一种适用于孔隙体积应变的有效应力方程

土力学奠基石Terzaghi有效应力原理被广泛应用于油藏孔隙和渗透率应力敏感研究中,然而其对于岩石孔隙体积应变的适用性存在争议。对颗粒不可压缩和颗粒可压缩的多孔介质分别进行了受力分析,推导了总体积、颗粒骨架、孔隙体积的有效应力表达式,与Biot、Skepmton有效应力方程对比,建立了适用于孔隙体积应变的新型有效应力方程,并进行了试验论证和应用举例。研究表明:在颗粒不可压缩多孔介质中,有效应力为超出平衡孔隙流压之外的颗粒间宏观等效应力;在颗粒可压缩变形多孔介质中,有效应力为其相同应变下的等效应力,有3种有效应力分别适用于总体积应变、颗粒体积应变、孔隙体积应变;新提出的孔隙体积有效应力方程与孔隙度、岩石总体积压缩系数、颗粒压缩系数、总应力和流压相关,4个理论计算式计算结果在3种多孔介质试验测试结果中的偏差均在5%以内;孔隙体积有效应力系数解决了如何定量增总应力来等效模拟储层降流压生产过程这一关键问题,3个压缩系数关系式理论计算准确方便。     

不同建模假定下岩石损伤黏弹模型的参数转换关系探讨

将外界因素对岩石变形的影响考虑为瞬间弹性损伤和长期蠕变损伤,并根据加载瞬间弹性模量及蠕变模量的劣化分别对瞬间弹性损伤变量和蠕变损伤变量进行定义,由此建立了考虑损伤的kBurgers模型。在此基础上,通过假定泊松比和体积模量为常量分别得到了对应的模型三维表达式,并得到了不同建模思路下模型参数间的换算关系。最后结合实际算例,对常体积模量假定下模型参数随含水率变化的损伤演化规律进行了分析,获得了常体积模量假定下模型的瞬间弹性损伤和长期蠕变损伤演化方程,检验了模型参数换算关系的有效性。     

基于多孔介质弹性理论的碳酸盐岩地层超压预测

碳酸盐岩地层超压预测目前仍然是国内外研究的难点问题。碎屑岩超压预测方法均是建立在明显的超压测井、地震宏观响应规律基础上的经验关系,这些经验性方法不适用于因岩性致密使得超压地球物理响应微弱的碳酸盐岩地层。通过碳酸盐岩样品超压岩石物理模拟实验,分析了在应力-孔隙压力共同作用下岩石中声波速度、弹性参数的变化规律;基于多孔介质弹性理论和广义胡克定律推导并建立了表征孔隙压力与岩石弹性参数定量关系的理论模型,即多孔介质弹性理论的超压预测量化模型。以川东北地区典型碳酸盐岩超压钻井为例,开展了碳酸盐岩地层超压预测应用研究:针对碳酸盐岩地层选择油气水测井综合解释模型获取岩石物性参数;利用Voigt-Reuss-Hill平均模量模型计算岩石基质体积模量,利用Wood模型和Patchy模型计算孔隙流体体积模量,利用BISQ模型计算岩石骨架体积模量,然后通过多孔介质弹性理论量化模型预测超压。预测结果显示预测压力与钻杆实测压力(DST)吻合较好,与泥浆密度换算压力和随钻监测压力变化趋势相近,表明这种基于多孔介质弹性理论的超压预测量化模型是一种解决碳酸盐岩地层超压预测的新途径。     

岩石滞后非线性弹性模拟的研究

在循环荷载作用下,孔隙饱和岩石呈现出闭合的应力-轴向（径向）应变滞后回线、轴向应变-径向应变滞后回线和X”形的瞬时弹性模量（杨氏模量和泊松比）等滞后非线性弹性特征,引入一种滞后非线性弹性材料的宏观模型 Preisach-Mayergoyz模型（PM模型）来描述岩石的这些特征。在PM模型中,孔隙饱和岩石的滞后非线性弹性特征由PM密度空间、施加的应力历史和岩石的滞后细观单元(HMU)的弹性特性所决定。在状态方程中,应变与关闭弹性单元数目占总单元数目的百分比成正比,而关闭弹性单元数目则与施加外力的历史有关,特别是在施加外力转向的时候。通过构造PM空间中不同的密度函数和设定HMU的弹性特性（平衡长度对）可以模拟性质不同的岩石,PM空间中不同的密度函数在一定程度上反映了岩石在循环荷载下的本构关系响应的不同性质。HMU中应变的响应与应力的路径有关,模型本身强调了施加于岩石的应力历史在决定岩石的弹性状态时的重要性,因此,可以用来模拟岩石的离散记忆,从这个意义上讲,孔隙饱和岩石的滞后特性是它具有离散记忆特性的原因。通过模拟,讨论了模型参数和岩石弹性模量之间的定量关系。     

砂土应力-应变关系的加载速率效应分析

分析研究了两种砂土在排水平面应变压缩PSC试验和不排水三轴压缩TC试验条件下的加载速率效应,既实现了不同恒定应变率加载条件下的试验,也实现了不同的加载阶段采用不同的恒定应变率（即应变率分阶段变化）的试验。在加载速率为不同恒定应变率时,砂土的应力-应变响应是唯一的,与应变率无关。在加载速率分阶段变化时,依据应力-应变关系对应变率突变的响应程度,对砂土的加载速率效应进行了评价。分析结果表明,砂土应力-应变关系的加载速率效应表现为黏性消散特性,在应变率发生突变的瞬间,由于应变加速度的影响,应力-应变曲线也相应地突变并表现为刚度很大,近似弹性的特性,随着应变的进一步增加,这一近似弹性的行为逐渐消失。     

粉砂岩的强度特性和变形特性

本文通过实验,研究了一种介于岩石与土之间的软岩--粉砂岩在不同应力状态和应力路径下的基本力学性质、时间效应和交叉效应,提出了一维率相关型本构方程、三维体积应变本构方程以及破裂准则。     

新疆伊犁盆地512矿床水文地球化学特征

在系统分析伊犁盆地 5 12砂岩型铀矿床成矿地质背景基础上 ,阐述了补给区、径流区和排泄区地下水水文地球化学特征 ,并由此得到矿区氧化带、矿化带地下水化学类型分别为SO4·HCO3-Na·Ca型和HCO3·SO4-Ca·Na型 ,其水化学成分演化过程与岩石中硫化物氧化和脱硫酸作用有关 ,水化学类型为铀矿化地段的确定提供了证据。     

热-力耦合作用下垃圾土体积变形特性和模型研究

城市生活垃圾填埋场因有机质降解产热导致其内部温度长期高于环境温度,引发工程运维问题。垃圾土温控三轴试验结果发现,温度变化引起的垃圾土体积应变与应力水平有关,且弹性体积应变占比较大,影响以塑性体积应变为硬化参数的弹塑性本构模型研究。在前期试验基础上,采用GDS温控应力路径三轴仪,研究了排水条件下温度对垃圾土中黏土体积变形特性和压缩特性的影响,并与相同条件下垃圾土体积变形特性进行比较,揭示了温度变化对垃圾土体积变形特性的影响机制。基于垃圾土温控三轴试验结果,推导了垃圾土热弹塑性压缩指数λ_T和热弹性压缩指数κ_T的确定方法;采用等效应力原则,假设温度变化引起的弹塑性体积应变等于某一等效应力增量引起的弹塑性体积应变,建立了垃圾土在热-力耦合作用下的体变计算模型,并对模型进行了验证分析。研究结果表明,孔隙比是影响垃圾土温度体积应变的主要因素;垃圾土的λ_T和κ_T随初始固结应力的增加而减小,比黏土高一个数量级;选取常温下相应固结应力水平的回弹指数κ和压缩指数λ比例值(κ/λ)能够较好地模拟热-力耦合作用下垃圾土的体...     

煤样全应力应变过程中的渗透系数—应变方程

借助现代化的电液伺服岩石力学试验系统,以数控瞬态渗透法进行了全应力应变过程的软煤样渗透特性试验。实验中首次设置了环向应变传感器,得出煤样渗透性与主应力差、轴应变、体积应变关系曲线,并拟合出相应方程。从中可知,煤样全应力应变过程对应的渗透系数是体积应变的双值函数,体积缩小时为2次多项式,体积膨胀时为5次多项式。该方程用在应力场—渗流场耦合的数值分析中,可使计算结果更符合工程实际。      

考虑筋材蠕变特性的加筋土流变模型

把加筋土体的分析看成黏弹性阶段和黏弹塑性两个阶段。考虑筋材的蠕变特性,给出了黏弹性阶段加筋体的弹性应变、筋材的应力和土体的水平微观应力。由方程可知,随着时间的增长,筋材发生按负指数衰减的应力松弛,筋材的应力降低、应变增加。给出了塑性阶段开始到达的时间和变形,在黏弹塑性阶段,加筋体中应力保持恒定,整个应变由于蠕变的发生逐渐增加。由此可针对具体的工程例子分析加筋土体的应力和变形情况,尽量减轻由于加筋土体强度、稳定性降低、变形增加造成的严重后果。     

The terrestrial fauna of the Late Triassic Pant-y-ffynnon Quarry fissures,South Wales,UK and a new species of Clevosaurus (Lepidosauria: Rhynchocephalia)

Pant-y-ffynnon Quarry in South Wales yielded a rich cache of fossils in the early 1950s, including articulated specimens of new species (the small sauropodomorph dinosaur Pantydraco caducus and the crocodylomorph Terrestrisuchus gracilis), but no substantial study of the wider fauna of the Pant-y-ffynnon fissure systems has been published. Here, our overview of existing specimens, a few described but mostly undescribed, as well as freshly processed material, provides a comprehensive picture of the Pant-y-ffynnon palaeo-island of the Late Triassic. This was an island with a relatively impoverished fauna dominated by small clevosaurs (rhynchocephalians), including a new species, Clevosaurus cambrica, described here from a partially articulated specimen and isolated bones. The new species has a dental morphology that is intermediate between the Late Triassic Clevosaurus hudsoni, from Cromhall Quarry to the east, and the younger C. convallis from Pant Quarry to the west, suggesting adaptive radiation of clevosaurs in the palaeo-archipelago. The larger reptiles on the palaeo-island do not exceed 1.5?m in length, including a small carnivorous crocodylomorph, Terrestrisuchus, and a possible example of insular dwarfism in the basal dinosaur Pantydraco.     

The effect of water on accessory phase solubility in subaluminous and peralkaline granitic melts

The solubilities of columbite, tantalite, wolframite, rutile, zircon and hafnon were determined as a function of the water contents in peralkaline and subaluminous granite melts. All experiments were conducted at 1035 °C and 2 kbar and the water contents of the melts ranged from nominally dry to approximately 6 wt.% H₂O. Accessory phase solubilities are not affected by the water content of the peralkaline melt. By contrast, solubilities are affected by the water content of the subaluminous melt, where the solubilities of all the accessory phases examined increase with the water content of the melt, up to 2 wt.% H₂O. At higher water contents, solubilities are nearly constant. It can be concluded that water is not an important control of accessory phase solubility, although the water content will affect diffusivities of components in the melt, thus whether or not accessory phases will be present as restite material. The solubility behaviour in the subaluminous and peralkaline melts supports previous spectroscopic studies, which have observed differences in the coordination of high field strength elements in dry vs. wet subaluminous granitic glasses, but not for peralkaline granitic glasses. Lastly, the fact that wolframite solubility increases with increasing water content in the subaluminous melt suggests that tungsten dissolved as a hexavalent species.     

Quaternary stresses revealed by calcite twinning inversion: insights from observations in the Savonnières underground quarry (eastern France)

Calcite samples were extracted both from the rock matrix and the superficial coating of a karstified fault plane of an underground quarry, located in the eastern border of the Paris basin. The karstification is dated as Quaternary. Analysis of mechanical calcite twinning reveals that only the calcite matrix has also undergone a compression trending WNW that can be attributed to the Mio-Pliocene alpine collision. Both coating and matrix have undergone a strike-slip regime with σ₁ roughly trending north–south, that could correspond to the regional present-day state of stress, a strike-slip compression rather trending NNW, modified by local phenomena. To cite this article: M. Rocher et al., C. R. Geoscience 335 (2003).     

HYDROGEOLOGY

正20141756 Chen Ruige(Mathematical College,China University of Geosciences,Beijing100083,China);Zhou Xun Numerical Simulation of Groundwater Level Fluctuation in a Coastal Confined Aquifer with Sloping Initial Groundwater Level Induced by the Tide(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,32(7),2013,p.1099-1104,6 illus.,16 refs.) Key words:confined water,groundwater level     

METAMORPHIC PETROLOGY

正20141408 Cai Jia(Institute of Geology,Chinese Academy of Geological Sciences,Beijing100037,China);Liu Fulai Petrogenesis and Metamorphic P-T Conditions of Garnet-Spinel-Biotitebearing Paragneiss in Danangou Area,Daqingshan-Wulashan Metamorphic Complex Belt(Acta Petrologica Sinica,ISSN1000-0569,CN11-1922/P,29(7),     

SERIALS

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GEOPHYSICAL EXPLORATION

正20142386An Guoying(China Aero Geophysical Survey and Remote Sensing Center for Land and Resources,Beijing 100083,China)Application of Satellite Remote Sensing in Regional Hydrogeological Investigation:Taking Cenozoic Strata in Wenquan Sheet(1∶250 000)of Karakoram Range as an Example(Geosci-     

QUATERNARY GEOLOGY & GEOMORPHOLOGY

正20141016An Chengbang(Key Laboratory of Western China’s Environmental Systems,Ministry of Education,Lanzhou University,Lanzhou 730000,China);Zhao Yongtao Lake Records during the Last Glacial Maximum from Xinjiang,NW China and Their Climatic Impli-     

PETROLEUM GEOLOGY

正20141538 Cao Qing(School of Earth Sciences and Engineering,Xi’an Petroleum University,Xi’an 710065,China);Zhao Jingzhou Characteristics and Significance of Fluid Inclusions from Majiagou Formation,Yichuan Huangling Area,Ordos Basin(Advances in Earth Science,ISSN1001-8166,CN62-1091/P,28(7),2013,p.819-828,7 illus.,3 tables,43 refs.)     

GEOCHEMISTRY

正20142002 Wei Hualing(Institute of Geophysical and Geochemical Exploration,Chinese Academy of Geological Sciences,Langfang065000,China);Zhou Guohua Element Content and Mineral Compositions in Different Sizes of Soil in Tongling Area,Anhui Province(Geological Bulletin of China,ISSN1671-2552,CN11-4648/P,32(11),2013,p.1861