7 research outputs found

    Use of numerical modelling when designing a full-scale field test of landfill top covers

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    Landfill closures typically include cover systems with a low-permeable barrier to limit the flow of water to and from the waste to minimize contamination of the surrounding environment. Commonly the lowpermeable barrier in the top cover consists of compacted clays and/or geomembranes. An ongoing fullscale pilot test in southern Norway examines the performance of landfill low-permeable barriers, sometimes called sealing layers, constructed of two different recycled clayey soils compared to a traditionally used dry crust clay. Four test cells have been constructed with a top cover consisting of a coarse protection layer overlying a sealing layer. A lysimeter lies at the base to collect and measure the water which percolates through the entire top cover. By modelling the seepage through a simplification of the pilot test top cover, this paper investigates how 2D numerical hydrogeological modelling may be used to inform the design and/or construction of top cover pilot tests in temperate climates. It assesses the effect of sealing layer inclination, thickness and saturated hydraulic conductivity, as well as how detailed, as-built cross-section models compare to simple column models. Saturated hydraulic conductivity was found to be the most important feature when varied within a realistic range. Further, it asserts that 2D modelling may provide an efficient way to assess the consequences of deviations from designed geometry. Simple column models were found to be as suitable for this as more detailed crosssection models.Use of numerical modelling when designing a full-scale field test of landfill top coverspublishedVersio

    Numerical hydrogeological modelling of drainage to an excavation

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    The report regards the conceptual and numerical modelling of drainage scenarios to a planned excavation in a deep clay deposit in Oslo, Norway. The modelling was performed in SEEP/W 2D. Ground investigations indicate that the clay lies directly on top of the bedrock, without a layer of moraine between them. The upper metres of the bedrock is assumed to be weathered and serve as a draining layer. The drainage of groundwater to the excavation along steel core piles, and the mitigating effect of cut-off walls of various lengths, were modelled. There were made several versions of the numerical model, with a variation of conductivity and upstream boundary conditions. The simulation results were compared with empirical pore pressure data presented by the R&D project BegrensSkade I (2012-2015). The simulation results deviated notably from the empirical data, leading to the conclusion that the model itself is unreliable. Although there were found weaknesses with the model that could have been improved and resulted in better compliance, some major uncertainties are considered to remain and to affect the results to a significant degree. The uncertainties are in particular related to the modelling of the (weathered) bedrock conductivity, i.e. how the groundwater flows horizontally, vertically and across large distances within the bedrock joints. The discussion of these uncertainties is only introductory, and there is first of all a need to study the literature in greater detail to find out whether these issues are as important as argued here, and whether researchers already have studied them sufficiently. If the literature study comes to the conclusion that more research is needed, two modelling tasks are proposed with the aim to get a better understanding of how the groundwater flow could have been modelled more realistically in a continuum two-dimensional model.Norges Forskningsråd Research Council of Norwa

    Assessing potential building damage caused by leakage to urban tunnels

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    Building damage is a major risk for urban tunnelling. In areas with soft soil conditions, water ingress to bedrock tunnels can cause significant pore pressure reduction, consolidation settle-ments and damage to nearby buildings and infrastructure. In Norway, guidelines to determine leakage limits are based on a national database, containing data on water ingress, pore pressure reduction and influence zone. To support future projects, the database has been implemented into an ArcGIS-tool and merged with the Ground Impact and Building Vulnerability (GIBV) method to assess potential building damage at early project stages. This paper presents the adopted methodology and shows its application for a new subway tunnel in Oslo, Norway.Assessing potential building damage caused by leakage to urban tunnelsacceptedVersio

    Sustainable impermeable landfill barriers: The potential of using geological waste and surplus masses

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    This study investigated the potential to reuse excavated cement stabilised clay (CSC) and press filter residual (PFR) as impermeable landfill barriers. First, laboratory experiments including particle size distribution, consistency limits, standard Proctor and permeability tests were carried out on reconstituted samples. Subsequently, a full-scale compaction trial was performed for both materials. Nuclear density tests and results from cylinder samples were compared to evaluate the compaction behaviour. The cylinder samples were utilised to quantify the properties of the compacted soil layers. Multi-sensor core logging (MSCL) and X-ray image techniques were adopted to visualise the homogeneity of the field samples. Results showed that both the CSC and PFR are well-graded and fine-grained soils which can be classified as high plastic silts or high plastic clays. For both materials, hydraulic conductivity values, k, less than 1x10-9 m/s were obtained when compacted in the laboratory to their maximum dry densities according to standard Proctor. The field compacted samples were, however, more permeable (e.g., k = 6.1x10-8 m/s (SD = 9.1x10-8, n = 3) for CSC and k = 1.5x10-9 m/s (SD = 4.3x10-10, n = 3) for PFR at a vertical stress, σv, of 40 kPa). Both materials reached the hydraulic conductivity requirements for barriers for inert waste landfills. For the PFR, an average k < 1x10-9 m/s was obtained at σv = 160 kPa which suggests that PFR might be reused as a bottom liner for ordinary and hazardous waste. The CSC results showed a considerable variability which can be explained by its innate heterogeneity.Sustainable impermeable landfill barriers: The potential of using geological waste and surplus massespublishedVersio

    Sustainable impermeable landfill barriers: The potential of using geological waste and surplus masses

    Get PDF
    This study investigated the potential to reuse excavated cement stabilised clay (CSC) and press filter residual (PFR) as impermeable landfill barriers. First, laboratory experiments including particle size distribution, consistency limits, standard Proctor and permeability tests were carried out on reconstituted samples. Subsequently, a full-scale compaction trial was performed for both materials. Nuclear density tests and results from cylinder samples were compared to evaluate the compaction behaviour. The cylinder samples were utilised to quantify the properties of the compacted soil layers. Multi-sensor core logging (MSCL) and X-ray image techniques were adopted to visualise the homogeneity of the field samples. Results showed that both the CSC and PFR are well-graded and fine-grained soils which can be classified as high plastic silts or high plastic clays. For both materials, hydraulic conductivity values, k, less than 1x10-9 m/s were obtained when compacted in the laboratory to their maximum dry densities according to standard Proctor. The field compacted samples were, however, more permeable (e.g., k = 6.1x10-8 m/s (SD = 9.1x10-8, n = 3) for CSC and k = 1.5x10-9 m/s (SD = 4.3x10-10, n = 3) for PFR at a vertical stress, σv, of 40 kPa). Both materials reached the hydraulic conductivity requirements for barriers for inert waste landfills. For the PFR, an average k < 1x10-9 m/s was obtained at σv = 160 kPa which suggests that PFR might be reused as a bottom liner for ordinary and hazardous waste. The CSC results showed a considerable variability which can be explained by its innate heterogeneity.Sustainable impermeable landfill barriers: The potential of using geological waste and surplus massespublishedVersio

    Deliverable D5.3. Work Package 5

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    GIBV-verktøyet er utviklet gjennom forsknings- og utviklingsprosjektet (FoU) BegrensSkade II som har pågått fra 2017 til 2022. GIBV står for "Ground-work Impact (GI) og Building Vulnerability (BV)". Verktøyet er utviklet for vurdering av risiko for bygningsskade i forbindelse med dype utgravinger og tunneler. Det vil gi en indikasjon på størrelsen av forventede setninger, og i sammenheng med bygningsinfo vil det gi indikasjon på risiko for bygningsskade. Verktøyet egner seg ikke for vurdering av enkeltbygninger, men vil kunne gi ingeniørteamet god oversikt over hvilke bygninger som står i fare for å få setningsskader og hvor det bør gjennomføres mer detaljerte vurderinger. I tillegg til at det raskt utføres setnings- og risikoberegninger for et stort område, presenteres resultatene i kartformat i ArcGIS, noe som gjør det lettere å visualisere og kommunisere konsekvenser av utbyggingen.Norges Forskningsråd The Research Council of Norwa
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