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Showing 5 results for Hydraulic Conductivity

Mahmood R. Abdi, Ali Parsapajouh, Mohammad A. Arjomand,
Volume 6, Issue 4 (12-2008)

Clay soils and their related abnormal behavior such as excessive shrinkage, swelling, consolidation settlement and cracking on drying has been the subject of many investigations. Previous studies mainly evaluated the effects of additives such as lime, cement and sand on these characteristics. Initial results indicated that the soil characteristics were improved. However, reportedly in many cases, these additives resulted in a decrease in plasticity and increase in hydraulic conductivity. As a result, there has been a growing interest in soil/fiber reinforcement. The present investigation has focused on the impact of short random fiber inclusion on consolidation settlement, swelling, hydraulic conductivity, shrinkage limit and the development of desiccation cracks in compacted clays. To examine the possible improvements in the soil characteristics, samples consisting of 75% kaolinite and 25% montmorillonite were reinforced with 1, 2, 4 and 8 percent fibers as dry weight of soil with 5, 10 and 15mm lengths. Results indicated that consolidation settlements and swelling of fiber reinforced samples reduced substantially whereas hydraulic conductivities increased slightly by increasing fiber content and length. Shrinkage limits also showed an increase with increasing fiber content and length. This meant that samples experienced much less volumetric changes due to desiccation, and the extent of crack formation was significantly reduced.
P. Alimohammadi, N. Shariatmadari, M.a. Abdoli, H. Ghiasinejad, A. Mansouri,
Volume 8, Issue 2 (6-2010)

Hydrologic Evaluation of Landfill Performance (HELP) model is one of the most accepted tools to simulate

the hydrological attributes of landfills. Although some major deviations from real values has been reported about the

calculated results for leachate generation by HELP model but other researchers and/or engineers in practice have

used it in some places to estimate amount of leachate produced in the landfills. On the Other hand this model is

elaborated and mainly used in developed countries with the waste having low moisture content and also in climatic

conditions with high precipitation. This research investigated the applicability of the model in arid areas, by

construction of two 30m× 50m (effective horizontal length) test cells in Kahrizak landfill (longitude=51°, 20',

latitude= 35° 27' degrees), and monitoring the real leachate generation from each one. A set of field capacity and

saturated water conductivity tests were also performed to determine basic hydrologic properties of municipal waste

landfilled. A comparison was made between values calculated by HELP model and recorded values, shows that a

prediction of leachate on annual basis can be done by HELP model with acceptable accuracy but when the infiltration

of water to waste body increases due to leachate production, the model intents to underestimate water storage capacity

of the landfill, which lead to deviation of calculated values from real ones.

Nader Shariatmadari , Marzieh Salami, Mehran Karimpour Fard,
Volume 9, Issue 2 (6-2011)

The main task in the design and construction of impermeable liners in landfills is to block the migration of pollutants to the groundwater

systems or to reduce its rate to a reasonable amount. That is why environmental regulations force governments to construct engineered

waste dumps for waste management purposes. These liners are exposed to various types of chemical, biological, and physical processes

and are affected by the leachate which is produced from decomposition of waste materials accompanying methane gas. The leachate

includes a lot of components such as water and different types of salts. For this reason, the geotechnical characteristics of clay liners

which are evaluated in laboratories using distilled water or tap water might be far different from the representative sample of the in-situ

conditions. There are some evidences regarding the effect of these salts on the physical and mechanical properties of clay barriers which

could affect the long-term performance of these liners. Since the main criterion for impermeable bottom liners in landfills is their

hydraulics conductivity, the increase of this parameter could have a considerable environmental impact. This paper embraces the results

of a recent study on the effect of three inorganic salts, NaCl, CaCl2 and MgCl2 on some geotechnical properties of a common used clay

soil in impermeable bottom barrier in Kahrizak landfill, the main waste disposal center of the Tehran Metropolitan. Also the effect of

bentonite content by adding different percentage of this special clay mineral, 10 and 20 percent, on these properties was investigated.

Laboratory tests like liquid limit, compaction, 1D consolidation and free swell tests were performed for this purpose. Results indicated

that all of these salts could have a considerable effect on the geotechnical properties of the mixtures. The main reason of such effects is

the changes which occur in diffuse double layer of clay particles.

J. Jalili, M. K. Jafari, A. Shafiee, J. Koseki, T. Sato,
Volume 10, Issue 2 (6-2012)

A series of tests and also numerical analyses were conducted to explore the mechanical behavior of a mixture of coarse gravelsize
particles floating in a matrix of silt, sand or clay. The research is a step forward in an ongoing investigation on behavior of
composite clay, which is used as the core material of some large embankment dams all over the world. After providing the reader
with an overall image about behavior of such materials through the literature, the paper focuses on a predominant feature of the
composite soil behavior: increase of non-deformable solid inclusions in a mixture leads to formation of heterogeneity of stress
field, excess pore water pressure and strain distribution along the specimens. This paper mainly probes formation of such
heterogeneity by the aid of special experiments and also numerical analyses. In addition to loading details, it is clarified through
the paper that position of inclusions relative to loading direction also affects heterogeneity of stress/strain and excess pore water
pressure distribution through the mixture. Despite the former, the latter redistributes with a rate proportional to material
hydraulic conductivity.

M. B. Esfandiari Sowmehsaraei, R. Jamshidi Chenari,
Volume 12, Issue 1 (1-2014)

Soil reinforced with fiber shows characteristics of a composite material, in which fiber inclusion has a significant effect on soil permeability. Concerning to the higher void ratio of carpet fibers, at first stages it may be expected that an increase in fiber content of the reinforced soil would result in an increase in permeability of the mixture. However, the present article demonstrates that fiber inclusion will decrease the permeability of sand-fiber composite.A series of constant head permeability tests have been carried out to show the effects and consequently, a new system of phase relationships was introduced to calculate the dry mass for the sand portion of the composite. Monte Carlo simulation technique adopted with finite element theory was employed to back calculate the hydraulic conductivity of individual porous fibers from the laboratory test results. It was observed that the permeability coefficient of the porous fibers are orders of magnitude less than the skeletal sand portion due to the fine sand particle entrapment and also the fiber volume change characteristics.

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