The Experts below are selected from a list of 312 Experts worldwide ranked by ideXlab platform
Tobias Mörz - One of the best experts on this subject based on the ideXlab platform.
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Influences on CPT-Results in a Small Volume Calibration Chamber
Springer Series in Geomechanics and Geoengineering, 2018Co-Authors: F.t. Stähler, Stefan Kreiter, M. Goodarzi, D. Al-sammarraie, T. Stanski, Tobias MörzAbstract:The cone penetration test (CPT) is a standard method for determining geotechnical subsoil properties. Different CPTs were performed in a small volume Calibration Chamber to quantify the influence of soil type, mean effective stress, relative density, boundary condition, dry or wet samples and vibratory CPT on the cone resistance. The results contribute to the interpretation of field and laboratory CPT-results.
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A Small Volume Calibration Chamber for Cone Penetration Testing (CPT) on Submarine Soils
Submarine Mass Movements and their Consequences, 2016Co-Authors: Matthias Fleischer, Stefan Kreiter, Tobias Mörz, Marc HuhndorfAbstract:A new small volume CPT Calibration Chamber with dynamically controlled boundary conditions has been built to improve the correlation between in-situ data and soil parameters. The sample volume in the new CPT Calibration Chamber has a diameter of 30 cm and a height of 54.5 cm. Therefore, it is possible to use reconstituted samples of limited quantity, e.g. from boreholes. The Chamber is able to simulate large overburden stresses and overconsolidation ratios (OCR) up to 5 MPa. Horizontal, vertical and pore pressures are independently applied via syringe pumps while recording volume changes. All pressures are dynamically controlled and allowing stress, strain and mixed stress-strain stress boundary conditions BC1–BC5 to be enforced. The sample deformation is measured by circumferential laser triangulation sensors. In a first series of tests using Cuxhaven Sand, a 12 mm cone and BC1 conditions, CPT tip resistances reach steady state about a length of at least 10 cm. The corrected tip resistances and the inferred relative densities for Cuxhaven Sand differ substantially from previously established correlations, confirming the need for more advanced correction factors and relationships between CPT data and in-situ soil properties.
S. Trilochana - One of the best experts on this subject based on the ideXlab platform.
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a walk in type Calibration Chamber facility for 222rn measuring devices and inter comparison exercises
Radiation Protection Dosimetry, 2019Co-Authors: S. Trilochana, H. M. Somashekarappa, M.p. Mohan, Srinivas S. Kamath, B. K. Sahoo, J.j. Gaware, Sudeep K Kumara, Rashmi S Nayak, Renita Shiny Dsouza, B.k. SapraAbstract:A walk-in type 222Rn Calibration Chamber of volume 22.7 m3, which has traceability to international standards, is established at the Centre for Advanced Research in Environmental Radioactivity, Mangalore University, India. It has a human-machine interface communication system, a programmable logic controller and sensor feedback circuit for controlling and data acquisition of relative humidity (RH) and temperature (T). An innovative method for the generation of desired 222Rn concentration (a few hundred Bq m-3 up to about 36 kBq m-3) using soil gas as a source was adopted. Leak rates of 222Rn from the Chamber for the mixing fan ON and OFF conditions were determined to be 0.0011 and 0.00018 h-1 respectively. With the exhaust system fully turned on, the maximum clearance rate of the Chamber was 0.58 ± 0.07 h-1. Excellent spatial uniformity in 222Rn concentration in the Chamber was confirmed (with a mean value of relative standard deviation < 12%) through measurements at 23 locations using CR-39 film-based passive devices. Demonstration of Calibration applications was performed using charcoal canister and PicoRad vials as the 222Rn adsorption devices. The study shows that gamma spectrometry is a convenient alternative approach to liquid scintillation analysis of PicoRad vials for 222Rn measurement.
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CFD-based simulation and experimental verification of ^222Rn distribution in a walk-in type Calibration Chamber
Journal of Radioanalytical and Nuclear Chemistry, 2019Co-Authors: S. Trilochana, H. M. Somashekarappa, K. Sudeep Kumara, Y.s. Mayya, N KarunakaraAbstract:A walk-in type ^222Rn Calibration Chamber (~ 22 m^3) is established at the Centre for Advanced Research in Environmental Radioactivity (CARER), Mangalore University, India which is being used by research groups working on ^222Rn in India and other countries as well. In recent times, computational fluid dynamics (CFD) technique is opted as an alternative approach for the prediction of ^222Rn concentration profile in the closed domain. CFD simulations were carried out to study the transient build-up and spatial behavior of ^222Rn concentration in the Calibration Chamber. Measurements were performed using active ^222Rn measuring devices and results of the CFD predictions and direct measurements were compared. A good agreement was observed between the simulated and experimental results with deviation between the two entities being ~ 3% in the case of transient build up and ~ 8% in the case of spatial distribution of ^222Rn concentration.
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CFD-based simulation and experimental verification of 222 Rn distribution in a walk-in type Calibration Chamber
Journal of Radioanalytical and Nuclear Chemistry, 2019Co-Authors: S. Trilochana, H. M. Somashekarappa, Y.s. Mayya, K. Sudeep Kumara, N KarunakaraAbstract:A walk-in type 222Rn Calibration Chamber (~ 22 m3) is established at the Centre for Advanced Research in Environmental Radioactivity (CARER), Mangalore University, India which is being used by research groups working on 222Rn in India and other countries as well. In recent times, computational fluid dynamics (CFD) technique is opted as an alternative approach for the prediction of 222Rn concentration profile in the closed domain. CFD simulations were carried out to study the transient build-up and spatial behavior of 222Rn concentration in the Calibration Chamber. Measurements were performed using active 222Rn measuring devices and results of the CFD predictions and direct measurements were compared. A good agreement was observed between the simulated and experimental results with deviation between the two entities being ~ 3% in the case of transient build up and ~ 8% in the case of spatial distribution of 222Rn concentration.
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A WALK-IN TYPE Calibration Chamber FACILITY FOR 222Rn MEASURING DEVICES AND INTER-COMPARISON EXERCISES
Radiation protection dosimetry, 2019Co-Authors: S. Trilochana, H. M. Somashekarappa, K. Sudeep Kumara, M.p. Mohan, S. Rashmi Nayak, Renita Shiny D’souza, Srinivas S. Kamath, B. K. Sahoo, J.j. Gaware, B.k. SapraAbstract:A walk-in type 222Rn Calibration Chamber of volume 22.7 m3, which has traceability to international standards, is established at the Centre for Advanced Research in Environmental Radioactivity, Mangalore University, India. It has a human-machine interface communication system, a programmable logic controller and sensor feedback circuit for controlling and data acquisition of relative humidity (RH) and temperature (T). An innovative method for the generation of desired 222Rn concentration (a few hundred Bq m-3 up to about 36 kBq m-3) using soil gas as a source was adopted. Leak rates of 222Rn from the Chamber for the mixing fan ON and OFF conditions were determined to be 0.0011 and 0.00018 h-1 respectively. With the exhaust system fully turned on, the maximum clearance rate of the Chamber was 0.58 ± 0.07 h-1. Excellent spatial uniformity in 222Rn concentration in the Chamber was confirmed (with a mean value of relative standard deviation
Abouzar Sadrekarimi - One of the best experts on this subject based on the ideXlab platform.
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Evaluation of Stress Normalization Methods for Cone-Penetration Testing in Quartz Sands
Journal of Geotechnical and Geoenvironmental Engineering, 2017Co-Authors: Abouzar SadrekarimiAbstract:AbstractThis paper describes the application of 10 reduced-scale Calibration Chamber cone penetration tests for evaluating empirical correlations employed for correcting CPT tip resistance to the o...
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Estimating relative density of sand with cone penetration test
Proceedings of the Institution of Civil Engineers - Ground Improvement, 2016Co-Authors: Abouzar SadrekarimiAbstract:As a result of difficulties in obtaining undisturbed samples in cohesionless soils, empirical correlations based on cone penetration test (CPT) results, often developed from Calibration Chamber experiments, are widely used for determining many soil parameters for geotechnical investigation. This paper describes the application of 19 reduced-scale Calibration Chamber CPTs for examining the empirical correlations used for predicting the relative density of loose to medium-dense sands. A reduced-scale subtraction cone with an apex angle of 60° and a net area ratio of 0·75 was used in the laboratory tests. Current methods for estimating relative density present very large differences among themselves as well as with the experiments of this study, rendering them meaningless for general application in all sands. The state parameter is suggested as a more reliable and universal alternative to relative density for estimating the degree of compaction of any sand deposit from CPT data. It is demonstrated that an em...
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Development of a Miniature Cone Penetrometer for Calibration Chamber Testing
Geotechnical Testing Journal, 2015Co-Authors: Sepideh Damavandi-monfared, Abouzar SadrekarimiAbstract:Cone penetration testing (CPT) has become the industry standard for in situ testing of cohesionless soils, and in particular, field liquefaction evaluation. The empirical methods for the interpretation of CPT data are either based on field data or the observation of CPT measurements in laboratory samples. In this study, a miniature cone penetrometer (with a diameter of 6 mm) is developed for understanding the response of loose to medium-dense sands. A modified triaxial cell is used for sample preparation and containment of the sample during cone penetration. The miniature cone can measure cone tip resistance, sleeve friction, and excess pore water pressure developed at the cone tip. While cone tip resistance is measured by a separate load cell, sleeve friction is obtained by subtracting cone tip resistance from a combined measurement of tip resistance and sleeve frictional force. Due to the free-draining nature of the sand tested in this study, no excess pore water pressure is developed during cone penetration. The measured data from the miniature cone are verified by comparison with CPT resistances measured in several other Calibration Chamber experiments on similar sands. Compared to a large Calibration Chamber with a standard size cone, the miniature cone allows quicker and less expensive CPT experiments in a more uniform sample.
J Tesař - One of the best experts on this subject based on the ideXlab platform.
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dynamic extension a new principle for a vacuum primary standard for uhv range 10 6 10 10 pa Calibration of hot cathode ionisation gauges
Vacuum, 2011Co-Authors: L Peksa, T Gronych, M Jeřab, P řepa, Martin Vicar, Z Krajicek, D Pražak, F Staněk, J TesařAbstract:Abstract The main obstacle in the construction of primary vacuum standards for very low pressures – ultra-high vacuum (UHV) – is outgassing from the walls of the apparatus. Thus, principles utilising a higher pumping rate in the Calibration Chamber, e.g., the pressure ratio technique, seem to be more useful for this range. However, a serious problem is inherent in this method, namely, that the gas in the Calibration Chamber is not in equilibrium and thus cannot be characterised by a single scalar pressure value, although such a value is then used to evaluate the measurement. This discrepancy can be overcome by using a hot cathode ionisation gauge as a transfer standard calibrated by the dynamic extension method. The dynamic extension method is explained and compared with the pressure ratio technique. The basic conditions for achieving acceptable uncertainty values are considered.
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Dynamic extension – A new principle for a vacuum primary standard for UHV-range (10−6–10−10 Pa) Calibration of hot cathode ionisation gauges
Vacuum, 2011Co-Authors: L Peksa, T Gronych, M Jeřab, Martin Vicar, Z Krajicek, D Pražak, F Staněk, P. Řepa, J TesařAbstract:Abstract The main obstacle in the construction of primary vacuum standards for very low pressures – ultra-high vacuum (UHV) – is outgassing from the walls of the apparatus. Thus, principles utilising a higher pumping rate in the Calibration Chamber, e.g., the pressure ratio technique, seem to be more useful for this range. However, a serious problem is inherent in this method, namely, that the gas in the Calibration Chamber is not in equilibrium and thus cannot be characterised by a single scalar pressure value, although such a value is then used to evaluate the measurement. This discrepancy can be overcome by using a hot cathode ionisation gauge as a transfer standard calibrated by the dynamic extension method. The dynamic extension method is explained and compared with the pressure ratio technique. The basic conditions for achieving acceptable uncertainty values are considered.
N Karunakara - One of the best experts on this subject based on the ideXlab platform.
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CFD-based simulation and experimental verification of ^222Rn distribution in a walk-in type Calibration Chamber
Journal of Radioanalytical and Nuclear Chemistry, 2019Co-Authors: S. Trilochana, H. M. Somashekarappa, K. Sudeep Kumara, Y.s. Mayya, N KarunakaraAbstract:A walk-in type ^222Rn Calibration Chamber (~ 22 m^3) is established at the Centre for Advanced Research in Environmental Radioactivity (CARER), Mangalore University, India which is being used by research groups working on ^222Rn in India and other countries as well. In recent times, computational fluid dynamics (CFD) technique is opted as an alternative approach for the prediction of ^222Rn concentration profile in the closed domain. CFD simulations were carried out to study the transient build-up and spatial behavior of ^222Rn concentration in the Calibration Chamber. Measurements were performed using active ^222Rn measuring devices and results of the CFD predictions and direct measurements were compared. A good agreement was observed between the simulated and experimental results with deviation between the two entities being ~ 3% in the case of transient build up and ~ 8% in the case of spatial distribution of ^222Rn concentration.
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CFD-based simulation and experimental verification of 222 Rn distribution in a walk-in type Calibration Chamber
Journal of Radioanalytical and Nuclear Chemistry, 2019Co-Authors: S. Trilochana, H. M. Somashekarappa, Y.s. Mayya, K. Sudeep Kumara, N KarunakaraAbstract:A walk-in type 222Rn Calibration Chamber (~ 22 m3) is established at the Centre for Advanced Research in Environmental Radioactivity (CARER), Mangalore University, India which is being used by research groups working on 222Rn in India and other countries as well. In recent times, computational fluid dynamics (CFD) technique is opted as an alternative approach for the prediction of 222Rn concentration profile in the closed domain. CFD simulations were carried out to study the transient build-up and spatial behavior of 222Rn concentration in the Calibration Chamber. Measurements were performed using active 222Rn measuring devices and results of the CFD predictions and direct measurements were compared. A good agreement was observed between the simulated and experimental results with deviation between the two entities being ~ 3% in the case of transient build up and ~ 8% in the case of spatial distribution of 222Rn concentration.
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A simple radon Chamber for use with soil gas for Calibration of radon measuring devices and instruments
International Journal of Low Radiation, 2011Co-Authors: Darwish Al-azmi, N KarunakaraAbstract:A simple and easy to use radon Calibration Chamber of volume of 216 litres was designed and constructed for applications in Calibration of radon measuring devices and for research studies. The main advantage of this Chamber is that instead of using 226 Ra source to generate the 222 Rn inside the Chamber, soil gas is utilised as a source of 222 Rn. Soil gas is drawn from the soil using a pump to fill the Chamber in order to obtain radon with high concentrations inside the Chamber. The advantage of this technique is that the desired radon concentration (ranging from few Bq/m 3 to about kBq/m 3 ) can be attained easily and fast at any time by filling the Chamber with different volumes of soil gas. After demonstrating the usefulness of the technique, Calibration experiments were carried out for radon measuring devices (charcoal canisters and scintillation cell) using the Calibration Chamber constructed in the present study.
