Experimental Investigation of Regular or Wavy Two-Phase Flow in a Manifold

An experimental study was conducted to investigate the properties of stratified regular or wavy two-phase flow in two parallel separators located after a manifold.A total of 103 experiments with various gas and liquid velocity combinations in three inlet pipes were conducted,including 77 groups of outlet pipe resistance symmetry and 26 groups of outlet pipe resistance asymmetry trials.The experimental results have revealed that when the gas-liquid flow rate is low,the degree of uneven splitting is high,and“extreme”conditions are attained.When the superficial gas velocity is greater than that established in the extreme case,the direction of the liquid-phase displacement is reversed,while that of the gas remains unchanged.Thus,the degree of gas phase bias tends to be mitigated with an increase in the gas velocity,while the uneven splitting degree of liquid approaches 10%.Finally,varying the gas-phase outlet pipe resistance is shown to effectively change the gas-liquid two-phase flow distribution.

Mapping Subsurface Seepage Flow Patterns in Proximity to a Coal Combustion Residual Landfill Using Electrical Resistivity Tomography

Electrical resistivity tomography data were acquired in proximity to the coal combustion residual landfill in an effort to image and analyze seepage pathways through the shallow residual soil and underlying karsted limestone bedrock. The water table is at a depth of more than 45 m. The most prominent subsurface seepage pathways identified on the acquired electrical resistivity tomography data are located immediately adjacent to the toe of the landfill and are attributed to stormwater run-off. The moisture content of the limestone appears to decrease gradually with increasing distance from the toe of the landfill, suggesting there is also a horizontal component of moisture flow in the subsurface. Shallow limestone with higher moisture content generally underlies or is in close proximity to anthropogenic features such as drainage ditches and clay berms that are designed to channel run-off. At one location, electrical resistivity tomography data were acquired along essentially the same traverse at different times of the year, and the resistivity of shallow limestone overall was lower on the data acquired after heavy rains.

Oil–water two-phase flow pattern analysis with ERT based measurement and multivariate maximum Lyapunov exponent

Oil–water two-phase flow patterns in a horizontal pipe are analyzed with a 16-electrode electrical resistance tomography(ERT) system. The measurement data of the ERT are treated as a multivariate time-series, thus the information extracted from each electrode represents the local phase distribution and fraction change at that location. The multivariate maximum Lyapunov exponent(MMLE) is extracted from the 16-dimension time-series to demonstrate the change of flow pattern versus the superficial velocity ratio of oil to water. The correlation dimension of the multivariate time-series is further introduced to jointly characterize and finally separate the flow patterns with MMLE. The change of flow patterns with superficial oil velocity at different water superficial velocities is studied with MMLE and correlation dimension, respectively, and the flow pattern transition can also be characterized with these two features. The proposed MMLE and correlation dimension map could effectively separate the flow patterns, thus is an effective tool for flow pattern identification and transition analysis.

The primary controlling parameters of porosity, permeability,and seepage capability of tight gas reservoirs:a case study on Upper Paleozoic Formation in the eastern Ordos Basin,Northern China

Tight sandstone gas(hereafter"tight gas")has become a subject of unconventional gas exploration globally.The large-scale development and use of tight gas resources in the USA,in particular,facilitated the rapid rebound of natural gas production in the USA,in addition to driving the rapid development of tight gas worldwide.In the eastern Ordos Basin,the Upper Paleozoic feature includes multiple layers of gas,a shallow depth,and notable potential for exploration and development.However,the reservoirs in the area are relatively tight,exhibit strong heterogeneity,and possess a complex micropore structure,thus restricting the eff ective economic development of oil and gas.Thus,research on the primary parameters controlling pore throat structure and the seepage capability of low-permeability reservoirs will be beneficial for the effcient exploration and development of natural gas in the eastern Ordos Basin.The parameters of reservoir porosity and percolation ability,as well as permeability,were analyzed using systematic sampling of the of the Upper Paleozoic Benxi,Taiyuan,and Shanxi Formations in the eastern Ordos Basin,constant-rate mercury injection experiments,nuclear magnetic resonance analysis,and gas–water-phase experimental studies.The results indicate that reservoir porosity is controlled by the effective pore volume and number,whereas permeability is controlled by the largest throat radius,rather than the average.The effective pore volume controls the movable fluid saturation,while reservoir percolation capability is controlled by the effective pore volume,irreducible water saturation,and size of the gas–water two-phase seepage zone.

Two-dimensional Dynamics Simulation of Two-phase Debris Flow

To investigate the movement mechanism of debris flow, a two-dimensional, two-phase, depthintegrated model is introduced. The model uses Mohr-Coulomb plasticity for the solid rheology, and the fluid stress is modeled as a Newtonian fluid. The interaction between solid and liquid phases, which plays a major role in debris flow movement, is assumed to consist of drag and buoyancy forces. The applicability of drag force formulas is discussed. Considering the complex interaction between debris flow and the bed surface, a combined friction boundary condition is imposed on the bottom, and this is also discussed. To solve the complex model equations, a numerical method with second-order accuracy based on the finite volume method is proposed. Several numerical experiments are performed to verify the feasibilities of model and numerical schemes. Numerical results demonstrate that different solid volume fractions substantially affect debris flow movement.

Occurrence and Evaluation of Chromium Reducing Bacteria in Seepage Water from Chromite Mine Quarries of Orissa, India

Chromium pollution due to leaching and weathering of chromite mine overburden in mine seepage water is a serious environmental problem. In an attempt to explore the indigenous chromate resistant and reducing bacteria from chromite mine quarry seepage, 145 aerobic, heterotrophic bacteria were isolated from 14 mine seepage samples derived from chromite mines of Sukinda valley and Baula-Nuasahi belt in Orissa, India. A total of 109 isolates which were tolerant to 2 mM Cr(VI) showed different degrees of Cr(VI) reducing activ-ity in complex KSC medium and synthetic Vogel Bonner (VB) broth. Ten isolates belonging to genera like Pseudomonas, Acinetobacter, Alcaligenes, Cupriavidus and Corynebacterium were selected on the basis of their chromate reducing efficiency and it was found that they could reduce more than 50 and 75% of Cr(VI) in VB broth and KSC medium respectively. The sole Gram-positive isolate, Corynebacterium paurometabo-lum SKPD 1204 (MTCC 8730) showed maximum chromate reducing capacity in both VB broth (63.7%) and KSC medium (92%) and was capable of reducing nearly 95% of the total Cr(VI) in the mine seepage when it was grown in the mine seepage supplemented with 2% VB concentrate.

Seepage behavior of soil mixed with randomly distributed recycled plastic materials

Seepage through embankment fill materials is crucial issue in the construction of embankments for irrigation and drainage projects.Proper ground improvement methods should be used to improve the strength and stability characteristics of soil used as fill material.Utilization of waste plastic materials to enhance the engineering properties of soil is a sustainable approach.Additionally,the use of raw products directly from plastic recycling units in the form of flakes and pellets as soil additives has the potential to further enhance the economic benefits of this method.This study randomly mixed plastic materials with soil for use in the construction of earth embankments,such as river levees,dykes,and canal diversion structures,and evaluated the effectiveness of these materials in reducing seepage failures in hydraulic structures.To achieve these goals,this study collected high-density polyethylene(HDPE)plastic from plastic recycling units and used soil mixed with HDPE plastic in the form of flakes and pellets in different contents as embankment fill materials,then evaluated how these materials affected the piping features.Laboratory experiments were conducted to determine the seepage velocity and critical hydraulic gradient of soil mixed with plastics in various contents and to compare the values with those of plain soil.The results showed that random distribution of waste plastics in the form of flakes and pellets in soil is an effective method for improving the piping resistance of soil.

Analysis of the Properties and Anti-Seepage Mechanism of PBFC Slurry in Landfill

As the landfill leachate has strong pollution on the underground water,surface water and soil.This paper develops the formula of impervious slurry with low permeability,good durability,strong adsorption and retardant based on the bentonite which is modified by polyvinyl alcohol.Through the simulation experiment,the optimum formula of polyvinyl alcohol is 0.2%.Its osmotic coefficient for 28 days is 0.53×10^-8~1.86×10^-8 cm/s and compressive strength is 0.5~1.5 MPa as well.This paper study on the retardant rule of the consolidation of slurry against the pollution in the leachate by self-made percolation instrument.The experiment shows that the retardant rate of the consolidation against inorganic pollutants and organic pollutants is over 85% and the retardant rate against heavy metal ion such as Hg and Pb is above 99%.The slurry has the characteristics of low permeability,high retardant against pollution,good durability and plasticity,no chemical additives,no pollution,wide source of raw materials and good economy which determine it can be used to new landfill or existing landfill,building foundation pit and water conservancy project.

Voidage Measurement of Air-Water Two-phase Flow Based on ERT Sensor and Data Mining Technology

Based on an electrical resistance tomography(ERT) sensor and the data mining technology,a new voidage measurement method is proposed for air-water two-phase flow.The data mining technology used in this work is a least squares support vector machine(LS-SVM) algorithm together with the feature extraction method,and three feature extraction methods are tested:principal component analysis(PCA),partial least squares(PLS) and independent component analysis(ICA).In the practical voidage measurement process,the flow pattern is firstly identified directly from the conductance values obtained by the ERT sensor.Then,the appropriate voidage measurement model is selected according to the flow pattern identification result.Finally,the voidage is calculated.Experimental results show that the proposed method can measure the voidage effectively,and the measurement accuracy and speed are satisfactory.Compared with the conventional voidage measurement methods based on ERT,the proposed method doesn't need any image reconstruction process,so it has the advantage of good real-time performance.Due to the introduction of flow pattern identification,the influence of flow pattern on the voidage measurement is overcome.Besides,it is demonstrated that the LS-SVM method with PLS feature extraction presents the best measurement performance among the tested methods.

Penetration Resistance of Composite Bucket Foundation with Eccentric Load for Offshore Wind Turbines

The penetration of the composite bucket foundation(CBF)is crucial in its construction process.In actual projects,the foundation is inevitably subjected to eccentric load caused by towers and turbines,as well as wind,wave,and flow,during the one-step installation.Moreover,the eccentric load is bound to affect the penetration method and penetration resistance of the foundation.To examine the above-mentioned issues,the penetration resistance of CBF with eccentric load was calculated and analyzed based on model tests,and the seepage field of the CBF under eccentric load was analyzed using ABAQUS.The influence of different magnitudes of eccentric load and various offset strategies on penetration resistance was analyzed,and the theoretical and measured values were compared.The result indicated that the negative pressure of the offset room was found to be smaller than that of other rooms when the CBF penetrated the soil under eccentric load.The penetration resistance of CBF under eccentric load was larger than that without eccentricity,and the larger the eccentric load is,the greater the penetration resistance.The influence of different eccentric load offset strategies on penetration resistance was found to be negligible.The calculated penetration resistance under eccentric load was in good agreement with the measured value.

Laboratory simulation of CO_(2) immiscible gas flooding and characterization of seepage resistance

CO_(2) flooding can significantly improve the recovery rate, effectively recover crude oil, and has the advantages of energy saving and emission reduction. At present, most domestic researches on CO_(2) flooding seepage experiments are field tests in actual reservoirs or simulations with reservoir numerical simulators. Although targeted, the promotion is poor. For the characterization of seepage resistance, there are few studies on the variation law of seepage resistance caused by the combined action in the reservoir. To solve this problem, based on the mechanism of CO_(2), a physical simulation experiment device for CO_(2) non-miscible flooding production manner is designed. The device adopts two displacement schemes, gas-displacing water and gas-displacing oil, it mainly studies the immiscible gas flooding mechanism and oil displacement characteristics based on factors such as formation dip angle, gas injection position, and gas injection rate. It can provide a more accurate development simulation for the actual field application. By studying the variation law of crude oil viscosity and start-up pressure gradient, the characterization method of seepage resistance gradient affected by these two factors in the seepage process is proposed. The field test is carried out for the natural core of the S oilfield, and the seepage resistance is described more accurately. The results show that the advancing front of the gas drive is an arc, and the advancing speed of the gas drive oil front is slower than that of gas drive water;the greater the dip angle, the higher the displacement efficiency;the higher the gas injection rate is, the higher the early recovery rate is, and the lower the later recovery rate is;oil displacement efficiency is lower than water displacement efficiency;taking the actual core of S oilfield as an example, the mathematical representation method of core start-up pressure gradient in low permeability reservoir is established.

岩心多孔介质中乳状液乳化性能评价和驱油效果研究

综合利用全能红外稳定分析仪、光学显微镜及多功能流变仪,从宏观和微观角度开展了不同复合体系在岩心渗流和机械搅拌下生成乳状液的稳定性、黏度及微观形态变化特征实验研究。在此基础上,辅以岩心驱油实验,研究了不同乳状液复合体系的驱油效果。结果表明,甜菜碱表面活性剂二元体系可在岩心多孔介质驱油过程中有效生成乳状液,机械搅拌状态下不同复合体系稳定性差异显著。二元、无碱A、三元体系的机械搅拌剪切与岩心渗流生成乳状液的TSI值具有反向关联的关系,而在乳状液黏度上二者具有正向关联的关系。相比于岩心剪切,机械搅拌剪切应力较大,不同体系生成的乳状液液滴粒径更小,能够更显著地区分出不同体系之间乳状液相态区别。岩心驱油实验过程中,整体渗流阻力与提高采收率幅度存在反向相关的关系,不同等黏度体系提高采收率幅度依次升高,且具有显著的梯度差异,二元、三元、无碱A体系不仅可以通过乳化封堵起到调剖作用,扩大波及体积,进而提高洗油效率,乳化流体还可以进入水驱难以波及的微孔区域中洗油、刮油,通过乳化携带作用,降低残余油饱和度,改善驱油效果。

岩心油水两相渗流启动压力梯度实验研究

低渗储层油水两相渗流时存在启动压力梯度,充分认清水驱油时启动压力梯度的变化和影响因素对油藏水驱开发至关重要。为了搞清油藏储层油水两相渗流启动压力梯度特点及其影响因素,对不同渗透率、不同含水饱和度、不同润湿性岩心水驱油两相渗流的启动压力梯度进行了室内实验测定,根据实验现象和实验结果,分析了产生启动压力的岩心孔隙内部的阻力效应和微观成因。研究结果表明:气体渗透率小于50×10^(-3)μm^(2)的低渗岩心随含水饱和度增加,启动压力梯度增大;气体渗透率大于50×10^(-3)μm^(2)的中高渗岩心启动压力梯度随含水饱和度变化不大,总体呈下降趋势,且数值较小;对于低渗油藏,启动压力梯度随岩心渗透率降低而增大,随岩心润湿指数增加而减小;岩心边界层液体厚度越大,启动压力梯度越大。产生启动压力的附加阻力效应有油滴毛管力产生的摩擦阻力、静润湿滞后导致油珠变形产生的阻力及液阻效应产生的阻力,其大小和岩石孔喉半径、润湿指数、微观孔隙的油水分布状态、边界层厚度及固液界面张力有关。

桥梁混凝土防腐蚀方法及其评价

为提升桥梁混凝土的耐久性,文中在对桥梁混凝土防腐蚀方法介绍基础上,提出了三种防腐蚀处治方案,并对其防腐蚀效果进行评价。结果表明,聚合物砂浆防腐、硅烷浸渍及复合防腐三种防腐蚀方案均能实现防腐蚀功能;采用聚合物砂浆以及复合防腐方案进行处理的混凝土试件,在经过4 d浸水及100次快速冻融循环后,其渗水深度及质量损失率均明显小于硅烷浸渍组试件,表明这两种方案的防腐性能更优。

基于疏水涂层改善混凝土防渗抗冻性的效果对比

在黑龙江省等高纬度寒冷地区,冬季降雪频繁,公路路面、桥面上的冰雪较多,出于交通安全和保通需要,降雪前后时常会在路面、桥面上撒布一定数量的除冰盐,容易导致路面、桥面的剥蚀损害,对桥梁混凝土钢筋的使用寿命也有较大影响。在混凝土表面进行疏水处理是改善混凝土防渗及抗冻性的有效措施之一。基于“氟化二氧化硅胶体”类疏水材料进行室内对比试验,确认采取常用涂布方式进行处理,可使混凝土的表面静态接触角达到145°以上,采取两遍喷涂或“先涂刷后喷涂”的方式效果最好。与未进行表面处理的试件相比,吸水率可降低68.3%;在冻融循环次数150次以内时,质量损失率可降低53.3%,100次以内时,抗弯拉强度损失率可降低79.5%。同时在抗盐冻,以及表面疏冰方面也有积极作用。

高密度电法在地下水渗流通道探测中的技术应用

地下水渗流可能会引起土体物理性质改变,引发地质灾害。高密度电法用于地下水探测宏观成像分辨率高,采用高密度电法对某居民区地下水渗流通道进行探测,通过观察分析视电阻率反演图像,追踪低电阻率异常来判断地下水渗流通道及富水区位置,最终发现场区内地下水在重力的作用下由西向东,通过地下车库顶板上方和地下车库外墙间两个渗流通道,在场区东南侧汇聚成富水区,造成下方毛石护坡局部涌水。该推断为下一步处理方案设计提供了准确的依据。

高密度电阻率法在调蓄水池渗流勘察中的应用

对高密度电阻率法在调蓄水池渗流勘察中的实际应用进行了研究,结合钻孔、探井等物探手段,分析高密度电阻率法的数据真实性,提出相应处理建议。

饰面高性能混凝土在地铁工程中的技术运用研究

随着城市化进程的加快和城市交通需求的不断增长,地铁作为城市主要的公共交通方式,其建设和发展日益成为城市规划和交通基础设施建设的重要组成部分。在地铁工程中,饰面高性能混凝土(HPC-SF)作为一种技术先进、性能优越的建筑材料,因其在耐久性、抗裂性和施工效率等方面的显著优势,逐渐成为地铁车站、隧道及相关结构中的首选材料之一。本文通过对HPC-SF在地铁工程中的应用实例和技术探讨,探索其优化应用的途径和策略,为地铁工程的可持续发展提供理论支持和实际指导。

Discrimination conditions and process of water-resistant key strata

Water-preservation mining is one of the most important parts of the ‘Green Mining' technology system,which can realize the effective regulation of groundwater resources by controlling strata movement,changing passive prevention and governance of water disasters to active conservation and utilization of groundwater resources and thus obtaining coal and water simultaneously in mining.The concept of water-resistant key strata further enriches the content of the key stratum theory and provides a theoretical basis for water-preservation mining.In order to realize the idea of water-resistant key strata as a guideline in the design of water-preservation mining and engineering applications,the conditions for discrimination in the process of water-resistant key strata,we have presented a mechanical model,as well as its corresponding computer program,based on a large number of theoretical analyses and field measurements,as well as on a comprehensive consideration of the position,structural stability and seepage stability of key strata.Practical engineering applications indicate that this discrimination method and its corresponding computer program on water-resistant key strata are accurate and reliable and can satisfy the actual design needs of water-preservation mining and thus have instructional importance for water-preservation mining in mining areas lacking water.

近松散层采掘抗渗透破坏评价方法Ⅰ:临界水力坡度

抗渗透破坏评价是近松散含水层煤层开采溃水溃砂防控的重要基础工作,但至今尚未形成规范性方法和标准。松散层和风化带抗渗透破坏评价的关键是确定水力坡度和临界水力坡度。首先综述了流土和内部侵蚀发生的临界水力坡度确定方法,指出近松散层煤层采掘诱发溃水溃砂临界水力坡度与传统的临界水力坡度的不同特点。针对集中通道获得考虑临空面出口尺寸和岩土层物理力学性质的松散砂层、黏土层和基岩风化带的抗渗透破坏临界水力坡度的计算公式,采用试验结果验证,溃水溃砂临界水力坡度公式的适用性。通过单因素和多因素参数对临界水力坡度的敏感性分析结果表明,裂隙宽度是影响临界水力坡度大小的最重要因素,也表明在实际工程中通过控制采掘诱发的覆岩破坏是减少溃水溃砂灾害的关键措施。煤系风化带的临界水力坡度与其中黏土成分的含量、施加荷载大小有密切的关系,当黏土在风化岩石中占比(质量分数)为5%~40%时,其变化范围为2.9~67.2,给出了用高斯函数的拟合估算关系式和考虑上覆荷载的估算公式。研究结果将为近松散层开采溃水溃砂评价临界水力坡度计算提供参考。