[Objective] Extreme precipitation is an important fact that lead to flood-waterlogging disaster and has an important impact on agricultural production.To explore the spatiotemporal evolution law of extreme precipitation indicators in the central area of Yunnan Province.[Methods] Based on the daily precipitation date at 44 stations from 1960 to 2020, the variation trends and period characteristics of extreme precipitation indices in central Yunnan Province is nalyzed.[Results] The result showed: Over the past 60 years, maximum 1-day precipitation(Rx1day), maximum 5-day precipitation(Rx5day), simple daily intensity index(SDII), ≥10 mm precipitation days(R10), days ≥20 mm precipitation days(R20), maximum consecutive wet days(CWD), very wet day precipitation(R95p), and Extremely wet day precipitation(R99p) exhibit an initial increasing trend followed by a subsequent decreasing trend. Conversely, maximum consecutive dry days(CDD) demonstrates an initial decreasing trend before transitioning into an increasing trend. Rx1day, SDII and R99phad a significant increasing trend, while CDD, Rx5day, R10, R20, R95p and Total precipitation amount(PRCPTOT) showed no significant change trend, and CWD had a significant decreasing trend. The high values of Rx1day, Rx5day, R10, R20, R95p, R99p and PRCPTOT are located in the northwest, northeast and southeast of the central Yunnan region, and the low values are located in the west-central Yunnan region. The high value of SDII is located in the northwest of the central Yunnan region, and the low value is located in the central western part of the central Yunnan region. The CDD exhibited a gradient of decrease from the northwest to the southeast. The high value of CWD is located in the northwest, southeast and central part of the central Yunnan region, and the low value is located in the west-central part of the central Yunnan region. Wavelet analysis shows that Rx1day, Rx5day, R10, R20, SDI, CDD, CWD, R95p, R99p and PRCPTOT all have periodicity within 8a.[Conclusion] Mann Kendall trend analysis can play an important role in analyzing the time series trends and mutation points of precipitation elements; The slope estimation of Sen plays a crucial role in trend analysis of long-term precipitation data; Continuous wavelet analysis can infer the periodic changes in precipitation elements, which has great value for promotion and application. By studying the spatiotemporal evolution of extreme precipitation indicators in central Yunnan, reference can be provided for irrigation and drainage planning, disaster prevention and reduction in the region.
[Objective] The surface flood pathway is a critical component of major drainage system. To ensure the safety and stability of vehicles when the road plays the role of drainage path, [Methods] Audi A4L was selected as the research object. The optimal Latin hypercube design was used to select the flow velocity and water depth of the flood. The VOF method and CFD numerical simulation are used to calculate the flow force on the vehicle and analyze the change of the free water level near the vehicle body, so as to reveal the instability mechanism of the vehicle under different flow conditions.[Results] The result show that the drag force and buoyancy of the vehicle are affected by the water depth and velocity at the same time. The value of the drag coefficient is stable within a certain range, and the buoyancy of the vehicle is significantly affected by the drastic change of the free surface height of the water flow.[Conclusion] When the flow velocity is less than 1 m/s, the threshold of instability water depth is 0.4 m; When the flow velocity is between 1 m/s and 4.5 m/s, and the friction coefficient is 0.25 or 0.35, the threshold of instability water depth can be expressed as a cubic function of the flow velocity; When the flow velocity is 4.5 m/s, the threshold of instability depth is 0.24 m(μ=0.25) and 0.27 m(μ=0.35). The area below the curve of the most unfavorable instability threshold is the safe zone, and the area between the two curves is defined as the instability risk area. Research result can provide reference for the risk assessment of vehicle instability in the roadway drainage path.
[Objective] To explore the water resource situation in the water source area of the Hanjiang-to-Weihe River Valley Water Diversion Project under climate change conditions, and to ensure the efficient and sustainable operation of major cross basin water transfer projects.[Methods] Three scenarios(SSP1-2.6, SSP3-7.0, SSP5-8.5) under the CMCC-ESM2 climate model in the 6th International Coupled Model Intercomparison Program(CMIP6) were used to drive the SWAT model of the water source area of the Hanjiang-to-Weihe River Valley Water Diversion Project, and to analyze the evolution trend of hydrological conditions in the water source area of the Hanjiang-to-Weihe River Valley Water Diversion Project under future climate scenarios.[Results] The result showed that from 2025 to 2100, under the SSP1-2.6 scenario, the precipitation and runoff in the water source area showed a decreasing trend, while the highest and lowest temperatures showed an increasing trend. However, the precipitation and runoff in the near future(2025—2050), medium term(2051—2075), and long term(2076—2100) were higher than those in the reference period(1980—2020); Under the SSP3-7.0 scenario, precipitation, runoff, and highest and lowest air temperatures all show an increasing trend. However, under the SSP3-7.0 scenario, the precipitation in the near, medium, and long term is lower than the baseline period, and the recent runoff is also lower than the baseline period; Under the SSP5-8.5 scenario, precipitation, runoff, and maximum and minimum temperatures also show an increasing trend, with recent, medium-term, and long-term precipitation and runoff all higher than the baseline period.[Conclusion] In the future, with the increase of radiation forcing, there will be a trend of warming and wetting in the water source area of Hanjiang-to-Weihe River Valley Water Diversion Project. By simulating future climate change and analyzing the evolution trend of hydrological conditions in the water source area of the Hanjiang-to-Weihe River Valley Water Diversion Project, scientific basis and theoretical support can be provided for the allocation and management of water resources in the project and the utilization of regional water resources.
[Objective] The frequency and duration of extreme climate events in Guizhou Province are intensified by its unique topography and diverse climate. However, research on extreme temperatures in the province is incomplete. This study aims to understand the spatiotemporal characteristics of extreme temperature indices and their main influencing factors using temperature data from 29 meteorological stations and large-scale climate indices(PDO, ENSO, SOI, AMO) from 1960 to 2020.[Methods] The study analyzes the spatiotemporal evolution and future trends of extreme temperatures in Guizhou Province using linear trend analysis, Mann-Kendall trend test, and R/S analysis. Correlation analysis and wavelet analysis are used to explore the relationships between extreme temperature indices and large-scale climate indices.[Results] The findings reveal a decreasing trend in the duration of cold waves and frost days, while monthly extreme minimum and maximum temperatures and summer days show an increasing trend. Abrupt changes in extreme temperature indices were concentrated in the late 20th to early 21st centuries, and this trend is expected to continue in the next five years. Spatially, low temperature indices decrease from west to east, while high temperature indices increase. The cold wave duration index is likely influenced by longer interannual cycles of ENSO and SOI, while the extreme high temperature index is affected by shorter cycles. Additionally, frost days and monthly extreme minimum temperatures are negatively correlated with altitude.[Conclusion] The main factors affecting extreme temperature indices are climate, topography, and human activities. The result provide a scientific basis for disaster prevention and climate impact decision-making.
[Objective] Water ecological health assessment is an important way of integrating water resources, water environment and water ecosystem management, often through a series of quantitative indicators to assess the state of water ecosystems. Benchmarks provide a “baseline” for changes in ecological health. The identification of ecological benchmarks that are both scientifically sound and reasonable often considers the ecological desirability of water ecosystems in conjunction with human management needs, with the aim of improving the accuracy of water ecological health assessments.[Methods] From the concept of baseline and the four forms of references, several typical baseline determination method are sorted out, and their respective characteristics, advantages and disadvantages are compared. It combs, summarizes and analyzes the determination method of benchmarks for three major categories of indicators: physical habitat, physical and chemical properties, and aquatic organisms.[Results] The practical application of ecological benchmarking in different aquatic ecosystems in the Yangtze River Basin is emphasized, and the similarities and differences of the water ecological assessment related standards/by-laws issued by different management departments in China are compared. Difficulties in ecological baseline determination are discussed, such as the selection of reference sites, the selection of monitoring indicators, the accumulation of monitoring data, the regional variability of baseline determination and innovative method of determination.[Conclusion] The ecological benchmark determination method are relatively complex, and have not yet formed a unified specification, future research should be combined with advanced technologies such as big data and artificial intelligence, in order to achieve scientific, accurate and differentiated formulation, and to provide reference and technical support for the evaluation of water ecological health in China.
[Objective] Joint optimal allocation of water and land resources is considered an effective approach to mitigating the mismatch between the spatial and temporal distribution patterns of water and land resources and regional ecological, social, and economic development, thereby promoting social stability and sustainable development.[Methods] Based on the theory of dualistic water cycle, soil water and reclaimed water are incorporated into the supply side of water resources. The interaction between water-soil-carbon and other elements within the eco-environment-economic and social system are comprehensively considered. A multi-objective optimal allocation framework of regional water and land resources responding to eco-economic-social demands is constructed. The iterative solution of the framework is implemented by a double-layer nested algorithm coupling nonlinear multi-objective programming(NLMOP) and successive approximation(SA) method, leading to the determination of a joint allocation scheme for water and land resources.[Results] The result of the joint optimization allocation of water and land resources in Luoyang city demonstrate that the land use pattern and water resource supply of each county have been collaboratively optimized. The total amount of water resources in the region has increased by 29.23 million m3, net carbon emissions have decreased by 0.381 4%(equivalent to 90,698 tons of standard coal), and GDP has remained stable. The difference in water supply and demand ratio among administrative units has been minimized.[Conclusion] The results provide strong scientific support for improving the comprehensive utilization efficiency of regional water and land resources and ensuring the sustainable development of regional eco-economy-society.
[Objective] The accurate analysis of the spatiotemporal evolution of watershed ecological environmental quality and its driving factors can provide scientific support for the comprehensive management and high-quality development of the watershed. [Methods] Using the Tao River Basin as an example, a Remote Sensing Ecological Index(RSEI) was constructed by coupling indices of greenness, humidity, temperature, and dryness to evaluate the ecological environmental quality of the basin. The spatiotemporal evolution characteristics of the ecological environmental quality in the Tao River Basin from 1990 to 2020 were then analyzed. On this basis, geographic detectors and structural equation models were introduced to explore the direct and indirect responses of the basin's ecological environmental quality to natural and human factors. [Results] The results show that the average RSEI in the study area first decreased and then increased over time. The ecological environmental quality levels in the watershed transitioned from large areas of poor and very poor to large areas of medium and good. Climate and terrain have a positive influence on the distribution of RSEI, while urbanization has a negative influence. The impact of land use types on RSEI first showed a negative and then positive relationship. The positive impact of climate gradually weakened, while the negative impact of urbanization gradually intensified. [Conclusion] The ecological environmental quality of the Tao River Basin has generally improved over time. The analysis of spatial pattern changes and driving factors can provide scientific support and practical guidance for comprehensive watershed management.
[Objective] The impact of vegetation on aspects such as water-sediment balance, exchange of biogenic elements, and ecosystem stability is considered important. The Lancang River is regarded as an important water conservancy project and water resources regulation center in southwest China, with its vegetation dynamics being deemed crucial for flood safety, water supply security, and ecological security in the basin.[Methods] The study area was focused on the Lancang River Basin. Utilizing time series meteorological data from 1998 to 2020, as well as Normalized Difference Vegetation Index(NDVI) data, the spatial-temporal variations of vegetation dynamics in the Lancang River Basin were analyzed. The analysis included the utilization of the Mann-Kendall trend test and Sen's Slope estimation, and the impacts of climate change and human activities on vegetation dynamics in the Lancang River Basin were quantitatively assessed using the Partial Least Squares Structural Equation Model.[Results] During the period from 1998 to 2020, it was observed that the annual growth rate of NDVI during the growing season in the Lancang River Basin was 0.004 2/year, indicating a significant increasing trend. The growth rates in the Qinghai and Tibet sections were 0.002 0/year and in the Yunnan section was 0.005 3/year. It was noted that the proportion of regions with significantly improved vegetation in the basin exceeded 40%, while regions with severe degradation were less than 5%. Furthermore, it was found that the NDVI in spring, summer, and autumn all exhibited significant growth, with the fastest growth being observed in spring and the slowest in summer. The fastest growth season in the Qinghai and Tibet sections was summer, with the slowest growth occurring in spring. In the Yunnan section, the fastest growth seasons were spring and autumn, with relatively slower growth in summer. The average impact of terrain factors on vegetation was-0.085, human activities were found to have an average impact of 0.009, and climate factors were noted to have an average impact of 0.451.[Conclusion] Currently, temperature is considered to be the main climate factor affecting vegetation growth in the study area, with human activities being identified as having a relatively weak impact on vegetation dynamics. It was also observed that terrain factors indirectly affect vegetation growth by regulating climate factors.
[Objective] To ensure the ecological water use of the Yarkand River and scientifically determine the ecological flow rate, [Methods] the area ratio index method based on long-term hydrological data was utilized to calculate the runoff of the studied river section. This approach yielded the long-term runoff result for the control section. Using these runoff calculations and measured cross-sectional information, hydraulic calculation method was applied to obtain hydraulic characteristics such as water depth, wetted perimeter, flow velocity, and water surface width under different flow conditions.To comprehensively determine the ecological flow rate of the section, there are four different method employeel: the Tennant method, the wetted perimeter method, the Q90 method, and the ecological hydraulic method. These method were based on the hydraulic parameters required for fish habitat. Subsequently, the changes in hydrological and hydraulic characteristics of downstream sections under two scenarios: natural inflow and ecological flow discharge.[Results] By comparing and analyzing multiple calculation method, the minimum ecological discharge during the dry season(October to March of the following year) at the Miskni dam site section in the Yarkand River Basin is 10% of the average annual flow, which is 14.3 m3/s. During the breeding season of fish and the wet season(April to September), the ecological flow discharge should be 30% of the average annual flow, which is 42.9 m3/s. Using these ecological flow discharge calculations, changes in the hydraulic parameters of the downstream river section. Compared to the natural inflow in normal years, the flow rate decreased by 79.6%, the flow velocity decreased by 48.3%, the water depth decreased by 31.4%, and the water surface width decreased by 26.1%.[Conclusion] The calculation method for river ecological flow, based on the habitat requirements of fish and combined with hydrological and hydraulic method, is relatively reasonable. It can accurately determine the ecological flow according to the spawning time of fish.However, releasing only the ecological flow in the river can cause significant changes in hydraulic parameters such as cross-sectional water depth, water surface width, and flow velocity. While ensuring the ecological flow for fish, the impact of reduced flow on other animals or vegetation should also be considered.
[Objective] With the large-scale development of China's infrastructure construction, the scale and depth of highway soft soil foundation treatment have been greatly improved in recent years, and new theories, new technologies, new materials and new processes of highway soft soil foundation treatment haveemerged constantly and been popularized and applied in engineering practice. In order to avoid blind selection of highway soft soil foundation treatment technologies, and make mature, reliable, cost-effective technical achievements more widely promoted and applied, it is necessary to timely update and summarize the current research progress of highway soft soil foundation treatment technology.[Methods] On the basis of combing the development period of highway soft soil foundation treatment technology in China, a variety of characteristic and representative new technologies developed in highway soft soil foundation treatment in recent years are classified from four aspects: drainage consolidation method, composite foundation method, replacement method and curing agent stabilization method, and some theoretical achievements and standardization of highway soft soil foundation treatment technology are summarized. At the same time, the shortcomings and future development trend of highway soft soil foundation treatment technology are put forward.[Results] The research shows that based on China's national conditions and the needs of social and economic construction, the development period of highway soft soil foundation treatment technology is reasonably divided into four stages(initial exploration stage → vigorous development stage → diversified innovation development stage → green and low-carbon development stage). Although the overall level of China's highway soft soil foundation treatment technology has been greatly improved, but with the scale and depth of China's soft soil foundation treatment has been greatly improved, it is still facing more and more challenges, such as the limited development of construction machinery, the technical construction and monitoring is not intelligent enough, the service toughness needs to be improved, the safety, environmental protection and economy are not enough.[Conclusion] combined with the national requirements for intelligent construction and environmental protection and energy saving, China's highway soft soil foundation treatment technology will continue to develop in the direction of multi-method combined technology, intelligent construction, intelligent operation and maintenance technology, high value utilization technology of green and low-carbon, standardized technology system in the future. The research result will point out the direction and provide reference for the treatment technology of highway soft soil foundation in China at present.
[Objective] To investigate the suitability of different Digital Elevation Models(DEMs) for extracting river networks in plain areas, [Methods] ALOS DEM, ASTER GDEM, and SRTM DEM data sources were collected. Seven representative watersheds were selected for the study, and the accuracy of river network extraction was analyzed using the fitting difference calculation.[Results] The result showed that all DEM data exhibited significant errors in extracting river networks in flat terrain, lake areas, and urban areas. ALOS DEM demonstrated the highest accuracy in extracting digital river networks. The precision of the digital river network can be significantly improved by using the DEM correction function of Arc Hydro Tools. ASTER GDEM exhibited higher accuracy in hilly areas compared to SRTM DEM, while SRTM DEM showed higher accuracy in lake, farmland, and urban terrain conditions compared to ASTER GDEM. The optimal threshold for watershed area extraction using ALOS DEM was 50,000, for ASTER GDEM it was 20,000, and for SRTM DEM it was 5,000.[Conclusion] By selecting multiple DEM sources and analyzing the extraction of digital river networks from different perspectives, this study provides valuable insights for extracting digital river networks in plain areas.
[Objective] To quantitatively assess the contribution of climate and land use changes to the inflow of Songhuaba reservoir, [Methods] based on multi-period climate and land-use data since the establishment of Songhuaba water conservation district, the climate change trend is analyzed by the method of Climate Propensity Rate and MK trend test, the spatio-temporal variation characteristics of land use are explored by the GIS spatial overlay tool, and the watershed hydrological processes are simulated by SWAT model, so as to analyze the impacts of climate and land use changes on the reservoir inflow of the study area. [Results] The results show that temperature of the study area increases at a rate of 0.586 ℃/10 a and precipitation decreases at a rate of 12.5 mm/10 a during 1980—2014. The main land use types in the study area include cropland, forest, shrub and grassland. Between 1980 and 2010, the size of cropland increases while forest slightly declines, which result ed in the increase of the reservoir inflow. [Conclusion] Climate change is the main cause of the reservoir inflow variation, and the autumn inflow is the most sensitive in the historical change scenarios. Changes in temperature and precipitation are not linearly related to the inflow amount, either jointly or individually. The average monthly inflow decreases by 0.636 million m3 with the temperature increase of 1℃, and increases by 4.234 million m3 with 10% increase of precipitation.
[Objective] Radon, an inert gas continuously exuded and decayed from the surrounding rock of underground chambers, is seriously interfered with cutting-edge physical experiments, such as dark matter research in deep underground laboratories, and poses health hazards to experimental personnel. To reduce radon levels in the experimental space and maintain the dryness of the chamber environment, [Methods] a special lightweight waterproof radon-suppressing structure was innovatively constructed in Phase II of the China Jinping Underground Laboratory. This structure was designed to isolate radon and groundwater exuded from the surrounding rock outside the experimental space while minimizing additional radiation background introduced by external materials. Measurements of air radon concentration under different protective structures and ventilation conditions were conducted in situ.[Results] It was shown that, under good ventilation conditions, an ultralow radon concentration of 11.1 Bq/m3 was achieved with the self-developed waterproof radon-suppressing structure, creating a clean air environment. Without a fresh air system, radon concentrations were reduced to 18.75% of the level in a chamber with conditions similar to the original chamber. One year after the construction of the waterproof radon-suppressing structure, radon concentrations in the laboratory remained stable, and no leakage was observed throughout the lifecycle of the chamber.[Conclusion] The self-developed waterproof radon-suppressing structure was demonstrated to significantly reduce radon concentration in indoor environments, maintain stable radon levels without leakage, and provide a novel method and technology for constructing waterproof and radon-suppressing environments in underground laboratories worldwide.
[Objective] The flaring gate pier contraction jet technology is commonly employed in narrow valley high arch dams to facilitate collision-free flood discharge and energy dissipation of the surface spillway and deep hole. Excessive contraction ratio of the flaring gate pier result in inadequate longitudinal tension of the jet flow, causing water inflow concentration and exacerbating downstream scouring. Conversely, if the contraction ratio is too small, backwater can develop in the flow channel, leading to a potential reduction in the discharge capacity of the surface spillway and degradation of the jet shape. Determining the critical value of the contraction ratio for backwater can serve as a foundation for designing the shape of the flaring gate pier.[Methods] The effects of contraction ratio, initial turning point, contraction section length, weir surface pitch angle, and head on weir crest on the flow state of a flaring gate pier are investigated through hydraulic model experiments and three-dimensional numerical simulations.[Results] The results indicate that, with all other parameters held constant and only the contraction ratio varied, a critical contraction ratio exists for the flaring gate pier. When the contraction ratio falls below this critical value, backwater flow occurs in the surface spillway. Through over 360 calculation cases, 48 sets of experimental data on the critical contraction ratio are collected.[Conclusion] The results provide a quantitative relationship between the critical contraction ratio and the head on weir crest, stereotyped design head, height difference between the crest and initial turning point, length of the contraction section, and angle of the weir surface. The formula's high accuracy has been verified, providing valuable reference for designing the flaring gate pier of a high arch dam.
[Objective] Phosphorus is the main pollutant and biogenic element in the Yangtze River, and the completion of the Three Gorges Dam has led to the interception of a large number of suspended sediment(particulate phosphorus) carrying phosphorus, which has affected the ecological environment of the Yangtze River Basin.Particle size(D) is an important physical property of suspended sediment, but there is a lack of information on particle size(D) in the study of particulate phosphorus in the Yangtze River.[Methods] Suspended sediment particle size gradation analysis and suspended sediment phosphorus content(PP′) monitoring were carried out monthly in eight hydrological sections of the Yangtze River mainstream and its tributaries Jialing River and Wujiang River in the reservoir area in 2021, and the PP′ values of suspended sediment at different time and different particle size sections were obtained.Sediment transport rate, flow velocity and other hydrological parameters, as well as total phosphorus(TP), dissolved phosphorus(DP) and particulate phosphorus(PP) concentrations, the temporal and spatial variation of suspended sediment particle size characteristics and phosphorus content in the reservoir area were summarized, the main suspended sediment components dominating the transport of particulate phosphorus in the reservoir area were analyzed, and the interception effect of the reservoir area on different suspended sediment components was estimated.[Results] The results show that:(1) The suspended sediment in the reservoir area was dominated by fine particles with D≤0.062 mm, and there was a trend of refinement from upstream to downstream. Silt is the main carrier of particulate phosphorus in the reservoir area, accounting for 77% of the annual suspended sediment flux(D≤0.062 mm) and 82% of the annual suspended sediment flux(D≤0.062 mm).(2) The average phosphorus content of suspended sediment in each section of the Yangtze River mainstream in the non-flood season is greater than that in the flood season, and the smaller the particle size is, the greater the PP′value is, but in the flood season, the clay with 0.002<D <0. 004 mm contains the most phosphorus, and the sediment transport rate determines the amount of suspended sediment flux, which is the main factor affecting the transport of particulate phosphorus. (3) The phosphorus in the reservoir water is mainly DP in the non-flood season and PP in the flood season, and the suspended sediment and PP are retained throughout the year, especially in the flood season, and the suspended sediment and particulate phosphorus retention in the flood period account for about 94.5% and 97.1% of the annual retention, respectively. The retention rate of silt particulate phosphorus in the reservoir area is more than 80%, and that of clay particulate phosphorus is more than 60%. [Conclusion] The results show that the combined monitoring method of particle size distribution of suspended sediment and soil phosphorus measurement could determine the phosphorus content of suspended sediment with different particle sizes in the reservoir area, which provided a new technical reference for phosphorus monitoring in the reservoir area. The ratio of suspended sediment composition has greater influence on the transport of particulate phosphorus than the particle size of suspended sediment in the reservoir area, and the greater the ratio of suspended sediment composition is, the greater the influence on the transport of particulate phosphorus is. Therefore, phosphorus control in the upper reaches of the Yangtze River should focus more on the ratio of suspension sediment composition.
[Objective] Accurate power prediction of a runoff hydropower station is crucial for formulating generation scheduling plans and ensuring a reliable power supply strategy. Considering the strong randomness in the generation output of runoff hydropower stations and the low accuracy of direct prediction, a combined prediction model based on Adaptive Variational Mode Decomposition(VMD) and Temporal Convolutional Network(TCN) was proposed.[Methods] Initially, the Whale Optimization Algorithm(WOA) is employed to optimize the parameters of Variational Mode Decomposition(VMD), achieving optimal adaptive decomposition of the original output sequence. Subsequently, TCN model is individually established for trend prediction of each decomposed component. Finally, the obtained result are reconstructed to obtain the final prediction.[Results] The result shows that, compares to other models, the model established has varying degrees of improvement in prediction performance under the same conditions.[Conclusion] The result indicates:(1) The WOA-VMD method can effectively extract the characteristics of the output sequence of a runoff-type hydropower station and reduce the influence of the instability of its own data on the prediction result.(2) Compared to the five models of VMD-TCN, TCN, LSTM, RNN and BP, the proposed WOA-VMD-TCN prediction model can effectively improve the prediction accuracy of hydropower station power, providing a new and effective modeling approach for power prediction of runoff hydropower stations.
[Objective] Karst channels in the mining area are abundant in karst areas, and the combined effect of heavy mining processes will lead to more complicated groundwater system. To identify the hydrogeological conditions of mines in karst areas, the Zimudang gold mine located in karst area in Guizhou was selected for a case study, and systematic hydrogeological investigations and 3D geological modeling were carried out in the gold mine.[Methods] A method combining geophysical exploration with 3D geologic modeling technology was proposed, and the fine 3D geological model of Zimudang gold mine was established based on integrating multi-source data such as exploration drilling holes, geological cross-section maps and geophysical result.The karst channels were depicted, and a hydrogeology conceptual model integrating the karst channel model was established.[Results] Result showed that mining activities have changed the flow direction of the underground river in the first level of the mine, which is opposite to flow direction of the Taipingdong underground river out of the mine. The fault F3 and F6 consisted the watertight boundaries in the east and west of the mine.[Conclusion] This study showed, the groundwater system was changed significantly by the heavy mining work. The karst channel and the hydrogeological boundary could be precisely identified, and the recharge-runoff-discharge groundwater system was also identified, which visualized the hydrogeological conditions of the mines in the karst area. This research could provide support for the scientific prevention and control of underground water pollution in mines in karst areas.
[Objective] Aiming at revealing the patterns of influence that random joints within different dip angle intervals have on the failure characteristics, shear strength, and size effect of the shear modulus of rock masses, [Methods] the SRM technology in PFC2D discrete element software is used combined with fractal theory and the Monte Carlo method, and numerical simulation of direct shear tests is conducted on rock-like materials of various sizes with embedded random joints.[Results] The result indicate that:(1) The shear strength of the rock body shows “S”-type nonlinear characteristics with the increase of the inclination angle of embedded random joints, and the minimum value mostly occurs in the interval of 15°~30°, and the maximum value is in the interval of 60°~75°.(2) Different sizes of embedded random joints have similar effects on the damage of the rock mass by the change of inclination intervals. The low inclination interval shows obvious dominant and subdominant damage surfaces, and as the inclination interval increases, the stress concentration is shifted to the middle of the joints, and the dominance of the two dominant damage surfaces is switched.(3) The variation of random joint dip intervals significantly affects the size effects of rock shear strength and shear modulus, and the effect on the size effect of rock shear strength is greater than the effect on the size effect of shear modulus.[Conclusion] The study investigates the impact of variations in the embedded random joint dip angle intervals on the shear strength and failure characteristics of jointed rock masses under the same size conditions, as well as the influence of variations in the embedded random joint dip angle intervals on the shear strength and the size effect of the shear modulus of jointed rock masses under different size conditions. It provides significant reference value for the prediction of rock mechanical properties and their engineering applications.
[Objective] To study the damage development and failure mechanism of the bedrock of pumped storage power station in karst area under cyclic loading, [Methods] the incremental cyclic loading-unloading test and cyclic loading-unloading test with large stress amplitude are carried out on the typical dolomite rock.[Results] The result show that:(1) For the incremental cyclic loading-unloading tesy, pore compaction dominates under low stress cycles [(0.15~0.35)σucs,(0.35~0.55)σucs], and irreversible strain appears under high stress [(0.75~0.95)σucs], indicating damage accumulates with loading and the elastic modulus decreases while the Poisson's ratio increases with cyclic loading.(2) When the stress exceeds the ‘fatigue stress threshold' [(0.85~0.90)σucs], the acoustic emission signal generates continuously during the cyclic loading and unloading process, and the damage accumulates until the rock failure.(3) For the cyclic loading-unloading test with large stress amplitude, for the test with the stress range of(0.30~0.85)σucs, the sample is not damaged. For the test with the stress range of(0.30~0.90) σucs, the damage process could be divided into three parts: the initial compaction stage, the stable damage accumulation stage, the damage accelerated accumulation stage. For the test with the stress range of(0.30~0.95)σucs, the damage of rock sample is rapidly accumulating to failure.[Conclusion] The energy evolution law and mechanical property degradation mechanism of dolomite during loading and unloading were studied, which could provide support for the design and engineering monitoring of pumped storage reservoirs.