Investigating the Stability of Engineered Structures Using Acoustic Validation of Numerical Models

2000 ◽  
Author(s):  
R. Paul Young ◽  
Will S. Pettitt
Keyword(s):  
Numerical Models ◽  
Engineered Structures ◽  
The Stability

Analysis of Global Stability, Anchor Spacing, and Support Cable Loads in Wire Mesh and Cable Net Slope Protection Systems

2005 ◽  
Vol 1913 (1) ◽  
pp. 205-213 ◽  
Author(s):  
Navaratnarajah Sasiharan ◽  
Balasingam Muhunthan ◽  
Shanzhi Shu ◽  
Thomas C. Badger
Keyword(s):  
Numerical Models ◽  
Wire Mesh ◽  
System Failures ◽  
Design Elements ◽  
The Past ◽  
Protection Systems ◽  
Vertical Support ◽  
Stability Of Slope ◽  
The Stability ◽  
Horizontal Support

Wire mesh and cable net slope protection have been in use for more than 50 years along North American highways to control rockfall on actively eroding slopes. The basic design of these systems is comparatively similar throughout North America. It consists of a top horizontal cable suspended by regularly spaced anchors, typically a perimeter or widely spaced grid of horizontal and vertical support cables, and double-twisted, hexagonal wire mesh laced to the support ropes. To date, the design of the slope protection systems has been based primarily on empirical methods, engineering judgment, and experience. Although these systems generally perform well, there is some consensus among geotechnical specialists that some elements in the system may be overdesigned or even unnecessary. In addition, system failures under a variety of loading conditions within the past few decades indicate that certain design elements may in fact be underdesigned for their desired application. Analytical and numerical models to evaluate the stability of slope protection systems are presented. The inclusion of interior horizontal support ropes in addition to the top horizontal rope does not reduce the stress within the mesh and accordingly provides no mechanical benefit. Results also show that the stresses on the vertical support rope are much smaller than the top horizontal support rope. Therefore, the vertical ropes do not need to be as strong as the top horizontal rope. Further, some useful design charts for the design of slope protection system are presented.

Sensitivity Analysis of Blade Mode Shape on Flutter of Two-Dimensional Turbine Blade Sections

2000 ◽  
Author(s):  
Olga V. Tchernycheva ◽  
Sébastien Regard ◽  
François Moyroud ◽  
Torsten H. Fransson
Keyword(s):  
Experimental Data ◽  
Turbine Blade ◽  
Mode Shape ◽  
Numerical Models ◽  
Suction Surface ◽  
Flow Models ◽  
Reduced Frequency ◽  
Stability Maps ◽  
Axis Position ◽  
The Stability

A parametric study on the flutter stability of a turbine cascade as a function of the torsion axis position, the bending direction and the reduced frequency is presented. In this process two different unsteady flow models are used in order to minimize the uncertainties of numerical modeling on the physical conclusions of the study. Comparisons are performed against available experimental data. It was found that the comparison of the global aerodynamic damping between numerical results and experimental data was reasonably good. It was observed that the stability was more sensitive to changes in the mode shape than in the reduced frequency. Comparisons of the local unsteady pressures showed similar tendencies for the numerical models and the experimental data, while discrepancies on the blade suction surface between the models were observed around the trailing edge for the subsonic flow and close to shock location for the transonic flow. The results indicated interesting agreement of the mode shape stability maps with results obtained on a largely different low-pressure turbine blade.

Modelling the effect of Nature Based Solutions on slope instability

2020 ◽  
Author(s):  
Stefano Tinti ◽  
Glauco Gallotti ◽  
Thomas Zieher ◽  
Jan Pfeiffer ◽  
Filippo Zaniboni ◽  
...  
Keyword(s):  
Slope Stability ◽  
Land Use Planning ◽  
Groundwater Level ◽  
Numerical Models ◽  
Slope Instability ◽  
Seismic Load ◽  
Technical Parameters ◽  
Hydrological System ◽  
The Stability ◽  
Open Air Laboratories

<p>In the framework of the OPERANDUM (OPEn-air laboRAtories for Nature baseD solUtions to Manage environmental risks) project, modelling the effect of the Nature Based Solutions (NBS) on selected open-air laboratories plays a determinant role. In this work, we focus the attention on the Vögelsberg (Tyrol, Austria) landslide case study, located in the municipality of Wattens. The 0.25 km<sup>2</sup> active part of the slope shows annual movement rates in the order of 3.5-6 cm/a. Recent studies provided evidence that the motion is mainly driven by variations of the groundwater level. The latter are related to prolonged moist periods during which excessive rainfall or snow melt water can infiltrate and act on the geo-hydrological system. With the aim of enhancing the slope stability employing NBS, a detailed analysis of the hydrogeology and the slope characteristics have been carried out, obtaining the required technical parameters describing the involved soil material. Furthermore, a slope stability analysis by means of different numerical models has been performed. Results prove that variations of the groundwater level in the range of 1-2 m can strongly affect the stability of the slope. Thus, specific NBS should aim at reducing the amount of infiltrating water. Examples of such NBS include the adaptation of forest management and land use planning, the introduction and re-activation of drainage channels and the sealing of leaky streams and channels. Beside the effects of the variation of the groundwater level, results have proved that the slope could fail under the action of a moderate seismic load. In this scenario, it is likely that the effects of the NBS would be insufficient to maintain the slope intact.</p>

Stability Analysis of Complex Multibody Systems

2005 ◽  
Vol 1 (1) ◽  
pp. 71-80 ◽  
Author(s):  
Olivier A. Bauchau ◽  
Jielong Wang
Keyword(s):  
Stability Analysis ◽  
Multibody Systems ◽  
Floquet Theory ◽  
Numerical Models ◽  
Characteristic Exponent ◽  
Prony's Method ◽  
Linearized Stability ◽  
The Stability ◽  
Curve Fitting Method ◽  
Prony’S Method

The linearized stability analysis of dynamical systems modeled using finite element-based multibody formulations is addressed in this paper. The use of classical methods for stability analysis of these systems, such as the characteristic exponent method or Floquet theory, results in computationally prohibitive costs. Since comprehensive multibody models are “virtual prototypes” of actual systems, the applicability to numerical models of the stability analysis tools that are used in experimental settings is investigated in this work. Various experimental tools for stability analysis are reviewed. It is proved that Prony’s method, generally regarded as a curve-fitting method, is equivalent, and sometimes identical, to Floquet theory and to the partial Floquet method. This observation gives Prony’s method a sound theoretical footing, and considerably improves the robustness of its predictions when applied to comprehensive models of complex multibody systems. Numerical and experimental applications are presented to demonstrate the efficiency of the proposed procedure.

Criteria for the Stability Limit Prediction of High Speed Centrifugal Compressors With Vaneless Diffuser: Part II — The Development of Prediction Criteria

2020 ◽  
Author(s):  
Carlo Cravero ◽  
Davide Marsano
Keyword(s):  
High Speed ◽  
Numerical Models ◽  
Fluid Dynamic ◽  
Stability Limit ◽  
Design Phase ◽  
Vaneless Diffuser ◽  
Centrifugal Compressors ◽  
Vaned Diffuser ◽  
The Stability ◽  
Computational Resources

Abstract The challenge to be able to predict the stability limit in high speed centrifugal compressor is particularly strategic in an initial design phase. Furthermore, to be able to predict the limit massflow rate through the use of simplified numerical models (which does not require excessive computational resources) is very important. In the literature there are several methods to predict the chocking condition, while there is a lack as regards the surge condition. The authors have already presented a criterion to predict the surge line valid for centrifugal compressors with vaned diffuser. Instead those with vaneless diffuser have a very different behavior. For this reason, in the first paper an in-depth fluid dynamic analysis has been carried out, in order to identify the main phenomena linked to the trigger of instability in this type of compressors. This analysis has allowed understanding that the rotational speed is a discriminating factor in the phenomenology. In this second part, using the previous information, different criteria to predict the limit massflow rate for centrifugal compressors with vaneless diffuser are described. All the criteria are based on different simplified CFD approaches that can be routinely used during the design phase.

Numerical Analysis of Slot Stability during the Supper-Deep Diaphragm Wall Construction

2013 ◽  
Vol 438-439 ◽  
pp. 1043-1047
Author(s):  
Bao Zhu Yang ◽  
Shu Chao Zhang ◽  
Kai Yun Luan
Keyword(s):  
Specific Gravity ◽  
Numerical Models ◽  
Silty Sand ◽  
Diaphragm Wall ◽  
Silty Clay ◽  
Soil Cement ◽  
Guide Wall ◽  
Wall Construction ◽  
Subway Stations ◽  
The Stability

Two subway stations of line Z1 were built in Tianjin cultural center and Tianjin Yujiapu traffic hub. The diaphragm wall depth of the two stations was more than 60 m. The geological and hydraulic conditions were different in the two site. Keeping stability of slot wall was the key of supper-deep diaphragm wall construction to the both stations. Two 3D numerical models were built by ABQUS software to simulate the grooving process. The conditions of different slurry specific gravity and grooving depth were calculated. The deformation laws of the slot wall and ground settlement around the slot wall were studied. The results showed the upper soft silty clay and deeper silty sand layers were easy collapse. Finally, some technologies such as "] [" type guide wall, properly improving slurry specific gravity, soil cement mixing reinforcement were suggested to improve the stability during the diaphragm wall construction of the two stations.

Numerical Investigation of the Stability of Toppling Rock Slopes Subjected to Glacier Retreat

2020 ◽  
Author(s):  
Nikola Toshkov ◽  
Jordan Aaron ◽  
Simon Loew ◽  
Franziska Glueer ◽  
Valentin Gishig
Keyword(s):  
Theoretical Analysis ◽  
Water Table ◽  
Rock Slope ◽  
Structural Model ◽  
Numerical Models ◽  
Back Analysis ◽  
Glacier Retreat ◽  
Glacial Retreat ◽  
Slope Instabilities ◽  
The Stability

<p>Glacial retreat is often cited as a cause of rock slope instabilities in mountain regions. Until recently, glacial debuttressing was thought to be the main mechanism by which glaciers influence slope stability, however recent work has questioned the efficacy of this mechanism.  It appears that other mechanisms, including slope kinematics and hydro-mechanical interactions between the glacier and slope are important drivers of paraglacial rock slope instabilities.  In the present work, we use discontinuum numerical models to investigate the interaction between rock slope kinematics, slope/glacial hydrology and glacial retreat. <br>We perform both a theoretical analysis using a simplified slope geometry, as well as a back-analysis of the Moosfluh Landslide.  For the theoretical analysis, we investigate the response of both toppling and sliding slopes to two factors: the weight of the ice, assumed to be applied as a ductile load acting normal to slope topography, and the variation of the slope water table, which is linked to the ice level and lowers as the glacier retreats. We then apply the insights from the theoretical analysis to investigate the Moosfluh Landslide.  This landslide, which is located at the left flank of the Great Aletsch Glacier Valley (Valais, Switzerland), at the present-day glacial terminus, underwent a dramatic acceleration in 2016 in response to glacier retreat.  The landslide was extensively monitored during this acceleration, and analysis of this data has revealed that the kinematics of movement changed from toppling to secondary sliding.  We simulate the behaviour of the Moosfluh Landslide by implementing a structural model determined from field mapping, and systematically lowering the ice level and slope water table, to simulate glacial retreat.<br>We find that the interaction between slope kinematics and glacial retreat leads to a complex slope response.  For sliding slopes, the stability of the slope is relatively insensitive to glacial ice loss.  For toppling slopes, the slope response is highly sensitive to ice loss, and the slope is the most unstable at a critical ice level, before ice has completely retreated.  For the Moosfluh instability, we are able to simulate the initial toppling kinematics of this landslide, as well as the transition to sliding triggered by the ice reaching a critical elevation.  Our analysis has important implications for understanding rock slope response to glacial retreat, and highlights the disparate behaviour of toppling and sliding slopes. </p>

The Study on Mechanical Properties of Karst Tunnel

2011 ◽  
Vol 243-249 ◽  
pp. 3399-3402
Author(s):  
Bin Li ◽  
Tai Yue Qi
Keyword(s):  
Mechanical Properties ◽  
Numerical Models ◽  
Side Wall ◽  
Surrounding Rock ◽  
Karst Tunnel ◽  
Safety Coefficient ◽  
Coefficient Distribution ◽  
Unfavorable Effect ◽  
Adverse Influence ◽  
The Stability

Several numerical models were built by FLAC3D to simulate tunnel with karst around spandrel, tunnel with karst around springe, tunnel with karst around inverted arch and tunnel with karst around side wall. The influence of karsts on the deformation of lining and the safety coefficient distribution of surrounding rock after excavation was analyzed. The results from the numerical modeling suggest as follows: karst around spandrel has extremely unfavorable effect on the deformation of lining and the safety of surrounding rock above the vault, karst around side wall also seriously affect the stability of tunnel due to the asymmetry pressure on tunnel caused by karst, consequently, auxiliary measures should be taken to handle these two cases; karst around springe and karst around inverted arch has limited adverse influence on the overall safety of tunnel, backfill measures are enough to handle these two cases.

scholarly journals Experimental study on the performance analysis of river levee using new substance for improving earth surface resistance

2018 ◽  
Vol 40 ◽  
pp. 03022
Author(s):  
Dongwoo Ko ◽  
Joongu Kang ◽  
Sungjoong Kim ◽  
Yonguk Ryu
Keyword(s):  
Cross Sections ◽  
Surface Resistance ◽  
Numerical Models ◽  
Earth Surface ◽  
Disaster Prevention ◽  
Image Measurement ◽  
Delay Effect ◽  
The Stability ◽  
Time Delay Effect ◽  
Study Development

The reasons why levee breaches during floods are largely due to overtopping, seepage, and structurally induced piping. According to an analysis of domestic and overseas reported cases of levee breaches, overtopping was found to be the cause for approximately 40% of all cases of breach. Despite such efforts of previous research to establish disaster prevention plans associated with levee breaches, to enhance our understanding of the processes and reasons, further research regarding the prediction of levee breaches must be undertaken by accumulating test data under several different conditions and further verification of the data using numerical models must also be undertaken. In this study, development of technologies regarding a new environmentally friendly bio-polymer capable of protecting levees from erosion is being undertaken. Breach mechanisms was assessed using an image measurement system that collected data regarding the breach progress of the levee, close-up views of the breaching surface, and the formation of the final breaching cross-sections. Further, levee slopes were covered with a bio-soil mixed with a new substance for the purpose of analyzing the stability and the time delay effect.

Quasi-3D Stability and Vibration Analyses of Sandwich Piezoelectric Plates with an Embedded CNT-Reinforced Composite Core

2016 ◽  
Vol 16 (02) ◽  
pp. 1450097 ◽  
Author(s):  
Chih-Ping Wu ◽  
Wei-Chen Li
Keyword(s):  
Free Vibration ◽  
Numerical Models ◽  
Three Dimensional ◽  
Functionally Graded ◽  
Matrix Methods ◽  
Reinforced Composite ◽  
System Equations ◽  
The Stability ◽  
Benchmark Solutions ◽  
Piezoelectric Plates

Quasi-three-dimensional (3D) stability and free vibration analyses of bi-axially loaded, simply-supported, sandwich piezoelectric plates with an embedded either a functionally graded (FG) carbon nanotube-reinforced composite (CNTRC) core or a multilayered fiber-reinforced composite (FRC) one are presented. Three different distributions of carbon nanotubes (CNTs) through the thickness of the CNTRC core, i.e. uniformly distributed and FG V-, rhombus- and X-type variations, are considered, and the effective material properties of the CNTRC core are estimated using the rule of mixtures. The Pagano method, which is conventionally used for the analysis of multilayered FRC plates, is modified to be feasible for the study of sandwich hybrid CNTRC and piezoelectric ones, in which Reissner mixed variational theorem, the successive approximation and transfer matrix methods, and the transformed real-valued solutions of the system equations are used. The modified Pagano solutions for the stability and free vibration of multilayered hybrid FRC and piezoelectric plates are in excellent agreement with the exact 3D ones available in the literature, and those for sandwich hybrid CNTRC and piezoelectric plates may be used as the benchmark solutions to assess the ones obtained by using various 2D theories and numerical models.

Sign in / Sign up

Export Citation Format

Share Document