Heterogeneity detection in an experimental clay liner

2003 ◽  
Vol 40 (1) ◽  
pp. 149-160 ◽  
Author(s):  
Dominique Guyonnet ◽  
Jean-Christophe Gourry ◽  
Lucien Bertrand ◽  
Nadia Amraoui
Keyword(s):  
Hydraulic Conductivity ◽  
Geophysical Methods ◽  
The Other ◽  
Dipole Mode ◽  
Compacted Clay ◽  
Clay Liners ◽  
Hydraulic Test ◽  
Clay Liner ◽  
Other Hand

In situ hydraulic tests to characterize the field hydraulic conductivity of clay liners used in landfill applications are often positioned randomly. Yet it is well known that the field performance of low permeability clay liners is generally controlled by heterogeneities that may provide preferential pathways for flow. In this paper, an experimental clay liner is investigated in which heterogeneities were incorporated in a controlled fashion. Heterogeneities were embedded within a compacted clay liner at different locations in the plane and at different depths. Heterogeneities of composition were installed by excavating compacted clay at specific locations and replacing it with a more permeable material. Heterogeneities of compaction were introduced by loosely backfilling the clay into the excavations. Two geophysical methods, ground penetrating radar (GPR) and the EM-38 electromagnetic method, were used to examine whether anomalies detected by geophysics were or were not correlated with the precise locations of the heterogeneities. Hydraulic tests were used to characterize the permeability of the intact clay on the one hand and of the heterogeneities on the other hand. Three different in situ hydraulic test methods were used: a pulse test performed in a hand-augered borehole, a sealed single ring infiltrometer test, and a large scale infiltration test (4 m2) that uses a color tracer to detect possible preferential flowpaths. The GPR showed no significant correlation with heterogeneity locations, nor did the EM-38 method when used in the vertical dipole mode. The EM-38 method used in the horizontal dipole mode, showed significant correlation with heterogeneities when they were apparent at the surface. On the other hand, the method did not clearly detect heterogeneities located at depth. There was consistency between the values of hydraulic conductivity obtained from the different hydraulic field and laboratory tests. "Intact" clay hydraulic conductivities were found to lie between 10–10 and 4 × 10–9 m/s, while the hydraulic conductivity of the heterogeneities of composition was approximately 10–7 m/s. The results of this experiment suggest that the EM-38 method may be useful to optimize hydraulic test locations when characterizing clay liners for landfill applications.Key words: clay liner, hydraulic conductivity, heterogeneity.

Statistical analyses of compacted clay landfill liners. Part 1: model development

1994 ◽  
Vol 21 (5) ◽  
pp. 872-882 ◽  
Author(s):  
Scott B. Donald ◽  
Edward A. McBean
Keyword(s):  
Hydraulic Conductivity ◽  
Geometric Mean ◽  
Model Development ◽  
Statistical Analyses ◽  
Compacted Clay ◽  
Clay Liners ◽  
Landfill Liner ◽  
Landfill Liners ◽  
Clay Liner ◽  
Spatial Correlation Structure

The acceptance of compacted clay liners, from a management point of view, has been a source of major concern because of the uncertainty associated with the hydrogeologic properties of the clay. By examining the flux of leachate through the compacted clay liner of a typical engineered landfill, where the hydraulic conductivity of the clay is represented by a stochastic process, an acceptance protocol suitable for compacted clay landfill liners is derived. Determination of the equivalent hydraulic conductivity of the clay liner is accomplished by comparing the flux of leachate through a homogeneous representation of the clay with the flux obtained by Monte Carlo analyses. Acceptance criteria are subsequently developed based on a statistical technique which calculates the confidence limits about a percentile of a probability distribution as well as about the mean of the distribution. For the landfill configuration simulated, the results indicate that the hydraulic conductivity of a compacted clay landfill liner follows a lognormal distribution and exhibits virtually no spatial correlation structure. In addition, for liners exhibiting a geometric mean conductivity of 10−7 cm/s and a standard deviation of 0.3, the geometric mean value is a conservative estimate of the hydraulic conductivity of the clay, provided the liner is constructed in a series of four 150 mm lifts. Key words: clay liners, hydraulic conductivity, statistical analyses, latin hypercube, equivalent hydraulic conductivity.

scholarly journals Hydraulic and Swell–Shrink Characteristics of Clay and Recycled Zeolite Mixtures for Liner Construction in Sustainable Waste Landfill

2021 ◽  
Vol 13 (13) ◽  
pp. 7301
Author(s):  
Marcin K. Widomski ◽  
Anna Musz-Pomorska ◽  
Wojciech Franus
Keyword(s):  
Hydraulic Conductivity ◽  
Exchange Capacity ◽  
Saturated Hydraulic Conductivity ◽  
Clay Soils ◽  
Compacted Clay ◽  
Clay Liner ◽  
Compacted Clay Liner ◽  
Drying And Rewetting ◽  
Swelling Characteristics ◽  
Shrinkage And Swelling

This paper presents research considering hydraulic as well as swelling and shrinkage characteristics of potential recycled fine particle materials for compacted clay liner for sustainable landfills. Five locally available clay soils mixed with 10% (by mass) of NaP1 recycled zeolite were tested. The performed analysis was based on determined plasticity, cation exchange capacity, coefficient of saturated hydraulic conductivity after compaction, several shrinkage and swelling characteristics as well as, finally, saturated hydraulic conductivity after three cycles of drying and rewetting of tested specimens and the reference samples. The obtained results showed that addition of zeolite to clay soils allowed reduction in their saturated hydraulic conductivity to meet the required threshold (≤1 × 10−9 m/s) of sealing capabilities for compacted clay liner. On the other hand, an increase in plasticity, swelling, and in several cases in shrinkage, of the clay–zeolite mixture was observed. Finally, none of the tested mixtures was able to sustain its sealing capabilities after three cycles of drying and rewetting. Thus, the studied clayey soils mixed with sustainable recycled zeolite were assessed as promising materials for compacted liner construction. However, the liner should be operated carefully to avoid extensive dissication and cracking.

Did Ground Cover Change Over Geologic Time?

2000 ◽  
Vol 6 ◽  
pp. 171-182 ◽  
Author(s):  
Ben A. LePage ◽  
Hermann W. Pfefferkorn
Keyword(s):  
Fossil Record ◽  
Ground Cover ◽  
The Other ◽  
Detailed Account ◽  
Geologic Time ◽  
The Past ◽  
Other Hand ◽  
Plant Fossil

When one hears the term “ground cover,” one immediately thinks of “grasses.” This perception is so deep-seated that paleobotanists even have been overheard to proclaim that “there was no ground cover before grasses.” Today grasses are so predominant in many environments that this perception is perpetuated easily. On the other hand, it is difficult to imagine the absence or lack of ground cover prior to the mid-Tertiary. We tested the hypothesis that different forms of ground cover existed in the past against examples from the Recent and the fossil record (Table 1). The Recent data were obtained from a large number of sources including those in the ecological, horticultural, and microbiological literature. Other data were derived from our knowledge of Precambrian life, sedimentology and paleosols, and the plant fossil record, especially in situ floras and fossil “monocultures.” Some of the data are original observations, but many others are from the literature. A detailed account of these results will be presented elsewhere (Pfefferkorn and LePage, in preparation).

II.—On upright Equisetites Stems in the Oolitic Sandstone in Yorkshire

1913 ◽  
Vol 10 (1) ◽  
pp. 3-7 ◽  
Author(s):  
T. G. Halle
Keyword(s):  
Lower Surface ◽  
Upright Position ◽  
The Other ◽  
Mineral Matter ◽  
Vertical Position ◽  
Other Hand ◽  
Mode Of Occurrence ◽  
Coal Measures

Stems of Ecquisetites columnaris (Brong.) have long been known to occur in a vertical position in the sandstones of the Inferior Oolite on the Yorkshire coast. This mode of occurrence has commonly been held as proving that the stems are preserved in the position in which they once grew, having been buried in situ beneath the layers of sand that accumulated on the spot. On the other hand, it has been argued that the upright position need not be primary; it might be as readily explained if the stems are regarded as drifted and secondarily deposited on the spots where they are now found. It is well known and has been pointed out, particularly in the discussions of the upright stems in the Coal-measures, that a drifting tree often has a tendency to sink in a vertical position, the root-end being heavier because of adhering mineral matter or from some other reason. Phillips describes, in his Geology of the Yorkshire Coast, a locality at High Whitby where upright stems of Equisetites columnaris occur in the sandstone. He continues: “They … are broken off or imperfect above, and seldom reach to the upper surface of the bed; they are also broken off below, but commonly pass to the lower surface; and some of the lower joints nearest the roots are found in the subjacent bed of shale.”

Temperature, strain rates, and rheology: the key parameters controling strength variations in the Australian lithosphere

2020 ◽  
Author(s):  
Magdala Tesauro ◽  
Mikhail Kaban ◽  
Alexey Petrunin ◽  
Alan Aitken
Keyword(s):  
Heat Flow ◽  
Seismic Tomography ◽  
Seismic Velocity ◽  
Gravity Data ◽  
Geophysical Methods ◽  
The Other ◽  
Crust And Upper Mantle ◽  
Large Variability ◽  
Other Hand ◽  
Australian Plate

<p>The Australian plate is composed of tectonic features showing progression of the age from dominantly Phanerozoic in the east, Proterozoic in the centre, and Archean in the west. These tectonic structures have been investigated in the last three decades using a variety of geophysical methods, but it is still a matter of debates of how temperature and strength are distributed within the lithosphere. We construct a thermal crustal model assuming steady state variations and using surface heat flow data, provided by regional and global database, and heat generation values, calculated from existing empirical relations with seismic velocity variations, which are provided by AusREM seismic tomography model. The lowest crustal temperatures are observed in the eastern part of the WAC and the Officer basin, while Central and South Australia are regions with anomalously elevated heat flow values and temperatures caused by high heat production in the crustal rocks. On the other hand, the mantle temperatures, estimated in a previous study, applying a joint interpretation of the seismic tomography and gravity data, show that the Precambrian West and North Australian Craton (WAC and NAC) are characterized by thick and relatively cold lithosphere that has depleted composition (Mg# > 90). The depletion is stronger in the older WAC than the younger NAC. Substantially hotter and less dense lithosphere is seen fringing the eastern and southeastern margin of the continent. Both crustal and mantle thermal models are used as input for the lithospheric strength calculation. Another input parameter is the crustal rheology, which has been determined based on the seismic velocity distribution, assuming that low (high) velocities reflect more sialic (mafic) compositions and thus weaker (stiffer) rheologies. Furthermore, we use strain rate values obtained from a global mantle flow model constrained by seismic and gravity data. The combination of the values of the different parameters produce a large variability of the rigidity of the plate within the cratonic areas, reflecting the long tectonic history of the Australian plate. The sharp lateral strength variations are coincident with intraplate earthquakes location. The strength variations in the crust and upper mantle is also not uniformly distributed: In the Archean WAC most of the strength is concentrated in the mantle, while the Proterozoic Officer basin shows the largest values of the crustal strength. On the other hand, the younger eastern terranes are uniformly weak, due to the high temperatures.</p>

GEOPHYSICAL ACTIVITY IN 1962

Geophysics ◽  
1963 ◽  
Vol 28 (6) ◽  
pp. 1049-1071
Author(s):  
Neal J. Smith
Keyword(s):  
Geophysical Methods ◽  
The Other ◽  
Free World ◽  
Geophysical Exploration ◽  
Other Hand ◽  
Ground Magnetic

Petroleum geophysical exploration in the Free World, consisting of seismic, gravity, ground magnetic, and other nonairborne geophysical methods, declined 10.0 percent over 1961. This is the sharpest in the continual series of declines that began in 1957 and amounts to a loss of 1,008 crew‐months; it is 32 percent down from the peak year of 1956. Airborne magnetometer activity, on the other hand, rose from 347,841 line‐miles in 1961 to 433,473, an increase of 25 percent.

Freeze–thaw cycling concurrent with cation exchange and the hydraulic conductivity of geosynthetic clay liners

2014 ◽  
Vol 51 (6) ◽  
pp. 591-598 ◽  
Author(s):  
Gregory P. Makusa ◽  
Sabrina L. Bradshaw ◽  
Erin Berns ◽  
Craig H. Benson ◽  
Sven Knutsson
Keyword(s):  
Hydraulic Conductivity ◽  
Cation Exchange ◽  
Pore Water ◽  
Geosynthetic Clay Liners ◽  
Clay Liners ◽  
Chemical Changes ◽  
Clay Liner ◽  
Freeze Thaw ◽  
Exchange Complex ◽  
Before And After

A study was conducted to assess the effect of cation exchange concurrent with freeze–thaw cycling on the hydraulic conductivity of a geosynthetic clay liner (GCL). GCLs were prehydrated by contact with silica flour moistened with synthetic subgrade pore water and subsequently permeated with a solution representing the pore water in the cover soil over a tailings facility. Control tests were conducted using the same procedure, except deionized (DI) water was used as the permeant liquid to preclude cation exchange from the permeant liquid. The GCLs were subjected to 1, 3, 5, 15, and 20 freeze–thaw cycles, and the hydraulic conductivity and exchange complex were determined before and after freeze–thaw cycling to assess chemical changes that occurred during freezing, thawing, and permeation. GCLs undergoing freeze–thaw cycling experienced little to no cation exchange through 5 freeze–thaw cycles. After 20 freeze–thaw cycles, 50% of the sodium (Na+) initially in the exchange complex was replaced by calcium (Ca2+). Dissolution of calcite within the bentonite is a likely source of the Ca2+. Hydraulic conductivity of the GCLs exposed to freeze–thaw cycling was lower than the hydraulic conductivity of a new GCL permeated with DI water (<2.2 × 10−11 m/s). A small increase in hydraulic conductivity (∼2.3 times), which may have been caused by cation exchange, occurred between 15 and 20 freeze–thaw cycles, but the hydraulic conductivity remained below the hydraulic conductivity of a new GCL unexposed to freeze–thaw cycling and permeated with DI water.

Remarks on the design of clay liners used in lagoons as hydraulic barriers

1992 ◽  
Vol 29 (3) ◽  
pp. 512-515 ◽  
Author(s):  
S. Leroueil ◽  
J. P. Le Bihan ◽  
R. Bouchard
Keyword(s):  
Hydraulic Conductivity ◽  
Key Words ◽  
Water Content ◽  
Compacted Clay ◽  
Plastic Limit ◽  
Clay Liners ◽  
Natural Soils ◽  
Compacted Clay Liner ◽  
Compacted Clays ◽  
Hydraulic Barriers

Considering that (i) the hydraulic conductivity of compacted clays is smaller on the wet side of optimum; (ii) the plastic limit is the water content below which the soil develops fissures under small stresses; (iii) the plastic limit and the optimum standard Proctor water content are similar for many natural soils; and (iv) the strength of compacted clays, thus the limit of trafficability, is a function of (w – wopt)/Ip, relevant conditions for the design of clay liners and the evaluation of their hydraulic conductivity are proposed. Key words : compacted clay, liner, hydraulic conductivity, strength, design.

scholarly journals Effect of Fluid Chemistry on the Consolidation and Hydraulic Conductivity of Sand-Clay Liners

2021 ◽  
Vol 13 (20) ◽  
pp. 11213
Author(s):  
Muawia Dafalla
Keyword(s):  
Hydraulic Conductivity ◽  
Saline Water ◽  
Dry Weight ◽  
Coastal Zones ◽  
Clay Liners ◽  
Clay Liner ◽  
Fine Grained ◽  
Fluid Media ◽  
Liner Surface ◽  
Inorganic Chemical

The clay swelling potential of sand-clay liners exposed to saline water or specific chemicals can influence their hydraulic conductivity and other consolidation properties. The effect of saline water or chemicals on the sand-clay liners was thus studied and evaluated. The consolidation characteristics of the sand-clay liner can be different when tested under different fluid media. Bentonite and cement grouts are chemicals that have a significant effect on the sand-clay liners. Cement and bentonite can be used to seal off the openings within the liner to repair a defect or a malfunction. In this study, Al-Qatif clay was used to form a sand-clay liner when mixed with fine-grained sand (clay is 20% by dry weight). Soil samples extracted from this liner were exposed to inorganic chemical solutions. NaCl and CaCl2 solutions with concentration ranges of 0.1%, 0.5%, and 1.5% were used. Acidic water with pH values of 4, 5, and 6 was similarly used as fluid media. The effects of NaCl, CaCl2, and water with different acidity on the consolidation characteristics and hydraulic conductivity were obtained and compared to those of the distilled water. The effects of grout materials containing bentonite (1%, 2%, and 3% by weight) and cement (2.5%, 5%, and 7.5% by weight) were also investigated. The addition of bentonite grout to the liner surface was found to improve its hydraulic conductivity. The cement effect on the compressibility was found to be very significant. The findings of this study can serve as a guide for selecting parameters in the design and assessment of sand-clay liners in semi-arid regions and coastal zones.

scholarly journals The Contribution of Geophysics to the Knowledge of the Hidden Archaeological Heritage of Montenegro

Geosciences ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 187 ◽  
Author(s):  
Marilena Cozzolino ◽  
Mile Baković ◽  
Nikola Borovinić ◽  
Giorgia Galli ◽  
Vincenzo Gentile ◽  
...  
Keyword(s):  
Cultural Heritage ◽  
Geophysical Methods ◽  
The Other ◽  
Buried Structures ◽  
Archaeological Heritage ◽  
Other Hand ◽  
The Rich ◽  
Non Destructive

Montenegro is a land of great history which needs attention and care for a deeper knowledge and its making at the disposal of new generations. It is still a territory to be discovered, studied, and disclosed. It is important to understand how much hidden heritage there is still in this area to explore and exploit, but on the other hand, how much known heritage exists to protect and monitor, preventing its destruction and loss. In this context, Montenegro is heavily investing in the management of cultural heritage through initiatives for identification, protection, preservation, enhancement and fruition of them. In the frame of the knowledge, the use of non-destructive geophysical methods can be helpful for a cognitive investigation immediately in the bud of any archaeological verification project, safeguarded through preventive archaeology operations and the exploration of large areas within archaeological parks. In this paper, the results of geophysical prospections at the Hellenistic-Illyrian site of Mjace, the roman towns of Doclea and Municipium S, the medieval city of Svač, and the Stećci medieval tombstones graveyards of Novakovići, Žugića, and Plužine are presented. The study allowed the reconnaissance of new buried structures in the soil and has provided an updated view of the rich archaeological heritage of Montenegro.

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