Measurement of streambed hydraulic conductivity and its anisotropy

 A method is described for the measurement of streambed hydraulic conductivity. Unlike permeameter methods, this method applies straight and l-shaped standpipes directly to streambeds for measurements of in-situ hydraulic conductivity in the vertical (K _v ) and horizontal (K _h ) directions, as well as in other oblique directions (K _s ). This method has advantages in determination of K _v values over grain-size analysis, permeameter tests, or slug test methods. Also unique to this method is that it provides K _s values of a streambed. The measured results can be used to construct a hydraulic conductivity ellipse and to evaluate the anisotropy of streambed sediments. Field examples from the Republican River, Nebraska, demonstrated the usefulness of this method in the determination of streambed hydraulic conductivity and anisotropy along or across a river channel. Results indicate that the K _h is about three to four times larger than K _v , whereas K _s values are larger than K _v but smaller than K _h . Received: 6 March 2000 · Accepted: 18 April 2000     

变渗透系数软土一维非线性固结沉降数值模拟

固结沉降计算是工程建筑中的重要内容之一。传统的固结沉降计算多是基于渗透数为常数的Terzaghi模型,这与实际的固结过程有较大的差别。采用Carman—Koze模型与一维非线性固结沉降模型进行耦合来模拟固结沉降过程。结果表明,固结导致的渗透系数的变化对固结有较大的影响,特别是在后期这种影响会越来越大。     

三维地下水流中常规观测孔水位的形成机理及确定方法

对地下水三维流中常规观测孔中水位的传统计算方法提出质疑, 认为计算观测孔中水位的Hantush Бочевер方程是缺乏物理基础的纯数学方法.分析了形成观测孔中水位的机理, 提出三维地下水流中常规观测孔中只是孔口的流量为零, 而孔内却存在"抽水"和"注水"的井孔; 多层井(multilayerwell) 不一定要求"多层"的条件, 在均质单一含水层中的井孔可以具有多层井的基本特征; 混合井孔的水位并不"混合", 混合观测孔中存在符合机理的水头分布和流量分布规律等观点.普遍而言, 三维流中的观测孔不能用通常所说的线汇/线源刻画, 也不能用近几年提出的孔内为层流(线性流) 的假定来研究该问题, 然而可用笔者于1993年提出的"渗流-管流耦合模型"和"等效渗透系数"方便、有效地模拟.就说明性算例而言, Hantush Бочевер方程只能近似用于孔径大于0.2m且径距大于10~20m的条件.      

渭河河漫滩宏观弥散度计算

宏观弥散度的确定对地下水溶质运移至关重要。利用竖管法野外现场测定900个点的垂向饱和渗透系数Kv值,然后进行统计分布检验,运用地质统计学中负指数模型在有块金效应影响的条件下拟合出ln Kv的空间相关尺度λ值,进而利用λ与宏观弥散度关系式求解渭河漫滩非饱和带的宏观弥散度。结果表明,研究区整体Kv平均值为0.012cm/s,方差为1.33,表明Kv空间差异性较大;垂向渗透系数基本服从对数正态分布规律,满足宏观弥散度计算条件;估算整体纵向宏观弥散度为21.27m,各排计算结果约2.11~4.65m。     

南方地区城市生活垃圾导热系数的试验研究

温度场对垃圾填埋场的衬垫系统、气体运移和垃圾土工程特性等存在显著影响,导热系数是研究填埋场内温度场的重要参数。以台州卢岙里垃圾填埋场为研究对象,采用DRCD-3030型智能化导热系数测定仪,测定了不同孔隙率和含水率条件下的垃圾导热系数。试验中,垃圾试样的含水率分别取0%、5%、10%、15%、20%、25%、30%、35%、40%、45%和50%;垃圾的孔隙率分别取77.8%、75.0%、71.4%和66.7%。试验结果表明：干垃圾导热系数较小,仅为标准状态空气导热系数的2.5～3.5倍,并随孔隙率的增大而减小;非饱和垃圾的导热系数随含水率的增加而增大,当含水率相等时,孔隙率越小,垃圾的导热系数越大。根据垃圾导热系数的实测数据,利用修正几何加权平均模型和线性拟合技术,建立了垃圾导热系数的计算公式,可以为垃圾填埋场温度场的研究提供重要参考。     

The relationship between hydrodynamic properties and weathering of soils derived from volcanic rocks,Galapagos Islands (Ecuador)

The aim of this interdisciplinary study is to examine a component of the hydrological cycle in Galapagos by characterizing soil properties. Nine soil profiles were sampled on two islands. Their physical and hydrodynamic properties were analyzed, along with their mineralogical composition. Two groups of soils were identified, with major differences between them. The first group consists of soils located in the highlands (>350 m a.s.l.), characterized by low hydraulic conductivity (<10⁻⁵ m s⁻¹) and low porosity (<25%). These soils are thick (several meters) and homogeneous without coarse components. Their clay fraction is considerable and dominated by gibbsite. The second group includes soils located in the low parts of the islands (<300 m a.s.l.). These soils are characterized by high hydraulic conductivity (>10⁻³ m s⁻¹) and high porosity (>35%). The structure of these soils is heterogeneous and includes coarse materials. The physical properties of the soils are in good agreement with the variations of the rainfall according to the elevation, which appears as the main factor controlling the soil development. The clayey alteration products constrain soils physical and hydrodynamic properties by reducing the porosity and consequently the permeability and also by increasing water retention.     

电导率法在入河排污口流量监测中的应用研究

鉴于目前入河排污口流量测验手段不足,尝试采用测试电导率方法进行排污口流量测量,并与常规流量测验方法容量法进行比对,试验证实本方法简便易行,适应性强,可以在实际工作中推广应用。     

河床水力传导度及其各向异性的测定

采用直接测定法观测了黑河中游段河床水力传导度及其各向异性,结果表明:河床水力传导度不仅存在较强的各向异性,而且存在空间尺度上的变异性.河床中心位置在垂直、水平和θ=30°方向的平均水力传导度分别为0.45、22.49和1.71 m/d,河床边分别为5.95、29.69、16.80 m/d.在同一测点,水力传导度随着与水平方向的夹角增大呈幂函数曲线下降.试验结果表明河床边是河水的主要渗漏区,并且以侧渗为主.     

沉积岩平行层面与垂直层面方向热导率与孔隙连通性之间的关系

根据对渤海湾盆地沾化凹陷泥质岩、粉砂岩、砂岩和白云岩平行层面与垂直层面方向热导率差异及孔隙连通性差异特征的研究,探讨了沉积岩平行层面与垂直层面方向热导率与孔隙连通性之间的关系。热导率实验结果表明:沾化凹陷泥质岩、粉砂岩和砂岩的平行层面方向热导率大于垂直层面方向热导率;白云岩的平行层面方向热导率小于垂直层面方向热导率。沉积岩平行层面与垂直层面方向热导率差异和孔隙连通性差异之间具有正相关性。孔隙特征分析结果表明:孔隙连通性较好方向,热导率也较高;孔隙连通性较差的的方向,热导率也较低。