scholarly journals Experimental Study of Cohesive Embankment Dam Breach Formation due to Overtopping

2020 ◽  
Author(s):  
Getachew Bereta ◽  
Peng Hui ◽  
Han Kai ◽  
Liwen Guang ◽  
Pan Kefan ◽  
...  
Keyword(s):  
Flow Velocity ◽  
Scale Model ◽  
Small Scale ◽  
Embankment Dam ◽  
Flow Discharge ◽  
Evacuation Plans ◽  
Using Data ◽  
Improved Design ◽  
The Stability ◽  
Headcut Erosion

The recurrent floods in recent decades have imposed a challenge of embankment dam breaching, which needs great attention through improved design methods that are based on risk approach, the evacuation plans for people at risk, etc. In this study, based on the small-scale model tests a series of experiments were conducted to determine the breaching process of cohesive embankment dam using a simplified physical based breach model due to overtopping; the breach process observed during tests in the laboratory and the results from analyzed parameters are described. Five dam models, three of which were constructed with homogenous clay soil while two were sandy-clay mixture tested. The heights of the embankments dam were 0.45 m, and the widths at the crest were 0.20 m. The data from these examinations indicated that headcut erosion played an important role in the process of breach development. Initiation of erosion, flow shear erosion, sidewall bottom erosion, and distinct soil mechanical slope mass failure from the headcut vertically and laterally were all observed during these tests. In this physical based experimental model, the initial scouring position calculated by applying a hydraulic method, the broad crested weir formula used for breaching flow discharge and flow velocity computed based on breach flow discharge. The stability of the side slope failures was estimated by comparing the resisting and deriving force. Further, using data from laboratory experiments, the calculated peak breach discharge, breach characteristics times, breach widths, and breach flow velocity generally agreed well with the measured data and also the knowledge acquired from observed breach process at several stages. Finally, the accuracy of model was checked by root-mean-square-error.

scholarly journals MODEL TESTING OF PILED CLUSTERS AND LARGE MONO-PILES OF IMPROVED DESIGN

2017 ◽  
Vol 2 (49) ◽  
pp. 38-44
Author(s):  
M. P. Doubrovsky ◽  
I. Yu. Dobrov ◽  
A. V. Gerashchenko ◽  
O. M. Dubrovska
Keyword(s):  
Laboratory Experiments ◽  
Model Testing ◽  
Scale Model ◽  
Small Scale ◽  
Pile Head ◽  
Laboratory Conditions ◽  
Improved Design ◽  
Energy Absorbing ◽  
Small Scale Model ◽  
Flexible Pile

When constructing piled clusters and structures supported by large mono-piles, piles designed are used to take up significant lateral and pressing-in loads. New effective and less resource-demanding design of piled cluster was considered before. At this paper some results of its model testing in laboratory conditions are analyzed and discussed. To increase energy-absorbing capacity of mooring/fender dolphins it was worked out and researched a new design of combined tubular mono-pile structure, incorporating internal flexible pile and damping element placed at the zone of pile head. This design has been tested by laboratory experiments using small scale model. Obtained results confirm its effectiveness and practicability.

scholarly journals RESPONSE OF SEADYKES DUE TO WAVE IMPACTS

1976 ◽  
Vol 1 (15) ◽  
pp. 149 ◽  
Author(s):  
A. Fuhrboter ◽  
H.H. Dette ◽  
J. Grune
Keyword(s):  
Laboratory Data ◽  
Breaking Waves ◽  
Scale Model ◽  
Small Scale ◽  
Air Entrapment ◽  
Small Areas ◽  
Impact Forces ◽  
The Stability ◽  
Short Time ◽  
The Impact

Damages on seadykes and revetments are mainly caused by wave impacts due to breaking waves. These impact forces act on small areas for a very short time and cause crater-like formations, when the forces are transmitted instantaneously to the side-walls of cracks in the cover of dykes or through joints into and below revetments. In this paper the results of investigations on impact forces are presented. A comparison of field data and laboratory data proves considerable differences, which must be explained mainly by the different air entrapment for prototype and small-scale conditions in the breaking waves. Both the data from field and small-scale model emphasize, that the slope of the dyke or revetment is responsible at first for frequency and magnitude of the impact forces. Furthermore the effect of impact forces is demonstrated by the results of investigations on the stability of stone revetments with joints.

scholarly journals Influence of the Existing Cavern on the Stability of Adjacent Tunnel Excavation by Small-Scale Model Tests

2014 ◽  
Vol 15 (12) ◽  
pp. 117-128
Author(s):  
Minchul Jung ◽  
Jungsoon Hwang ◽  
Jongseob Kim ◽  
Seungwook Kim ◽  
Seungcheol Baek
Keyword(s):  
Model Tests ◽  
Scale Model ◽  
Small Scale ◽  
Tunnel Excavation ◽  
The Stability ◽  
Small Scale Model

scholarly journals Experimental Tests on a Small-Scale Model of a Mine Stope to Study the Behavior of Waste Rock Barricades during Backfilling

Minerals ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 941
Author(s):  
Mutaz Nujaim ◽  
Tikou Belem ◽  
Albert Giraud
Keyword(s):  
Volumetric Strain ◽  
Experimental Tests ◽  
Waste Rock ◽  
Scale Model ◽  
Small Scale ◽  
Downstream Face ◽  
Solid Mass ◽  
The Stability ◽  
Reduced Scale ◽  
Small Scale Model

This paper presents a reduced-scale physical model of a mine stope used to reproduce the underground stope backfilling practiced in some Canadian mines. The objective is to study the geomechanical behavior of the waste rock barricades in interaction with the mine backfill. The instrumentations, along with visual observations and preliminary results, are presented. The main results demonstrated that: (i) the stability of the barricade depends on its physical properties (e.g., size, location, particles gradation and compaction) and the frictional behavior at the barricade/drift walls interface, and (ii) for two backfill formulations, cemented and uncemented, prepared with 70% of solid mass concentration, the volumetric strain due to self-weight consolidation of the backfilled room was higher for uncemented backfill (16%) than for the cemented one (4.5%). In addition, the results highlighted the importance of using shotcrete around the downstream face of the barricade, mostly at the top, to close the gaps and bind the barricade particles, which improves its stability.

scholarly journals ON THE STABILITY OF RUBBLE-MOUND BREAKWATERS Jose Joaquim

2011 ◽  
Vol 1 (7) ◽  
pp. 34
Author(s):  
Jose Joaquim Reis De Carvalho ◽  
Daniel Vera-Cruz
Keyword(s):  
Model Tests ◽  
Scale Model ◽  
Small Scale ◽  
Existing Structures ◽  
Rubble Mound ◽  
The Stability ◽  
Steep Slopes ◽  
Rubble Mound Breakwaters ◽  
The Waves ◽  
Level 2

Until the beginning of the second quarter of the present century, characteristics of rubble-mound breakwaters were determined by entirely empirical methods, although harbour engineers had been deal ing with this problem for man;> centuries. As a rule, designers merely compared the case under study with existing structures, prescribing sturdier breakwaters when those located in shores with a similar exposure had not withstood the most violent storms acting on them. The first empirical formula for breakwater design did not appear before 1933, but this and other similar formulas did not go beyond ordering and reducing the use of arbitrary methods in the choice of the elements making up the breakwater slopes more directly subjected to wave action; no sensible progress resulting there? From for the design methods of these structures.lt can even be stated that, due to the use of Iribarren's formula - the most widely used in Europe - which leads to the utilization of too heavy blocks placed in steep slopes (about ^/3)» a tendency began to be observed in designers, towards a considerable reduction of these slopes. Such a situation which, bearing in mind the knowledge available until about 10 years ago, was perfectly admissible, has been subjected to considerable changes thanks to: 1) the enormous advances achieved in the theoretical field, which placed our knowledge on the majority of Maritime Hydraulics subjects on a satisfactory level; 2) the invaluable help of small scale model tests, and3) our improved knowledge on natural phenomena which makes possible a comparatively satisfactory estimate of the characteristics of the waves to be anticipated at any point of the coast*We have merely to persevere along the route followed in the latter years in order to determine more accurate values fir the coefficients of the available formulas, representing the results obtained by means of graphs and tables, resorting for that purpose both to model tests and to a careful observation of the behaviour of completed structures throughout the world, above all those which underwent damages. On the other hand efforts should not be spared in concentrated attempts to discover new formulas as phenomena are, no doubt much too complex in the destruction of a breakwater to allow of a single satisfactory scheaetization. It should be borne in mind that, in spite of the laboratory tests recently carried out, our knowledges is limited to the area directly affected by the wave breaking and so a total knowledge of the stability of rubble-mound breakwaters lies still a long way ahead.

scholarly journals SMALL-SCALE MODEL TESTS ON THE HYDRAULIC STABILITY OF STRUCTURES IN TIDAL WATERWAYS

2017 ◽  
pp. 46
Author(s):  
Theide Wöffler ◽  
Moritz Kreyenschulte ◽  
Jan Oetjen ◽  
Klemens Uliczka ◽  
Holger Schüttrumpf
Keyword(s):  
Periodic Wave ◽  
Model Tests ◽  
Scale Model ◽  
Small Scale ◽  
Wave System ◽  
Periodic Waves ◽  
Wave Loads ◽  
Traffic Volumes ◽  
The Stability ◽  
Stability Of Structures

During the last years, an increased amount of damage has been observed on estuarine and riverine waterway structures such as groins or training walls in tidal waterways. The cause of these damages could be attributed to ship-induced long-periodic waves. Because of higher traffic volumes and increased ship dimensions these loads have risen. In contrast to short-periodic secondary waves, the long-periodic wave system is not taken into account in existing design approaches so far. In the framework of the project “Ship-induced long-periodic loads for the design of cover layers on maritime waterway structures” small-scale 2D physical model tests have been performed in order to quantify the specific overflow and overtopping rate taking into account different geometries, surface roughnesses and permeabilities of the structures as well as stationary overflow, short- and long-periodic waves. Furthermore, the stability of the structures under short- and long-periodic wave loads has been observed. These tests provide the basis for the design of cover layers on river structures in maritime waterways.

scholarly journals DESIGN ASPECTS OF BLOCK REVETMENTS

1988 ◽  
Vol 1 (21) ◽  
pp. 151
Author(s):  
K.W. Pilarczyk
Keyword(s):  
Large Scale ◽  
Rapid Development ◽  
Concrete Block ◽  
Scale Model ◽  
Small Scale ◽  
Design Criteria ◽  
Advantages And Disadvantages ◽  
Different Types ◽  
The Stability ◽  
The Moment

The increasing shortage and costs of natural materials in certain geographical areas has resulted in recent years, inter alia, in the rapid development of artificial (concrete) block revetments. In general, two main types of revetments can be distinguished: permeable (stone pitching, placed relatively open block-mats) and (relatively-) impermeable (closed blocks, concrete slabs). Regarding the shape and/or placing technique a distinction can be made between: a) free (mostly rectangular-) blocks and b) interlocking blocks of different design (tongue-and-groove connection, ship- lap, cabling, blocks connected to geotextile by pins etc.). In all these cases the type of sublayer (permeable/impermeable) and the grade of permeability of the toplayer are very important factors in the stability of these revetments. The design also needs to be made (executed) and maintained. Both aspects must therefore already be taken along within the stadium of designing. At the moment there is a large variety of types of revetment-blocks and other defence systems (i.e. block-mats), see Fig. 1. Until recently no objective design-criteria were available for most types/systems of blocks. The choice (type and size) of the revetments built sofar is only based on experience and on personal points of view, sometimes supported by small-scale model investigations. In the light of new (stricter) rules regarding the safety of the Dutch dikes, as they have been drawn up by the Delta-Commission, the need for proper design-criteria for the revetments of dikes has evidently grown. Because of the complexity of the problem no simply, generally valid mathematical model for the stability of the revetment are available yet. For restricted areas of application however, fairly reliable criteria (often supported by large-scale tests) have been developed in the Netherlands not only for the kind of revetment, but also for conditions of loads. This new approach is discussed in (Klein Breteler, 1988). This paper presents a short state-of-the-art review of existing knowledge on the designing of different types of revetments and, where ever possible, the available stability criteria are mentioned. There is also given some comparison of the different types of revetments with their advantages and disadvantages and suggestions regarding their practical application.

Influence of Geometric Scaling on the Stability and Range of a Turbocharger Centrifugal Compressor

2005 ◽  
Author(s):  
Matthias Schleer ◽  
Reza S. Abhari
Keyword(s):  
Flow Structure ◽  
Centrifugal Compressor ◽  
System Stability ◽  
Scale Model ◽  
Small Scale ◽  
Operating Characteristics ◽  
Design Features ◽  
Geometric Scaling ◽  
Wide Range ◽  
The Stability

In this work the stability behavior of small-scale centrifugal compressor is evaluated in detail and the influence of design features typical for small-scale applications is shown. The impeller used in this study represents the design features of machines typically used in small turbochargers like a low blade count, high blade loading and a large relative tip gap. The work is evaluating data obtained in an enlarged research facility and in an actual scale turbocharger application. Both facilities are using a geometrical similar impeller and all nondimensional parameter are maintained. The Reynolds number is adjusted by changing the inlet pressure and thus the density of the air. This setup allows measurements with high accuracy on the enlarged research stage and simple parameter studies on the small-scale model. Comparing the operating characteristics of both scales shows the validity of this approach. For the range of Reynolds numbers present, the stability of the compressor is not affected by the geometric scaling. As the user of the compressor system wishes to operate at a wide range and under varying load demands but always in stable condition the knowledge of the stability margin and the kind of instabilities is vital. An analysis of the instable phenomena limiting the range of the centrifugal compressors is shown. The analyses are interpreting the pressure fluctuations gained with high response pressure transducer located in the diffuser for the characterization of the system stability. A similar overall compressor characteristic and stability range is obtained for both scales investigated. The flow structure within the diffuser is shown in a time-resolved manner using a 3D Laser Doppler Anemometer. It is shown how the flow structure is affected by the leakage flow through the tip gap. It is forming a strong jet-wake pattern resulting in a non-uniform flow and sheared velocity triangles.

ESTIMATION OF TECHNICAL, SPECIALIZED AND ECONOMIC EFFICIENCY OF CULTIVATED POTATO VARIETIES USING DATA ENVELOPE ANALYSIS METHOD (DEA) IN IRAQ FOR SPRING LUG 2018

2020 ◽  
pp. 119-131
Keyword(s):  
Technical Efficiency ◽  
Economic Efficiency ◽  
Potato Crop ◽  
Economic Status ◽  
Analysis Method ◽  
Envelope Analysis ◽  
Variable Capacity ◽  
Data Envelope Analysis ◽  
Using Data ◽  
The Stability

Research highlights the importance of potato crop, which occupies a prominent food and economic status in food security besides rice, wheat and corn at the local and global level. Despite the expansion of the cultivation of potato crop in Iraq in general and Ameriyah district in particular However, potato productivity remains substandard, this may be due to a lack of knowledge of the most efficient varieties and not to use productive resources at the levels at which technical, specialized and economic efficiency is achieved. Therefore, the aim of the research is to determine the technical, specialized and economic efficiency according to the cultivated seed category. The data envelope analysis (DEA) method was used to estimate technical, specialized and economic efficiency, assuming constant and variable capacity returns. As a result of the study, the Safrana variety achieved the highest average technical efficiency according to the stability of the yield and capacity efficiency in addition to achieving the highest average specialized and economic efficiency, The Lapadia variety achieved the highest average technical efficiency, assuming that capacity returns have changed. Therefore, we recommend the adoption of items that achieve higher efficiency and the need to redistribute the elements of production better and Achieving the optimum levels at which technical, specialized and economic efficiency is achieved and saving what has been wasted.

Sign in / Sign up

Export Citation Format

Share Document