Debris flow interaction with structures: challenges to traditional load models

2020 ◽  
Author(s):  
Alessandro Leonardi ◽  
Andrea Pasqua ◽  
Marina Pirulli
Keyword(s):  
Debris Flow ◽  
Relative Size ◽  
Nonlinear Function ◽  
Field Measurements ◽  
Italian Alps ◽  
Load Model ◽  
Flow Energy ◽  
Load Models ◽  
Maintenance Work ◽  
Flow Through

<p>Debris flow barriers often feature one or more filter elements, i.e. narrow outlets that induce deposition of the coarsest sediments, while allowing water and fines to filter through. Slit dams and steel nets are examples of this type of barriers. The design of the filter elements must balance the need to trap boulders and to dissipate the flow energy, while keeping maintenance work as low as possible.</p><p>Filter barriers elude the traditional load model prescribed by guidelines. Under some conditions, the outlets can clog with large boulders. The time necessary for this to happen mainly depends on the relative size between boulder and outlet, and is a nonlinear function of the flow composition. In any case, the main clogging mechanism is the formation of granular arches. These can induce significant load also in directions different from the main direction of the incoming flow.</p><p>Unless the barrier is specifically designed to withstand this type of load, granular arches, but also prolonged flow through the outlet, can induce deterioration and loss of functionality of the structure. In this work, we estimate these effects employing a combination of discrete- and continuum-based numerical methods. We evaluate the performance of two types of debris-resisting barriers, comparing the results with laboratory measurements and with the outcome of a monitoring campaign on a real barrier located in the Italian alps.</p><p> </p><p> </p><p>References:</p><p>Leonardi, A., Goodwin, G. R., & Pirulli, M. (2019). The force exerted by granular flows on slit dams. Acta Geotechnica, 14(6), 1949–1963.</p><p>Leonardi, A., & Pirulli, M. (2020). Analysis of the load exerted by debris flows on filter barriers : Comparison between numerical results and field measurements. Computer & Geotechnics, 118, 103311.</p>

scholarly journals Load Model Verification, Validation and Calibration Framework by Statistical Analysis on Field Data

2017 ◽  
Vol 18 (6) ◽  
Author(s):  
Xiangqing Jiao ◽  
Yuan Liao ◽  
Thai Nguyen
Keyword(s):  
Statistical Analysis ◽  
System Analysis ◽  
Research Work ◽  
Field Measurements ◽  
Model Verification ◽  
Verification And Validation ◽  
Load Model ◽  
Load Models ◽  
Utility System ◽  
Model Verification And Validation

AbstractAccurate load models are critical for power system analysis and operation. A large amount of research work has been done on load modeling. Most of the existing research focuses on developing load models, while little has been done on developing formal load model verification and validation (V&V) methodologies or procedures. Most of the existing load model validation is based on qualitative rather than quantitative analysis. In addition, not all aspects of model V&V problem have been addressed by the existing approaches. To complement the existing methods, this paper proposes a novel load model verification and validation framework that can systematically and more comprehensively examine load model’s effectiveness and accuracy. Statistical analysis, instead of visual check, quantifies the load model’s accuracy, and provides a confidence level of the developed load model for model users. The analysis results can also be used to calibrate load models. The proposed framework can be used as a guidance to systematically examine load models for utility engineers and researchers. The proposed method is demonstrated through analysis of field measurements collected from a utility system.

Failure analysis of steel open dam against an extreme boulder debris flow

2020 ◽  
pp. 204141962097056
Author(s):  
Toshiyuki Horiguchi ◽  
Hiroshi Kokuryo ◽  
Nobutaka Ishikawa
Keyword(s):  
Debris Flow ◽  
Failure Analysis ◽  
Safety Assessment ◽  
Distinct Element ◽  
Rigid Wall ◽  
Reduction Factor ◽  
Second Step ◽  
Uniform Load ◽  
Load Model ◽  
Level Ii

This paper presents a failure analysis for a steel open-type Sabo dam (hereafter, steel open dam) against an extreme boulder debris flow load (hereafter, level II load) by a two-step analysis. The first step analysis is to estimate the level II load against the rigid wall by using the revised distinct element method (DEM). In the second step, the failure mechanism of a steel open dam is examined by using a dynamic elastic plastic analysis, in which the level II load-time relations obtained by the first analysis are multiplied by a reduction factor and then used. For the second step, the effects of the flange joint and dent deformation of the connection between column and beam are considered. Finally, a simple entire uniform load onto the steel open dam is proposed as a level II load model for the safety assessment.

Flume investigation of cylindrical baffles for dissipation of debris flow energy

2021 ◽  
Author(s):  
Chan-Young Yune ◽  
Beom-Jun Kim
Keyword(s):  
Energy Dissipation ◽  
Debris Flow ◽  
Debris Flows ◽  
High Speed ◽  
Flow Characteristics ◽  
Digital Camera ◽  
Major Effect ◽  
Small Scale ◽  
Design Guideline ◽  
Flow Energy

<p>A debris flow with a high speed along valleys has been reported to cause serious damages to urban area or infrastructure. To prevent debris flow disaster, countermeasures for flow-impeding structures are installed on the flow path of debris flows. Recently, an installation of cylindrical baffles which are open-type countermeasures has increased because of a low construction cost, filtering out rocks, and an increased hydraulic continuity. However, a comprehensive design guideline for specification and arrangement on cylindrical baffles has not yet been suggested. Moreover, the design of baffle installation is mainly based on empirical approaches as the influence of baffle array on debris mobility is not well understood. In this study, to investigate the effect of cylindrical baffles on the flow characteristics of debris flow, a series of small-scale flume tests were performed according to the varying baffle height and row numbers of installed baffles. High-speed cameras and digital camera to record the flow interaction with baffles were installed at the top and side of the channel. To reproduce the viscosity of debris flows caused by fine-grained soil in the flume, glycerin was mixed with debris materials (sand and gravel). After the test, the velocity and energy dissipation according to various baffle arrays were estimated. Test results showed that the installation of baffles reduced the frontal velocity of debris flows. Furthermore, taller baffles also increased the effect of the energy dissipation in debris flows, but additional rows of the baffle did not have a major effect on the energy dissipation. Thus, increasing the height of baffle led to an increased efficiency of energy dissipation of debris flows.</p>

Effects of human-induced load models on tuned mass damper in reducing floor vibration

2019 ◽  
Vol 22 (11) ◽  
pp. 2449-2463
Author(s):  
Jun Chen ◽  
Ziping Han ◽  
Ruotian Xu
Keyword(s):  
Response Spectra ◽  
Tuned Mass Damper ◽  
Design Guidelines ◽  
Degree Of Freedom ◽  
Dynamic Responses ◽  
Single Degree Of Freedom ◽  
Load Model ◽  
Load Models ◽  
Single Degree ◽  
Mass Damper

Dozens of human-induced load models for individual walking and jumping have been proposed in the past decades by researchers and are recommended in various design guidelines. These models differ from each other in terms of function orders, coefficients, and phase angles. When designing structures subjected to human-induced loads, in many cases, a load model is subjectively selected by the design engineer. The effects of different models on prediction of structural responses and efficiency of vibration control devices such as a tuned mass damper, however, are not clear. This article investigates the influence of human-induced load models on performance of tuned mass damper in reducing floor vibrations. Extensive numerical simulations were conducted on a single-degree-of-freedom system with one tuned mass damper, whose dynamic responses to six walking and four jumping load models were calculated and compared. The results show a maximum three times difference in the acceleration responses among all load models. Acceleration response spectra of the single-degree-of-freedom system with and without a tuned mass damper were also computed and the response reduction coefficients were determined accordingly. Comparison shows that the reduction coefficient curves have nearly the same tendency for different load models and a tuned mass damper with 5% mass ratio is able to achieve 50%–75% response reduction when the structure’s natural frequency is in multiples of the walking or jumping frequency. All the results indicate that a proper load model is crucial for structural response calculation and consequently the design of tuned mass damper device.

scholarly journals Inundation, flow dynamics, and damage in the 9 January 2018 Montecito debris-flow event, California, USA: Opportunities and challenges for post-wildfire risk assessment

Geosphere ◽  
2019 ◽  
Vol 15 (4) ◽  
pp. 1140-1163 ◽  
Author(s):  
J.W. Kean ◽  
D.M. Staley ◽  
J.T. Lancaster ◽  
F.K. Rengers ◽  
B.J. Swanson ◽  
...  
Keyword(s):  
Debris Flow ◽  
Debris Flows ◽  
Field Measurements ◽  
Economic Loss ◽  
Flow Dynamics ◽  
Dynamic Constraints ◽  
Fire Debris ◽  
Velocity Information ◽  
Intense Burst ◽  
Comprehensive Framework

Abstract Shortly before the beginning of the 2017–2018 winter rainy season, one of the largest fires in California (USA) history (Thomas fire) substantially increased the susceptibility of steep slopes in Santa Barbara and Ventura Counties to debris flows. On 9 January 2018, before the fire was fully contained, an intense burst of rain fell on the portion of the burn area above Montecito, California. The rainfall and associated runoff triggered a series of debris flows that mobilized ∼680,000 m3 of sediment (including boulders >6 m in diameter) at velocities up to 4 m/s down coalescing urbanized alluvial fans. The resulting destruction (including 23 fatalities, at least 167 injuries, and 408 damaged homes) underscores the need for improved understanding of debris-flow runout in the built environment, and the need for a comprehensive framework to assess the potential loss from debris flows following wildfire. We present observations of the inundation, debris-flow dynamics, and damage from the event. The data include field measurements of flow depth and deposit characteristics made within the first 12 days after the event (before ephemeral features of the deposits were lost to recovery operations); an inventory of building damage; estimates of flow velocity; information on flow timing; soil-hydrologic properties; and post-event imagery and lidar. Together, these data provide rare spatial and dynamic constraints for testing debris-flow runout models, which are needed for advancing post-fire debris-flow hazard assessments. Our analysis also outlines a framework for translating the results of these models into estimates of economic loss based on an adaptation of the U.S. Federal Emergency Management Agency’s Hazus model for tsunamis.

Power Flow Calculation in Distribution System Considering Different Load Model

2013 ◽  
Vol 722 ◽  
pp. 103-106 ◽  
Author(s):  
Tian Shu ◽  
Wang Li
Keyword(s):  
Power Flow ◽  
Simulation Software ◽  
Constant Current ◽  
Power Flow Calculation ◽  
Constant Power ◽  
Flow Calculation ◽  
Load Model ◽  
Load Models ◽  
Power Load ◽  
Constant Power Load

In traditional power flow calculation used constant power load model, it was completely unreasonable to assume that all load nodes in power system can be classified as PQ nodes.In that the result of constant power load model does not accurately reflect the distribution characteristics of network power flow. To put forward power flow calculation considering load models ,such as constant power load ,constant current load and constant resistance load, derives error equations of the node power, calculates element of Jacobian matrix. So, by using MATLAB simulation software ,the program for power flow are presented, which based on the method of different load models, taking 21-node system for example and makes comparative calculations. The research shows that power flow calculation considering different load models can get more reasonable solution.

Analysis on Load Model for Cost Optimization Using Embedded Meta EP-Firefly Algorithm for DG Installation

2015 ◽  
Vol 793 ◽  
pp. 478-482
Author(s):  
S.R.A. Rahim ◽  
Ismail Musirin ◽  
Muhammad Murtadha Othman ◽  
Muhamad Hatta Hussain
Keyword(s):  
Distributed Generation ◽  
Distribution System ◽  
Firefly Algorithm ◽  
Cost Optimization ◽  
Load Model ◽  
Load Models ◽  
Generation Planning ◽  
Voltage Dependent ◽  
The Cost

This paper presents the analysis on load models for cost optimization for distributed generation planning. The Embedded Meta EP – Firefly Algorithm technique is performed in order to identify the optimal distributed generation sizing. The result obtained show that the proposed technique has an acceptable performance to simulate the data and voltage dependent load models have a significant effect on total losses of a distribution system consequently will affect the cost of the system.

scholarly journals On compressible and piezo-viscous flow in thin porous media

2018 ◽  
Vol 474 (2209) ◽  
pp. 20170601 ◽  
Author(s):  
F. Pérez-Ràfols ◽  
P. Wall ◽  
A. Almqvist
Keyword(s):  
Porous Media ◽  
Pressure Drop ◽  
Viscous Fluid ◽  
Linear Equation ◽  
Nonlinear Function ◽  
Viscous Fluids ◽  
Total Flow ◽  
Thin Porous Media ◽  
Flow Through ◽  
The One

In this paper, we study flow through thin porous media as in, e.g. seals or fractures. It is often useful to know the permeability of such systems. In the context of incompressible and iso-viscous fluids, the permeability is the constant of proportionality relating the total flow through the media to the pressure drop. In this work, we show that it is also relevant to define a constant permeability when compressible and/or piezo-viscous fluids are considered. More precisely, we show that the corresponding nonlinear equation describing the flow of any compressible and piezo-viscous fluid can be transformed into a single linear equation. Indeed, this linear equation is the same as the one describing the flow of an incompressible and iso-viscous fluid. By this transformation, the total flow can be expressed as the product of the permeability and a nonlinear function of pressure, which represents a generalized pressure drop.

scholarly journals Electric field measurements on Cluster: comparing the double-probe and electron drift techniques

2006 ◽  
Vol 24 (1) ◽  
pp. 275-289 ◽  
Author(s):  
A. I. Eriksson ◽  
M. André ◽  
B. Klecker ◽  
H. Laakso ◽  
P.-A. Lindqvist ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Cold Plasma ◽  
Field Measurements ◽  
Low Energy ◽  
Electron Drift ◽  
Double Probe ◽  
Flow Energy ◽  
Potential Control ◽  
Spacecraft Potential

Abstract. The four Cluster satellites each carry two instruments designed for measuring the electric field: a double-probe instrument (EFW) and an electron drift instrument (EDI). We compare data from the two instruments in a representative sample of plasma regions. The complementary merits and weaknesses of the two techniques are illustrated. EDI operations are confined to regions of magnetic fields above 30 nT and where wave activity and keV electron fluxes are not too high, while EFW can provide data everywhere, and can go far higher in sampling frequency than EDI. On the other hand, the EDI technique is immune to variations in the low energy plasma, while EFW sometimes detects significant nongeophysical electric fields, particularly in regions with drifting plasma, with ion energy (in eV) below the spacecraft potential (in volts). We show that the polar cap is a particularly intricate region for the double-probe technique, where large nongeophysical fields regularly contaminate EFW measurments of the DC electric field. We present a model explaining this in terms of enhanced cold plasma wake effects appearing when the ion flow energy is higher than the thermal energy but below the spacecraft potential multiplied by the ion charge. We suggest that these conditions, which are typical of the polar wind and occur sporadically in other regions containing a significant low energy ion population, cause a large cold plasma wake behind the spacecraft, resulting in spurious electric fields in EFW data. This interpretation is supported by an analysis of the direction of the spurious electric field, and by showing that use of active potential control alleviates the situation.

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