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Author: JP. Stewart Publisher: ISBN: Category : Compacted soils Languages : en Pages : 10
Book Description
This paper describes the use of single ring infiltrometers for evaluating the hydraulic conductivity of compacted soil liners. Procedures are presented for installation and monitoring of infiltrometers in the field. Results of hydraulic conductivity estimated from infiltrometer tests on six laboratory model liners are presented and compared with the results of conventional laboratory tests. In addition, the distribution of soil saturation after prolonged infiltration testing showed that the permeant tended to follow preferred paths and did not generally advance as a uniform front as commonly assumed.
Author: JP. Stewart Publisher: ISBN: Category : Compacted soils Languages : en Pages : 10
Book Description
This paper describes the use of single ring infiltrometers for evaluating the hydraulic conductivity of compacted soil liners. Procedures are presented for installation and monitoring of infiltrometers in the field. Results of hydraulic conductivity estimated from infiltrometer tests on six laboratory model liners are presented and compared with the results of conventional laboratory tests. In addition, the distribution of soil saturation after prolonged infiltration testing showed that the permeant tended to follow preferred paths and did not generally advance as a uniform front as commonly assumed.
Author: D. Cazaux Publisher: ISBN: Category : Clay liner Languages : en Pages : 25
Book Description
Field infiltration tests are commonly used to assess the hydraulic conductivity of low permeability materials such as natural clay barriers and compacted clay liners. The soils used for compacted clay liners are always partially saturated and require very long testing times to reach steady-state flow conditions. Consequently, because they are less time consuming, laboratory tests are usually preferred for construction quality control. Nevertheless, it is well-known that field tests are more representative of the clay liner because of the scale effect. This is why, since the 1980s, the main issues associated with field procedures have been studied and several methods proposed for testing low-permeability materials within short time periods. The proposed methods are based on early-time flow analysis in unsaturated conditions and have been applied to various compacted soils under field and laboratory conditions. To evaluate these methods, we carried out a comprehensive testing program using a hydraulic field infiltrometer method (sealed single-ring infiltrometer) and a laboratory rigid-wall permeameter method that reproduces surface field test conditions. The laboratory tests were continued until saturated hydraulic conductivity was obtained so that this value could be compared against the hydraulic conductivity estimated from early-time analysis on the same specimen. The obtained results show the influence of (a) the initial moisture content, (b) the sorptivity and hydraulic head on the early-time infiltration rate, and (c) the final estimated hydraulic conductivity. A comparison of analysis methods shows the limitations of some and tries to explain the reasons for such inadequacies in the description of early-time unsaturated flows. Nevertheless, the conclusions of our study show that conventional early-time analyses give a good estimation of saturated hydraulic conductivity within a short time period compatible with construction quality-control procedures.
Author: DE. Daniel Publisher: ISBN: Category : Case history Languages : en Pages : 12
Book Description
A method of measuring the hydraulic conductivity of compacted clay liners in the field using single-ring infiltrometers has been developed. It is assumed that the ring has a diameter that is no less than the thickness of the clay liner and that the clay liner is underlain by a freely draining material with negligible suction. Finite element analyses were performed to develop correction factors that account for horizontal seepage for cases in which the ring infiltrometer is partially embedded into the liner. The correction factors were developed for a range in diameter of the ring and for ratios of horizontal to vertical hydraulic conductivity of 1, 10, and 100. Laboratory experiments were conducted to verify the results of finite-element analyses, but the laboratory results showed considerable scatter and were successful only in demonstrating that the finite-element results show the proper trends. Finally, the test method was tried in the field on a full-sized clay liner in which the actual hydraulic conductivity of the entire liner could be calculated from the known rate of leakage. The hydraulic conductivity measured in the infiltration test agreed almost perfectly with the computed overall hydraulic conductivity of the entire liner. It is concluded that the single-ring infiltration test can be used to measure the hydraulic conductivity of clay liners, although it is difficult to measure hydraulic conductivities that are substantially lower than 1 x 10-7 cm/s. In addition, the field tests may take several weeks to complete.
Author: JO. Sai Publisher: ISBN: Category : Collection lysimeter Languages : en Pages : 11
Book Description
Field hydraulic conductivity tests are required to determine the in situ hydraulic conductivity of compacted clay soils used in the liners for hazardous waste management facilities. The test must be capable of measuring hydraulic conductivities of 1 × 10-9 m/s or less, and the values obtained must be representative of the overall soil liner. Few of the methods available are capable of both measuring low hydraulic conductivities and obtaining representative values. Test methods which meet these requirements include large single-ring infiltrometers, sealed double-ring infiltrometers, and collection lysimeters. The main drawback in the use of collection lysimeters is that it can take months to obtain steady-state hydraulic conductivity values. Sealed double-ring infiltrometers are practical to use and have the advantage of few ambiguities in the experimental procedures, few possibilities for yielding false low values, and are large enough to yield results representing the overall liner characteristics.
Author: GP. Boutwell Publisher: ISBN: Category : Borehole test Languages : en Pages : 40
Book Description
The most important geotcchnical parameter for soil liners or caps for waste facilities is hydraulic conductivity. In typical practice, the vertical conductivity normally governs the barrier effect. Regulatory agencies are increasingly requiring in situ tests in addition to laboratory- tests to verify hydraulic conductivity. Many different in situ tests have been proposed; seven have some usage. These are discussed with reference to their suitability for liner/cap evaluation. Of these, the Sealed, Double-Ring Infiltrometer and the Two-Stage Borehole test have received widest acceptance and use; each has already been used on 50 to 100 projects. Both tests are examined in detail, including theoretical basis, field procedures, and data reduction. Reasons for their preference over other methods are discussed.
Author: JP. Stewart
Author: JP. Stewart
Author: David Edwin Daniel
Author: D. Cazaux
Author: Joseph O. Sai
Author: DE. Daniel
Author: Arnold Ivan Johnson
Author: JO. Sai
Author: GP. Boutwell
Author: A. S. Rogowski
Author: Eric Scott Steinhauser