A.I. Johnson

Geostatistics for environmental and geotechnical applications

This conference was held January 26--27, 1995 in Phoenix, Arizona. The purpose of this conference was to provide a multidisciplinary forum for exchange of state-of-the-art information on the technology of geostatistics and its applicability for environmental studies, especially site characterization. Individual papers have been processed separately for inclusion in the appropriate data bases.

Specific yield - laboratory experiments showing the effect of time on column drainage

The increasing use of ground water from many major aquifers in the United States has required a more thorough understanding of gravity drainage, or specific yield. This report describes one phase of specific yield research by the U.S. Geological Surveys Hydrologic Laboratory in cooperation with the California Department of Water Resources. An earlier phase of the research concentrated on the final distribution of moisture retained after drainage of saturated columns of porous media. This report presents the phase that concentrated on the distribution of moisture retained in similar columns after drainage for various periods of time. Five columns, about 4 cm in diameter by 170 cm long, were packed with homogenous sand of very fine, medium, and coarse sizes, and one column was packed with alternating layers of coarse and medium sand. The very fine materials were more uniform in size range than were the medium materials. As the saturated columns drained, tensiometers installed throughout the length recorded changes in moisture tension. The relation of tension to moisture content, determined for each of the materials, was then used to convert the tension readings to moisture content. Data were then available on the distribution of retained moisture for different periods of drainage from 1 to 148 hours. Data also are presented on the final distribution of moisture content by weight and volume and on the degree of saturation. The final zone of capillary saturation was approximately 12 cm for coarse sand, 13 cm for medium sand, and 52 cm for very fine sand. The data showed these zones were 92 to 100 percent saturated. Most of the outflow from the columns occurred in the earlier hours of drainage 90 percent in 1 hour for the coarse materials, 50 percent for the medium, and 60 percent for the very fine. Although the largest percentage of the specific yield was reached during the early hours of drainage, this study amply demonstrates that a very long time would be required to reach drainage equilibrium. In the layered columns the middle (medium sand) layer functioned as a hanging water column accelerating the drainage of the overlying coarse-sand layer. After the middle layer started to drain, the moisture distribution as retained in all three layers showed trends similar to that obtained when the same materials were tested in homogenous columns. Bl B2 HYDROLOGIC PROPERTIES OF EARTH MATERIALS INTRODUCTION The increasing use of ground water from many major aquifers in the United States has required a more thorough understanding of gravity drainage, or specific yield. Recognizing this need, the California Department of Water Resources and the U.S. Geological Survey began cooperative studies to identify and determine accurately the parameters that are related to and affect specific yield and to perfect more accurate and reliable techniques for laboratory and field determinations of specific yield. The specific yield of a rock or soil has been defined by Meinzer (1923, p. 28) as the ratio of (1) the volume of water which, after being saturated, the rock or soil will yield by gravity to (2) its own volume. Specific retention represents the water retained against gravity drainage and when added to the specific yield will equal the total interconnected porosity of the rock and soil. Both specific yield and specific retention are usually expressed as a percentage. SCOPE OF RESEARCH As the first phase of this study, an annotated bibliography on specific yield and related properties was prepared and released as an open-file report (Johnson, Morris, and Prill, 1961). To the second phase of the research project namely, to investigate laboratory methods for determining specific yield a detailed study was made of the centrifuge-moisture-equivalent and column-drainage methods (Johnson, Prill, and Morris, 1963). Among other results this -study showed that the effect of temperature on the centrifuge moisture equivalent was of sufficient magnitude to warrant establishment of a standard temperature for the test (Prill and Johnson, 1959). Also a comparison was made between the centrifuge and the columndrainage techniques (Prill, 1961), and a standard method was developed for packing columns or porous media (Morris and Kulp, 1961). The column-drainage study concentrated on the final distribution of water retained after drainage of saturated columns of porous media. Another step in the laboratory phases of the research has been a detailed study of moisture tension and centrifuge scale modeling, and reports on these investigations are in preparation. A third and final phase of the research project involves the detailed study of gravity drainage (specific yield) at a number of field sites in California and the evaluation of, and eventual correlation between, laboratory and field methods. The field phases also include detailed studies of the nuclear moisture meter as applied to the determination of changes in moisture content as drainage progresses. SPECIFIC YIELD EFFECT OF TIME ON COLUMN DRAINAGE B3 PURPOSE AND SCOPE OF THIS REPORT This report, which is the second report of the laboratory phase of the research, presents the results of a study of laboratory drainage of columns continued beyond that summarized in the earlier report on column drainage (Johnson, Prill, and Morris, 1963). The scope of this report concentrates on the distribution of water retained in columns of three different sand-size materials after drainage for various periods of time up to approximately 6 days. Both layered and nonlayered conditions are included in this study. All laboratory work was done in the Hydrologic Laboratory, U.S. Geological Survey, Denver, Colo. The report was prepared under the general supervision of H. D. Wilson and Fred Kunkel, successive district engineer and district geologist of the Ground Water Branch, U.S. Geological Survey, Sacramento, Calif., and under the direct supervision of A. I. Johnson, chief of the Hydrologic Laboratory. The following personnel of the Hydrologic Laboratory assisted with the various laboratory experiments: R. P. Moston, A. H. Ludwig, W. K. Kulp,andN.N.Yabe. ACKNOWLEDGMENTS Valuable technical advice was provided by J. F. Poland, research geologist, U.S. Geological Survey in Sacramento, Calif., and V. C. Fishel, district engineer, Ground Water Branch, Lawrence, Kans., who provided useful ideas on the construction of drainage columns. Many individuals at university and private research laboratories contributed to this report by giving advice and furnishing information relative to the problem. Especially valuable assistance was provided by Mr. R. T. Bean, supervising engineering geologist, and others on the staff of the California Department of Water Resources, Sacramento, Calif.; also Prof. A. T. Corey, Colorado State University, Fort Collins, Colo. REVIEW OF PREVIOUS WORK Most methods for obtaining specific yield first require the determination of specific retention. Methods using the drainage of saturated columns of porous media almost universally rely upon the determination of retained moisture. As indicated earlier, the specific yield then may be found by subtracting the specific retention from the total porosity. During the past 70 years the drainage of columns of porous media has been the subject of many research studies, but very few of these studies have determined the moisture retained in the media after different periods of drainage. A few of these studies are summarized below. B4 HYDROLOGIC PROPERTIES OF EARTH MATERIALS Hazen (1892) presented significant results of tests of the waterretaining and water-yielding capacities of eight different sands used for filtering sewage. These tests related specific yield and specific retention to the effective size and uniformity coefficient as obtained from particle-size analyses. King (1899) packed five sorted sands of different particle sizes in columns 8 feet in length and 5 inches in diameter. The materials were slowly saturated from below and then drained for 2i/£ years. Outflow readings were taken during the period of drainage and the moisture content was then determined at the end of the drainage period. The apparatus was designed to prevent moisture loss by evaporation. The results of Kings tests showed some discrepancy between the porosity and the total water content and gave lower values for specific retention than Hazens tests, especially for the coarser samples. Lebedeff (1927) drained tubes, 4 to 5 cm in diameter and 1 to 3 m in length, filled with sandy soils. A head of water of 2 cm was used to saturate the soil. After drainage, the water retained in 10-cm segments of the column was determined gravimetrically and showed that a uniform moisture content prevailed in the upper part of the columns. The author also saturated 6 pairs of sand tubes 10, 20, 30, 40, 50 and 100 cm high. One tube of each pair was immediately sampled for moisture content. The other tube was allowed to drain until drainage ceased and then sampled to determine the moisture-content distribution throughout the tube. In the longest column, after drainage for 3i£ days, the moisture content became constant at a height of about 40 cm. Changing the height of column did not change this distribution; it gave only a longer section of column with constant moisture content. Saturated columns with layers of sand and loess also were drained. More water was retained in the fine-textured material when underlain by coarse-textured material than when underlain by material of the same type. Stearns, Robinson, and Taylor (1930) collected undisturbed columns of soil in metal cylinders of 18-inch diameter and 36-inch length in the Mokelumne area of California. A bottom was soldered on each cylinder after it was collected, and small-diameter observation wells were installed in each soil column. A water table was established at a high stage in the column. Measured volumes of water were then withdrawn and adde

Remote sensing and GIS for site characterization : applications and standards

This conference was held January 27--28, 1994 in San Francisco, California. The purpose of this conference was to provide a multidisciplinary forum for exchange of state-of-the-art information on recent techniques and applications of remote sensing and geographic information systems for site characterization. Individual papers have been processed separately for inclusion in the appropriate data bases.

Some factors contributing to decreased well efficiency during fluid injection

Many factors affecting fluid injection through wells involve clogging of the well and injection zone. Extensive field research carried out in the Grand Prairie Region of Arkansas, supported by special laboratory testing, involved the injection of surface waters into native waters of the local aquifers. The principal causes of clogging were found to be gas binding or air entrainment in the injection zone, suspended particles in the injection fluid, bacterial contamination of the injection zone by the injection fluid and subsequent clogging by bacterial growths, mechanical jamming of the injection zone and gravel pack around the well caused by particle rearrangement when the direction of fluid movement into and through the injection zone is reversed, and chemical reactions between the injection fluid and the native groundwater or the particles in the injection zone. The results indicated that the efficiency of the injection well could be reduced by as much as 50 percent by such factors and that treated injection fluid therefore would be advisable. Other problems in operating an injection well included the effects of injecting fluid of a different temperature and viscosity and the interpretation of fluid-level changes in the injection zone during the injection tests because most clogging was found to take place within a few feet of the injection well. Laboratory tests were used successfully to make preliminary estimates of the hydraulic characteristics of the injection zone prior to field testing of those properties. Laboratory experiments also showed that a permeability reduction of as much as 45 percent resulted from compaction of the gravel pack caused by surging action during well development and from the pumping and injection tests.

VIBRATORY COMPACTION IN THE LABORATORY OF GRANULAR MATERIALS IN LONG COLUMNS

FOR A LABORATORY STUDY OF THE DRAINAGE OF LONG COLUMNS OF POROUS MEDIA, A MAXIMUM DENSITY, UNIFORMLY DISTRIBUTED THROUGHOUT THE COLUMN, WAS REQUIRED. RESEARCH RESULTED IN THE DEVELOPMENT OF A MECHANICAL TECHNIQUE FOR THE PACKING OF DRAINAGE COLUMNS, AS MUCH AS 60 IN. LONG, WITH GLASS BEADS AND NATURAL SANDS OF VARIOUS PARTICLE SIZES. A VIBRATORY PACKER USED TO PACK THESE COLUMNS, WHICH ARE 1 TO 8 IN. IN DIAMETER, PROVIDED GOOD REPRODUCIBILITY OF DRY UNIT WEIGHT AND POROSITY BETWEEN DUPLICATE COLUMNS AS WELL AS A VERTICAL UNIFORMITY OF THESE PROPERTIES WITHIN THE SAME OR DUPLICATE COLUMNS. TO DEVELOP THE STANDARD METHOD OF PACKING COLUMNS, A STUDY WAS MADE OF THE EFFECTS OF TIME, AMPLITUDE, AND SURCHARGE WEIGHT ON THE UNIFORMITY AND REPRODUCIBILITY OF RESULTS. THE TECHNIQUE WAS STANDARDIZED AT A PACKING PERIOD OF 10 S AND A VIBRATORY AMPLITUDE OF 0.09 CM. /AUTHOR/

Fourth International Symposium on Land Subsidence

Subsidence, or land-surface sinking, is a phenomenon that occurs in many parts of the world. Subsidence results from the heavy withdrawal of groundwater, geothermal fluids, oil, and gas; the extraction of coal, sulphur, and other solids through mining; the hydro-compaction of sediments; oxidation and shrinkage of organic deposits; the catastrophic development of sinkholes in karst terrain; and other phenomena. Over 150 areas of contemporary subsidence are known, some at rates of 10 m in countries such as Mexico, Japan, and the United States, for example. More areas of subsidence are likely to develop in the next few decades due to the accelerated exploitation of natural resources necessary to meet the demands of increasing population and industrial development in many countries.

Use of Ultrasonic Energy for Disaggregation of Soil Samples

A method for faster and more nearly complete dispersion of soil samples for particle size analysis now appears feasible. Using agitation by ultrasonic energy, disaggregation and dispersion appeared to be as thorough in 10min as by mechanical preparation through a sieve with 0.0625-mm openings. The ultrasonic agitation appeared to cause no deleterious effect on the primary particle sizes. The time and effort required to obtain high quality dispersion is much less for ultrasonic than for mechanical techniques, especially for heavy soils.