To reduce structural and ground safety hazards induced by high-speed air-water mixtures during geyser events inside baffle-drop shafts, a three-dimensional numerical simulation was carried out. This work systematically investigates how void fraction and inlet pipe diameter influence internal pressure and geyser strength, analyzes the distribution of impact loads acting on bottom baffles, and proposes mounting a throttling orifice plate at the shaft midsection to suppress violent geysers. Results reveal inlet pipe pressure declines first then rises as void fraction grows, hitting the lowest value within the void fraction range of 0.2-0.4. Geyser intensity peaks when the diameter ratio of the inlet pipe to the drop shaft equals 1:2. Moreover, baffle impact loads gradually weaken from the shaft bottom upward; loads near partition and shaft walls far exceed those at baffle edges. A midshaft orifice plate delivers reliable geyser suppression, yet it bears impact loads 10 times larger than those on bottom baffles. The conclusions provide practical guidance for the safety-oriented structural design of baffle-drop shafts.

Accurate prediction of burial depth and suspended length for oil and gas pipelines crossing rivers is critical for ensuring structural integrity. Systematic flume experiments were employed to examine local scour under varying hydrodynamic conditions, emphasizing relationships between scour hole expansion rate and flow velocity, water depth, and pipe diameter. Bedload transport predominantly governs riverbed evolution and scour hole development. Larger pipe diameters significantly reduce scour hole formation beneath the pipeline. Vertical expansion rate peaks immediately upon initial erosion, then progressively declines due to canalized flow, while cumulative scour depth continues increasing. Vertical dynamics at the pipe bottom conform to a first-order dynamic response equation, yielding a normalized time-dependent scour depth equation. Ultimate scour depth is collectively influenced by hydraulic parameters, pipe diameter, and sediment characteristics. Dimensionless correlations among scour depth, relative sediment size, and Froude number (Fr) were established via Gauss-Seidel iteration. Horizontal expansion exhibits distinct regimes: single-phase dominates at Fr > 0.6, whereas a secondary phase emerges at Fr <= 0.6. Integrating experimental data with empirical vertical expansion models, we propose a comprehensive horizontal scour expansion calculation model. These findings provide substantive insights into scour evolution mechanics and directly inform safety assessments for river-crossing pipelines.

Accurate prediction of the burial depth and suspended length for oil and gas pipelines crossing mountainous rivers is critical for ensuring structural integrity. In this study, systematic flume experiments are employed to examine the local scour characteristics under varying hydrodynamic conditions, with a particular emphasis on quantifying the relationships between the scour hole expansion rate and key parameters, including flow velocity, water depth, and pipe diameter. The experimental results demonstrate that riverbed evolution and scour hole development are predominantly governed by bedload transport. Notably, as the pipe diameter increases, the incidence of scour hole formation beneath the pipeline decreases significantly. The vertical expansion rate of scour holes peaks immediately upon initial erosion of the pipe bottom. The subsequent development of canalized flow leads to a progressive decline in the vertical scour rate, whereas the cumulative scour depth continues to increase. The vertical expansion dynamics at the pipe bottom conform to a first-order dynamic response equation, yielding a normalized time-dependent scour depth equation. Hydraulic parameters, pipe diameter, and sediment characteristics collectively influence the ultimate scour depth. Dimensionless correlations between the scour depth, relative sediment size, and Froude number (Fr) are established via Gauss–Seidel iteration. Distinct horizontal expansion regimes are identified: single-phase expansion dominates at Fr > 0.6, whereas a secondary expansion phase emerges at Fr ≤ 0.6. By integrating experimental data with empirical vertical expansion models, we propose a comprehensive horizontal scour expansion calculation model. These findings provide substantive insights into scour evolution mechanics and directly inform safety assessments for river-crossing pipelines in mountainous terrain.

Geyser in deep tunnel drainage system will cause huge inverted impact load on the shaft baffle. To study the law of load variation, a hydraulic test of a geyser model with a length scale of 1:50 was carried out. Four significant factors affecting the intensity of geyser were set up, including inlet air pressure, inlet air volume, initial water depth, and contact tube access. The baffles in the main loading area of the shaft are taken as the research object and their impact load data were collected. Then the influence of the value variation of the above key factors on the impact load was analyzed. The experimental results show that there is an obvious peak value of impact load in the process of geyser, which can reach more than 20 times the forward hydrodynamic load. The peak time corresponds to the moment when the baffle is hit. The inhomogeneity of gas-liquid two-phase flow results in strong randomness of impact load. Impact load is positively correlated with both inlet air pressure and air volume. And the sensitivity of the impact load on different baffles to the change of inlet air volume is quite different. There is no significant correlation between the impact load and the initial water depth. However, when the free liquid level in the shaft is “adjacent” to the baffle, the baffle will bear a large impact load. When the contact tube is connected to the dry zone, the baffle will have a greater probability of bearing a great impact load. Based on the experimental study, the prediction formula of the maximum impact load is fitted respectively when the contact tube is connected to the wet zone and dry zone. The research results can provide important technical support and theoretical guidance for the safe operation and structural design optimization of the baffle-drop shaft.

为研究水深、进气压、进气量和干/湿区连通面积等参数与气爆产生机制之间的响应关系,首先,构建了1∶50水力模型试验系统,观测气爆喷射过程并分析竖井内压强变化规律;其次,通过气爆定义建立了竖井最大喷射高度预测模型及产生气爆临界条件;最后,对比分析了多种变量对竖井底部不同折板冲击荷载的影响.结果表明:气爆过程中折板型竖井内压强剧烈波动,一方面是由于高压气团的释放所导致,另一方面是因高速运动的水气混合物使得竖井内局部气压不平衡所形成;采用多元线性回归模型建立的经验公式可有效预测折板型竖井气爆最大喷射高度;结合不同变量与气爆强度之间响应关系提出的临界条件能够准确判断气爆是否发生;产生气爆时竖井底部折板的水冲击荷载除了与进气压、折板淹没状态、测点位置等因素有关以外,还与水气混合物喷射在折板底部时的随机性有关,气爆过程中折板下方最大水冲击荷载大于10倍正常泄流状态下折板表面的水动力荷载.

水流冲刷引起河床变形的不确定性对水下穿越管道的安全运行造成威胁.为了探究裸露穿河管道在压重块保护措施下的冲刷特性,通过水槽模型试验,研究压重块长度、压重块布置间距、水流流速、河道水深等因素对管道周围河床地形和冲刷深度的影响.试验结果表明:水下穿越管道在压重块保护措施下的冲刷过程可分为冲刷坑形成、压重块迎流侧悬空、管道迎流侧悬空和冲刷平衡4个阶段;管道的最大冲刷深度与流速和压重块长度正相关,与水深和压重块布置间距负相关;采用量纲分析法得到了无量纲冲刷深度与压重块长度、压重块布置间距、弗劳德数之间的函数关系式.研究成果可为水下穿越管道压重块保护措施的设计、建造及运营维护提供重要的理论支撑.

深隧排水系统作为一种灰色海绵技术措施,在解决大城市内涝灾害和水资源短缺、防止外溢污染等方面具有显著的效果.但在前期结构设计及后期调度运行过程中,存在一系列关键水力学技术难题亟待解决,包括不同类型竖井的泄流能力计算、主隧道内的瞬变流与涌浪问题以及系统快速充水过程中的气爆现象.在归纳分析国内外深隧排水系统典型案例的基础上,对相关水科学技术问题进行全面回顾和评述,并结合研究现状做出展望,为城市深隧排水系统结构的科学设计和合理应用提供科学依据和参考.

The possibility of servicing lifelines such as highways, railways, pipelines, and tunnels is of great social importance. The characteristic that separates the buried pipeline from other structures is that its dimensions are very long compared to its other dimensions. Ground vibrations caused by earthquakes, construction activities, traffic, explosions, and machinery can damage these structures. Lifeline integrity can be compromised in two ways: (1) direct damage due to excessive dynamic loading of the lifeline, and (2) indirect damage due to soil failures such as liquefaction, slope instability, and differential settlements. 3D printing (also known as additive manufacturing) is an advanced manufacturing process that can automatically produce complex geometric shapes from a 3D computer-aided design model without tools, molds, or fixtures. This automated manufacturing process has been applied in diverse industries today because it can revolutionize the construction industry with expected benefits. This research study on the performance of buried pipelines under static loads to the structure's safety against the possible development of progressive failure. This research study includes a numerical study, where it was studied many parameters to value the performance of the pipeline. The parameters are (a) the material of the pipeline (steel, traditional concrete, and 3D concrete printed), (b) the thickness of the pipeline (20, 30, and 40 mm), and (c) soil type (moist sandy soil, saturated sandy soil, moist cohesive soil, and saturated cohesive soil). Different results were obtained depending on the type of soil where all pipelines materials' behavior was similar in the case of moist soil. Doi: 10.28991/CEJ-2022-08-01-01 Full Text: PDF

The flow field distribution around the suspended pipeline is closely related to the mechanical characteristics and local scour characteristics of the underwater crossing pipelines. To fully investigate the velocity distribution and wake structure characteristics around the suspended pipeline under oblique flows, a flume model test and a numerical simulation based on the LES (Large Eddy Simulation) method were performed. The results showed that the velocity distribution near the suspended pipeline under oblique flows had obvious three-dimensional characteristics. The influence range of pipeline on velocity is 1 d before to 6 d behind the pipeline (d is pipeline diameter). The smaller the flow angle, the more disordered the velocity distribution is. The larger the flow angle, the greater the variation degree of the velocity at each section at the same section is, as well as the higher the velocity deficit value is. In addition, the larger the angle of pipe flow, the more violent the wake structure changes with the flow velocity, and the stronger the regularity of vortex street shedding. This research provides a theoretical reference for the scour prevention design and safe operation of crossing pipelines.

When a metro is constructed by the shield method in the strata containing boulder group, it is prone to some engineering problems such as serious cutter wear, deformation of the cutter holder head, damage of the cutter spindle, which seriously affects the construction efficiency and bring enormous problems to the shield construction. This paper proposes the vibration reduction measures for the boulder deep-hole blasting to meet the construction safety. To achieve this purpose, the field test was applied to investigate the vibration response of adjacent building under five blasting areas. Then, three-dimensional numerical model was employed to discuss the vibration characteristics of the boulder and adjacent buildings under vibration reduction measures. The results show that increasing the damping hole and the isolation hole and changing the charging layout of the blasting areas can blast the boulder under the condition of ensuring effective and safe construction. Damping hole and isolation hole have a positive role in the control and attenuation of blasting stress wave. All of them have good vibration reduction effect, and the vibration reduction efficiency is more than 90%. The double row damping holes with 12.7 cm diameter and 20 cm spacing have good vibration reduction effect and economic benefit. When double row damping holes are used, the maximum particle velocity of the shaft structure under the influence of blasting stress wave is 1.47 cm/s, which is within the reasonable safety range.

The baffle-drop shaft is widely used in deep tunnel drainage system due to its fine applicability and high energy dissipation. To fully reveal the high speed water–air two-phase flow characteristics in baffle-drop shaft during discharge process, a scale of 1∶25 physical model test and the numerical simulation based on the Realizable k–ε model and volume of fluid (VOF) method were carried out. The distribution law of water and air in the baffle-drop shaft was studied under different flow conditions. The formation mechanism of cavity area in wet side and the variation process of air pressure in dry side were expounded. And the distribution law of shaft wall pressure and hydrodynamic loadings on different baffles were analyzed. The results showed that the formation of “cavity area” in the baffle-drop shaft was caused by the internal air compressed to the limit, and another reason came down to the negative pressure caused by the entrainment of the water flow in wet side. At large inflow, the distribution law of flow velocity in drop shaft was low velocity on central baffles and high velocity on upper and lower baffles. But when the inflow was small, the flow velocity decreased gradually along the direction of the shaft depth. The air pressure varied from –0.96 to 2.46 kPa under the top-sealed condition, and the air pressure on the dry side did not change over time when the relative vent diameter of shaft cover is greater than 0.105. The wall pressure of the drop shaft increased with the decrease of the shaft height, and the maximum wall pressure of the upper, central and lower baffles of the shaft were 42.25 kPa, 21.5 kPa and 16.75 kPa, respectively. The research results provided a scientific basis for the design theory and safe running of the baffle-drop shaft of deep tunnel drainage system.

The baffle drop shaft is widely used in deep tunnel drainage systems due to its fine applicability and high energy dissipation. To fully study the turbulence characteristics and energy dissipation mechanism of baffle drop shafts, a 1:25 scale physical model test and a numerical simulation based on the Realizable k-ε model and Volume of Fluid (VOF) method were performed. The results showed that a baffle spacing that is too dense or too sparse is not conducive to energy dissipation and discharge. The minimum baffle spacing is the optimal structural design at the design flow rate when the flow regime is free-drop flow. The energy dissipation calculation model established in this paper has high accuracy for calculating the energy dissipation rate on the baffles in free-drop flow. The energy dissipation modes of the shaft can be divided into inlet energy dissipation, baffle energy dissipation, and shaft-bottom energy dissipation. Baffles play a major role in the energy dissipation at low flow rates, and the proportions of inlet and shaft-bottom energy dissipation increase with the increase in flow rate.

The baffle-drop shaft structure is usually applied in deep tunnel drainage systems to transfer shallow storm water to underground tunnels. At present, the definition of the maximum operational capacity of baffle-drop shafts is lack of scientific and reasonable analysis, and the researches on hydraulic and energy dissipation characteristics have been insufficient. In this paper, a 1:25 scale hydraulic model test was conducted to observe the flow phenomena during the discharge process, analyze the relationship between the maximum inflow discharge and the baffle parameters, and calculate the energy dissipation rate of the shaft under different flow conditions. The results demonstrated that three kinds of flow regimes were presented in the discharge process: wall-impact confined flow, critical flow, and free-drop flow. The impact wave majorly brought about the energy dissipation of water on the baffle. The impingement and breakup of the inflow at the bottom of the drop shaft, as well as the reverse flow, resulted in the final energy loss. The time-averaged pressure value of the upper baffle was 1.5-3 times that of the central and lower baffles. The baffle with a design angle could effectively reduce the time-averaged pressure of the water flow acting on the baffle. The energy dissipation rate of the drop shaft decreased with the increase in the inflow discharge, and the energy dissipation rate was found to range from about 63.14% to 96.40%. The optimal size of the baffle-drop shaft with the maximum energy dissipation rate was d/B = 0.485 and θ = 10° (d, B, and θ are the baffle spacing, width, and angle, respectively).

It is of important significance to study the evolution law of the riverbed near underwater crossing line pipes for ensuring the safe operation of oil and gas pipelines and reducing the risk of damage by water flood disasters. In order to clarify the evolution law of the riverbed near underwater crossing line pipes and its negative effects, this paper conducted flume model experiments on underwater crossing line pipes. The physical process of riverbed evolution near pipes was observed and the effect of hydrodynamic conditions on the local pipe scour was studied. What's more, the formation mechanism of local scour at underwater crossing line pipes was revealed. And the following research results were obtained. First, when the water flow is slow, the riverbed evolution process near underwater crossing line pipes is mainly divided into six stages, including riverbed undercutting, pipe exposure, micro-pore formation, scour hole propagation, pipe suspension and scour equilibrium. Second, vortex and seepage flow are the reasons for the local scour of underwater crossing line pipes. Before pipes are exposed, the silt around the pipes is reduced by vortex. After pipes are exposed, micro-pores occur at the pipe bottom under the joint action of vortex and seepage flow. And thus, local scour is formed. Third, flow velocity and water depth jointly influence the riverbed scour duration of each stage and the maximum scour depth at the pipe bottom. When the Froude number (Fr) is in the range of 0.306–0.808, with the increase of Fr, water flow gets fast, the maximum scour depth at the pipe bottom increases, the duration for scour equilibrium decreases, the riverbed undercutting depth increases and the riverbed topographically gets flatter. The maximum scour depth at the pipe bottom is 0.9–1.6 times the pipe diameter, and the duration for scour equilibrium is between 1650 min and 2620 min. In conclusion, the experimental results provide important reference for predicting the burial depth of underwater crossing line pipes and ensuring their safe operation.

为了研究生物滞留带构造参数及组合方式对其渗蓄效果的影响,提出了判定生物滞留带渗蓄效果的评价指标,并对16组不同构造的生物滞留带开展模拟降雨径流正交试验,研究了种植土和填料层成分及含量、透水土工布位置、砂层颗粒级配和构造厚度对生物滞留带渗蓄效果的影响.研究结果表明:影响生物滞留带渗蓄效应程度大小的排序为:砂层级配＞填料层成分和含量＞结构层厚度＞土工布位置＞种植土成分和含量;生物滞留带最佳组合形式从上至下依次为:20 cm厚种植土,35 cm厚填料层(其中珍珠岩、蛭石、土壤和砂的体积占比为10％、5％、10％和75％),10 cm厚砂层(其中砂层颗粒级配为0～0.5 mm占15％、0.5～0.7 mm占40％、0.7～1.0 mm占30％、1.0～2.0 mm占15％),20 cm厚砾石层以及不设置透水土工布.

为了研究泄流过程中折板型竖井的湍流耗散特性及消能机理,对9种不同体型的竖井开展水力模型试验与数值模拟,分析不同流量下竖井内湍动能、湍动能耗散率和水动力荷载分布规律,建立折板消能计算模型,探究竖井消能机理.结果表明:折板间距过密或过疏均不利于竖井的泄流和消能,在设计流量下竖井内的流态为自由跌水流时,对应的最小折板间距为最优结构设计;10°折板倾角可提升竖井的消能效果,并减小折板上水动力荷载;建立的折板消能计算模型可较为准确地计算自由跌水流态下的消能率;竖井消能方式分为入口消能、折板消能和井底消能,不同流量下各种消能方式的能耗占比不同,小流量时以折板消能为主,随着流量的增加,入口消能和井底消能的能耗占比随之增大.

合理预测山地河流穿越管道的未来埋深和悬空长度对其安全运营至关重要.本文以北干线输气管道穿越工程为研究对象开展了水槽模型试验,观测分析河流穿越管道附近河床演变趋势,研究流量、水深和管径等因素对冲坑扩展规律的影响.结果表明:河床演变主要由推移质泥沙输移引起,而随着管径的增大,在管底形成冲坑点的次数逐渐减少;管底形成冲刷之时冲坑竖向扩展速率很大,随着管涌的发生,冲刷速率逐渐减小,冲刷深度逐渐增大;管底冲坑竖向扩展过程满足一级动力学反应方程,归一化处理后得到了冲刷深度与冲刷时间之间关系式;水动力条件、管径和沙粒特性共同影响管底极限冲刷深度,采用Gauss-Seidel迭代法得到无量纲冲刷深度与相对泥沙粒径和弗劳德数Fr参数的关系式;当Fr>0.6时,冲坑横向扩展仅为初级扩展一个阶段,当Fr<0.6时,冲坑横向扩展过程包含初级扩展和次级扩展两阶段;最后,结合试验数据和冲坑竖向扩展经验模型,推导出冲坑横向扩展速率计算公式,且模型预测结果较好.研究结果可为探究山地河流穿越管道冲坑扩展规律及管道后期安全运营维护提供重要参考价值.

为了研究含软弱夹层场地中埋地管道的地震反应特性,基于管土接触模型,运用ADINA软件,采用非线性分析,研究埋深、厚度和倾角等因素对含软弱夹层场地中埋地管道地震反应的影响规律.结果 表明:软弱夹层各因素对埋地管道地震动力响应产生影响不同,一定厚度和埋深条件下,软弱夹层具有隔震作用,当软弱夹层的存在增大其场地不均匀程度,则会对埋地管道地震动响应具有非常不利的影响;管道有效应力和位移随着软弱夹层厚度的增大而减小,当厚度达到一定值时,软弱夹层起到一定的缓冲作用;管道有效应力和位移随着软弱夹层埋深的增大而减小,但影响程度小于夹层厚度所产生的;软弱夹层因倾角变大增大了场地不均匀程度,导致管道有效应力和位移变大.

针对深隧排水系统竖井泄流过程中高速气-水两相流动特性进行了水力模型试验研究,观测竖井内水流下泄过程中的型态,分析最大泄流量与折板间距的关系,计算不同工况下的竖井消能率,并揭示折板型竖井在泄流过程中的消能机理.试验结果表明:竖井在泄流过程中存在3种水流型态:撞壁受限流、临界流和自由跌水流;泄流过程中水跃是水流在折板上消能的主要原因,水流流至井底与反向流体互相撞击破碎使竖井达到最终消能的目的;当竖井直径D=0.4 m、折板间距d介于16.02～24.56 cm时,竖井最大泄流量介于(8.7～14.7)×10?3 m3/s,且d与最大泄流量Qm存在线性关系;根据能量守恒定律推导出消能率公式,得到d=19.4 cm、倾角θ=10°时的竖井消能率为最优;竖井盖板开孔直径Ф对竖井顶部压强的影响较大,当Ф≥4 cm时,竖井顶部相对压强基本为0,并且具有一定倾角的折板有利于加速竖井的泄流过程;上、中、下折板冲击力(Fu、Fm、Fd)呈现Fu>Fm>Fd的分布规律,上、中、下折板最大面荷载分别为42.8、30.7、22.8 kN/m2.深隧排水折板型竖井最佳泄流量和最优消能率的试验研究成果对深隧竖井工程的设计与运行提供了一定参考价值.

The pressured gravity water transmission system with long distance and high fall head was widely applied in municipal water supply engineering projects in cities and towns,espe-cially in mountainous area.However,pipe burst accidents happened in this kind of water transmis-sion pipe frequently,which had been a serious threat to municipal water supply system security. Through theoretical study and case study,this paper analyzed the impacts of pipe length (L)and fall head (H)on maximum water hammer inside pipe when the end valve was closed.It was found in the research that the increase of L would reduce the maximum water hammer pressure before the valve;the increase of H would enhance the maximum water hammer before valve;the increase of both L and H would affect the maximum water hammer before valve simultaneously.