scholarly journals Levee reliability analyses for various flood return periods – a case study in southern Taiwan

2015 ◽  
Vol 15 (4) ◽  
pp. 919-930 ◽  
Author(s):  
W.-C. Huang ◽  
H.-W. Yu ◽  
M.-C. Weng
Keyword(s):  
Water Level ◽  
Cross Sections ◽  
Retaining Wall ◽  
Failure Mechanisms ◽  
Friction Angle ◽  
Return Periods ◽  
Scouring Depth ◽  
Southern Taiwan ◽  
Potential Failure

Abstract. In recent years, heavy rainfall conditions have caused disasters around the world. To prevent losses by floods, levees have often been constructed in inundation-prone areas. This study performed reliability analyses for the Chiuliao First Levee in southern Taiwan. The failure-related parameters were the water level, the scouring depth, and the in situ friction angle. Three major failure mechanisms were considered: the slope sliding failure of the levee and the sliding and overturning failures of the retaining wall. When the variability of the in situ friction angle and the scouring depth are considered for various flood return periods, the variations of the factor of safety for the different failure mechanisms show that the retaining wall sliding and overturning failures are more sensitive to the change of the friction angle. When the flood return period is greater than 2 years, the levee could fail with slope sliding for all values of the water level difference. The results of levee stability analysis considering the variability of different parameters could aid engineers in designing the levee cross sections, especially with potential failure mechanisms in mind.

scholarly journals Levee reliability analyses for various flood return periods – a case study in Southern Taiwan

2015 ◽  
Vol 3 (1) ◽  
pp. 457-495
Author(s):  
W.-C. Huang ◽  
H.-W. Yu ◽  
M.-C. Weng
Keyword(s):  
Water Level ◽  
Cross Sections ◽  
Retaining Wall ◽  
Failure Mechanisms ◽  
Friction Angle ◽  
Return Periods ◽  
Scouring Depth ◽  
Southern Taiwan ◽  
Potential Failure

Abstract. In recent years, heavy rainfall conditions have caused damages around the world. To prevent damages by floods, levees have often been constructed in prone-to-inundation areas. This study performed reliability analyses for the Chiuliao 1st Levee located in southern Taiwan. The failure-related parameters were the water level, the scouring depth, and the in-situ friction angle. Three major failure mechanisms were considered, including the slope sliding failure of the levee, and the sliding and overturning failures of the retaining wall. When the variabilities of the in-situ friction angle and the scouring depth are considered for various flood return periods, the variations of the factor of safety (FS) for the different failure mechanisms show that the retaining wall sliding and overturning failures are more sensitive to the variability of the friction angle. When the flood return period is greater than 2 years, the levee can undergo slope sliding failure for all values of the water level difference. The results for levee stability analysis considering the variability of different parameters could assist engineers in designing the levee cross sections, especially with potential failure mechanisms in mind.

Study on In Situ Shearing Strength Test for the Retaining Wall Bottom in a Bank Revetment Project

2012 ◽  
Vol 214 ◽  
pp. 333-337
Author(s):  
Guang Zhang ◽  
Jun Rong Ma ◽  
Jing Xi Chen ◽  
Hua Lin Zhou ◽  
Dong Hua Wang
Keyword(s):  
Shear Strength ◽  
Retaining Wall ◽  
Friction Angle ◽  
Strength Test ◽  
Composite Foundation ◽  
Undisturbed Soil ◽  
Shear Strength Test ◽  
Geological Conditions ◽  
Shearing Strength

To obtain the necessary shear strength parameters of the retaining wall bottom in a bank revetment project, in-situ shearing strength test must be conducted. There are 3 kinds of foundations. One is undisturbed soil foundation, and the other two are composite foundations. Due to the limited of the engineering conditions, each kind of foundation has prepared one specimen only. So the single shearing strength test can't separate cohesion c and friction angle φ. To solve this problem, a method which is a combination of shear strength test and sliding strength test is used. Sliding strength test is carried on specimens that have already failed after shearing strength test. This test is carried in wet conditions and cohesion values and friction angle values are obtained. In addition, the influence of the processing of composite foundation to equivalent friction coefficient is analyzed. Test result can be referenced by bank revetment projects which have similar geological conditions.

Applicability of Photogrammetry for Inspection and Monitoring of Dry-Stone Masonry Retaining Walls

2020 ◽  
Vol 2674 (9) ◽  
pp. 287-297
Author(s):  
Alexandra Hain ◽  
Arash E. Zaghi
Keyword(s):  
Cross Sections ◽  
Structural Integrity ◽  
Retaining Wall ◽  
Retaining Walls ◽  
3D Models ◽  
Field Trials ◽  
Aerial Photographs ◽  
Stone Masonry ◽  
In Situ Conditions

Dry-stone masonry retaining walls are vulnerable to bulging and leaning because of the lack of cohesion between stones. Currently, the structural integrity of these walls is mainly assessed by qualitative judgments informed by visual inspections. Photogrammetry has the potential to increase the quality and objectivity of retaining wall inspections. This technology uses a series of images to generate a detailed 3D model of a structure. Currently, this technology is most commonly used in civil engineering applications for mapping large areas, often using aerial photographs. In this study, photogrammetry is used in two field trials to evaluate its ability to create accurate, high-resolution 3D representations of masonry retaining walls in Connecticut. The 3D models were used to document the current in-situ conditions to provide a baseline for future comparisons, as well as show cross sections of vulnerable areas, such as bulges or tilts. In one trial, data were collected on two dates to show the progression of movement of the wall. This paper gives an overview of best practices for data collection and discusses results and observations from the field trials. The generated 3D models provide an enhanced form of inspection documentation including detailed representations of geometry and colors. The contribution of this paper is to provide material facilitating the adoption of this promising technology for the inspection of masonry retaining walls and other transportation infrastructure.

scholarly journals The effect of the setback angle on overturning stability of the retaining wall

2021 ◽  
Vol 72 (1) ◽  
pp. 66-75
Author(s):  
Nguyen Thi Thu Nga ◽  
Ngo Van Thuc ◽  
Lam Thanh Quang Khai ◽  
Nguyen Thanh Trung
Keyword(s):  
Cross Sections ◽  
Retaining Wall ◽  
Friction Angle ◽  
Key Factors ◽  
Construction Costs ◽  
Technical Requirements ◽  
Overturning Stability ◽  
Natural Terrain ◽  
The Stability ◽  
Selection Of

Retaining walls are a relatively common type of protective structure in construction to hold soil behind them. The form of the retaining wall is also relatively diverse with changing setback angle. Design cross-selection of retaining wall virtually ensures the stability of the retaining wall depends on many aspects. It is essential to consider these to bring the overall picture. For this reason, the authors selected a research paper on the influence of the setback angle on the overturning stability of the retaining wall. To evaluate the behavior stability of retaining wall with some key factors having different levels such as setback angle, internal friction angle of the soil, the slope of the backfill is based on the design of the experiment (DOE) with useful statistical analysis tools. These, proposing the necessary technical requirements in choosing significant cross-sections of retaining structure to suit natural terrain and save construction costs, ensure safety for the project.

scholarly journals Ultraviolet Absorption Cross-Sections of Ammonia at Elevated Temperatures for Nonintrusive Quantitative Detection in Combustion Environments

2021 ◽  
pp. 000370282199044
Author(s):  
Wubin Weng ◽  
Shen Li ◽  
Marcus Aldén ◽  
Zhongshan Li
Keyword(s):  
Cross Section ◽  
Cross Sections ◽  
Absorption Cross Section ◽  
Elevated Temperatures ◽  
Uv Absorption ◽  
Energy Utilization ◽  
Quantitative Detection ◽  
Absorption Cross ◽  
Hot Gas

Ammonia (NH3) is regarded as an important nitrogen oxides (NOx) precursor and also as an effective reductant for NOx removal in energy utilization through combustion, and it has recently become an attractive non-carbon alternative fuel. To have a better understanding of thermochemical properties of NH3, accurate in situ detection of NH3 in high temperature environments is desirable. Ultraviolet (UV) absorption spectroscopy is a feasible technique. To achieve quantitative measurements, spectrally resolved UV absorption cross-sections of NH3 in hot gas environments at different temperatures from 295 K to 590 K were experimentally measured for the first time. Based on the experimental results, vibrational constants of NH3 were determined and used for the calculation of the absorption cross-section of NH3 at high temperatures above 590 K using the PGOPHER software. The investigated UV spectra covered the range of wavelengths from 190 nm to 230 nm, where spectral structures of the [Formula: see text] transition of NH3 in the umbrella bending mode, v2, were recognized. The absorption cross-section was found to decrease at higher temperatures. For example, the absorption cross-section peak of the (6, 0) vibrational band of NH3 decreases from ∼2 × 10−17 to ∼0.5 × 10−17 cm2/molecule with the increase of temperature from 295 K to 1570 K. Using the obtained absorption cross-section, in situ nonintrusive quantification of NH3 in different hot gas environments was achieved with a detection limit varying from below 10 parts per million (ppm) to around 200 ppm as temperature increased from 295 K to 1570 K. The quantitative measurement was applied to an experimental investigation of NH3 combustion process. The concentrations of NH3 and nitric oxide (NO) in the post flame zone of NH3–methane (CH4)–air premixed flames at different equivalence ratios were measured.

scholarly journals In-situ observation of trapped carriers in organic metal halide perovskite films with ultra-fast temporal and ultra-high energetic resolutions

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Kanishka Kobbekaduwa ◽  
Shreetu Shrestha ◽  
Pan Adhikari ◽  
Exian Liu ◽  
Lawrence Coleman ◽  
...  
Keyword(s):  
Cross Sections ◽  
High Energy ◽  
High Energy Resolution ◽  
In Situ Observation ◽  
Trap States ◽  
Tunneling Mechanism ◽  
Photocurrent Spectroscopy ◽  
Metal Halide Perovskite ◽  
Halide Perovskite

AbstractWe in-situ observe the ultrafast dynamics of trapped carriers in organic methyl ammonium lead halide perovskite thin films by ultrafast photocurrent spectroscopy with a sub-25 picosecond time resolution. Upon ultrafast laser excitation, trapped carriers follow a phonon assisted tunneling mechanism and a hopping transport mechanism along ultra-shallow to shallow trap states ranging from 1.72–11.51 millielectronvolts and is demonstrated by time-dependent and independent activation energies. Using temperature as an energetic ruler, we map trap states with ultra-high energy resolution down to < 0.01 millielectronvolt. In addition to carrier mobility of ~4 cm2V−1s−1 and lifetime of ~1 nanosecond, we validate the above transport mechanisms by highlighting trap state dynamics, including trapping rates, de-trapping rates and trap properties, such as trap density, trap levels, and capture-cross sections. In this work we establish a foundation for trap dynamics in high defect-tolerant perovskites with ultra-fast temporal and ultra-high energetic resolution.

Diamond film nucleation and interface characterization

1992 ◽  
Vol 7 (8) ◽  
pp. 2151-2159 ◽  
Author(s):  
P. Bou ◽  
L. Vandenbulcke ◽  
R. Herbin ◽  
F. Hillion
Keyword(s):  
Cross Sections ◽  
Deposition Time ◽  
Sample Surface ◽  
Simultaneous Recording ◽  
Carbon Activity ◽  
Nucleation Density ◽  
Carbide Formation ◽  
Interface Characterization ◽  
Film Nucleation

A powerful micro SIMS technique coupled to a computer driven acquisition system has allowed the simultaneous recording of C−, MoO−, and Si− images of the sample surfaces, or of the transverse cross sections of the Mo-diamond interface. Diamond deposition has been shown to take place on a Mo2C layer, and the influence on the nucleation process of Si contamination, coming from the quartz tube etched by H atoms, has been investigated. Contamination can in fact occur during the shutdown procedures or during the whole experiment. This last contamination can be avoided by using suitable pressure ranges or gas combinations. Moreover, the deposition time necessary to obtain well-crystallized diamond films and the nucleation density could be optimized by an in situ pretreatment stage. This treatment reduces the delay observed before nucleation (which would correspond to the carbide formation), and increases the carbon activity at the sample surface.

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.

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