A pore-scale numerical model for flow through porous media     

Yi Zhu  Patrick J. Fox  Joseph P. Morris 《国际地质力学数值与分析法杂志》1999,23(9):881-904

A pore-scale numerical model based on Smoothed Particle Hydrodynamics (SPH) is described for modelling fluid flow phenomena in porous media. Originally developed for astrophysics applications, SPH is extended to model incompressible flows of low Reynolds number as encountered in groundwater flow systems. In this paper, an overview of SPH is provided and the required modifications for modelling flow through porous media are described, including treatment of viscosity, equation of state, and no-slip boundary conditions. The performance of the model is demonstrated for two-dimensional flow through idealized porous media composed of spatially periodic square and hexagonal arrays of cylinders. The results are in close agreement with solutions obtained using the finite element method and published solutions in the literature. Copyright © 1999 John Wiley & Sons, Ltd.  相似文献   

Effects of experimental uncertainty on the calculation of hillslope flow paths     

Mark D Sherlock  Nick A Chappell  Jeffrey J McDonnell 《水文研究》2000,14(14):2457-2471

Measurement uncertainty is a key hindrance to the quantification of water fluxes at all scales of investigation. Predictions of soil‐water flux rely on accurate or representative measurements of hydraulic gradients and field‐state hydraulic conductivity. We quantified the potential magnitude of errors associated with the parameters and variables used directly and indirectly within the Darcy – Buckingham soil‐water‐flux equation. These potential errors were applied to a field hydrometric data set collected from a forested hillslope in central Singapore, and their effect on flow pathway predictions was assessed. Potential errors in the hydraulic gradient calculations were small, approximately one order of magnitude less than the absolute magnitude of the hydraulic gradients. However, errors associated with field‐state hydraulic conductivity derivation were very large. Borehole (Guelph permeameter) and core‐based (Talsma ring permeameter) techniques were used to measure field‐saturated hydraulic conductivity. Measurements using these two approaches differed by up to 3\9 orders of magnitude, with the difference becoming increasingly marked within the B horizon. The sensitivity of the shape of the predicted unsaturated hydraulic conductivity curve to ±5% moisture content error on the moisture release curve was also assessed. Applied moisture release curve error resulted in hydraulic conductivity predictions of less than ±0\2 orders of magnitude deviation from the apparent conductivity. The flow pathways derived from the borehole saturated hydraulic conductivity approach suggested a dominant near‐surface flow pathway, whereas pathways calculated from the core‐based measurements indicated vertical percolation to depth. Direct tracer evidence supported the latter flow pathway, although tracer velocities were approximately two orders of magnitude smaller than the Darcy predictions. We conclude that saturated hydraulic conductivity is the critical hillslope hydrological parameter, and there is an urgent need to address the issues regarding its measurement further. Copyright © 2000 John Wiley & Sons, Ltd.  相似文献   

某引水工程中长输水隧洞断面初选设计分析     

赵鹏博 《地下水》2020,(1):215-217,259

断面比选设计是为了研究输水隧洞在复杂的地质条件中能够更好的施工,在运行期具有更好的过流能力,并且在建设中节省工程投资而进行的不同断面设计分析。以在建某长输水隧洞为例,选择城门洞型和马蹄形两种不同设计断面,从水力参数设计、施工方法、工程量及工程投资等各个方面进行对比分析计算,选择出易于施工,水利条件好并节省投资的设计断面,再进行输水隧洞正常水深、临界水深、临界底坡的水力计算,并分析了设计断面的水力特性。最后,提出了在输水隧洞断面设计上的几点建议,供水利设计和施工人员参考。  相似文献   

利用室内和现场水压致裂试验联合确定地应力与岩石抗拉强度     

王成虎  高桂云  王洪  王璞 《地质力学学报》2020,26(2):167-174

钻杆式水压致裂原地应力测试系统的柔性会影响最大水平主应力的计算精度。利用空心岩柱液压致裂试验获得的岩石抗拉强度来取代重张压力计算最大水平主应力是降低钻杆式测试系统柔性的负面影响的重要途径。在福建某隧道深度为65 m的钻孔内开展了8段的高质量水压致裂原地应力测试,随后利用钻孔所揭露的完整岩芯开展了17个岩样的空心岩柱液压致裂试验。利用空心岩柱液压致裂所得的抗拉强度平均值为8.40 MPa,与经典水压致裂法确定的岩体抗拉强度8.22 MPa接近。对于20 m的范围内8个测段的原地应力量值,最小水平主应力平均值为8.41 MPa,基于重张压力P_r的最大水平主应力平均值为16.70 MPa;基于空心岩柱抗拉强度的最大水平主应力量值平均值为16.88 MPa,两种方法获得的最大水平主应力平均值基本一致。最大最小水平主应力与垂直主应力之间的关系表现为σ_H > σ_V > σ_h,这种应力状态有利于区域走滑断层活动。通过对比分析可知,对于钻杆式水压致裂原地应力测试系统,当测试深度小且测试系统柔性小时,基于重张压力和基于空心岩柱抗拉强度得到的最大水平主应力量值差别不大,这说明基于空心岩柱的岩石抗拉强度完全可以用于水压致裂最大水平主应力的计算,同时基于微小系统柔性的水压致裂测试系统获得的现场岩体强度也是可靠的。   相似文献   

Analytical compensation between DTM grid resolution and effective values of staurated hydraulic conductivity within the TOPMODEL framework     

GEORGES-MARIE SAULNIER  CHARLES OBLED  KEITH BEVEN 《水文研究》1997,11(9):1331-1346

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CONSEQUENCES OF FLUID LAG IN THREE-DIMENSIONAL HYDRAULIC FRACTURES     

S. H. Advani  T. S. Lee  R. H. Dean  C. K. Pak  J. M. Avasthi 《国际地质力学数值与分析法杂志》1997,21(4):229-240

Research investigations on three-dimensional (3-D) rectangular hydraulic fracture configurations with varying degrees of fluid lag are reported. This paper demonstrates that a 3-D fracture model coupled with fluid lag (a small region of reduced pressure) at the fracture tip can predict very large excess pressure measurements for hydraulic fracture processes. Predictions of fracture propagation based on critical stress intensity factors are extremely sensitive to the pressure profile at the tip of a propagating fracture. This strong sensitivity to the pressure profile at the tip of a hydraulic fracture is more strongly pronounced in 3-D models versus 2-D models because 3-D fractures are clamped at the top and bottom, and pressures in the 3-D fractures that are far removed from the fracture tip have little effect on the stress intensity factor at the fracture tip. This rationale for the excess pressure mechanism is in marked contrast to the crack tip process damage zone assumptions and attendant high rock fracture toughness value hypotheses advanced in the literature. A comparison with field data is presented to illustrate the proposed fracture fluid pressure sensitivity phenomenon. This paper does not attempt to calculate the length of the fluid lag region in a propagating fracture but instead attempts to show that the pressure profile at the tip of the propagating fracture plays a major role in fracture propagation, and this role is magnified in 3-D models. © 1997 by John Wiley & Sons, Ltd. Int. J. Numer. Anal. Meth. Geomech., vol. 21, 229–240 (1997).  相似文献   

基于氡同位素的平原湖荡枯水期湖水地下水补排通量     

卢小慧  吴潮峰  龚绪龙  王梦瑶  王磊  张海涛  卫岩曈  严子豪  武鑫 《湖泊科学》2024,36(3):939-950

水是人类生存之源,而湖荡被称为地球之“肾”,是河湖水系连接的关键缓冲节点,与人类生存和发展息息相关。长三角平原水系众多,河流纵横,天然湖泊与人工沟渠遍布,平原湖荡湖水与周边地下水的水力联系较为频繁,而地下水对湖泊水均衡贡献尚不明确,对平原湖荡地下水赋存和运移规律的认识不足。本研究以苏州吴江区元荡湖为研究对象,选取氡同位素作为湖水和地下水水力交换过程的示踪剂,建立氡箱模型,揭示元荡湖不同区段与地下水的水力联系过程和补给关系,并通过水位动态验证分析湖水—地下水交互关系。枯水期元荡湖水位和氡浓度空间分布特征指示研究区内地下水向湖水排泄,其中以湖泊西侧较为明显,地下水入流补给的氡为7.137×10⁶ Bq/d,输入量源项占比为90%,地下水流入量为4540.801 m³/d,地下水每日流入量对元荡湖水量的贡献率为2.551%。参数敏感性分析结果表明,风速与地下水²²²Rn活度为特别敏感参数,取值差异较大时会导致计算误差急剧增大,改善测点布置和提高模型参数精度能有效提高模型计算结果的准确性和可靠程度。借助氡同位素示踪方法,建立湖泊...  相似文献   

WT－22型单桅杆液压伸缩钻塔     

周幼宗 《煤田地质与勘探》1994,22(4):57-61

介绍了为煤田地质GZY-1200型全液压钻机设计的WT-22型单桅杆液压伸缩钻塔。重点讨论了塔的结构及工作原理、主体结构、起落机构与伸缩机构、钻塔的底部支承与锁定、绷绳以及液压系统的设计。   相似文献   

颗粒形状对粗粒土孔隙特征和渗透性的影响     

彭家奕  张家发  沈振中  叶加兵 《岩土力学》2020,41(2):592-600

粗粒土的颗粒级配、形状和密实度都是影响其孔隙结构,进而影响其渗透特性的重要因素。但长期以来,对颗粒形状影响的关注度较少,其主要原因在于不容易定量描述颗粒形状及其影响的孔隙结构特征。选取已获取长宽比和圆形度的不规则形状碎石、规则形状的球和八面体颗粒分别装填试样,针对颗粒级配和颗粒形状的差异,开展孔隙结构特征和渗透性的对比研究。通过CT扫描试样内部结构图像,重构试样的三维孔隙结构并计算孔隙比表面积。通过渗透试验测得试样的渗透系数。结果表明：试样孔隙比表面积是表达孔隙结构特征的有效参数,在相同级配和孔隙率的条件下,试样孔隙比表面积随颗粒圆形度和趋近球形程度的增加而减小;相同级配和孔隙率的条件下,渗透系数随孔隙比表面积的减小而增大,随颗粒圆形度增大而增大;球形颗粒试样的渗透性最强,试样颗粒越偏离球形,孔隙系统中水流阻力越大,试样渗透性越弱。  相似文献   

间断级配砂砾石土的渗透变形试验研究     

田大浪  谢强  宁越  傅翔  张建华 《岩土力学》2020,41(11):3663-3670

渗透变形是颗粒材料中细颗粒在渗流作用下发生重分布且导致土体的内部结构、水力及力学特性发生变化的现象,是导致砂砾石土地基及堤防结构破坏的主要原因之一。利用自主研发的刚性壁渗透仪对不同级配及细颗粒含量的间断级配砂砾石土在恒定水头渗流作用下进行渗透变形全过程试验,监测了渗流过程中的局部水力梯度空间分布以及竖向位移变化,分析了渗透试验结束后土体的颗粒级配空间分布变化。研究结果表明：土粒中细颗粒所处的欠填、满填及过填3种堆积状态决定了粗、细颗粒间不同的接触方式,影响其渗透性。渗透试验结束后细颗粒流失量沿试样高度的空间分布可以划分为3个区域,即顶部流失区、中部均匀区及底部流失区。局部水力梯度的快速下降伴随着竖向位移的突变,意味着渗透变形的开始;渗透变形启动时的局部水力梯度大于全局水力梯度,证实了采用大尺寸试验执行渗透试验的必要性。细颗粒处于过填状态的试样依然会发生渗透变形且导致强烈的沉降变形,值得进一步的研究。  相似文献