pressure difference and absolute humidity at the burial depths of 0.6 m；with water vapor pressure difference， sunshine hours， and relative humidity at the burial depths of 1 m. In the yellow tidal soil， the phreatic evaporation coefficient was significantly correlated with the water vapor pressure at the burial depths of 0.2 m， 0.4 m and 1.0 m； with water vapor pressure difference， absolute humidity， and average temperature at the burial depths of 0.4 m. ②The regression models of maize evapotranspiration and meteorological factors were constructed under different soil qualities and burial depths， and the models met the accuracy requirements （R ²>0.810 for the model of sandy ginger and black soil， and R ²>0.800 for the model of yellow tidal soil）. ③The nonlinear fitting of the phreatic evaporation coefficient to the burial depth showed a logarithmic function relationship （R ²>0.75） for sand-ginger black soil maize； an inverse function relationship （R ²>0.800） for yellow tidal soil maize at the early and late stages， and an exponential function relationship （R ²>0.950） for the developmental stage and the middle stage. ④The maximum burial depth Z_{m of summer maize in sandy ginger-black soil was in the range of 2.7~3.1 m； Zm in yellow tidal soil was in the range of 3.5~4.6 m. The calculation model meets the accuracy requirements and can be used for the calculation of phreatic evaporation of maize during the growing period.}

The purpose of this study was to investigate the effects of different brackish water irrigation modes on salinity distribution， physiological and ecological characteristics of rice， and yield in saline-alkali soils. According to the utilization of brackish water， four irrigation modes were set up： freshwater irrigation （control group）， re-irrigation， freshwater-brackish water shallow wet alternate irrigation and freshwater-brackish water alternating irrigation. The results showed that： ① Freshwater-brackish water shallow wet alternating irrigation and freshwater-brackish water alternating irrigation could reduce the maximum photochemical quantum yield （F_v /F_m ）， actual quantum yield （Ф _PSⅡ） and photochemical quenching （q_p ） of rice leaves， while these two treatments could also reduce the net photosynthetic rate （P_n ）， transpiration rate （Trmmol） and stomatal conductance （Cond） of rice leaves， while the decrease of rice photosynthetic rate was caused by non-stomatal factors. ② Compared with freshwater irrigation， freshwater-brackish water shallow and wet alternate irrigation and freshwater-brackish water alternating irrigation significantly increased the salinity of the upper layer of soil， and the reirrigation of retreat water could mainly reduce the soil salinity by 0~30 cm. All irrigation modes carried out different degrees of soil salt washing， and the desalting rate of 0~50 cm soil layer was more than 40%， in which the desalting effect was the most significant with the re-irrigation mode， reaching 58.3%. ③ Different brackish water irrigation modes inhibited the growth of rice， and the yield of rice gradually decreased with the increase of irrigation water salinity concentration， and the yield was in the order of re-irrigation> freshwater irrigation> freshwater-brackish water shallow and wet alternate irrigation >freshwater-brackish water alternating irrigation. During the growth period of rice， the water consumption of freshwater-brackish water shallow and wet alternate irrigation was the least， and the crop water use efficiency was the largest. In this study， the implementation of freshwater-brackish water shallow-wet alternating irrigation strategy in saline-alkali soil can not only effectively improve rice yield， but also significantly improve the water use efficiency of crops. This provides a practical and sustainable agricultural irrigation solution for saline-alkali areas with limited freshwater resources， and has important practical significance and promotion value.

To examine how cotton responds to varying drip irrigation flow rates in different soil types， we conducted a pot experiment in which we evaluated changes in growth， physiology responses， and yield of cotton grown in sandy loam and chalky sandy loam soils with four drip irrigation rates of 0.4， 0.8， 1.2 and 1.6 L/h. In addition， we synthesized and analyzed the relationship of each index with drip irrigation flow rate and soil sand content through structural equation modeling to explore the interactions between cotton growth， physiology and yield indexes at bud stage and boll stage. The results revealed that the net photosynthetic rate （P_n ） at bud stage of cotton varied significantly under different soil types and drip irrigation flow rates.The Leaf Area Index（LAI） at boll stage of cotton varied significantly under different drip irrigation flow rates. Cotton yield reached the highest at 1.2 L/h drip irrigation flow rate in sandy loam soil and at 1.6 L/h drip irrigation flow rate in chalky sandy loam soil. Cotton yield was overall higher in sandy loam soil than in chalky sandy loam soil. Through structural equation modeling， initial fluorescence （F_o ） in bud stage cotton had direct negative effect on maximum fluorescence （F_m ） at bud stage. At boll stage， LAI had a direct inhibitory effect on transpiration rate （T_r ）， and SPAD had a direct promoting effect on LAI. LAI， P_n and SPAD are key indicators of cotton yield. In conclusion， sandy loam soil is the recommended soil type for cotton cultivation. 1.2 L/h and 1.6 L/h are the recommended drip irrigation flow rates for sandy loam and chalky sandy loam soils. This study can provide theoretical reference for high quality and efficient production of cotton.