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Title: Geostatistical analysis of field hydraulic conductivity in compacted clay

Hydraulic conductivity (K) of fractured or porous materials is associated intimately with water flow and chemical transport. Basic concepts imply uniform flux through a homogeneous cross-sectional area. If flow were to occur only through part of the area, actual rates could be considerably different. Because laboratory values of K in compacted clays seldom agree with field estimates, questions arise as to what the true values of K are and how they should be estimated. Hydraulic conductivity values were measured on a 10 x 25 m elevated bridge-like platform. A constant water level was maintained for 1 yr over a 0.3-m thick layer of compacted clay, and inflow and outflow rates were monitored using 10 x 25 grids of 0.3-m diameter infiltration rings and outflow drains subtending approximately 1 x 1 m blocks of compacted clay. Variography of inflow and outflow data established relationships between cores and blocks of clay, respectively. Because distributions of outflow rates were much less and bore little resemblance to the distributions of break-through rates based on tracer studies, presence of macropores and preferential flow through the macropores was suspected. Subsequently, probability kriging was applied to reevaluate distribution of flux rates and possible location of macropores. Sitesmore » exceeding a threshold outflow of 100 x 10/sup -9/ m/s were classified as outliers and were assumed to probably contain a significant population of macropores. Different sampling schemes were examined. Variogram analysis of outflows with and without outliers suggested adequacy of sampling the site at 50 randomly chosen locations. Because of the potential contribution of macropores to pollutant transport and the practical necessity of extrapolating small plot values to larger areas, conditional simulations with and without outliers were carried out.« less
Authors:
;
Publication Date:
OSTI Identifier:
6413799
Report Number(s):
CONF-8704137-
Journal ID: CODEN: IMGJB
Resource Type:
Conference
Resource Relation:
Journal Name: J. Int. Assoc. Math. Geol.; (United States); Journal Volume: 20:4; Conference: MGUS '87, Redwood City, CA, USA, 13 Apr 1987
Research Org:
Dept. of Agriculture, University Park, PA (USA)
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; CLAYS; HYDRAULIC CONDUCTIVITY; GEOLOGIC DEPOSITS; STATISTICAL MODELS; POLLUTANTS; ENVIRONMENTAL TRANSPORT; TOXIC MATERIALS; COMPACTING; COMPUTERIZED SIMULATION; FILTRATION; FRACTURED RESERVOIRS; GROUND WATER; HYDROLOGY; KRIGING; LAND POLLUTION CONTROL; MAPPING; PERMEABILITY; POROSITY; PROBABILITY; SAMPLING; TRACER TECHNIQUES; WATER INFLUX; WATER POLLUTION CONTROL; CONTROL; HYDROGEN COMPOUNDS; ISOTOPE APPLICATIONS; MASS TRANSFER; MATERIALS; MATHEMATICAL MODELS; MATHEMATICS; OXYGEN COMPOUNDS; POLLUTION CONTROL; SEPARATION PROCESSES; SIMULATION; STATISTICS; WATER 510200* -- Environment, Terrestrial-- Chemicals Monitoring & Transport-- (-1989); 520200 -- Environment, Aquatic-- Chemicals Monitoring & Transport-- (-1989)