Pre-swirl in the approach flow towards a pump leads to a decreased efficiency or even to malfunct... more Pre-swirl in the approach flow towards a pump leads to a decreased efficiency or even to malfunctioning of a pump. Especially for pumping stations with large rotodynamic pumps, the risk of malfunctioning should be minimized. For this reason, hydraulic investigations are performed prior to the construction of pumping stations to assess the amount of pre-swirl in the approach flow and if needed, to design local measures to decrease it. This article presents a test set-up of a simplified pump sump in which the pump performance characteristics are measured at a real pump for a wide range of predefined corotating and counterrotating swirl angles. The swirl angles are measured in a transparent model pump at scale 1:1 with a swirl meter at four bell diameters above the bell-mouth. The findings discussed in this paper provide insight in the relation between pre-swirl in the approach flow and pump performance.
Detecting internal erosion processes in porous media by an Arduino-based electrical impedance tom... more Detecting internal erosion processes in porous media by an Arduino-based electrical impedance tomography system developed on laboratory scale
A major cause of failure of embankment dams is internal erosion that is mostly driven by two diff... more A major cause of failure of embankment dams is internal erosion that is mostly driven by two different mechanisms, suffusion and concentrated leakage. Suffusion mechanism was studied for a cohesionless soil by laboratory experiments using an especially designed erosion apparatus which was capable of applying simultaneous hydraulic and mechanical loading while the erosion process was monitored. The main novel outcomes of the work are i) a new criterion for detecting the internal erosion initiation, ii) a modified theoretical model, namely the Modified Hydromechanical Envelop (MHE), for encountering the soil in-situ stresses and seepage-induced shear stress on internal erosion initiation and its continuation and iii) a semi-empirical constitutive law of internal erosion where the coefficients of this law were extracted experimentally. The MHE was proposed based on Mohr-Coulomb shear failure criterion. The constitutive law was defined as the rate of removal of mass due to the applicati...
Since the United States Environmental Protection Agency (USEPA) launched its “Green remediation&q... more Since the United States Environmental Protection Agency (USEPA) launched its “Green remediation" program and EU member states began to reassess their national regulations for environmental remediation in order to reach a Europe-wide consensus on policy and standards, the need for the sustainable removal of contaminants from brownfields has grown considerably. Concomitantly, the ability to calculate and assess the suitability as well as the environmental footprints and associated risks of a growing number of remediation techniques has become a priority. This thesis aims to evaluate two of the most widely-used free commercial tools for this purpose, SiteWise TMv.1 and SRT, for their practicability, quality and range of results and suitability specific to Swedish conditions. A number of ex-situ and in-situ methods are described in this thesis, a combination of which are then used to model twenty-six remediation scenarios for two documented contaminated sites in the Gothenburg reg...
Abstract Internal erosion phenomena are a major threat to all earthen structures, such as river l... more Abstract Internal erosion phenomena are a major threat to all earthen structures, such as river levees and dams. Studying these phenomena has been limited because they occur concealed inside the material, which makes them difficult to observe and monitor. Non-destructive geophysical monitoring techniques are powerful tools that can provide insight into the processes involved. For this reason, a test rig has been specifically designed to conduct three-dimensional electrical resistivity tomography of soil specimens undergoing internal erosion due to seepage. Two suffusion tests were conducted where the erosion evolution has been monitored. The time-series of eroded mass weight were then used to correlate the changes in three-dimensional resistivity distribution to the porosity change in media by means of Archie’s law. The results from the first suffusion test were used to calibrate Archie’s model parameters. It was found that the resistivity variations were able to predict changes in the porous matrix structure. The data obtained from the second test were used to validate the model parameters and confirmed that the time-lapse three-dimensional inverted resistivity images were able to successfully quantify the global erosion rate.
IRAN 1. INTRODUCTION One of the most critical stages in designing embankment dams is evaluation o... more IRAN 1. INTRODUCTION One of the most critical stages in designing embankment dams is evaluation of pressure heads and hydraulic gradients in different parts of the dam body as well as evaluation of water discharge rates from the core and foundation. When seepage rates or hydraulic gradients increase unexpectedly or become uncontrolled, undesirable conditions may prevail to progress the piping or internal erosion that leads to dam instability or ultimate failure. The study of 77 embankment dam failures which have occurred in the United States until early 1980s indicates that seepage piping accounts for approximately 50% of all dam failures, the majority of which progress inside the dam embankment and foundation [1]. * Comparaison entre une analyse en deux et en trois dimensions de l'infiltration d'un barrage en enrochement construit dans une vallée étroite : étude de cas.
Pre-swirl in the approach flow towards a pump leads to a decreased efficiency or even to malfunct... more Pre-swirl in the approach flow towards a pump leads to a decreased efficiency or even to malfunctioning of a pump. Especially for pumping stations with large rotodynamic pumps, the risk of malfunctioning should be minimized. For this reason, hydraulic investigations are performed prior to the construction of pumping stations to assess the amount of pre-swirl in the approach flow and if needed, to design local measures to decrease it. This article presents a test set-up of a simplified pump sump in which the pump performance characteristics are measured at a real pump for a wide range of predefined corotating and counterrotating swirl angles. The swirl angles are measured in a transparent model pump at scale 1:1 with a swirl meter at four bell diameters above the bell-mouth. The findings discussed in this paper provide insight in the relation between pre-swirl in the approach flow and pump performance.
Detecting internal erosion processes in porous media by an Arduino-based electrical impedance tom... more Detecting internal erosion processes in porous media by an Arduino-based electrical impedance tomography system developed on laboratory scale
A major cause of failure of embankment dams is internal erosion that is mostly driven by two diff... more A major cause of failure of embankment dams is internal erosion that is mostly driven by two different mechanisms, suffusion and concentrated leakage. Suffusion mechanism was studied for a cohesionless soil by laboratory experiments using an especially designed erosion apparatus which was capable of applying simultaneous hydraulic and mechanical loading while the erosion process was monitored. The main novel outcomes of the work are i) a new criterion for detecting the internal erosion initiation, ii) a modified theoretical model, namely the Modified Hydromechanical Envelop (MHE), for encountering the soil in-situ stresses and seepage-induced shear stress on internal erosion initiation and its continuation and iii) a semi-empirical constitutive law of internal erosion where the coefficients of this law were extracted experimentally. The MHE was proposed based on Mohr-Coulomb shear failure criterion. The constitutive law was defined as the rate of removal of mass due to the applicati...
Since the United States Environmental Protection Agency (USEPA) launched its “Green remediation&q... more Since the United States Environmental Protection Agency (USEPA) launched its “Green remediation" program and EU member states began to reassess their national regulations for environmental remediation in order to reach a Europe-wide consensus on policy and standards, the need for the sustainable removal of contaminants from brownfields has grown considerably. Concomitantly, the ability to calculate and assess the suitability as well as the environmental footprints and associated risks of a growing number of remediation techniques has become a priority. This thesis aims to evaluate two of the most widely-used free commercial tools for this purpose, SiteWise TMv.1 and SRT, for their practicability, quality and range of results and suitability specific to Swedish conditions. A number of ex-situ and in-situ methods are described in this thesis, a combination of which are then used to model twenty-six remediation scenarios for two documented contaminated sites in the Gothenburg reg...
Abstract Internal erosion phenomena are a major threat to all earthen structures, such as river l... more Abstract Internal erosion phenomena are a major threat to all earthen structures, such as river levees and dams. Studying these phenomena has been limited because they occur concealed inside the material, which makes them difficult to observe and monitor. Non-destructive geophysical monitoring techniques are powerful tools that can provide insight into the processes involved. For this reason, a test rig has been specifically designed to conduct three-dimensional electrical resistivity tomography of soil specimens undergoing internal erosion due to seepage. Two suffusion tests were conducted where the erosion evolution has been monitored. The time-series of eroded mass weight were then used to correlate the changes in three-dimensional resistivity distribution to the porosity change in media by means of Archie’s law. The results from the first suffusion test were used to calibrate Archie’s model parameters. It was found that the resistivity variations were able to predict changes in the porous matrix structure. The data obtained from the second test were used to validate the model parameters and confirmed that the time-lapse three-dimensional inverted resistivity images were able to successfully quantify the global erosion rate.
IRAN 1. INTRODUCTION One of the most critical stages in designing embankment dams is evaluation o... more IRAN 1. INTRODUCTION One of the most critical stages in designing embankment dams is evaluation of pressure heads and hydraulic gradients in different parts of the dam body as well as evaluation of water discharge rates from the core and foundation. When seepage rates or hydraulic gradients increase unexpectedly or become uncontrolled, undesirable conditions may prevail to progress the piping or internal erosion that leads to dam instability or ultimate failure. The study of 77 embankment dam failures which have occurred in the United States until early 1980s indicates that seepage piping accounts for approximately 50% of all dam failures, the majority of which progress inside the dam embankment and foundation [1]. * Comparaison entre une analyse en deux et en trois dimensions de l'infiltration d'un barrage en enrochement construit dans une vallée étroite : étude de cas.
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