Simulation of dilatancy-controlled gas migration processes in saturated bentonite using a coupled multiphase flow and elastoplastic H2 M model

Dilatancy-controlled gas flow in preferential pathways plays a key role in the safety analysis of radioactive waste repositories.This is particularly the case for bentonite,an often-preferred barrier material.Gas flow in preferential pathways is characterized by localization and spontaneous behavior,which is challenging to simulate in numerical models due to strong hydro-mechanical coupling.To analyze a laboratory experiment in the framework of the DECOVALEX-2023 project,this study introduced a new approach of combining continuous modelling methods with spatial material properties derived from material heterogeneities and experimental observations.The proposed model utilized hydro-mechanical spatial distributions,namely Young’s modulus and gas entry pressure,and elastoplasticity combined with a linear swelling model.A conceptual strain-dependent permeability approach simulated dilatancycontrolled gas flow based on hydro-mechanical coupling.To test the effectiveness of the presented approach,a gas injection test in a compacted,saturated bentonite sample was simulated using the opensource code OpenGeoSys 5.8 and compared with experimental observations.The presented methodology is capable of simulating localized gas flow in preferential pathways.The spatial distributions of Young’s modulus and gas entry pressure affect the swelling pressure,relative permeability and,in combination with the strain-dependent permeability model,also the intrinsic permeability.

Multiparameter least-squares reverse time migration for acoustic–elastic coupling media based on ocean bottom cable data

In marine seismic exploration,ocean bottom cable technology can record multicomponent seismic data for multiparameter inversion and imaging.This study proposes an elastic multiparameter lease-squares reverse time migration based on the ocean bottom cable technology.Herein,the wavefield continuation operators are mixed equations:the acoustic wave equations are used to calculate seismic wave propagation in the seawater medium,whereas in the solid media below the seabed,the wavefields are obtained by P-and S-wave separated vector elastic wave equations.At the seabed interface,acoustic–elastic coupling control equations are used to combine the two types of equations.P-and S-wave separated elastic migration operators,demigration operators,and gradient equations are derived to realize the elastic least-squares reverse time migration based on the P-and S-wave mode separation.The model tests verify that the proposed method can obtain high-quality images in both the P-and S-velocity components.In comparison with the traditional elastic least-squares reverse time migration method,the proposed method can readily suppress imaging crosstalk noise from multiparameter coupling.

Numerical simulation and experimental validation of moisture-heat coupling for saturated frozen soils

In seasonally frozen regions,freezing-and-thawing action is the main cause responsible for the destruction of canals,which is closely linked to the temperature gradient and water transport.To investigate the behaviour of soils under freezing-and-thawing actions,many numerical models have been established that consider the important coupling of moisture transport and temperature evolution;but they contain excessive parameters,some of which are rather difficult to determine.Based on the well-known Harlan's theory,a simple moisture-heat coupling model was recently proposed to quantify the coupled moisture-heat transport performance of soils in terms of the central temperature and porosity.The mathematical module of COMSOL Multiphysics was further employed to solve the governing equations numerically.To validate our model,a thorough experimental scheme was carried out in our lab.The measured temperature distribution was found to be consistent with the predicted results.

Numerical simulation and analysis of moisture-heat coupling of soft rock tunnels in the cold regions

With the western development in China, more problems with rock and soil engineering in cold regions will be encountered. To study the stability of rock mass under the frost and thaw condition is of far significance. We attempt to simulate and analyze the temperature and moisture field in the surrounding rock of Dabanshan tunnel at its exit KI06＋025 in the cold region by software Femlab. First, introduced the common numerical solution to the moisture and heat coupled about the soft rock in tunnels of cold region. Then gave emphasis on simulation of the law of temperature distribution coupled temperature-moisture field and draw a parallel between temperature fields with different coefficient of percolation. In the course of simulation we considered the problem of caloric receptivity, thermal conductivity and critical heat varying with temperature.

A coupled cryogenic thermo-hydro-mechanical model for frozen medium:Theory and implementation in FDEM

This paper presents the development of a coupled modeling approach to simulate cryogenic thermo-hydro-mechanical(THM)processes associated with a freezing medium,which is then implemented in the combined finite-discrete element method code(FDEM)for multi-physics simulation.The governing equations are deduced based on energy and mass conservation,and static equilibrium equations,considering water/ice phase change,where the strong couplings between multi-fields are supplemented by critical coupling parameters(e.g.unfrozen water content,permeability,and thermal conductivity).The proposed model is validated against laboratory and field experiments.Results show that the cryogenic THM model can well predict the evolution of strongly coupled processes observed in frozen media(e.g.heat transfer,water migration,and frost heave deformation),while also capturing,as emergent properties of the model,important phenomena(e.g.latent heat,cryogenic suction,ice expansion and distinct three-zone distribution)caused by water/ice phase change at laboratory and field scales,which are difficult to be all revealed by existing THM models.The novel modeling framework presents a gateway to further understanding and predicting the multi-physical coupling behavior of frozen media in cold regions.

Numerical simulation on proppant migration and placement within the rough and complex fractures

Hydraulic fracturing is a key technology for the development of unconventional hydrocarbon resources.The proppant placement morphology determines the fracture conductivity,thus affecting the reservoir stimulation effect.In this paper,the proppant migration and placement within complex fractures was studied by considering the fracture wall roughness through computational fluid mechanics-discrete element method(CFD-DEM)in numerical simulation,which is a key approach to study the proppant migration and placement.The results show that the proppant placement non-uniformity,proppant migration capacity,and proppant volume filled in the far-end and the secondary branched fracture are enhanced within the rough fracture compared with those within smooth fractures.The proppant migration capacity is increased within the fracture at low inclination angles(<60°)and low approach angles(<90°),and the proppant placement area is larger in the inclined fracture than that in the vertical fracture.The rise of injection rate and fracturing fluid viscosity causes more proppants migrate to far-end or secondary fractures,resulting in a non-proppant area within the near-wellbore fracture.An increase by 1.3 times in the injection rate and 3 times in the fracturing fluid viscosity leads to a decrease by 26.6%and 27%,respectively,in the proppant placement area within the near-wellbore fracture.The staged injection with small size proppants followed by large size proppants increases the proppant placement area in the primary fracture by 13%-26%,and that with large size proppants followed by small size proppants increases the proppant placement area by 19%-25%,which is due to that the latter method facilitates filling of the secondary branched fracture.The injection location mainly affects the proppant filling degree within the near-wellbore fractures.Compared with the upper injection,the middle and lower injection is not beneficial to filling of proppants within the near-wellbore fracture.

Synthesis and characterization of the flower-like La_(x)Ce_(1-x)O_(1.5+δ) catalyst for low-temperature oxidative coupling of methane

Lanthanum-based oxides are promising candidates for low-temperature oxidative coupling of methane(OCM).To further lower the OCM reaction temperature,the Ce doped flower-like La_(2)O_(2)CO_(3)microsphere catalysts were synthesized,achieving a significantly low reaction temperature (375℃) while maintaining high C_(2) hydrocarbon selectivity (43.0%).Doping Ce into the lattice of La_(2)O_(2)CO_(3)created more surface oxygen vacancies and bulk lattice defects,which was in favor of the transformation and migration of oxygen species at 350–400℃.The designed H_(2) temperature-programmed reduction (H_(2)-TPR) experiments provided strong evidence that the low reaction temperature of La_(x)Ce_(1-x)O_(1.5+δ)can be attributed to the transformation and migration of oxygen species,which dynamically generated surface oxygen vacancies for continuous oxygen activation to selectively convert methane.Moreover,designed temperatureprogrammed surface reaction (TPSR) clarified that two kinds of surface oxygen species in La_(x)Ce_(1-x)O_(1.5+δ)catalysts were concerned with catalytic performance,that is,the surface chemisorbed oxygen species for the activation of CH_(2)and the formation of CH_(2)·intermediates,surface La-Ce-O lattice oxygen species that caused the excessive oxidation of CH_(2)·intermediates.Finally,the factors affecting the transformation and migration of oxygen species were explored.

Constitutive models and salt migration mechanisms of saline frozen soil and the-state-of-the-practice countermeasures in cold regions

A series of saline soil-related problems,including salt expansion and collapse,frost heave and thaw settlement,threaten the safety of the road traffic and the built infrastructure in cold regions.This article presents a comprehensive review of the physical and mechanical properties,salt migration mechanisms of saline soil in cold environment,and the countermeasures in practice.It is organized as follows:(1)The basic physical characteristics;(2)The strength criteria and constitutive models;(3)Water and salt migration characteristics and mechanisms;and(4)Countermeasures of frost heave and salt expansion.The review provides a holistic perspective for recent progress in the strength characteristics,mechanisms of frost heave and salt expansion,engineering countermeasures of saline soil in cold regions.Future research is proposed on issues such as the effects of salt erosion on concrete and salt corrosion of metal under the joint action of evaporation and freeze-thaw cycles.

电感耦合等离子体质谱法测定纹身贴中17种有害元素及其迁移量

建立电感耦合等离子体质谱法测定纹身贴中硼、铝、铬、锰、钴、镍、铜、锌、砷、硒、锶、镉、锡、锑、钡、汞和铅17种元素的分析方法。纹身贴样品经纯水湿润后,用刮刀取下覆在膜上的油墨,干燥后用微波消解法消解,以电感耦合等离子体质谱法测定纹身贴中17种元素含量。分别用模拟胃液和模拟汗液提取纹身贴中17种元素,以电感耦合等离子体质谱法测定17种元素的迁移量。汞元素的质量浓度在0~10μg/L范围内、其余16种元素的质量浓度在0~100μg/L范围内与质谱响应值具有良好的线性关系,相关系数均大于0.999,17种元素的检出限为0.001~0.397μg/kg,定量限为0.003~1.32μg/kg;迁移量检出限为0.0015~1.638μg/dm^(2),定量限为0.005~5.46μg/dm^(2)。纹身贴中17种有害元素及其在模拟胃液、模拟汗液中迁移量测定结果的相对标准偏差为2.9%~15.0%(n=7),样品加标回收率为80.0%~119.2%。该方法灵敏度高,适用于纹身贴中有害元素的测定。

球状风化花岗岩类土质边坡土-岩界面优势流潜蚀特性研究

受降雨作用,球状风化花岗岩类土质边坡的土-岩差异风化界面极易演化为优势渗流通道而发生渗流潜蚀,进而加速该类边坡的变形失稳,然而当前有关其渗流潜蚀作用特征、细颗粒迁移规律等的研究仍鲜见开展。基于多孔介质非饱和渗流理论,综合考虑细颗粒运移、潜蚀启动响应与非饱和渗流的耦合关系,提出一种可准确描述土-岩界面渗流潜蚀过程的数值计算框架。采用有限元方法,构建优势流作用下非饱和花岗岩残积土的渗流潜蚀模型,并以均质土柱的渗流潜蚀过程为参考,系统研究3种典型土-岩界面埋藏状态下的优势流潜蚀特性。结果表明:球状风化花岗岩类土质边坡的土-岩界面与基质渗透性存在高度差异性,湿润锋形成向下凹陷的渗透漏斗,且随着降雨的持续,湿润锋的凹陷程度愈发明显;细颗粒流失程度与土-岩界面的埋藏状态相关,其中下填土体工况的优势流潜蚀最为显著,其界面处甚至出现超孔隙水压力,最不利于该类边坡的稳定性。研究成果可为降雨条件下球状风化花岗岩类土质边坡稳定性的准确评价提供科学依据。

我国煤层瓦斯运移模型研究进展

煤层瓦斯运移是矿井瓦斯抽采与煤矿区煤层气开发领域的基础科学问题。从理论分析、试验方法 2个方面,阐述了我国煤层瓦斯运移理论及其渗透特性测试方法的研究现状,重点围绕煤层瓦斯非线性渗流特性、多场耦合作用下的渗流理论等关键问题的最新成果开展论述;进一步对当前普遍采用的煤层瓦斯运移特性的试验方法进行分析。研究建议:深入研究钻孔周围煤体真实应力-应变状态、瓦斯渗透过程中煤孔隙率的演化特性测试等问题,深化对煤层瓦斯非线性渗流模型、与增透或增产措施相适应的瓦斯运移特征演化等问题的认识。

粗颗粒硫酸盐渍土水盐迁移规律及变形特性研究

针对封闭系统下粗颗粒硫酸盐渍土在冻结过程中的水盐迁移和变形特性开展了理论和试验研究。基于非饱和多孔介质热弹性理论,考虑孔隙水盐相变,建立了适用于粗颗粒盐渍土水-热-盐-力多场耦合模型,并对单向冻结条件下粗颗粒盐渍土的温度场、水分场、盐分场和位移场分布进行了数值模拟。通过配制含硫酸盐的细砂作为土样开展了单向冻结条件下的室内试验,测定了冻结过程中的温度、水分、盐分以及变形的分布,并与数值结果进行了比较,验证了理论模型的有效性。结果表明:砂土结构孔隙更大,水分和盐分更容易渗透和迁移,在单向冻结试验中,水盐迁移速度更快;细砂的轴向位移呈现先下降后上升的变化趋势,且收缩变形持续时间较黏土更长;由于暖端水分向冷端迁移致使暖端土体孔隙减小,下部土体变得更加密实,土柱下部侧壁压力大于上部。

微波注热与传导注热对煤层瓦斯运移的激励效应对比分析

为探究微波注热和传导注热对煤层瓦斯运移的影响,建立了热-流-固耦合模型,通过COMSOL Multiphysics数值软件分别模拟传统传导注热和2450 MHz微波注热对煤层瓦斯运移的激励效应,以相同注热功率为基础,对比分析了2种注热方式下煤层温度、渗透率比例、瓦斯含量、瓦斯抽采率、热损失的演化规律。结果表明:2种不同注热方式对瓦斯运移的激励效应相似,随着抽采时间的延长,煤层温度逐渐升高,渗透率比例先减小后增大,煤层总瓦斯含量逐渐减小,瓦斯抽采率先增大后减小;相对于传导注热,微波注热效果更佳,煤层渗透率整体较大,吸附瓦斯含量较低,残余瓦斯含量整体较高,瓦斯抽采量较高,瓦斯抽采率较大、热损失较小。微波注热比传导注热对煤层具有更好的激励效应,能更好地加速煤层瓦斯吸附解吸,更有利于煤层瓦斯的抽采,且传热效率高,热损失小,更节能。

不同材质的一次性生物基餐具中22种元素迁移及其安全风险分析

目的分析39个聚乳酸(polylactic acid,PLA)基、淀粉基、纤维基材质的一次性生物基餐具中的22种元素迁移,并评估其安全风险。方法样品经迁移实验得到迁移液,使用电感耦合等离子体质谱法对迁移液中的22种元素进行分析。结果锑、铊未检出,20种元素(铍、硼、镁、铝、钛、钒、铬、锰、铁、钴、镍、铜、锌、镓、砷、锶、镉、锡、钡、铅)均有检出,其中铝、锰、锌、镓、锶、钡迁移的检出率为100%。各元素迁移量范围为1.0×10^(-4)~6.9×10^(1)mg/kg,镁的平均迁移量最高为3.5 mg/kg。22种元素在PLA基与淀粉基制品中的迁移水平整体低于纤维基制品且不存在元素迁移的安全风险。纤维基样品中铝、铬、锰、锌、铅超出特定迁移限量,锌、镉、铅的日暴露量可能存在潜在的安全风险,而且还出现了多个金属元素迁移同时超标的现象。结论部分纤维基样品中金属迁移存在超标现象及潜在安全风险,需要重点对纤维基样品的金属迁移加强关注和监管。本研究为不同材质一次性生物基餐具中金属迁移的安全性研究及监管提供了科学依据。

寒旱区温度效应下土壤水盐运移多因素耦合理论研究进展

土壤盐碱化是一个全球性问题,严重制约着农业发展,了解水盐运移规律是改善和预防土壤盐碱化的关键。在寒冷干旱地区农田非耕作期,土壤水盐运移规律主要受冻融作用的影响,而冻融循环下正负温交替对土壤水盐的迁移起到了决定性作用。基于冻融循环作用,从正、负温度效应入手,综述了水-热-气-力-盐耦合等一系列研究成果,分析了正、负温度驱动力的产生及数值模型与试验研究的发展,并在此基础上展望了变化环境条件下土壤盐碱化研究未来的发展方向。盐碱地是世界上最重要的后备耕地资源之一,合理、科学地利用盐碱地,对盐渍土进行改良,防止土壤进一步盐碱化,显得尤为重要。改良盐碱地在农业发展中凸显了节水、生态、低能耗的趋势。研究不同条件下土壤盐分演变的驱动机制和生态调控机制,对改善土壤盐分具有重要意义。

水热力作用下铁路基床翻浆冒泥力学特征试验研究

考虑基床水位线高度与冻融循环的影响,开展有砟轨道基床翻浆冒泥试验,分析动荷载作用下有砟轨道基床翻浆冒泥过程中水与细粒土迁移和泥浆形成特征。研究结果表明:在常温加载初期,水分自下而上发生迁移,随着动荷载的持续施加,基床填土内部孔隙水压力逐渐消散,孔隙水压力梯度减小,各层土体含水率趋于稳定;水位线位于基床中部时,基床上部土体处于非饱和状态,体积含水率较小,仅为26%左右,未能发生细颗粒迁移,基床表层有效应力远大于0,未形成泥浆造成翻冒;水位线位于基床顶部时,颗粒迁移较为明显,且基床表层有效应力在荷载的作用下迅速减小到0以下,并发生翻浆冒泥现象;冻结加载相较于单向冻结,冻结锋面下降速率慢,水分迁移量更大;融化加载条件下,基床上部土体先于下部土体融化形成冻土夹层,由于冻土夹层阻隔,上部土体含水率较大,在荷载作用下基床表层有效应力迅速发展到负值,更易形成泥浆导致翻浆冒泥。

页岩气水平井暂堵坐封机制与可控暂堵压裂工艺

水平井暂堵转向压裂技术是页岩气增产的关键技术之一。文中采用流体动力学软件FLUENT与离散元方法(DEM)相结合的数值建模方法,研究了水平井暂堵转向压裂技术中暂堵球在井筒中的运移规律以及颗粒间的相互作用。通过建立DEM-DDPM耦合模型发现,施工排量、暂堵球密度、暂堵球直径和压裂液黏度是影响暂堵球坐封效果的主要因素。模拟结果表明:当施工排量在4~6 m^(3)/min时,暂堵球的密度小于或等于流体密度;射孔炮眼磨蚀率在6.15%以内可以有效提高封堵效率;同时,随着压裂液黏度的增加,封堵效率先升后降。该研究结果对于优化水平井压裂暂堵球用量以及施工工艺具有重要的理论意义和指导价值。

煤矿地下水库技术原创试验平台体系研制及应用

煤炭是我国主体能源,西部是我国煤炭主产区,矿井水保护利用是煤炭开发面临的重大技术难题。国家能源集团煤炭绿色开采技术研发团队经过20多年持续技术攻关,首创了煤矿地下水库技术,在西部神东矿区推广应用,为矿区开发提供了95%以上用水,确保了矿区可持续开发。为进一步丰富完善煤矿地下水库理论和技术体系,在西部煤炭主产区不同地质和工况条件下推广应用该技术,保障国家能源安全和水资源安全,研发团队构建了煤矿地下水库原创技术试验平台体系,包括煤炭开采地下水运移与保护综合智能试验平台、多煤层开采煤矿地下水库模拟试验平台、煤矿地下水库坝体结构试验平台、西部深部井工矿井筒施工模拟试验台、地下水库水岩耦合机理试验、水处理工艺集成试验平台、煤矿地下水库冲击试验平台等,能够开展西部矿区不同煤层赋存条件下地下水运移规律、坝体结构参数优化、水库安全稳定性、水岩耦合作用机理、矿井水处理工艺参数优化、垮落岩体垮落冲击对坝体影响等研究,为煤矿地下水库建设、运行和安全提供理论支撑和技术验证。利用上述试验平台,开展了多煤层开采煤矿地下水库稳定性及渗流规律模拟、煤矿地下水库坝体结构安全、煤矿地下水库水岩耦合机理等多项试验研究,相关研究成果已应用于现场工程实践,确保了煤矿地下水库安全稳定运行。

基于风流运动的粉尘运移研究进展及趋势

矿井机械化、智能化水平提升所导致的粉尘问题愈发严重,探究风流-粉尘运移规律,掌握工作面风流、粉尘的运动特征,对改进工作面控尘措施,改善井下作业环境,加速实现绿色矿山目标具有重要意义。通过查阅国内外文献资料,调研相关研究进展与实践经验,从粉尘受力运动原理、相似实验设计、数值模拟研究、组合方法效果评估等方面,研究当前风流场及其对粉尘分布的影响,认为当前存在风流场与粉尘之间相互作用复杂,粉尘受力运动机理与运动路径研究不透彻,不同因素组合作用与粉尘运移规律关系不明朗等问题。从提高规律向实用性和普遍性转变的角度,提出风流-粉尘运移规律的研究重点应向明晰粉尘运移受力机理和作用力协同机制、建立多参数表征运移规律、提升监测仪器精密度、减弱次要因素对相似实验结果影响程度、增强对风流场和粉尘运移力学特征的认知、明朗影响因素间的耦合关系、构建适用于气-固两相流的数学模型及完善颗粒运动扩散方程8个方面转变。

信号识别颗粒14调控肝细胞癌进程并影响患者预后

目的:探究信号识别颗粒14(SRP14)在肝细胞癌(HCC)中的表达及功能。方法:利用生物信息学、定量逆转录聚合酶链反应(qRT-PCR)、免疫组织化学染色和蛋白质印迹法等明确SRP14在HCC中的表达;应用Kaplan-Meier法分析SRP14 mRNA表达变化与HCC患者的总生存期、无进展生存期及疾病特异性生存期的相关性;通过5-乙基-2′-94脱氧尿苷(EdU)染色、MTS实验、Transwell小室实验及细胞划痕实验等探索SRP14对HCC细胞增殖和迁移的作用;利用京都基因与基因组百科全书(KEGG)和基因本体(GO)富集分析以及qRT-PCR初探SRP14在HCC中的作用机制。结果:在GSE14520数据集、TNMplot数据库和临床标本中,与配对癌旁组织、非配对癌旁组织或正常组织比较,HCC组织的SPR14 mRNA表达均有不同程度的升高(均P<0.05)。在临床标本中,与配对癌旁组织比较,HCC组织的SPR14蛋白表达上调(P<0.05)。SRP14表达上调的HCC患者具有更长的总生存期、无进展生存期及疾病特异性生存期(均P<0.05)。细胞实验结果显示,SRP14能抑制HCC细胞的体外增殖和迁移。KEGG和GO富集分析结果显示,在HCC中,与SRP14共表达的基因主要调控蛋白质合成、加工和运输等相关细胞活动或功能;在非酒精性脂肪性肝病相关HCC中,与SRP14共表达的基因主要调控MAPK、cAMP、PI3K-Akt、Wnt等多条信号传导通路。SRP14抑制HCC细胞中已知抑癌基因GPRC5A的mRNA表达(P<0.05)。结论:SRP14可能调控HCC进程并影响患者预后。