水膜理论在非饱和土中吸力的应用研究

非饱和土中总吸力问题一直是非饱和土土力学研究的一个重要分支。本文引用并引伸了水膜理论,把水膜理论的水膜范围扩展到包括结合水和毛细作用及基质吸力等引起的自由水（重力水）等部分,相应的水膜分离压也包括基质吸力和毛细作用,因此,非饱和土中的总吸力相应地可表示为扩展后的水膜分离压。从广义水膜理论及土性方面分析非饱和土总吸力,探讨了非饱和土中水膜对总吸力的影响,导出了广义非饱和土水膜理论下的总吸力公式,给出了非饱和土总吸力当土颗粒大小不同时与饱和度的关系。理论计算与试验结果吻合较好,表明了广义水膜理论对研究非饱和土总吸力具有一定的指导意义。     

水泥基渗透结晶型防水材料对硫铝酸盐水泥固化土性能影响及机制分析

水泥土固化过程中Ca2+浓度会随水化反应的进行而逐步降低,导致水泥颗粒未完全水化,固化土强度增长受限,而水泥基渗透结晶型防水材料（CCCW）中活性物质能催化未水化水泥颗粒反应。选择硫铝酸盐水泥（SAC）为胶凝材料、CCCW为添加剂,通过单掺与复掺的方式,结合X射线衍射（XRD）、电镜扫描（SEM）表征,分析了固化土的无侧限抗压强度、水稳定性、耐干湿循环性能及微观结构。结果表明,复掺16%混合料（4%CCCW+12%SAC）的固化土强度是同掺量下单掺SAC固化土强度的1.5倍,且比单掺20%SAC的固化土强度高1.41 MPa;复掺16%混合料（4%CCCW+12%SAC）的固化土泡水2～8 d软化系数平均达0.97,而同掺量下SAC固化土平均仅为0.73;单掺的固化土强度随干湿循环次数增加逐级降低,而复掺混合料的固化土强度呈波浪式发展;CCCW中活性物质能增加固化土中钙矾石生成量并修复微裂缝,钙矾石长径比显著增大,可直接连接两个甚至多个土颗粒,形成三维网状结构,显著提高结晶体的微观加筋、骨架及填充作用,改善SAC固化土强度、水稳定性及耐干湿循环性能。     

镇原-泾川地区储层下限标准的研究

镇原-泾川地区延长组长6-长8储层属于低孔-特低渗透型储层,储层下限标准的研究是划分有效储层的基础,也是油层识别和容积法储量计算的前提.通常认为,低于下限标准的储层是不具备产能的.依据毛管压力资料,通过帕塞尔法、渗透率敏感法、相对渗透率曲线与毛管压力曲线叠合法、孔喉分布4种方法对该区储层下限进行研究. 结果表明,有效储层的孔喉下限约为0.25μm,与孔喉下限对应的渗透率为0.1×10-3μm2,孔隙度为8%.然而储层下限受地质因素和现有储层改造技术的影响,其值也不是一成不变的.因此,必须结合油藏的实际情况,对储层下限做出适当的调整.     

毛细管离子电泳分离间接紫外光度法测定镍矿石中镍钴铜

研究了以咪唑为背景吸收电解质,α羟基异丁酸为络合剂,毛细管离子电泳分离,间接紫外光度法测定镍矿石中Ｎｉ、Ｃｏ、Ｃｕ含量。考察了背景电解质的ｐＨ值、α羟基异丁酸（αＨＩＢＡ）和咪唑浓度对Ｆｅ３＋、Ｃｏ２＋、Ｎｉ２＋、Ｚｎ２＋、Ｃｕ２＋分离的影响。在优化的条件下,几种离子在８ｍｉｎ内完成分离,检测限低至０．２ｍｇ／Ｌ。以Ｚｎ作内标,改善了方法的精密度,对于２０ｍｇ／Ｌ各离子峰面积的相对标准偏差（ＲＳＤ,ｎ＝９）＜６．５％。采用内标标准曲线法对镍矿样中Ｎｉ、Ｃｏ、Ｃｕ的含量进行了测定,线性范围分别在０．５～８０ｍｇ／ＬＮｉ２＋和Ｃｏ２＋,５～８０ｍｇ／ＬＣｕ２＋,结果与其它方法一致。     

一种新型人工“流体包裹体”：融合二氧化硅毛细管技术

利用融合二氧化硅毛细管技术制作了纯H2O体系、纯CO2体系、H2O-NaCl体系和H2O-CO2体系的人工包裹体样品,并对样品进行了显微测温和激光拉曼光谱测试工作。实验结果显示毛细管样品中的流体成分具有代表性,而且常规的流体包裹体显微测温和显微激光拉曼光谱分析技术完全适于毛细管样品的测试。对样品的显微测温和拉曼光谱研究...     

荧光标记微卫星分析人工饲养中华绒螯蟹的遗传多样性

分析中华绒螯蟹的遗传多样性,采集来自无锡、苏州和上海人工养殖样品102个,运用毛细管电泳检测荧光标记（FAM或HEX）的10个中华绒螯蟹微卫星DNA位点。在所有的3个群体中,单一位点等位基因数从15～42个,平均值为22．9;多态信息含量（PIC）和有效等位基因数（E）分别高达0．826和7．699。结果表明10个位点均为高度多态位点,中华绒螯蟹人工养殖群体具有较高的遗传多样性。欧氏遗传距离、遗传相似性和群体各亚群体内固定系数（Fst）平均值分别为0．439,0．825和0．099,结果显示不同的人工养殖群体之间也存在较大的遗传多样性。除上海群体在同步突变模式（SMM）下,近期不会有瓶颈（P=0．35）;所有群体在SMM和无限等位基因模式（IAM）下均有显著或极显著的瓶颈（P〈0．01或0．05）,结果说明科学的品种保护计划的迫切性。本研究首次选择遗传标记微卫星DNA评估中华绒螯蟹的遗传多样性,并采用高精度的毛细管电泳检测技术,将对中华绒螯蟹的品种保护和合理利国提倡科学依据。     

Molecular dynamics modeling of a partially saturated clay-water system at finite temperature

The mechanical and hydraulic properties of unsaturated clay under nonisothermal conditions have practical implications in geotechnical engineering applications such as geothermal energy harvest, landfill cover design, and nuclear waste disposal facilities. The water menisci among clay particles impact the mechanical and hydraulic properties of unsaturated clay. Molecular dynamics (MD) modeling has been proven to be an effective method in investigating clay structures and their hydromechanical behavior at the atomic scale. In this study, we examine the impact of temperature increase on the capillary force and capillary pressure of the partially saturated clay-water system through high-performance computing. The water meniscus formed between two parallel clay particles is studied via a full-scale MD modeling at different elevated temperatures. The numerical results have shown that the temperature increase impacts the capillary force, capillary pressure, and contact angle at the atomic scale. The capillary force on the clay particle obtained from MD simulations is also compared with the results from the macroscopic theory. The full-scale MD simulation of the partially saturated clay-water system can not only provide a fundamental understanding of the impact of temperature on the interface physics of such system at the atomic scale, but also has practical implication in formulating physics-based multiscale models for unsaturated soils by providing interface physical properties of such materials directly through high-performance computing.     

Morphed block-crack preferential sedimentation in a reservoir bed: a smart design and evolution in nature

Abstract

A pedological study of the reservoir bed of Al-Khoud Dam, Oman, revealed an unusual sedimentation pattern which evolved into an intricate composition of silt blocks surrounded by vertical cracks and horizontal layers filled with a “proppant” sand. The discovered soil morphology reflects the complex topology of water motion (infiltration–seepage–evaporation) through the sand-filled cracks/layers and blocks during both the rare flood events and ensuing periods of ponding, and the long, intervening dry periods. These naturally formed soils demonstrate an ability to preserve a large quantity of water inside the silty blocks at depths of 0.5 to 1.5 m, despite the high temperature and dryness of the topsoil. The hydrological optimality and “smartness” of these soils is attributed to the unique block-crack system. Natural, lush vegetation was found in adjacent zones of the reservoir bed, and acted as a footprint of the shallow “fractured perched aquifer”. Planted “ivy” (Convolvulaceae) in the vertical face of one pedon showed intensive growth without irrigation. Soil moisture content data confirmed the hydrological immobility of water in the blocks if not depleted by transpiration. The novel phenomena reported unveil the possible alteration of soil heterogeneity for optimization of the soil–water system in arid zone soils.

Editor D. Koutsoyiannis; Associate editor F.F. Hattermann

Citation Al-Ismaily, S.S., Al-Maktoumi, A.K., Kacimov, A.R., Al-Saqri, S.M., Al-Busaidi, H.A., and Al-Haddabi, M.H., 2013. Morphed block-crack preferential sedimentation in a reservoir bed: a smart design and evolution in nature. Hydrological Sciences Journal, 58 (8), 1779–1788.     

The effect of capillary pressure on the saturation equation of two‐phase flow in porous media

A complete and accurate simulation of two‐phase flow in porous media requires knowledge of all the controlling physics (and values of physical parameters) that play a relevant role and an understanding of the effects of each one on the solution. Of particular concern here is the effect of capillary pressure and the length scale over which it is relevant. The goal of this paper is to provide guidance onto when to include the effects of capillary pressure in the model, and onto what are the resulting length scale restrictions if those effects are to be included. Copyright © 2011 John Wiley & Sons, Ltd.     

A new analytical expression for ultimate specific yield and shallow groundwater drainage

The ultimate specific yield, i.e. the specific yield under steady‐state condition, is generally dependent on the water table depth in the shallow groundwater systems. This paper presents a new expression to describe this relationship. The expression is based on the relationship between soil water content–soil depths below ground surface near the saturation zone, i.e. water content profile, which can be fitted by the van Genuchten model. Because this model is highly nonlinear, a Taylor series expansion was used to solve the integral equation for specific yield in our study. The new expression was verified by a drainage experiment, and the results demonstrated that the new expression is reliable for eolian sand when the range of water table fluctuation is less than 30 cm. The expression is easily applicable because knowledge of the water content profile near the saturation zone is the only requirement. Compared with the expression obtained from the Brooks–Corey model, the new expression can be used for a variety of aquifer and soil media. The improved accuracy of the specific yield provides a better estimate of discharge rates in shallow groundwater systems with water table fluctuations. Copyright © 2014 John Wiley & Sons, Ltd.