不同土壤转换函数预测砂土非饱和导水率的对比分析

以现有的4种土壤转换函数(Pedotransfer Functions, PTFs)(包括ROSETTA、RAWLS、CAMPBELL和VAUCLIN)为例,将其用于土壤水力性质数据库UNSODA中56个典型砂土样本的非饱和导水率预测,对4种PTFs的预测结果进行了误差分析,探讨了饱和导水率对非饱和导水率预测的影响。结果表明,当同种PTFs预测的饱和导水率作为输入时,在4种PTFs中VAUCLIN的预测精度最高,其次为ROSETTA和RAWLS,CAMPBELL的误差最大;当实测饱和导水率作为输入时,RAWLS、CAMPBELL和ROSETTA的预测精度有了不同程度提高,但VAUCLIN的预测误差反而有所增大;饱和导水率对非饱和导水率预测的影响较大,实测饱和导水率作为输入时CAMPBELL预测的非饱和导水率与实测值最为接近。     

包气带增厚区土壤水力参数及其对入渗补给的影响

为探讨包气带深部增厚区土壤水力参数变化对入渗补给过程的影响,采用压力膜仪对河北正定深部包气带(8.0~21.0 m)10个原状土样进行水分特征曲线测试,利用RETC软件中Mualem-van Genuchten导水率模型对其拟合,获取含水率与非饱和导水率的关系曲线,并根据达西法对其进行分析讨论.结果表明:场地包气带深埋区的非饱和导水率为25~240 mm/a.当某一埋深历史水位下降速度越快,该埋深处相同含水率情况下土壤非饱和导水率越大,说明对应土层的入渗补给强度越大;因包气带厚度增大使原来位于饱水带的层状非均质土层转变为包气带,潜水位波动下降过程中深部包气带土层因排水压密作用,使得土壤水力特性发生变化,进而影响垂向入渗补给过程.      

不同地应力测试方法在三山岛金矿2 005 m竖井建井区域的应用及其地应力分布规律研究

地应力对地下工程安全施工及长期稳定性是极其重要的。运用声发射法、非弹性恢复(ASR)法、水压致裂法对三山岛金矿西岭矿区2 005 m竖井工程勘察区域进行地应力测量,获取了其地应力分布规律及其异常区域,并分析了不同地应力测试方法的测试原理、适用条件及测试结果的差异性。结果表明：不同埋深水平最大主应力始终为第一主应力;当埋深增加到一定程度后,第二主应力发生转换,由最小水平主应力转变为垂直主应力;声发射法测量结果表明,第三主应力Kaiser效应点与ASR法、水压致裂法测试结果存在较大差异;分析了σ_H/σ_v、σ_h/σ_v、σ_H/σ_h随埋深的变化趋势(σ_H为水平最大主应力,σ_h为水平最小主应力,σ_v为垂直主应力),并对测试区域地应力异常区域进行了圈定。上述分析为竖井的设计、施工及长期稳定性提供了有效的数据支撑。     

岩体单裂隙非饱和渗流毛管压力-饱和度关系研究

在进行裂隙岩体非饱和渗流研究中,选用合理的裂隙岩体毛管压力-饱和度关系曲线非常关键。基于裂隙岩体非饱和渗流特点,简述当前国内外非饱和裂隙岩体毛管压力-饱和度关系曲线模型的研究状况。总结出非饱和裂隙渗透具有毛细管流、薄膜流、优先流、裂隙-基质相互作用和沟槽流特点;分析了建立单裂隙岩体非饱和渗流毛管压力-饱和度关系曲线模型的主要方法,包括物模试验法、数值计算法和数学推导法,并归纳这些方法的计算结果;最后,结合渗流特点,对各种曲线模型结果进行比较,进一步分析得出：(1) 目前的曲线关系均建立在毛管理论基础之上,几乎没有反映渗流其他特点的关系曲线;(2) 运用数值计算法和数学推导建立曲线模型较为简便;(2) 在排水曲线初始时段,Brooks-Corey(BC)模型模拟得到的结果比van Genuchten(VG)模型要好些,而在末尾时段VG模型要好些。     

分段循环荷载作用下二维非饱和土固结特性分析

基于Dakshanamurthy和Fredlund提出的二维非饱和土固结理论,利用Fourier正弦级数展开、Laplace变换,分别给出了分段循环荷载作用下二维非饱和土固结问题的超孔隙气压力、超孔隙水压力和沉降的半解析解,并应用退化法验证了本文所得半解析解的正确性。然后,结合3种具体的荷载形式,分析了分段循环荷载作用下气相与液相渗透系数之比(k_a/k_w)、水平方向与竖直方向渗透系数之比(k_x/k_z)和荷载特征参数(a)对二维非饱和土固结特性的影响。结果表明：k_a/k_w和k_x/k_z的增大均会加速固结沉降进程;荷载特征参数越大,沉降发展越早,沉降值越小;二维非饱和土固结特性受分段循环荷载作用影响明显。因此,在实际施工过程中改变施工速度和设置径向排水装置可有效控制二维条件下非饱和土体的固结过程,该研究成果可为非饱和土地基的设计和施工提供重要理论依据。     

土壤饱和导水率空间预测的不确定性分析

当土壤转换函数应用于土壤水力性质估计时,对于预测值的不确定性往往容易被忽视。为了有针对性地提出减少这种不确定性的方法和措施,提高土壤转换函数的实际应用能力,以两种现有的土壤转换函数(Vereecken和HYPRES模型)为例,将其应用于山东省平度市土壤饱和导水率的空间预测,并利用拉丁超立方抽样(LHS)方法对预测结果的不确定性进行了分析。结果表明,饱和导水率空间预测的不确定性主要来源于土壤基本性质的空间插值误差和土壤转换函数自身的预测误差。当Vereecken模型应用于饱和导水率空间预测时,预测结果的不确定性主要由土壤基本性质空间插值误差所决定,土壤转换函数预测误差的影响较小,而HYPRES模型则是受二者的双重影响。     

联合核磁共振测井与Thomeer模型评价碳酸盐岩储层饱和度

碳酸盐岩储层孔隙类型多样、孔隙结构复杂,传统的饱和度评价模型无法表征岩石的微观结构,给饱和度评价工作带来了极大的困难。针对该问题,本文以毛管压力曲线资料与核磁共振测井资料为基础,提出了结合核磁共振测井的Thomeer饱和度模型。分析压汞资料的孔隙系统结构信息,利用Thomeer函数拟合得到多孔隙类型的毛管压力曲线分布,将复杂的孔隙结构表征为多条Thomeer曲线的共同作用。核磁共振测井是唯一能够连续定量表征储层孔隙结构特征的测井方法,利用核磁共振横向弛豫时间谱参数T2算术平均值(T2LM)与核磁孔隙度(MPHS),结合R35岩石物理分类计算Thomeer参数B_v、P_d、G和最大孔喉直径模态元素Porositon,构建复杂孔隙结构碳酸盐岩的饱和度评价模型,该模型解决了实验手段无法开展连续地层孔隙结构评价研究的问题。将该模型应用到中东X油田复杂孔隙结构碳酸盐岩储层进行饱和度评价,与J函数模型、阿尔奇公式进行对比。结果表明该联合模型方法相比于J函数模型与阿尔奇公式,相对误差分别从0.496、0.442降低到0.272,且能较好地表征变化趋势,无论是...     

非饱和重塑黄土的土水特性及压缩屈服与湿陷性的研究

利用改造的非饱和土固结仪对Q_3重塑黄土分别进行了无应力作用的分级增湿试验和控制基质吸力的压缩试验,测试得到了土–水特征曲线和压缩应力–应变曲线,研究了饱和度与基质吸力和含水率与基质吸力之间关系、压缩屈服应力随基质吸力的变化规律和湿陷系数随基质吸力的变化规律。研究结果表明,非饱和重塑黄土的吸力较大时土的强度较大,其压缩变形较小,非饱和重塑黄土的结构屈服压力较大;非饱和土基质吸力一定时,随着压力的增大,湿陷系数呈现出先增大后减小的趋势;同一净压缩应力下非饱和土基质吸力越大,湿陷系数越大,吸力越小,土样的?_s(p=200 k Pa)越小,当?_s(p=200 k Pa)超过约0.1时,?_s(p=200 k Pa)与基质吸力(u_a-u_w)近似呈指数增加。     

黄土高原北部坡面尺度土壤饱和导水率分布与模拟

为探明黄土高原北部坡面土壤饱和导水率(K_s)空间分布特征,为土壤水文过程模拟与预测提供理论依据,采用经典统计学和地统计学的空间变异分析方法,分析了坡面尺度土壤K_s的空间变异特征,并用一阶自回归状态空间模型对K_s的空间分布进行了模拟.研究区坡面尺度K_s的变异为中等程度变异,具有中等程度空间依赖性,变程为42 m.K_s与容重、砂粒、粉粒和黏粒含量在不同滞后距离下均具有自相关关系和交互相关关系.容重和土壤颗粒是影响坡面K_s空间分布的主要因素.状态空间模拟结果表明,基于容重和土壤颗粒的状态空间方程可以很好地解释坡面K_s的变异状况(R2>0.9).一阶自回归状态空间模型可用于田间条件下坡面尺度K_s分布特征的预测.     

定水位均质土壤稳定蒸发的极限强度计算

非饱和土壤水分运动规律,一般采用简化的数学模型,在定水位条件下,稳定蒸发计算αψ/αt=0,将偏微分方程化为常微分方程求解。在积分中,导水系数κ(θ)及扩散系数     

煤岩水力压裂起裂压力和裂缝扩展机制实验研究

为了研究煤岩水力压裂的起裂压力和水力压裂裂缝扩展规律,采用型煤试样,利用自主研发的水力压裂实验系统,参照现场压裂施工制定了“施加三向应力-顶部注水”的煤岩水力压裂物理模拟实验方案并开展了水力压裂实验,分析了不同条件下泵注压力和水力压裂裂缝。实验结果表明:压裂液泵注排量越大,起裂压力越大。三向应力满足最大水平主应力σ_H > 垂向应力σ_v > 最小水平主应力σ_h,水力压裂裂缝沿着垂直于σ_h的方向扩展。σ_v和σ_h一定,随着σ_H的增大,煤岩起裂压力先增大后减小,水力压裂裂缝扩展路径越平直。当σ_H远大于σ_v和σ_h时,水力压裂裂缝扩展路径越复杂,分叉缝角度越大。研究结果可为煤岩水力压裂理论的完善提供一定的参考和借鉴。      

Effects of rock anisotropy and heterogeneity on stress distributions at selected sites in North America

Provinces of regionally consistent horizontal stress orientations persist throughout the upper crust, and these may contain local areas where horizontal stress (σ_H) orientations seem to rotate relative to the regional stress orientations in a consistent manner. We suggest that the concept of aninclusion with anisotropy and heterogeneity of mechanical properties may be useful to explain some cases of σ_H rotations. σ_H rotations up to 50° and magnitude changes of 40% could reasonably be expected, based on simulations. Patterns correlate well with crustal observations; rotation of σ_H orientation reaches 25° to 58° in the different cases studied. We also model a strike-slip fault zone as a soft inclusion, showing reorientations of σ_Hmax which agree with observed rotations near the Murre Fault in the Jeanne d'Arc Basin, Canada. Results imply that understanding the behaviour of soft and stiff inclusions, or expanding and contracting thermal inclusions for that matter, can help explain a number of geophysical and geological phenomena related to stress patterns.     

正断层上盘煤与瓦斯突出特征与地应力场控制机理

断层带是煤与瓦斯突出发生的主要地质单元.大量煤与瓦斯突出案例统计显示,对于正断层,发生在上盘的突出次数和强度明显大于下盘,但造成这一现象的地质机理研究不多,特别是正断层上盘的地应力场在采动前后的变化规律及其对突出发生的控制机理尚未完全揭示.基于此,以河南焦作矿区中马村煤矿DF4正断层为地质模型,应用FLAC3D软件,模...     

Negative Ce Anomaly in the Indian Banded Iron Formations: Evidence for the Emergence of Oxygenated Deep-Sea at 2.9-2.7 Ga

Abstract: Major and rare earth element contents are reported for Late Archean banded iron formations (BIFs) in the Bababudan Group of the Dharwar Craton, South India. The BIFs are mostly composed of SiO₂ (average1ρ = 54.88.1 wt%) and Fe₂O₃* (44.38.2 wt%). The Al₂O₃ and TiO₂ contents are remarkably low, suggesting that detrital components were starved during the BIF deposition. The BIFs have a LREE-enriched pattern with a relatively high (La/Yb)_N (6.644.07). Total REE concentrations (RE) vary from 5.2 to 65.3 ppm. The REE patterns are characterized by the presence of a very large negative Ce anomaly (Ce/Ce*: 0.13-0.83) and a positive Eu anomaly (Eu/Eu*: 0.96-2.45). The Eu/Eu* decreases and (La/Yb)_N increases with a increase of RE. These correlations of REE indices are similar to those of modern hydrothermal iron-rich sediments near a mid-ocean ridge (MOR). Greenstones associated with the BIFs have MORB-like geochemical features. These geochemical and geological lines of evidence indicate that the depositional site of the BIFs was remote from a continent and/or island arc and that the BIFs were in situ hydrothermal sediments near a MOR. A striking negative Ce anomaly in the BIFs indicates that oxygenated deep-sea environments emerged at 2.9-2.7 Ga. The existence of contemporaneous Mn deposits in the Dharwar Craton supports this assertion. Our scenario of oxygen in the Earth's surface of the Late Archean is different from long-held notion that the atmosphere and ocean were persistently anoxic throughout the Archean.     

承压含水层中非完整井附近“非达西-达西”两区渗流模型近似解析解

抽水井附近由于流速过快往往发生非达西流,而远离抽水井随着流速下降又变为达西流.为了描述这些特征,建立了承压含水层中非完整井附近“非达西-达西”两区渗流模型,即距离抽水井较近的区域由于流速较快假设发生非达西渗流,并利用Izbash公式刻画,而距离抽水井较远由于流速较慢假设仍然满足达西定律,含水层中垂向流速较小也利用达西定律描述.通过线性化近似方法结合Laplace变换和有限Fourier余弦变换对模型进行了求解,分析探讨了该两区模型下水位降深曲线特征.结果表明:抽水初期,非达西渗流区域水位降深与全非达西渗流模型结果吻合,而抽水后期两区模型非达西渗流区域的水位降深与全达西模型水位降深基本一致,但大于全非达西渗流模型的水位降深;抽水初期,两区模型中达西渗流区域的水位降深比全达西渗流模型结果大,但比全非达西渗流模型结果小;对不同时间的水位降深随井距变化曲线分析发现非达西渗流区域水位降深随Izbash公式中的幂指数n增大而减小,而在达西渗流区域水位降深基本不受n值的影响.研究成果对非完整井抽水试验参数反演具有重要理论意义.      

湖北竹山杨家堡组硅质岩成因及沉积环境分析

竹山地区位于扬子陆块北缘,寒武纪早期发育一套深水硅质岩系。该岩系由纯硅质岩夹少量白云岩、页岩所组成。硅质岩中微晶石英含量均超过85%,还含有少量碳质、燧石及微量绢云母。地球化学分析表明,该硅质岩的SiO₂含量较高,平均为93.4%;Al₂O₃和TiO₂含量较低,分别为0.19%~1.45%和0.01%~0.09%,TFe₂O₃为0.053%~0.342%,Al/(Al+Fe+Mn)比值为0.58~0.83,平均为0.71,Eu/Eu*为0.74~3.61,平均为1.65,表明其硅质主要来源于生物本身或其生命活动产物,海底热液活动亦提供了一部硅质物质;同时,硅质岩具有较低的TFe₂O₃/TiO₂比值(2.16~12.56,平均值为5.86)和Al₂O₃/(Al₂O₃+Fe₂O₃)比值(0.65~0.87,平均值为0.78),Y的正异常(Y/Ho值为34.81~60.19,平均为47.0)及Ce的负异常(Ce/Ce*值为0.28~0.92),表明它们形成于远离陆源物质干扰的边缘海盆环境,且Ce负异常从底部到顶部有逐渐减小的趋势,记录了寒武纪时期扬子北缘被动陆缘裂谷盆地不断扩大,水体逐渐变深的过程。     

Groundwater-recharge estimation in the Ordos Plateau, China: comparison of methods

Groundwater recharge is a key factor in water-balance studies, especially in (semi-)arid areas. In this study, multiple methods were used to estimate groundwater recharge in the Ordos Plateau (China), including reference to water-table fluctuation, Darcy’s law and the water budget. The mean annual recharge rates found were: water-table-fluctuation method (46??09?mm/yr); saturated-zone Darcian method (17??4?mm/yr); and water-budget method (21??09?mm/yr). Generally, groundwater-recharge rates are higher in the eastern part of the plateau where the land surface is covered by permeable sand that is favorable for infiltration. Along with results from previous studies using the empirical method, the chloride-mass-balance method, the unsaturated-zone Darcian method and the hydrograph-separation method, groundwater recharge rates were compared. There is no one method that would consistently produce the largest or smallest estimate of annual recharge for all groundwater systems. The largest recharge estimates were usually determined using the unsaturated-zone Darcian method and the smallest estimates were usually determined using the chloride-mass-balance method. Comparison of multiple methods is found to be valuable for determining the range of plausible recharge rates and for highlighting the uncertainty of the estimates.     

黄土记录的中亚干旱区东部全新世气候与环境演化

选取位于中亚干旱区东部新疆天山地区的两个典型黄土沉积剖面,通过磁学参数（χ_ARM/SIRM）、亮度（L^*）、有机碳/氮同位素（δ¹³C_org和δ¹⁵N）等记录,对研究区内全新世以来的气候环境进行重建。结果表明：早全新世,χ_ARM/SIRM、L^*指示黄土成壤较弱、有机质含量低,δ¹³C_org记录表明区域降水较少,共同反映该时期地表植被覆盖低、相对干旱的气候环境;中晚全新世,χ_ARM/SIRM、L^*和δ¹³C_org记录的湿度逐渐增加,黄土δ¹⁵N偏正变化,指示地表生态系统生产力增强、植被覆盖增加,表明该区域气候适宜期发生在中晚全新世。中亚干旱区东部全新世以来的气候环境特征,与北半球高纬度冰盖、太阳辐射强度的变化密切相关。     

海相碳酸盐岩岩相的模糊模式识别

基于模糊式识别,本文提出聚类分析与贴近度识别相结合应用于海相碳酸盐岩岩相的分类和识别,聚类用F-PFS法,识别用本文建议的一种带参数的名为加权逆距离贴近度的新公式:S（X_i,Y_j）=sum from k=s_A-1∑ W_k(1-D_ijk)p。其中权重Wk使用一种按单因素判对率确定的新技术。该权重并可用于模糊综合评判。模糊特征向量采用扩展的正则化式计算。上述方法在湖北三叠系海相碳酸盐岩地层得到了应用,并将其划分为六个相.选用12-21个特征因素（颜色、矿物成分、古生物、颗粒组分、填隙物、沉积构造等）,并定量化赋值。聚类分析可分出四个相,贴近度识别的判对率达81.8%,按划分为六个相的贴近度识别,确切判对率达79.2%。     

Simulating flow in karst aquifers at laboratory and sub-regional scales using MODFLOW-CFP

Groundwater flow in a well-developed karst aquifer dominantly occurs through bedding planes, fractures, conduits, and caves created by and/or enlarged by dissolution. Conventional groundwater modeling methods assume that groundwater flow is described by Darcian principles where primary porosity (i.e. matrix porosity) and laminar flow are dominant. However, in well-developed karst aquifers, the assumption of Darcian flow can be questionable. While Darcian flow generally occurs in the matrix portion of the karst aquifer, flow through conduits can be non-laminar where the relation between specific discharge and hydraulic gradient is non-linear. MODFLOW-CFP is a relatively new modeling program that accounts for non-laminar and laminar flow in pipes, like karst caves, within an aquifer. In this study, results from MODFLOW-CFP are compared to those from MODFLOW-2000/2005, a numerical code based on Darcy’s law, to evaluate the accuracy that CFP can achieve when modeling flows in karst aquifers at laboratory and sub-regional (Woodville Karst Plain, Florida, USA) scales. In comparison with laboratory experiments, simulation results by MODFLOW-CFP are more accurate than MODFLOW 2005. At the sub-regional scale, MODFLOW-CFP was more accurate than MODFLOW-2000 for simulating field measurements of peak flow at one spring and total discharges at two springs for an observed storm event.