Xinjian Fan

Confined dropshafts equipped with suspended internal gas-recirculation pipes can experience pressure rebound and increased air demand when the continuous gas pathway breaks down near the pipe outlet. Yet, the coupled roles of outlet clearance, gas-phase inertia, pipe diameter, and downstream backpressure remain unclear. Here, visual observations and time-averaged measurements of pressure, external air intake, and circulating-gas flow were integrated in a 1:4-scale physical model and reorganized in a dimensionless Cg–Frg framework, where Cg quantifies outlet clearance and Frg represents measured gas-transport capacity. The results reveal a transition from stable gas-dominated transport to blockage-prone liquid intrusion and liquid-dominated operation. Among the tested conditions, Cg ≈ 1.6 with Frg close to unity marked the most favorable balance, maintaining continuous gas transport and maximizing pressure-reduction efficiency. Further reducing Cg and driving Frg below unity promoted bottom-outflow intrusion into the pipe outlet, intermittent obstruction of the gas pathway, circulation weakening, and hydraulic deterioration. At Q* = 1.032, increasing L* from 0.709 to 0.877 increased the overall pressure difference by 68.39% and the maximum negative pressure by 69.28%, while external air intake exceeded the reference shaft by 16.76%. Pipe diameter regulated the transition through competing effects of internal gas-transport enhancement and external annular-passage confinement, with d* = 0.466 producing the strongest stable circulation. Downstream baffle height modulated post-transition pressure and air-intake responses through local backpressure rather than shifting the transition condition. These findings establish outlet-clearance restriction and insufficient gas-phase inertia as coupled controls on gas-transport breakdown, linking local blockage to system-scale pressure and air-demand deterioration.

This research focuses on the problem of frost heave damage in trapezoidal concrete-lined canals in cold regions. Using the main canal of the Jingdian Irrigation District, China, as the engineering prototype, the control effect of the thickness of the sand-gravel replacement layer on the temperature field, moisture field, and frost heave deformation of the canal foundation was systematically analyzed through a combination of prototype monitoring experiments and numerical simulation. The optimal sand-gravel replacement thickness suitable for trapezoidal concrete-lined canals in cold regions is proposed. The results indicate that the sand-gravel cushion layer significantly inhibits water migration and frost heave development during the freezing process of the foundation soil by blocking the capillary water migration path and regulating the heat conduction characteristics. Increasing the replacement thickness can effectively delay the advancement rate of the freezing front, significantly reducing the frost heave deformation, normal frost heave force, and tangential freezing force of the canal, resulting in a more uniform distribution. With a gradient replacement scheme ranging from 30 cm at the top to 70 cm at the bottom of the canal, the peak normal frost heave force and tangential freezing force were reduced by 40.3% and 38.7%, respectively, and the maximum normal displacement decreased from 4.26 cm of the original foundation soil to 0.95 cm, meeting the specification requirements of 0.5 to 1.0 cm, thereby achieving the frost-heave mitigation goal in a cost-effective manner. The results provide a theoretical basis for the design and application of sand-gravel replacement canal foundations in cold regions.

To address the frost heave damage issue of the trapezoidal lined canals in seasonally frozen regions and further ensure the stable operation of canals while reducing operation and maintenance costs, this study conducted a gradient sand-gravel cushion replacement experiment on the main canal of the Jingdian Irrigation District, China. For the experiment, east–west and north–south-oriented canal sections were selected, with frost heave meters and soil temperature-humidity meters installed. Dynamic changes in canal ground temperature, moisture content, and frost heave were monitored over two full freeze–thaw cycles. The results indicate the following: (1) The variation of ground temperature lags behind air temperature by 2–3 days; the ground temperature change on the canal slope is more pronounced than that at the canal bottom; and for the east–west-oriented canal, the ground temperature on the sunny slope is higher than that on the shady slope, while the ground temperatures on the two slopes of the north–south-oriented canal are similar. (2) The moisture content of the east–west-oriented canal changes drastically during the freezing period, showing a decreasing trend in the early freezing stage and a significant increasing trend in the thawing stage, whereas the moisture content of the north–south-oriented canal fluctuates slightly. (3) Canals with different orientations exhibit spatial differences in frost heave due to variations in solar radiation distribution. (4) The frost heave is negatively correlated with ground temperature, and its variation lags behind ground temperature by 1–2 days. (5) Increasing the replacement thickness of sand-gravel can significantly reduce the frost heave, with a reduction rate exceeding 50%. Under the action of freeze–thaw cycles, canals with gradient sand-gravel exhibit remarkable anti-frost effects. Thus, for trapezoidal lined canals in seasonally frozen regions, a gradient replacement scheme is recommended: For east–west canals, the replacement thickness is 40–100 cm for shady slopes and 30–70 cm for sunny slopes; for north–south canals, the replacement thickness is 30–70 cm for both slopes. In conclusion, gradient sand-gravel replacement is an effective anti-frost heave measure, providing a theoretical basis for the design of sand-gravel replacement for lined canals in seasonally frozen regions.

Water demand has increased due to population growth and rapid socioeconomic development, creating conflicts between human activities and water resources and having a substantial impact on the balance between blue and green water supplies. Existing study lacks a spatial perspective to examine the inherent relationship between blue and green water supply and demand, particularly in terms of geographical differentiation characteristics and rational allocation of blue and green water supply–demand balance in inland river basins. Using the Taolai River Basin as a case study, this research uses the distributed hydrological model SWAT from a blue–green water resources viewpoint to simulate the spatiotemporal distribution features of blue and green water resources at the sub-basin scale from 2002 to 2021. The supply and demand balance relationship of blue and green water resources within the basin was investigated, an assessment index system for water resource security was developed, and the realizable potential of blue water resources was quantified using various indicators. The findings show that during the study period, the average annual green water resources in the Taolai River Basin were 1.95 times greater than blue water resources, making green water the most abundant component of regional water resources. Spatially, both blue and green water resources showed considerable latitudinal zonality, with a declining tendency from south to north and very consistent distribution patterns. Blue water resources showed high geographic variability, with a safety index more than one, suggesting that supply–demand imbalances were most concentrated in the upper and intermediate ranges of the irrigated region, as well as the desert zone, where safety levels were relatively low. In contrast, green water resources had a safety score ranging from 0.7 to 1.0, indicating great overall safety and negligible regional variability. During the research period, the average annual theoretical transferable blue water resources were 4.06 × 108 m³, based on cross-regional water resource allocation potential analysis. This reveals tremendous potential for enhancing regional water resource allocation, hence providing substantial support for effective water consumption within the Taolai River Basin and regional economic growth. In conclusion, the assessment method developed in this work provides a solid foundation for improving water resource allocation and sustainable management in river basins. It provides technical assistance in the construction of water network systems in inland river basins, which is critical in establishing reasonable water resource distribution across various areas within these basins.

With population growth and rapid socioeconomic development, water demand has increased, exacerbating conflicts between human activities and water resources, significantly impacting the balance between blue and green water supply and demand. Existing research lacks a spatial perspective to analyze the intrinsic relationship between blue and green water supply and demand, particularly regarding the spatial differentiation characteristics and rational allocation of blue and green water supply-demand balance in inland river basins. Taking the Taolai River Basin as a case study, this paper employs the distributed hydrological model SWAT from a blue-green water resources perspective to simulate the spatiotemporal distribution characteristics of blue and green water resources at the sub-basin scale for the period 2002–2021. The supply and demand balance relationship of blue and green water resources within the basin was analyzed, the assessment index system of water resources security was constructed, and the realizable potential of blue water resources under different indicators was quantified. The results indicate that during the study period, the average annual green water resources in the Taolai River Basin were 1.95 times higher than blue water resources, constituting the dominant component of regional water resources. Spatially, both blue and green water resources exhibited pronounced latitudinal zonality, showing a decreasing trend from south to north, with highly consistent distribution patterns. Blue water resources demonstrated significant spatial heterogeneity, with a safety index exceeding 1, indicating that supply-demand imbalances were primarily concentrated in the upper and middle reaches of the irrigated area and the desert zone, where safety levels were relatively low. In contrast, green water resources exhibited a safety index ranging from 0.7 to 1.0, suggesting overall high safety and minimal spatial variability. Based on the analysis of cross-regional water resource allocation potential, the calculated average annual theoretical transferable blue water resources during the study period reached 4.06×10⁸ m³. This demonstrates significant potential for optimizing regional water resource allocation, providing strong support for efficient water utilization within the Tala River basin and regional economic development. In summary, the evaluation system established in this study provides a scientific basis for optimizing water resource allocation and sustainable management within river basins. It offers technical support for constructing water network systems in inland river basins, playing a crucial role in achieving rational water resource allocation across different regions within these basins.

Sustainable urban water management has emerged as a pressing issue that has to be resolved immediately due to the increasing severity of water environment issues brought on by urbanization. While the seasonal storage pool is an important part of urban stormwater management, optimizing the ecological dynamics of its water ecosystem is of great significance for maintaining the quality of the regional water environment. Currently, the majority of research on seasonal rivers focuses on the exploration of ecological restoration programs and governance evaluation research. As a result, there is relatively little research on the ecosystem restoration of species change process and community change law. This study used the AQUATOX ecological modeling technique to simulate and forecast the seasonal dynamics of aquatic biological communities in the recently built terraced storage ponds in the upper reaches of the Shuifu River. The study’s findings showed that the simulated and real observed values of the water quality indicators were highly consistent, and the model’s fitting efficiency, which varied from 0.73 to 0.98, showed that the simulation results and the real situation agreed well. Subsequent investigation revealed that if the transfer ponds are run until 2026, the aquatic biomass increases by 0.02–16.24%. The summer and fall seasons showed a larger biomass than the winter and spring months between 2023 and 2026. Additionally, seasonal fluctuations had a substantial impact on the impoundment’s biodiversity. In particular, populations of phytoplankton and zooplankton rise quickly in the spring, reach their maximum in the summer and then progressively decline in the fall and winter. Despite their relative stability, fish populations did exhibit minor seasonal variations. Redundancy analysis revealed that the primary drivers affecting the seasonal succession of the biological community in the storage pond were environmental parameters such as water temperature (WT), five-day biochemical oxygen demand (BOD5), total phosphorus (TP) and total nitrogen (TN). Therefore, a scientific foundation for the logical optimization of the water ecosystem function of the urban seasonal storage pond is provided by the targeted optimization of these environmental factors to support the stable and healthy development of the water ecosystem of the storage pond. This is crucial for advancing the sustainable management of the urban water environment.

The numerical simulation and field investigation of solid-liquid two-phase flow are carried out in a large-scale forward intake forebay with various diffusion angles at the Jingtaichuan Pumping Irrigation Project in Gansu Province, China. The purpose is to investigate the properties of sediment deposition in the pumping station forebay. The results indicate that the low-sediment concentration area is in the forebay’s centre, whereas the high-sediment is near the two side walls flanks. The sediment concentration increases dramatically from the centre to the sides. Both the high-sediment concentration area and the sediment concentration increase with water depth. The forebay’s narrowing diffusion angle causes the high-concentration area to gradually decrease while the low-concentration area gradually increase. Furthermore, the amount of siltation and sediment deposition efficiency decrease, resulting in a large increase in forebay sediment concentration and sedimentation efficiency. The sediment concentration and water flow velocity reveal a quadratic polynomial relationship. This study can provide a guide and reference for the design and construction of comparable large-scale pumping station forebays.