Hydraulic conductivity for a glacial clay till liner

Ramy Saadeldin, Gene Froc

In the proceedings of: GeoRegina 2014: 67th Canadian Geotechnical Conference

Session: Geotechnical Practice / Risk Assessment and Reliability

ABSTRACT: conductivity for a glacial clay till liner Ramy Saadeldin, M.Sc., P.Eng. & Gene Froc., P.Eng. AMEC Environment & Infrastructure, Regina, Saskatchewan, Canada ABSTRACT Past experience with many glacial clay till deposits investigated in central and southern Saskatchewan has demonstrated that saturated in-situ hydraulic conductivities vary from about 10-6 cm/sec to 10-9 cm/sec. Regulatory compliance for sewage lagoons and critical water containment structures typically requires measurement of hydraulic conductivity to confirm the competency of soil liners. The desired as-built hydraulic conductivity value for a soil liner is typically < 10-7 cm/sec. In some applications and regulatory references, an accepted practice in the past was to assume that the field hydraulic conductivity value for a soil liner will be one order of magnitude (i.e. 10 times) greater than the confirmed laboratory hydraulic conductivity value for a remoulded sample composed of the same soil. In fact, experience has shown that measured as-built field hydraulic conductivity values for a soil liner can be several orders of magnitude greater than the laboratory value if the liners are poorly constructed and, therefore, would not be compliant with regulatory criteria. The reliability of artificially applying any correction factor to a laboratory value to obtain an assumed field value is, therefore, questionable. Past studies have shown that the hydraulic conductivity for a soil liner can be affected by many factors, the most important of which is quality of construction and engineering controls implemented during construction. For this example case study, laboratory measurements of hydraulic conductivity for remoulded soil samples were undertaken using a flexible wall permeameter (FWP). Air-entry permeameter (AEP) tests were performed on a test pad prior to construction and then on the completed liner immediately after construction to measure the as-built hydraulic conductivity. Both the FWP and AEP tests resulted in comparable hydraulic conductivity values that were in the order of 10-8 cm/sec to 10-9 cm/sec. A preceding and preliminary empirical approach was also found to be adequate and reasonable for purposes of determining soil suitability and raulic conductivity value. The preliminary estimate was determined to be conservatively greater than the values determined by both the FWP and AEP test methods. RÉSUMÉ L'expérience du passé avec de nombreux dépôts dSaskatchewan a démontré que la conductivité hydraulique in situ à saturation varie de 10-6 à 10-9 cm / sec. La conformité réglementaire des étangs d'eaux usées et les structures critiques de confinement de l'eau nécessite généralement la mesure de la conductivité hydraulique pour confirmer la bonne qualitédes revêtements du sol. La valeur de la conductivité hydraulique souhaitée pour un revêtement de sol est typiquement < 10-7 cm / sec. Dans certaines applications et références réglementaires, une pratique acceptée dans le passé a été de supposer que la valeur de la conductivité hydraulique de domaine pour un revêtement de sol sera un ordre de grandeur (soit 10 fois) plus grand que la valeur de conductivité hydraulique confirmée pour un échantillon remaniée composée du même sol. En fait, l'expérience a montré que mesurée sur le terrain a des valeurs de conductivité hydraulique peut être de plusieurs ordres de grandeur supérieure à la valeur de laboratoire si les revêtements sont mal construits et, par conséquent, ne seraient pas être conformes aux critères réglementaires. La fiabilité de l'applicationartificielle facteur de correction à une valeur obtenue au laboratoire afin d'obtenir une valeur applicable au terrain est une action douteuse. Des études antérieures ont montré que la conductivité hydraulique pour un revêtement de sol peut être affectée par de nombreux facteurs, dont le plus important est la qualité Dans cette étude, par exemple, des mesures en laboratoire de la conductivité hydraulique pour les échantillons de sol remaniés ont été entreprises à l'aide d'un perméamètre à paroi flexible (PPF). Des tests d'entrée d'air perméamètre (EAP) ont été réalisés sur un support de test avant la construction et sur le revêtement du sol immédiatement après la construction pour mesurer la conductivité hydraulique. Les deux essais du PPF et EAP ont produit des valeurs de conductivité hydraulique comparables qui étaient de l'ordre de 10-8 cm / sec à 10-9 cm / sec. Une approche empirique préliminaire a également été jugée adéquate et raisonnable aux fins de la déterminer l'aptitude des sols et l'estimation de la valeur ' réalisable ' de la conductivité hydraulique. L'estimation préliminaire a été jugée conservatrice et supérieure aux valeurs fixées par les deux méthodes d'essai PPF et EAP. 1 INTRODUCTION The study of water flow through a soil structure is an important aspect of soil mechanics. Hydraulic conductivity of soils is derived from voids through which water can flow from points of high head to points of low head. It is necessary to estimate or, in some cases, accurately determine the hydraulic conductivity for a variety of engineering projects which are affected or dependent on fluid flow through soil. Measuring the hydraulic conductivity is an important task during the design and construction of soil liner systems. Minimizing hydraulic conductivity is the primary goal when constructing a soil liner as a barrier to fluid flow.

RÉSUMÉ: ulic conductivity for a glacial clay till liner Ramy Saadeldin, M.Sc., P.Eng. & Gene Froc., P.Eng. AMEC Environment & Infrastructure, Regina, Saskatchewan, Canada ABSTRACT Past experience with many glacial clay till deposits investigated in central and southern Saskatchewan has demonstrated that saturated in-situ hydraulic conductivities vary from about 10-6 cm/sec to 10-9 cm/sec. Regulatory compliance for sewage lagoons and critical water containment structures typically requires measurement of hydraulic conductivity to confirm the competency of soil liners. The desired as-built hydraulic conductivity value for a soil liner is typically < 10-7 cm/sec. In some applications and regulatory references, an accepted practice in the past was to assume that the field hydraulic conductivity value for a soil liner will be one order of magnitude (i.e. 10 times) greater than the confirmed laboratory hydraulic conductivity value for a remoulded sample composed of the same soil. In fact, experience has shown that measured as-built field hydraulic conductivity values for a soil liner can be several orders of magnitude greater than the laboratory value if the liners are poorly constructed and, therefore, would not be compliant with regulatory criteria. The reliability of artificially applying any correction factor to a laboratory value to obtain an assumed field value is, therefore, questionable. Past studies have shown that the hydraulic conductivity for a soil liner can be affected by many factors, the most important of which is quality of construction and engineering controls implemented during construction. For this example case study, laboratory measurements of hydraulic conductivity for remoulded soil samples were undertaken using a flexible wall permeameter (FWP). Air-entry permeameter (AEP) tests were performed on a test pad prior to construction and then on the completed liner immediately after construction to measure the as-built hydraulic conductivity. Both the FWP and AEP tests resulted in comparable hydraulic conductivity values that were in the order of 10-8 cm/sec to 10-9 cm/sec. A preceding and preliminary empirical approach was also found to be adequate and reasonable for purposes of determining soil suitability and

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Cite this article:
Ramy Saadeldin; Gene Froc (2014) Hydraulic conductivity for a glacial clay till liner in GEO2014. Ottawa, Ontario: Canadian Geotechnical Society.

@article{GeoRegina14Paper396,author = Ramy Saadeldin; Gene Froc,title = Hydraulic conductivity for a glacial clay till liner,year = 2014}