Lay-out criteria, in situ tests and operational experience of the Kühtai pump-turbine groups

1990 ◽  
pp. 215-228
Author(s):  
H. Schmid ◽  
R. Erlacher
Keyword(s):  
Operational Experience ◽  
In Situ Tests ◽  
Pump Turbine

scholarly journals Experimental and CFD Simulations of the Aerosol Flow in the Air Ventilating the Underground Excavation in Terms of SARS-CoV-2 Transmission

Energies ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4743
Author(s):  
Tomasz Janoszek ◽  
Zbigniew Lubosik ◽  
Lucjan Świerczek ◽  
Andrzej Walentek ◽  
Jerzy Jaroszewicz
Keyword(s):  
Numerical Calculations ◽  
Mining Institute ◽  
Ventilation Network ◽  
Underground Excavation ◽  
In Situ Tests ◽  
Ansys Fluent ◽  
Aerosol Emission ◽  
Ansys Cfx ◽  
Computational Fluid Dynamics Cfd

The paper presents the results of experimental and model tests of transport of dispersed fluid droplets forming a cloud of aerosol in a stream of air ventilating a selected section of the underground excavation. The excavation selected for testing is part of the ventilation network of the Experimental Mine Barbara of the Central Mining Institute. For given environmental conditions, such as temperature, pressure, relative humidity, and velocity of air, the distribution of aerosol droplet changes in the mixture of air and water vapor along the excavation at a distance was measured at 10 m, 25 m, and 50 m from the source of its emission. The source of aerosol emission in the excavation space was a water nozzle that was located 25 m from the inlet (inlet) of the excavation. The obtained results of in situ tests were related to the results of numerical calculations using computational fluid dynamics (CFD). Numerical calculations were performed using Ansys-Fluent and Ansys-CFX software. The dimensions and geometry of the excavation under investigation are presented. The authors describe the adopted assumptions and conditions for the numerical model and discuss the results of the numerical solution.

scholarly journals Experimental Evaluation of Shear Behavior of Stone Masonry Wall

Materials ◽  
2021 ◽  
Vol 14 (9) ◽  
pp. 2313
Author(s):  
Maria Luisa Beconcini ◽  
Pietro Croce ◽  
Paolo Formichi ◽  
Filippo Landi ◽  
Benedetta Puccini
Keyword(s):  
Shear Behavior ◽  
Stone Masonry ◽  
Masonry Walls ◽  
Mechanical Parameters ◽  
In Situ Tests ◽  
Capacity Curves ◽  
Historical Structures ◽  
Definition Of

The evaluation of the shear behavior of masonry walls is a first fundamental step for the assessment of existing masonry structures in seismic zones. However, due to the complexity of modelling experimental behavior and the wide variety of masonry types characterizing historical structures, the definition of masonry’s mechanical behavior is still a critical issue. Since the possibility to perform in situ tests is very limited and often conflicting with the needs of preservation, the characterization of shear masonry behavior is generally based on reference values of mechanical properties provided in modern structural codes for recurrent masonry categories. In the paper, a combined test procedure for the experimental characterization of masonry mechanical parameters and the assessment of the shear behavior of masonry walls is presented together with the experimental results obtained on three stone masonry walls. The procedure consists of a combination of three different in situ tests to be performed on the investigated wall. First, a single flat jack test is executed to derive the normal compressive stress acting on the wall. Then a double flat jack test is carried out to estimate the elastic modulus. Finally, the proposed shear test is performed to derive the capacity curve and to estimate the shear modulus and the shear strength. The first results obtained in the experimental campaign carried out by the authors confirm the capability of the proposed methodology to assess the masonry mechanical parameters, reducing the uncertainty affecting the definition of capacity curves of walls and consequently the evaluation of seismic vulnerability of the investigated buildings.

scholarly journals Digital Image Correlation for Evaluation of Cracks in Reinforced Concrete Bridge Slabs

2021 ◽  
Vol 6 (7) ◽  
pp. 99
Author(s):  
Christian Overgaard Christensen ◽  
Jacob Wittrup Schmidt ◽  
Philip Skov Halding ◽  
Medha Kapoor ◽  
Per Goltermann
Keyword(s):  
Reinforced Concrete ◽  
Digital Image Correlation ◽  
Crack Initiation ◽  
Laboratory Test ◽  
Digital Image ◽  
Crack Detection ◽  
Image Correlation ◽  
In Situ Tests ◽  
Stop Criterion

In proof-loading of concrete slab bridges, advanced monitoring methods are required for identification of stop criteria. In this study, Two-Dimensional Digital Image Correlation (2D DIC) is investigated as one of the governing measurement methods for crack detection and evaluation. The investigations are deemed to provide valuable information about DIC capabilities under different environmental conditions and to evaluate the capabilities in relation to stop criterion verifications. Three Overturned T-beam (OT) Reinforced Concrete (RC) slabs are used for the assessment. Of these, two are in situ strips (0.55 × 3.6 × 9.0 m) cut from a full-scale OT-slab bridge with a span of 9 m and one is a downscaled slab tested under laboratory conditions (0.37 × 1.7 × 8.4 m). The 2D DIC results includes full-field plots, investigation of the time of crack detection and monitoring of crack widths. Grey-level transformation was used for the in situ tests to ensure sufficient readability and results comparable to the laboratory test. Crack initiation for the laboratory test (with speckle pattern) and in situ tests (plain concrete surface) were detected at intervals of approximately 0.1 mm to 0.3 mm and 0.2 mm to 0.3 mm, respectively. Consequently, the paper evaluates a more qualitative approach to DIC test results, where crack indications and crack detection can be used as a stop criterion. It was furthermore identified that crack initiation was reached at high load levels, implying the importance of a target load.

Effects of corrosion on a steel bowstring bridge in marine environment: A case-study of assessment and retrofit

2021 ◽  
Vol 16 (4) ◽  
pp. 121-137
Author(s):  
Michele Fabio Granata
Keyword(s):  
Corrosion Protection ◽  
Marine Environment ◽  
Spray Coating ◽  
Thermal Spray Coating ◽  
In Situ Tests ◽  
Limit States ◽  
Intervention Measures ◽  
Near Future

The case-study of a steel bowstring bridge set in a marine environment and highly damaged by corrosion is presented. The bridge was built in 2004 and was repainted for corrosion protection in 2010. Despite the recent construction and the maintenance interventions, many structural elements like hangers are highly damaged by corrosion with decreasing performance in terms of serviceability and ultimate limit states. A deep investigation was carried out in order to assess the bridge and to establish the necessary retrofit actions to be carried out in the near future. In-situ tests reveal the reduced performance of the original steel in terms of strength and corrosion protection, together with the inefficiency of the successive maintenance interventions. The paper presents assessment of the bridge and retrofit measures, including replacement of the hangers and galvanization through thermal spray coating technology, in order to increase its service life. The results of the investigations and the intervention measures are outlined and discussed.

scholarly journals Laboratory and In Situ Determination of Hydraulic Conductivity and Their Validity in Transient Seepage Analysis

Water ◽  
2021 ◽  
Vol 13 (8) ◽  
pp. 1131
Author(s):  
Soonkie Nam ◽  
Marte Gutierrez ◽  
Panayiotis Diplas ◽  
John Petrie
Keyword(s):  
Hydraulic Conductivity ◽  
Field Measurements ◽  
Natural Soil ◽  
In Situ Tests ◽  
Seepage Analysis ◽  
Soil Deposits ◽  
Seepage Modeling ◽  
Sample Disturbance

This paper critically compares the use of laboratory tests against in situ tests combined with numerical seepage modeling to determine the hydraulic conductivity of natural soil deposits. Laboratory determination of hydraulic conductivity used the constant head permeability and oedometer tests on undisturbed Shelby tube and block soil samples. The auger hole method and Guelph permeameter tests were performed in the field. Groundwater table elevations in natural soil deposits with different hydraulic conductivity values were predicted using finite element seepage modeling and compared with field measurements to assess the various test results. Hydraulic conductivity values obtained by the auger hole method provide predictions that best match the groundwater table’s observed location at the field site. This observation indicates that hydraulic conductivity determined by the in situ test represents the actual conditions in the field better than that determined in a laboratory setting. The differences between the laboratory and in situ hydraulic conductivity values can be attributed to factors such as sample disturbance, soil anisotropy, fissures and cracks, and soil structure in addition to the conceptual and procedural differences in testing methods and effects of sample size.

scholarly journals Sub-Level Stoping in an Underground Limestone Quarry: An Analysis of the State of Stress in an Evolutionary Scenario

2016 ◽  
Vol 61 (1) ◽  
pp. 199-216 ◽  
Author(s):  
Marilena Cardu ◽  
Sergio Dipietromaria ◽  
Pierpaolo Oreste
Keyword(s):  
Numerical Models ◽  
The State ◽  
In Situ Tests ◽  
Future Scenario ◽  
Limestone Quarry ◽  
Geomechanical Properties ◽  
State Of Stress ◽  
Upper Level ◽  
Pillar Structure

Abstract The aim of this study was to evaluate the state of stress of a „voids-pillar“ structure excavated by means of the sub-level stoping method in an underground limestone quarry near Bergamo (Italy). Both the current structure of the quarry (i.e. the rooms exploited till now) and a possible future scenario were analysed using the (FDM) FLAC 2D code. The quarry has been in operation since 1927; at present, exploitation is carried out underground via the sub-level stoping method. Exploitation involves two levels, with 5 rooms on the upper level and 9 rooms on the lower level. After analysing data obtained from laboratory and in situ tests carried out on rock samples and natural discontinuities, the geomechanical properties of the medium, knowledge of which is essential in order to establish the parameters that must be included in the numerical model, were evaluated. The implementation of three numerical models made it possible to study both the present conditions of quarry exploitation and the evolution of the exploited rooms, as well as a possible expansion involving a third level of rooms. Using the results obtained regarding the stress-strain present in the pillars, a potential change in room geometry was proposed aimed at reducing the stress state inside the pillars, decreasing plasticity and increasing overall quarry safety.

Effect of temperature on streambed vertical hydraulic conductivity

2013 ◽  
Vol 45 (1) ◽  
pp. 89-98 ◽  
Author(s):  
Weihong Dong ◽  
Gengxin Ou ◽  
Xunhong Chen ◽  
Zhaowei Wang
Keyword(s):  
Hydraulic Conductivity ◽  
Water Temperature ◽  
Sediment Cores ◽  
Effect Of Temperature ◽  
In Situ Tests ◽  
Effect Of Water ◽  
Vertical Hydraulic Conductivity ◽  
Increasing Trend ◽  
Streambed Vertical Hydraulic Conductivity

In this study, in situ and on-site permeameter tests were conducted in Clear Creek, Nebraska, USA to evaluate the effect of water temperature on streambed vertical hydraulic conductivity Kv. Fifty-two sediment cores were tested. Five of them were transferred to the laboratory for a series of experiments to evaluate the effect of water temperature on Kv. Compared with in situ tests, 42 out of the 52 tests have higher Kv values for on-site tests. The distribution of water temperature at the approximately 50 cm depth of streambed along the sand bar was investigated in the field. These temperatures had values in the range 14–19 °C with an average of 16 °C and had an increasing trend along the stream flow. On average, Kv values of the streambed sediments in the laboratory tests increase by 1.8% per 1 °C increase in water temperature. The coarser sandy sediments show a greater increase extent of the Kv value per 1 °C increase in water temperature. However, there is no distinct increasing trend of Kv value for sediment containing silt and clay layers.

Assessment of the range of variation of Nγ from 60 estimation methods for footings on sand

2013 ◽  
Vol 50 (7) ◽  
pp. 793-800 ◽  
Author(s):  
Edgar Giovanny Diaz-Segura
Keyword(s):  
Friction Angle ◽  
Standard Penetration Test ◽  
Estimation Methods ◽  
Penetration Test ◽  
In Situ Tests ◽  
Vertical Loading ◽  
Simplified Method ◽  
Bearing Capacity Factor ◽  
Range Of Variation

The range of variation of the bearing capacity factor, Nγ, was assessed using 60 estimation methods for rough footings on sand subjected to static vertical loading. The influence on the Nγ values of the use of correlations for the estimation of the friction angle, [Formula: see text], derived from in situ tests was also assessed. The analysis shows a marked dependency on the methods used to determine Nγ, showing differences for the same [Formula: see text] values of up to 267% between estimated values. Uncertainty in the estimation of [Formula: see text], due to the use of correlations with in situ tests, leads to a range of variation for Nγ higher than that seen using the 60 estimation methods. Finally, given the regular use of the in situ standard penetration test (SPT) on sands, and based on a series of analyses using finite elements, a simplified method in terms of the SPT N-values is proposed for estimation of Nγ in footings on sands.

In situ estimation of the coefficient of consolidation in clays

1990 ◽  
Vol 27 (1) ◽  
pp. 58-67 ◽  
Author(s):  
Mohammed G. Kabir ◽  
Alan J. Lutenegger
Keyword(s):  
Key Words ◽  
Pore Pressure ◽  
Reference Values ◽  
Time Factors ◽  
In Situ Tests ◽  
Coefficient Of Consolidation ◽  
Oedometer Test ◽  
Undisturbed Samples ◽  
Oedometer Tests

An investigation was conducted to demonstrate the applicability of cylindrical piezocone and flat piezoblade tests for providing reliable estimates of the coefficient of consolidation in clays. Coefficients of consolidation were calculated from piezocone dissipation tests for different degrees of consolidation using theoretical time factors to provide a comparison with laboratory oedometer tests. Three techniques were developed to calculate the coefficient of consolidation from piezoblade dissipation tests. Results from in situ pore pressure dissipation tests were compared with laboratory oedometer tests performed on undisturbed samples oriented in both the vertical and horizontal directions, to provide reference values of cv and ch. The results of investigations conducted at several clay sites are presented. Key words: in situ tests, piezocone, piezoblade, coefficient of consolidation, oedometer test, clays.

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