Guide to Permeability Indices
Guide to Permeability Indices
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渗透率指数指南
DOI：
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发表时间：
2006
期刊：
影响因子：
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通讯作者：
B. O. Dochartaigh
中科院分区：
文献类型：
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作者：
Lewis;C. Cheney;B. O. Dochartaigh
本报告介绍了如何准备BGS渗透率指数数据集，包括
指导如何使用它。它讨论了指数的含义以及数据如何
被衍生。它描述了用于对数字地质单元中的每个地质单元进行分类的方法。
英国地质图1：50 000比例（DiGMapGB-50），根据其
主要流动类型和可能的渗透率。
渗透性指数是对垂直运动估计速率的定性分类
水从地表通过非饱和带，即土地之间的地带
地表和地下水。渗透指数代码已分配给每个
已绘制的每个命名岩石单元的岩性（或岩性组合）
DiGMapGB-50。这已对所有四种存款进行了分类
DiGMapGB-50中的地层（人工地面、块体运动沉积物、浅层沉积物
和基岩）数据集。
渗透率指数由三部分代码组成，代表：
·主导流动机制
·最大渗透率
·最小渗透率
主导流动机制代码表明流体将如何从地面迁移
地表通过各岩石单元和岩性组合的非饱和带，
三种类型，晶间型、断裂型或混合型（晶间型和断裂型）。
第二和第三个代码（最大和最小渗透率）表示
各岩石单元和岩性在非饱和带中可能遇到的流速
组合.最大和最小渗透率使用了五个等级
代码：非常高、高、中等、低和非常低。最大和最小
渗透率值表示特定命名岩石单元的可能渗透率范围，
露头处及其正下方的岩性组合（而不是任何重要的
深度）。
最大渗透率代表了最快的潜在垂直迁移速率，
可能遇到的不饱和带。最小渗透率表示
最小的，在某些情况下更正常的，垂直运动的整体速度可能是
遇到的。当岩石单元内出现广泛变化的岩性组合时，
值反映了在渗透性最低的区域中可能遇到的可能移动速率
视野
编码是基于专家判断，但有以下假设：
·绘制的特定命名岩石单元的岩性成分，
DiGMapGB-50是正确的，无论这是否是预期的或正常的给定
阵
·岩性“串”中沉积物的顺序具有相关性;人们假设
占主导地位的岩性被放在第一位，其他岩性按其
产状，如砾石、砂、粉砂和粘土，与之不同，且更具渗透性，
粘土、淤泥、沙子和砾石。
·所有可能的地质层（人工，质量运动，表面）
沉积物和岩床）可能存在于某个地点的地图。然而，众所周知，如果地图陈旧，表面上的
存款并不总是记录在案。同样，人工沉积物的存在也是
不断变化，只记录调查时在场的人
This report describes how the BGS Permeability Index dataset has been prepared and includes
guidance on how it can be used. It discusses what the indices mean and how the data have
been derived. It describes the methodology used to classify each geological unit in the Digital
Geological Map of Great Britain at 1:50 000 scale (DiGMapGB-50) according to its
predominant flow type and probable permeability.
The Permeability Index is a qualitative classification of estimated rates of vertical movement
of water from the ground surface through the unsaturated zone, the zone between the land
surface and the water table. The Permeability Index codes have been allocated to every
lithology (or combination of lithologies) for each named rock unit that has been mapped in
DiGMapGB-50. This has been carried out for all four types of deposit shown as separate
layers in the DiGMapGB-50 (artificial ground, mass movement deposits, superficial deposits
and bedrock) dataset.
The Permeability Index consists of a three-part code representing:
• Predominant Flow Mechanism
• Maximum Permeability
• Minimum Permeability
The Predominant Flow Mechanism code indicates how fluid will migrate from the ground
surface through the unsaturated zone of each rock unit and lithology combination and has
three classes, intergranular, fracture or mixed (intergranular and fracture).
The second and third codes (Maximum and Minimum Permeability) indicate the range of
flow rates likely to be encountered in the unsaturated zone for each rock unit and lithology
combination. Five classes have been used for the Maximum and Minimum Permeability
codes: very high, high, moderate, low and very low. The Maximum and Minimum
Permeability values represent a likely permeability range for the specific named rock unit and
lithology combination at, and immediately below, outcrop (rather than at any significant
depth).
The Maximum Permeability represents the fastest potential vertical rate of migration through
the unsaturated zone likely to be encountered. The Minimum Permeability represents the
minimum, and in some cases more normal, bulk rate of vertical movement likely to be
encountered. Where a widely variable lithology combination occurs within a rock unit this
value reflects the probable movement rate likely to be encountered in the least permeable
horizons
The coding was based on expert judgement but with the following assumptions:
• the lithological component(s) for a particular named rock unit mapped within
DiGMapGB-50 was correct, whether or not this was expected or normal for the given
formation.
• the order of the deposits in a lithological ‘string’ was of relevance; it was assumed that
the dominant lithology was placed first, with the other lithologies in order of their
occurrence, e.g. gravel, sand, silt and clay was different to, and more permeable than,
clay, silt, sand and gravel.
• that all of the possible geological layers (artificial, mass movement, superficial
deposits and bedrock) that could be present at a site were mapped. It is, however, known that this is not the case where the maps are old and the presence of superficial
deposits was not always recorded. Similarly the presence of artificial deposits is
constantly changing and only those present at the time of survey were recorded