Under intense human interference and extreme climate events, the flow-sediment regimes, deposition and erosion patterns, and river-lake interactions in the middle and lower reaches of the Yangtze River have undergone significant transformations. After the impoundment of the Three Gorges Project, the annual upstream sediment supply to the middle and lower Yangtze River has decreased by 70% to 93%, and the flow process has become more concentrated. However, the post-flood recession has accelerated due to the operation of cascade hydropower stations. The annual water supply from the four rivers and three outlets flowing into the Dongting Lake has shown no significant adjustments, with a decline of 9%, while the annual sediment supply has decreased significantly by 38%. The annual water and sediment supply of the five rivers into the Poyang Lake have decreased by 2% and 57%, respectively, while the annual water and sediment outflow from the Poyang Lake have increased by 1% and 5%, respectively. These adjustments have altered the deposition and erosion patterns in the middle and lower Yangtze River. To be specific, from 2003 to 2021, the cumulative erosion of the mainstream reached 5.03 billion m3, with an average annual erosion of 265 million m3per year. The deposition-erosion state of the Dongting Lake has shifted from being deposition-dominated to slight erosion-dominated, and the riverbed of the three outlets generally exhibits an erosion trend. Similarly, the deposition-erosion state of the Poyang Lake has changed from deposition to erosion, and the channel connecting the Poyang Lake to the mainstream Yangtze River shows severe erosion and down-cutting. A predictive model indicates that over the next three decades, the mainstream of the middle and lower Yangtze River will continue to experience significant erosion. By the end of 2050, the cumulative total erosion of the mainstream from Yichang to Datong and the three outlets will be 3.58 billion m3 and 117 million m3, respectively. The Dongting Lake is expected to be slightly silted, while the Poyang Lake area will be slightly eroded. Based on these findings, the impacts of the river-lake evolution on flood control, water supply, navigation, ecology, and safety of water-related structures are expounded systematically. Countermeasures and suggestions are also put forward.
River confluences are areas where environmental elements such as flow structures, sediment deposition, water quality, and organisms undergo significant changes in river networks, and are the key nodes for flooding and pollutant transport. This review summarizes the basic characteristics of flow structures and pollutant transport at river confluences and their responses to different conditions, along with the important impacts of complex flow structures and habitats on water safety issues in previous field measurements, laboratory experiments, numerical simulations, and theoretical studies. Future research should focus on enhancing the understanding of the hydraulic characteristics of river confluences under unsteady flow conditions, further clarifying the response mechanisms between pollutant transport and hydraulic parameters, and improving the flood safety and the water ecological environmental quality through the combination of engineering layout and hydraulic optimization and regulation.
As an important river morphology, meandering channels widely exist in the middle and lower reaches of the Yangtze River. Due to the complex evolution, the regulation of meandering channels had always been a hot and difficult issue for water conservancy and transportation sectors. We made a review on the evolution rules, the theories and regulation technologies of meandering channels in the middle and lower reaches of the Yangtze River before and after the construction of the Three Gorges Reservoir. On this basis, we propose that the regulation of meandering channels should be in line with the evolution rules and trends of river regime, stabilizing favorable river regime while improving unfavorable river regime. Furthermore, we delve into the directions of future regulation: the long-term evolution trend of meandering channels under low sediment concentration and the demand for multi-objective regulation, the risk of bank collapse under the long-term scouring of near-shore riverbed and the monitoring and early warning of river channel, as well as the comprehensive regulation technology for flood control and navigation and the application of new materials for regulation.
In the background of climate change, seasonal precipitation forecasting is of great importance for mid-long term allocation and comprehensive utilization of water resources. Given that each forecasting product has its unique advantages and disadvantages, we evaluated and compared the forecasting performance of deterministic and ensemble forecasts of eight models with 1-6 months forecast lead time (FLT) for the upstream of the Three Gorges Reservoir (TGR) to select the optimal model for each sub-basin. Results demonstrate that the optimal model may vary across different sub-basins and FLTs. In general, the ECCC3, ECMWF, CMCC models exhibit superior forecasting performance. Specifically, in the upstream of the TGR, the ECCC3 model performs best when the FLT is 1 month, while the ECMWF model excels for FLTs of 2-6 months. In the upstream of the Jinsha River and the Wudongde Project, the ECCC3 model performs the best. Conversely, in the downstream of the Jinsha River, Wujiang River, Xiangjiaba-Cuntan sub-basin, and Cuntan-Three Gorges sub-basin, the CMCC model outperforms other models. The ECMWF model performs the best for the Minjiang River while the MF model for the Tuojiang River. Based on the forecasting results of the optimal models in different sub-basins, we calculated the forecasting precipitation in the upstream of the TGR. Compared with the forecasting results of single best-performing models, the integration of forecasting result for each sub-basin reduces the root mean squared error by 9.33%-17.86%.
The runoff of the Mekong River is undergoing transformation under the influence of environmental changes. Enhancing the scientific understanding of Mekong River drought and the role of cascade reservoir operations on the Lancang River contributes to the effective management of cross-border water resources and the development of the Lancang-Mekong Cooperation. Based on the discharge data from Jinghong Hydropower Station and runoff measurements from hydrological stations along the Mekong River, as well as the Standardized Precipitation Evapotranspiration Index (SPEI), temperature, and precipitation data, this study examines the impact of cascade hydropower stations on the Lancang River during the dry season. Results reveal that over the past 40 years, the meteorological drought frequency in the Mekong River was 25.6%, with higher frequency in flood season reaching 35.7%, and 21.4% in dry season. SPEI during flood season exhibited a decreasing trend of 0.14 per decade. Persistent warming and interannual precipitation variability since 2000 have resulted in sustained meteorological droughts in the Mekong River. Following the operational adjustments of cascade hydropower stations since 2010, the average discharge from Jinghong Hydropower Station during dry season has increased by 92.9% compared to the multi-year average. The discharge from Jinghong accounts for significant proportions of the runoff at key hydrological stations along the Mekong River, specifically 83.5% at Chiang Saen, 68.1% at Vientiane, 37.3% at Pakse, and 35.0% at Kratie. Notably, the proportion of water replenishment to Kratie can reach approximately 45% during the lowest runoff period from March to April. Particularly during drought conditions in the Lancang-Mekong Basin, these replenishments effectively alleviate water demand downstream. The operations of the Lancang River cascade hydropower stations significantly enhance water replenishment in the Mekong River during dry season, highlighting their substantial regulatory role and positive impact on downstream regions.
The construction of large reservoirs alters the spatial and temporal distribution of regional precipitation. This study focuses on the impact of the construction of Wanfeng Lake, a large reservoir situated in karst region, by analyzing the annual and seasonal variations of regional average precipitation before and after the reservoir’s construction using high-resolution precipitation data. We compared the spatial distribution patterns of precipitation before and after the reservoir construction and examined how factors such as flux and path direction of water vapor transport, reservoir construction, and topographic characteristics influence precipitation. The results indicate that the construction of Wanfeng Lake significantly changes the spatial distribution of local precipitation, with seasonal variations in precipitation amounts: decreases in summer and autumn, and increases in spring and winter. The Random Forest Feature Importance analysis identifies the flux and path direction of water vapor transport as the primary factors influencing regional precipitation. Moreover, the relative distance to reservoir plays a slightly more significant role after construction, suggesting an increased contribution of water vapor from the reservoir. These findings offer important insights for sustainable water resource management and flood/drought disaster prevention in reservoir regions.
Understanding the climatic characteristics of flood season precipitation in the headwater region of Minjiang River is crucial for advancing meteorological and hydrological research and ecological conservation in the upstream of the Yangtze River. Based on the tree-ring-revealed precipitation data in Songpan County of Sichuan Province, we investigated the flood season (May-September) precipitation variation from 1901 to 2014 using dendroclimatology and climatological statistics methods. Results indicated that: 1) Tree radial growth and CRU (Climatic Research Unit) data were significantly correlated with flood season precipitation, and precipitation over the past century could be well reconstructed using multiple regression equations as tree-ring data improves CRU data quality. 2) Flood season precipitation contributed about 72% of annual precipitation; the climatic tendency of precipitation was -10.7 mm/century, showing insignificant decrease. 3) Flood season precipitation was stable with no significant abrupt changes over the past century, but with a primary periodicity of 35-37 years and multiple time scale periods of 15-20 and 10-11 years. The research findings offer valuable meteorological information for ecological research and regional development in the headwater region of Minjiang River.
The diffusion of leachates from phosphate solid wastes is a major source of contaminants. Based on the existing and increment of phosphate solid waste in China as well as its environmental impacts, this study reviews the current status of researches on phosphate solid waste accumulation in China focusing on the composition, diffusion, and migration of leachates from phosphate solid wastes. More stringent requirements for leaching experiments and the design of impermeable barriers are essential as the permeability coefficient of impermeable materials may increase due to high pollutant concentration in leachate, low pH value of phosphogypsum, and large overburden pressure. Current researches on leachate release and diffusion often fail to replicate actual landfill conditions. Future studies should integrate field-specific parameters such as ambient temperature, rainfall infiltration, and effective stress from overburden weight. Thermal-humid-mechanical (THM) leaching test apparatus is also recommended for multifield coupling investigation. This approach will provide a more comprehensive theoretical understanding of leachate prevention and control in phosphate waste landfills.
To investigate the impact of hydrothermal conditions on vegetation net primary productivity (NPP) in the “Three Water Lines” (Heihe-Tengchong Line, Yangguan Line, and Qitai-Cele Line) region of Northwest China, we employed an enhanced version of the CASA (Carnegie-Ames-Stanford Approach) model to estimate NPP in the study area from 2001 to 2020 based on remote sensing and meteorological datasets. Regression and correlation analyses were also conducted to scrutinize the temporal and spatial NPP variations and their responses to hydrothermal factors. Our findings revealed a fluctuating upward trend in vegetation NPP from 2001 to 2020, with an average annual increase of 1.54 gC/(m2·a). Notably, region III, located west of the Qitai-Cele line, exhibited the most rapid growth rate at 2.39 gC/(m2·a). Spatially, the majority of the study area demonstrated an increasing NPP trend, with 47.27% showing significant increases, predominantly in the central and southern parts of region I (east of the Yangguan Line) and the southwestern portion of region III. Conversely, only 0.79% of the area experienced a significant decrease in NPP. Regarding the influence of hydrothermal conditions, precipitation emerged as the dominant factor, contributing to 31.53% of NPP variation, surpassing the contribution of air temperature at 9.58%. This suggests that both temperature and precipitation positively influence NPP changes in the region, with precipitation playing a more pivotal role.
The effect of warming on soil respiration plays a crucial role in the global carbon cycle. To investigate the effects of global climate change on soil respiration, a meta-analysis was conducted to quantitatively assess the changes in soil respiration rate under warming conditions. Using 160 effective datasets from relevant studies both in China and abroad, we explored the responses of soil respiration to warming. Results indicate that compared to unheated conditions, warming significantly increases soil respiration rate (by 12.4%, P<0.05). Warming magnitude has the largest impact on soil respiration (increased by 22.9%), followed by annual mean temperature (increased by 14.4%), annual precipitation (increased by 12.4%), climate type (increased by 11.8%), and soil type (increased by 11.1%) in descending order. Principal component analysis reveal that annual mean temperature is the most influential factor affecting soil respiration under warming conditions. Statistical methods provide a deeper understanding of the effects of warming on soil respiration, contributing to the enrichment of ecosystem carbon cycle theories under changing environments and offering scientific evidence for the implementation of the national “dual carbon” strategy.
To optimize the drainage engineering layout in the Lixia River water network area, it is essential to consider the interaction between the internal lowland and the incidence of heavy rainfall in adjacent waterlog-prone areas. Using the Copula function, we constructed a joint distribution of rainfall frequencies for these waterlogged areas to calculate the heavy rainfall probability. Pearson Type-III marginal distributions for the rainfall frequencies in the Fubu and Doubei areas, together with Frank Copula function for the fitting of their two-dimensional joint distribution, facilitates the calculation of the probabilities of heavy rainfall for specified durations and return periods. By integrating observed rainfall time series with frequency analysis, we found that the risk of both waterlog-prone areas (namely the Fubu and Doubei areas) experiencing heavy rainfall beyond design standards is minimal. Specifically, when heavy rainfall in the Fubu area exceeds design drainage criteria, the likelihood of heavy rainfall in the Doubei area surpassing design flood control thresholds remains low. These findings support the feasibility of the proposed drainage channel scheme in the Doubei area.
To elucidate the near-field propagation characteristics of waves generated by subaerial landslides, we developed a three-dimensional numerical model of subaerial landslide impulse waves using FLOW-3D. We simulated the landslide body’s entry into water and subsequent wave propagation, and analyzed the 3D impulse wave’s temporal-frequency evolution via wavelet transform. Our findings reveal that the energy of the 3D landslide impulse wave primarily shifts from the main radial direction to the sides. Beyond a distance of two times the water depth from the plunging point, the energy spectrum’s evolution in other radial directions closely resembles that in the main radial direction. Additionally, the decay rate of local energy across all radial directions becomes consistent, and the energy transmission velocity of wave components near the dominant frequency does not vary with the radial angle. We further introduce the concepts and estimation formulas for the near-field characteristic wave energy peak and its transmission velocity, which are valuable for assessing landslide surge disasters.
Based on the FVCOM hydrodynamic model and the FVCOM-SWAVE wave model, we developed a wave-current coupled storm surge model for the Bohai sea, Yellow sea, and East China Sea during Typhoon “Chan-hom”. Following rigorous validation of surge elevations and significant wave heights, we quantified the impact of wave-current interaction on storm surge and identified key dynamic factors. Findings indicate that wave-current interaction significantly influences surge elevations in near-shore shallow waters, contributing approximately 14% to peak surge water levels. During high tide periods, wave-current interaction tends to reduce surge elevations, but increases surge levels during low tide periods. Accounting for wave-current interaction, the simulated significant wave heights show better agreement with observations. Additionally, the study compares the contributions of tide-surge interaction, wind field, and pressure to surge elevation. The wind field primarily drives surge elevations, with its effects most pronounced in the coastal waters of Zhejiang Province and Hangzhou Bay, where maximum surge elevations reach up to 2 m. In open sea areas, air pressure dominates surge elevations within the typhoon center’s radius. However, in coastal waters, particularly at the head of Hangzhou Bay, nonlinear tide-surge interaction and wave-current interaction significantly impact surge elevations, with respective maxima of 1.2 m and 0.5 m. These findings offer critical insights for enhancing coastal disaster prevention and mitigation strategies.
Since the completion of the Three Gorges Dam in 2003, its flood discharge and energy dissipation structures have withstood many flood tests. To further evaluate and summarize the design and actual performance of these structures, the discharge capacity of the Three Gorges Project was comprehensively assessed during the first regular dam safety inspection. The flow capacity of the power station units was verified using data from the Huanglingmiao Hydrological Station. The measured flow data from the power station indicate that the turbine output curve accurately reflects the actual flow rates of the left bank, right bank, and underground power stations. The actual discharge capacities of deep holes and surface holes were also evaluated and compared with their respective design values and model test results. The comparison reveals that the measured discharge capacity of deep holes matches the design value, while the measured discharge capacity of surface holes is slightly higher than the design value. However, the combined discharge capacity of deep holes and surface holes is basically consistent with the design value.
This study aims to address the turbulent flow patterns and significant water surface fluctuations in the original stilling basin, which lead to the formation of repelled downstream hydraulic jumps and subsequent scouring damage to the apron slab. To mitigate these problems, a combined chute block and trapezoidal block energy dissipator is employed, and the hydraulic characteristics of this dissipator are investigated. Physical model testing and numerical simulation techniques are combined to study the energy dissipation behavior under various flow rates. The energy conversion processes within the flow are analyzed, and flow velocity reduction ratios are calculated to assess the effectiveness of the dissipator. Findings indicate that, for the chute block-trapezoidal block joint dissipator with double rows of trapezoidal blocks arranged in a staggered manner, the velocity reduction ratios at three different flow rates are 60.00%, 75.34%, and 73.75%, respectively. Compared to the original stilling basin, this arrangement reduces the length of the hydraulic jump by 11.29%, 14.17%, and 10.22% across the respective flow rates. The energy dissipation mechanism is categorized into four distinct zones: the flow contraction and diversion area, the hydraulic jump swirl area, the vortex areas on both sides, and the post-jump mainstream area. The findings provide a valuable reference for the design of joint dissipators and the optimization of stilling basins.
At present, large-scale triaxial tests are used to investigate the mechanical properties of the filling of earth-rockfill dams, which are generally under plane strain state. Because the intermediate principal stress is equal to the minor principal stress in triaxial stress state, the mechanical properties of the filling under plane strain state will be underestimated. To fully comprehend the potential of the fill material for scientific design and rational evaluation of earth-rockfill dams, it is necessary to conduct plane strain test of the filling material. Large-scale plane strain tests were performed on the filling material using a large-scale true triaxial apparatus. A series of plane strain isotropic consolidation and drainage shear tests were carried out on coarse-grained soils with four different initial dry densities. Test results indicate that the stress-strain relationship predominantly exhibits strain hardening, with a rising stress curve and shear shrinkage-induced volumetric changes. Under a given minor principal stress, the maximal difference between the major and minor principal stresses increases linearly with the initial dry density. Similarly, when the initial dry density remains constant, this difference also increases linearly with minor principal stress. During the initial shear stage, the slope of the stress ratio curve between deviatoric and spherical stresses rises with increasing initial dry density. As shear deformation progresses, the stress ratio curves for different initial dry densities converge. A monotonically increasing deviatoric stress with spherical stress denotes strain hardening, whereas a deviatoric stress that first rises and then falls indicates strain softening. The initial elastic modulus under the same minor principal stress rises linearly with the initial dry density. At a specific initial dry density, the initial modulus increases linearly with the minor principal stress. The intermediate principal stress coefficient grows with the strain in the major principal stress direction, forming a three-segment broken line curve. Initially, the growth is slow during shear stage, but it accelerates linearly with increasing shear deformation. A slightly downward-bent curve end correlates with strain hardening, while a slightly upward-bent end corresponds to strain softening.
To more accurately investigate the anchorage mechanism of pressure cables,in consideration of plane stress conditions,we derived the approximate theoretical solutions for both the compressive stress of the grouting body of pressure anchor cable and the shear stress between anchor solid and rock-soil layer based on Mindlin’s fundamental solution. Through example analysis,we revealed an inverse relationship between the anchorage angle and the stress distribution curve of the grouting body, as well as a power function relationship between the anchorage angle and the peak stress of the grouting body in the anchoring section. The anchorage angle significantly influences both the compressive stress of the grouting body at the anchoring section and the shear stress at the interface between anchor solid and rock-soil layer. These findings not only enrich the understanding of the pressure cable anchorage mechanism but also provide valuable references for the development and application of new anchoring technologies. Additionally,they offer theoretical support for the design of pressure anchor cables in rock and soil engineering.
To investigate the effects of polypropylene fiber length, content, and distribution on loess reinforcement, a large-scale indoor direct shear test was designed for both uniform and non-uniform reinforcement schemes. In the non-uniform reinforcement, the fiber content was varied on both sides of the shear box and rammed into the soil in three layers. The curves of shear strength versus shear strain and shear strength indices of the reinforced loess were obtained. The results indicate: 1) Incorporating polypropylene fibers significantly enhances loess shear strength, with the reinforcement effect influenced by fiber length, dosage, and normal stress coupling. 2) In the uniform reinforcement scheme, a fiber length of 12 mm and a content of 0.5% achieves the best reinforcement effect. In the non-uniform reinforcement scheme, the influence range of the shear plane is less than 15 mm at normal stress of 50 kPa, slightly greater than 35 mm at 100 kPa, and further increased at 200 kPa. 3) The distribution pattern of fibers significantly impacts the reinforcement effect. Compared to a uniform 0.8% content group, non-uniform reinforcement with 0.5% content on both sides yields better results, as it avoids fiber agglomeration and ensures soil-fiber adhesion. These findings are expected to provide valuable insights for optimizing loess fiber reinforcement.
The safety of the tunnel traversing an active fault is a critical issue for the deep-buried long tunnel crossing the Tongcheng River in the Yangtze-to-Hanjiang River Diversion Project. This study addresses this challenge by employing an analysis of the geostress field and numerical simulation methods.Specifically,it examines the lining’s response in scenarios where adaptive structures are not utilized, estimates the design parameters for hinges, and verifies the lining’s behavior under these hinge parameters. Findings reveal that: 1) The angle between the horizontal principal stress and the tunnel axis is approximately 35°. The horizontal stress component along the tunnel axis is about 20 MPa, while the horizontal stress component perpendicular to the axis is around 21 MPa. The vertical stress component is approximately 18 MPa. 2) Without any fault mitigation measures,the tunnel’s relative deformation primarily exhibits convergence between the vault and floor. This convergence is most pronounced within the fault zone. The maximum principal stress values in the vault and floor occur in the fault zone and its affected area, with most of the lining in these regions experiencing damage. 3) Using the proposed method for estimating tunnel hinge design parameters, a reinforcement section length of 6 meters and a hinge section width of 2-4 cm are initially suggested. Following sensitivity analysis of these parameters, it is recommended that the reinforcement section length remains 6 meters, while the hinge section width is set to 5 cm. 4) When the tunnel is reinforced according to the proposed hinge structure parameters, the design effectively reduces the tension experienced by the entire lining in the fault zone. Under hinge design conditions, there is a significant decrease in relative deformation, stress levels, and lining damage. This demonstrates that the hinge structure enhances the tunnel’s resistance to fault-related issues.
Slope stability charts offer a rapid and efficient alternative to the iterative method for assessing the stability of two-stage soil slopes. Employing the upper bound theorem of limit analysis,the global and local failure mechanisms were constructed for two-stage soil slopes. By incorporating the pore water pressure coefficient ru,the expressions for internal and external work rates of the failure mechanism were derived,and the relationship curves between c/(γH) and tanφ for two-stage soil slopes in ultimate equilibrium state were obtained,referred to as the limit state curve (g-line). Based on this g-line,a series of two-stage soil slope stability charts were developed. The validity of these charts was confirmed through comparative analysis,and the effects of slope pore water pressure,geometry,and internal friction angle on slope stability and failure modes were systematically investigated. Results reveal that pore water pressure leads to the outward shift of the limit state curve,reducing slope stability. The failure mode of slopes is significantly influenced by their geometric shapes: convex and concave slopes are susceptible to local failures,with the extent of local failure expanding under the influence of pore water pressure. Additionally,as the internal friction angle of soil increases,the critical sliding surface shifts toward the slope surface,transitioning from global to local failure. The developed slope stability charts enable the simple and rapid evaluation of slope’s safety factors and corresponding failure modes,providing a valuable reference for stability assessments in similar slope engineering projects.
To investigate the influence of circumferential loading rates on the mechanical properties of sandstone, uniaxial compression tests were conducted on sandstone specimens at various circumferential control rates using an MTS rigid servo testing machine. The effects of circumferential control rate on stress-strain curves, failure modes, and energy evolution were analyzed. Results indicate that circumferential control rates have minimal impact on pre-peak deformation and peak strength, while reducing post-peak stress and strains. As circumferential control rate decreases, the post-peak axial stress-strain curves experience alternating stress decreases and increases. Post-peak volumetric strain exhibit the same trend. Although circumferential control rate does not significantly affect rock brittleness, the time required for rock failure increases sharply as the control rate decreases. Circumferential control yields predominantly shear failure, with lower total dissipated energy during pre-peak stage. As circumferential control rate decreases, dissipated energy gradually increases during post-peak stage, which weakens the post-peak failure and makes it controllable. On the contrary, under axial control mode, axial splitting is the dominant failure mode, with sharp increases in lateral strain post-peak and violent failure. These findings provide valuable insights for understanding the rock loading ratio effect and the brittle rock deformation characteristics under circumferential control conditions.
There are a large number of rock slopes in the difficult and dangerous mountainous areas of southwest China. Long-term freeze-thaw action deteriorates the mechanical properties of the rock mass, leading to decreased slope stability. To study the damage degradation law of rock mass under freeze-thaw action, uniaxial compression tests were conducted on low-porosity quartzite from a high and steep slope in the southwest hazardous mountainous area. The mechanical deterioration and energy evolution were analyzed. Based on the energy evolution law, a method for determining the complete compaction point of rock was proposed. A piecewise damage constitutive model of the rock in consideration of the compaction section was established by taking the complete compaction point as the piecewise point. Results show that early freeze-thaw cycles have little effect on the quartzite. However, when the number of freeze-thaw cycles exceeds 40, the mechanical properties of quartzite deteriorate significantly, and the failure mode gradually changes from shear failure to a combination of tensile and shear failure. The point corresponding to an elastic energy consumption ratio K (ratio of dissipated energy to elastic energy) of 1.2 is determined as the complete compaction point. The strain corresponding to the complete compaction point increases linearly with the increase in freeze-thaw cycles. The proposed piecewise damage constitutive model matches well with experimental data and more accurately describes the deformation and failure characteristics of freeze-thaw damaged quartzite.
Due to its concealed development process and severe consequences, seepage failure poses a significant threat to hydraulic engineering projects. To investigate the strength degradation characteristics of piping soils before and after seepage failure, an internal erosion stress path triaxial apparatus was developed for geotechnical testing. Seepage failure tests and triaxial degradation tests were conducted using this apparatus, considering the influences of three critical factors: fine particle content, consolidation pressure, and hydraulic gradient. Results revealed that: 1)These three factors significantly impact the seepage failure process, thereby affecting the strength degradation behavior of piping soils. Specifically, higher fine particle content and consolidation pressure tend to mitigate the degree of degradation, while a higher hydraulic gradient significantly amplifies it. 2)A hyperbolic curve function was used to model the degradation degree of piping soils, and a seepage failure strength degradation model was established through numerical simulation software. These findings provide valuable insights for the structural integrity analysis of hydraulic constructions and the prediction of seepage-related disasters.
To investigate the fundamental physical properties of foamed mixture lightweight soil using river sludge (FMLSS), river sludge collected from a river in Suzhou was used as the research material. An optimized orthogonal test was conducted to study the effects of various factors on the density and permeability of FMLSS, and sensitivity analysis was performed using the range analysis method. Results show that: 1) The density of FMLSS decreased significantly with increasing air foam content and water content, but increased significantly with increasing cement content, and changed slightly with increasing curing age. 2) The permeability coefficient of FMLSS increased with rising air foam content, reduced with increasing cement content, nearly multiplied with increasing water content in a linear manner, and plunged with extending curing age before gradually stabilizing. 3)Density was most sensitive to air foam content, followed by water content, cement content, and curing age in a descending order; permeability coefficient was most sensitive to water content, followed by curing age, cement content, and air foam content in a descending order. 4)In engineering applications, air foam content should be the primary control factor for density and lightweight properties of FMLSS, while water content should be the primary control factor for permeability coefficient. The research findings serve as valuable reference for the resource utilization of dredged silt and environmental protection.
Addressing the challenge of obtaining global optimal solutions for steel gate optimization problems, this study introduces an active target particle swarm optimization (APSO) algorithm for the optimization design of emersed plane steel gates. APSO incorporates an active target individual into the conventional particle swarm optimization (PSO) population and integrates it into the algorithm’s iterative update mechanism. This enhancement bolsters the algorithm’s capability to escape local optima and enhances its global optimization performance. Furthermore, the APSO algorithm employs a comprehensive learning factor in place of multiple individual learning factors used in traditional PSO, thereby improving the convergence rate and stability. Under constraints imposed by steel structure strength requirements, the APSO algorithm optimizes key structural parameters, including those of the main beam, side columns, panel, and secondary beams, with the objective of minimizing the total weight of the gate. After optimization, finite element analysis (FEA) is conducted using ABAQUS to verify the strength integrity of the main beam based on the optimized design parameters. Findings indicate that the APSO algorithm effectively optimizes the design of emersed plane steel gates, yielding improved structural dimensions. Specifically, the optimized gate design achieves a 15.38% reduction in total weight compared to previous literature examples, while stringent strength checks confirm compliance with allowable stress limits.
Industrial solid wastes, such as steel slag, blast furnace slag (BFS), and gasified fly ash, possess inherent reactive properties that can be utilized for detoxifying hazardous waste, thereby facilitating waste remediation through waste-derived solutions. In this study we selected a range of materials, including BFS-based cementitious materials, aluminate cement, BFS-clinker-vitamin C composites, red mud-coal gangue geopolymers, and steel slag-gasified fly ash geopolymers, to develop a life cycle model dedicated to the solidification/stabilization (S/S) of municipal solid waste incineration (MSWI) fly ash. Results indicate that: 1)the primary environmental impact of solid waste-based S/S technologies is on human health, with industrial chemical inputs being the main contributors. 2) Among the various activation methods examined, mechanochemical activation exhibited the least environmental impact. However, the environmental impact of geopolymer systems, particularly due to the extensive use of alkaline activators, was found to be the most significant. 3) In contrast, the BFS-clinker-vitamin C S/S method demonstrated the lowest environmental impact. Therefore, optimizing activation methods for solid waste-based materials and reducing the use of activators and additives are crucial to minimizing toxicological risks to human health.
