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1.
Horizontal drains, used independently or as part of a more complex remediation scheme, are frequently installed to mitigate the effects of increased groundwater in slope stabilization projects. Due to a general trial and error approach to their design, the need for improved design practices has been recognized. The procedures established by Crenshaw and Santi in 2004 made some advances in this direction, but did not account for slopes with drains that were not horizontal or for sloping low-permeability layers underneath the slide mass. Furthermore, the method outlined by Crenshaw and Santi is time-consuming and requires some trial and error calculations to achieve convergence. Therefore, the method has been modified to account for nonhorizontal elements, and a horizontal drain spreadsheet has been developed to streamline the design for projects where horizontal drains will be installed. The horizontal drain spreadsheet may be used to: (1) predict a conservative piezometric profile in a drained slope for use in slope stability analyses, (2) predict piezometric heads in any single piezometer in a drainage field, and (3) predict drain spacing for design purposes. This document explains the revisions to Crenshaw and Santi’s procedures and provides instructions for applying the method. The instructions may be used for hand calculations, but are specifically intended for use with the horizontal drain spreadsheet. The spreadsheet may be used for slopes composed of silty or clayey sands, silts, and silty or sandy clays. 相似文献
2.
Ella M. Zelikson 《GeoJournal》1995,36(2-3):223-228
Basic climatic indexes for loess deposits may be determined by the floristic method of palaeoclimatic reconstruction. Spectra of loess pollen are selective, thus may or may not reflect adequately the original composition of the vegetation. Presence of a steppe may be unambiguously stated based on pollen of taxa characteristic for a steppe cenose or of taxa zonally restricted to steppes. Family ranked taxa may often not be regarded as indicating a steppe, because inferior taxa included may be of different cenotic requirements. In order to determine the vegetation and other conditions during the deposition of loess it is important to take into consideration the palaeofloristic data as well. 相似文献
3.
Estimation of semivariogram parameters and evaluation of the effects of data sparsity 总被引：1，自引：0，他引：1
Semivariogram parameters are estimated by a weighted least-squares method and a jackknife kriging method. The weighted least-squares method is investigated by differing the lag increment and maximum lag used in the fit. The jackknife kriging method minimizes the variance of the jackknifing error as a function of semivariogram parameters. The effects of data sparsity and the presence of a trend are investigated by using 400-, 200-, and 100-point synthetic data sets. When the two methods yield significantly different results, more data may be needed to determine reliably the semivariogram parameters, or a trend may be present in the data. 相似文献
4.
The spatial distribution of rock properties in porous media, such as permeability and porosity, often is strongly variable. Therefore, these properties usefully may be considered as a random field. However, this variability is correlated frequently on length scales comparable to geological lengths (for example, scales of sand bodies or facies). To solve various engineering problems (for example, in the oil recovery process) numerical models of a porous medium often are used. A need exists then to understand correlated random fields and to generate them over discretized numerical grids. The paper describes the general mathematical methods required to do this, with one particular method (the nearest neighbor model) described in detail. How parameters of the mathematical model may be related to rock property statistics for the nearest neighbor model is shown. The method is described in detail in one, two, and three dimensions. Examples are given of how model parameters may be determined from real data. 相似文献
5.
针对浅埋暗挖洞桩法理论分析落后于工程实践的实际情况,依据地下结构设计计算理论的地层--结构法,以有限单元法作为分析手段,建立三维计算模型,系统开展了浅埋暗挖洞桩法施工过程的数值模拟,以及参数变化对洞周围岩稳定性和位移场的影响分析。结果表明：浅埋暗挖洞桩法用于大断面洞室或超浅埋洞室暗挖施工时,洞周围岩稳定性良好,并可有效控制地表沉降。洞室跨度为14 m左右时控制地表沉降的效果最好;在不同埋深条件下控制地表沉降的效果基本相同;洞室高度的影响则不明显。研究的结论对今后浅埋大断面单跨洞室暗挖施工方案比选和采用浅埋暗挖洞桩法施工具有指导 作用。 相似文献
6.
Nicholas J. Milton 《Tectonophysics》1980,64(1-2)
An ellipsoid is defined by, and may be re-constructed from, any three sections through it. In the field, calculation of the strain ellipsoid from general sections (two-dimensional strain ellipses determined from measured strain markers) is complicated by the fact that, due to experimental error and/or strain inhomogeneity, the three ellipses may not come from the same ellipsoid. The ellipses must first be adjusted to make them compatible. A method is suggested by which an adjustment ellipse is determined analytically for each of the three sections. Application of these adjustment ellipses makes the three sections compatible, and the strain ellipsoid may be determined. The principal axes of the ellipsoid are derived from the ellipsoid matrix by eigenvector analysis. Examples are given of practical applications of this method. 相似文献
7.
Douglas M. Hawkins 《Mathematical Geology》1984,16(4):393-406
The borehole slotting method previously proposed by Gordon and Reyment for two boreholes may be extended to three or more boreholes, but soon becomes computationally intractable. We propose another method based on the mixture model of cluster analysis, the computational labor of which increases linearly with the number of boreholes. This method produces profiles of the unknown strata to which the individual boreholes are easily matched by the two-borehole slotting method. 相似文献
8.
This study outlines an improved method, DIVERSITY, for delineating and rating groundwater sensitivity. It is an acronym for DIspersion/VElocity-Rated SensitivITY, which is based on an assessment of three aquifer characteristics: recharge potential, flow velocity, and flow directions. The primary objective of this method is to produce sensitivity maps at the county or state scale that illustrate intrinsic potential for contamination of the uppermost aquifer. Such maps can be used for recognition of aquifer sensitivity and for protection of groundwater quality. We suggest that overriding factors that strongly affect one or more of the three basic aquifer characteristics may systematically elevate or lower the sensitivity rating. The basic method employs a three-step procedure: (1) Hydrogeologic settings are delineated on the basis of geology and groundwater recharge/discharge position within a terrane. (2) A sensitivity envelope or model for each setting is outlined on a three-component rating graph. (3) Sensitivity ratings derived from the envelope are extrapolated to hydrogeologic setting polygons utilizing overriding and key factors, when appropriate. The three-component sensitivity rating graph employs two logarithmic scales and a relative area scale on which measured and estimated values may be plotted. The flow velocity scale ranging from 0.01 to more than 10,000 m/d is the keystone of the rating graph. Whenever possible, actual time-of-travel values are plotted on the velocity scale to bracket the position of a sensitivity envelope. The DIVERSITY method was developed and tested for statewide use in Kentucky, but we believe it is also practical and applicable for use in almost any other area. 相似文献
9.
Norman Fry 《Journal of Structural Geology》1979,1(3):221-229
For a homogeneously deformed rock composed initially of an isotropic distribution of object shapes, finite strain may be determined from the correlation between the orientations of either two-dimensional or one-dimensional sample cuts and the frequencies with which they intersect marker objects. Mimran previously published an incorrect method for planar samples under the heading ‘density distribution technique’. Methods are described by which the three-dimensional strain may be directly determined from six general samples, either linear or planar. Construction of two-dimensional ellipses as an intermediate step is unnecessary and enforces practical difficulties.These methods may be simplified by use of samples parallel to known principal axes or planes of the finite strain. In this case the same large errors may arise from slight misorientation of samples as with other methods of strain measurement. A new quick method is proposed, combining linear and planar measurements of frequencies of intersected objects, which is thought to be the first method to circumvent a large part of the error from this error source. For example, if true X:Z ratio is 9 : 1, and orientations in the XZ plane are misjudged by 8°, normal methods give 38% error where the new method gives, with care, an error of 1.9%. For methods of strain measurement such as are described here the concept of strain ellipsoid is unnecessarily limiting, and should be abandoned. 相似文献
10.
据“东北寨式”金矿的成矿模式,结合松潘地区的成矿条件、地球化学异常评价以及资料水平和工作程度等,选择“有利因素相关法”对本区内334资源量进行了远景预测,取得了很好的结果。该方法实际上可归入“矿床模拟估计法”中,其主要原理是：通过对已知对象的研究,阐明控矿因素(地质变量)与矿产资源量之间的关系,建立一定矿床类型的矿产储量与地质条件之间的定量关系(定量预测模型)。将其移植到地质条件类似的预测区应用时,只要预测区上获得预测模型中相同的地质变量及其相同的数据类型值,代入模型,就可估算预测区内的矿产资源量。预测结果,在松潘地区,“东北寨式”金矿可望增长的3341外资源量约为81吨,3342资源量约65．9吨,为下步在该区部署地质工作提供了依据。 相似文献
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13.
We review and perform comparison studies for three recent multiscale methods for solving elliptic problems in porous media
flow; the multiscale mixed finite-element method, the numerical subgrid upscaling method, and the multiscale finite-volume
method. These methods are based on a hierarchical strategy, where the global flow equations are solved on a coarsened mesh
only. However, for each method, the discrete formulation of the partial differential equations on the coarse mesh is designed
in a particular fashion to account for the impact of heterogeneous subgrid structures of the porous medium. The three multiscale
methods produce solutions that are mass conservative on the underlying fine mesh. The methods may therefore be viewed as efficient,
approximate fine-scale solvers, i.e., as an inexpensive alternative to solving the elliptic problem on the fine mesh. In addition,
the methods may be utilized as an alternative to upscaling, as they generate mass-conservative solutions on the coarse mesh.
We therefore choose to also compare the multiscale methods with a state-of-the-art upscaling method – the adaptive local–global
upscaling method, which may be viewed as a multiscale method when coupled with a mass-conservative downscaling procedure.
We investigate the properties of all four methods through a series of numerical experiments designed to reveal differences
with regard to accuracy and robustness. The numerical experiments reveal particular problems with some of the methods, and
these will be discussed in detail along with possible solutions. Next, we comment on implementational aspects and perform
a simple analysis and comparison of the computational costs associated with each of the methods. Finally, we apply the three
multiscale methods to a dynamic two-phase flow case and demonstrate that high efficiency and accurate results can be obtained
when the subgrid computations are made part of a preprocessing step and not updated, or updated infrequently, throughout the
simulation.
The research is funded by the Research Council of Norway under grant nos. 152732 and 158908. 相似文献
14.
元古宙蛇绿岩地质年代学研究方法探讨 总被引：4，自引：2，他引：2
确定元古宙蛇绿岩形成时代的最佳方法是同位素地质年代学研究。元古宙蛇绿岩往往遭受过多期热-构造事件的改造,其地质年代学研究应依据单颗粒锆石U－Pb稀释法或Pb－Pb蒸发法的年龄数据,在具体操作上须正确区分岩浆结晶锆石和变质重结晶锆石。Sm－Nd、Rb－Sr及Pb－Pb等时线年龄具有多解性的特点．不宜用于元古宙蛇绿岩的定年,其地质意义的解释应结合区域地质构造背景及地质地球化学特征的综合研究。 相似文献
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16.
A portable, battery-operated electrochemical instrument which enables the method of staircase voltammetry to be implemented may be coupled with the method of abrasive stripping voltammetry for the direct identification of minerals in the field. Small amounts of solid mineral samples are mechanically transferred to a paraffin-impregnated graphite electrode by rubbing the electrode against the crushed mineral. The electrode is then transferred to a conventional electrochemical cell containing electrolyte, and experiments analogous to the well known method of stripping voltammetry are then completed to provide an “electrochemical spectrum” or fingerprint of the mineral. Since the technique can be applied directly with battery-operated equipment, the method can be used by geochemists and mineralogists undertaking field work in areas remote from sophisticated laboratories and mains-powered instruments normally used to characterize minerals. The method has been successfully applied to the identification of minerals such as galena, stibnite, cuprite, pyrite and chalcopyrite, although further work is required to investigate any limitations that might apply with complex mixtures or minerals, and, at the present stage of development, the method is qualitative rather than quantitative. 相似文献
17.
A Fourier transform technique is presented which may be used to analyse three-dimensional consolidation problems for soils which are loaded by embankment shaped loadings that are rectangular in plan (or of arbitrary shape which can be divided into rectangles in plan). The introduction of a Fourier transform effectively reduces the three-dimensional problem to one involving only two spatial dimensions and this reduces computer storage and saves computing and data preparation time. The material properties of the soil may vary arbitrarily in the plane which is perpendicular to the axis associated with the variable eliminated during the Fourier transform. Solutions obtained using the method are compared with existing solutions in order to verify the theory and assess accuracy, and illustrative examples are given for problems involving the consolidation of soils under embankment loadings. 相似文献
18.
Isobel Clark 《Mathematical Geosciences》1983,15(4):517-536
One traditional method of estimating ore reserves is to allocate the arithmetic mean of local samples to each block or stope within the deposit. Thirty years ago, Krige showed that this method produced a “bias” in the estimates, in that high values were commonly overestimated and low values underestimated. This bias became known as the “regression effect” because it could usually be corrected by an empirical regression relationship derived from previously mined areas. This paper shows how the regression effect can be reconciled with the geostatistical method of kriging and how a simple regression line may be derived before any areas are mined out. The method is similar to kriging with known mean, but acknowledges that the overall mean of the deposit may not be known precisely. 相似文献
19.
将描述示踪剂为非保守、瞬时投源条件下的一维河流水团示踪试验的解析表达式进行2次适当的变形,分别得到一个二元和一元线性方程。对二元线性方程应用相关系数极值法,可以推导出计算河流横断面平均流速的公式;利用直线图解法或一元线性回归法能够计算出一元线性方程中的2个常数值,据此可以计算河流的纵向离散系数DL与示踪剂的一级反应速率常数k。与现有的数据分析方法相比较,该方法具有:(1)适用于示踪剂为非保守的情况;(2)利用一组野外试验数据可以同时计算河流离散系数DL、河流横断面平均流速V与示踪剂的一级反应速率k常数3个参数值;(3)全部数据分析过程可以程序化,由计算机完成等特点。 相似文献
20.
跨孔电阻率法是探测地下埋深较大的微细地质结构的一种行之有效的方法；利用跨孔法所测得的数据绘出的信息剖面图可以用来确定复杂情况下目的体位于孔区内外的位置。 相似文献