为充分认识平陆运河航道整治工程建设完成后(简称整治工程实施后)不同洪潮组合作用下感潮河段的水力条件,采用Flow-3D软件建立感潮河段水动力模型,基于实测数据验证计算模型可靠性,构建工程实施前天然河道与工程实施后规划航道2种数学模型。以工程实施前工况为基准,设置7种不同泄洪量与天文大潮遭遇的工程实施后计算工况,对比分析感潮河段水位、比降及流速的变化特征及分布规律。研究结果表明:受航道疏浚、裁弯及桥墩拆除等工程措施影响,河段过流阻力显著降低,导致工程实施后枯水期低潮位大幅下降(降幅约1 m),潮波特征趋向河口化;得益于过流能力的提升,即便在最大设计泄洪量与天文大潮遭遇的极端工况下,沿程水位仍低于警戒水位,防洪安全裕度显著提高;在最大通航流量工况下,虽然局部最大流速(1.46 m/s)超过常规标准,但工程实施后航道有效宽度的拓宽可补偿流速影响,经论证仍满足5 000 t级船舶双向安全通航要求。

[Objective] Pinglu Canal is a pivotal project for China’s Western Land-Sea Corridor, directly connecting the Pearl River Basin and the Beibu Gulf. Its tidal reach is subject to the coupled effects of runoff, tides, and artificial regulation, leading to complex flow conditions that pose challenges to flood control, navigation safety, and ecological protection. However, existing studies have rarely focused on hydrodynamic changes in the narrow, multi-branch artificial canal under combined flood discharge and full-tide processes, lacking targeted research on post-construction flow characteristics. This study aims to fill this gap by predicting the flow conditions (water level, slope, and velocity) of Pinglu Canal’s tidal reach under different flood-tide combinations, thereby providing technical support for post-operation flood control, navigation management, and sluice group regulation. [Methods] A 2D shallow water hydrodynamic model was established using Flow-3D software, leveraging its Tru-VOF method and FAVORTM technology to accurately simulate free surface flow. Rhino software was used for terrain modeling: CAD files with contour lines were imported to generate an STL model of the tidal reach, which was then imported into Flow-3D. The model was validated against field data. Validation results met the accuracy requirements of technical code (JTS/T 231—2021). Seven scenarios were designed to simulate different flood discharges (0, 500, 1 000, 1 500, 2 000, 2 500, 3 300 m³/s) combined with astronomical spring tides, with 11 monitoring points arranged to analyze flow parameter distributions. [Results] No-runoff condition (Scenario 1): Post-construction, the minimum tide level at 3^# and 7^# stations decreased by 1.06 m and 0.92 m, respectively, while the maximum tide level decreased by only 0.07 m and 0.04 m—indicating a more significant drop in low-tide levels. The average ebb and flood velocities at 3^# station decreased by 44.4% (to 0.15 m/s) and 70.0% (to 0.07 m/s), respectively, due to increased cross-sectional area (3^# station’s post-construction area was 182.4% of the original) and reduced channel slope (from 0.1‰ to 0). In contrast, velocity changes at 9^# station were slight (≤13% reduction) as its cross-sectional expansion was limited (43.7% of the original).With-runoff conditions (Scenarios 2-7): Flood waves reached Shajing Estuary approximately 40 minutes after discharge from Qingnian Hub, with minimal phase difference. Under the maximum design discharge (3 300 m³/s, Scenario 7) combined with high tide, the maximum water levels at 3^#, 7^#, 9^#, and 10^# stations were 4.39, 4.02, 3.44 m, and 3.38 m—all lower than the respective warning levels (7.00, 4.60, 4.00 m) and the existing embankment elevation (3.7-4.0 m). The 5^# station’s water level (4.21 m) was 0.09 m below the maximum operating water level of the nearby drainage sluice, enabling gravity drainage without pumping.Slope and velocity characteristics: The maximum channel slope was 0.33‰ (under low-tide combination), well below the 2‰ threshold for safe navigation. Under the maximum navigable discharge (1 000 m³/s, Scenario 3), the maximum velocity (1.5 m/s at 8^# station) exceeded the 1.0 m/s standard but still met the two-way navigation requirements for 5 000-ton bulk carriers and 250TEU container ships, thanks to the widened channel design. Additionally, the 6^# station (near Qinzhou Service Area) maintained the minimum velocity across all scenarios, facilitating safe ship berthing. [Conclusions] This study innovatively focuses on the hydrodynamic response of Pinglu Canal’s narrow, multi-branch tidal reach to combined flood-tide processes, addressing a gap in existing research on artificial canal systems. The 2D shallow water model, validated by high-precision field data, effectively predicts post-construction flow conditions. Key findings confirm that: (1) Post-construction channel improvements (dredging, bend cutoff, bridge pier removal) significantly enhance water conveyance capacity, reducing low-tide levels and upstream velocities while aligning tide levels with the estuary; (2) The tidal reach meets the 20-year flood control standard, with maximum water levels below warning levels even under extreme discharge-tide combinations; (3) The maximum velocity under the design navigable discharge, though exceeding the nominal 1.0 m/s limit, is compatible with safe navigation due to optimized channel geometry. These results provide direct technical support for flood control strategy formulation, navigation flow regulation, and sluice operation management in the Pinglu Canal basin, ensuring long-term safe and efficient canal operation.