Major Engineering Problems Research Articles

Investigation of the effect of aggregate shape and surface roughness on the slake durability index using the fractal dimension approach

Argillaceous rocks cover about one thirds of the earth's surface. The major engineering problems encountered with weak- to medium-strength argillaceous rocks could be slaking, erosion, slope stability, settlement, and reduction in strength. One of the key properties for classifying and determining the behavior of such rocks is the slake durability. The concept of slake durability index (SDI) has been the subject of numerous researches in which a number of factors affecting the numerical value of SDI were investigated. In this regard, this paper approaches the matter by evaluating the effects of overall shape and surface roughness of the testing material on the outcome of slake durability indices. For the purpose, different types of rocks (marl, clayey limestone, tuff, sandstone, weathered granite) were broken into chunks and were intentionally shaped as angular, subangular, and rounded and tested for slake durability. Before testing the aggregate pieces of each rock type, their surface roughness was determined by using the fractal dimension. Despite the variation of final values of SDI test results (values of I d), the rounded aggregate groups plot relatively in a narrow range, but a greater scatter was obtained for the angular and subangular aggregate groups. The best results can be obtained when using the well rounded samples having the lowest fractal values. An attempt was made to analytically link the surface roughness with the I d parameter and an empirical relationship was proposed. A chart for various fractal values of surface roughness to use as a guide for slake durability tests is also proposed. The method proposed herein becomes efficient when well rounded aggregates are not available. In such condition, the approximate fractal value for the surface roughness profile of the testing aggregates could be obtained from the proposed chart and be plugged into the empirical relation to obtain the corrected I d value. The results presented herein represent the particular rock types used in this study and care should be taken when applying these methods to different type of rocks.

Issues of effectiveness in empirical methods for describing swelling soils

Swelling soils are a major engineering problem and the establishment of new and fast methods for their identification continues to be a major subject of research. Several engineering methods were here used to obtained indices used in the estimation of swelling potential in a group of soil samples with a wide variation in swelling and to classify them into swelling potential classes. The indices were then reduced through factor analysis to obtain a new swell index that was used to obtain the spectral parameters to best correlate with the index where absorption feature mapping, optical density, and derivative spectral data analysis methods were used to establish these parameters. The spectral parameters found to have high correlations with the swell index were then used to establish statistical empirical models to quantify soil swelling from spectral data. The physical understanding of these spectral parameters was also sought and the results show a close relationship between the clay mineralogy related bound water and hydroxyl spectral features in the soil spectra and the swelling index. The bound water parameters gave positive and the hydroxyl related parameters negative correlations to this index. The results confirm the strong influence of the clay mineralogy on the soil properties.

Cation Exchange Capacity (CEC) determination from spectroscopy

Swelling soils are a major engineering problem and their detection is one of the most important site investigation undertakings in the construction industry. Methods of their detection have been developed over the years, most of which utilize the soil physical properties as the indices of their identification. Some of these have proved quite expensive and time-consuming. In this research an alternative, relatively faster and cheaper method is explored. The method involves the use of Methylene Blue Absorption (MBA) as the engineering index to estimate the Cation Exchange Capacity (CEC) and spectral absorption feature characteristics as the mineral identification method. The relationship between the MBA and the characteristics of the absorption features is used to explore the possibility of estimating CEC from spectral data.

Fuel Cells: State-of-the-Art and Major Scientific and Engineering Problems

Basic results of research and engineering-technical work on fuel cells (mostly membrane and methanol systems), obtained mainly in the last decade, are reviewed, with attention focused on the electrocatalytic aspect. Many works on the engineering, construction, and production of fuel cells and on the mass transfer remain outside this review, as do intrinsically theoretical works on electrocatalysis. Questions of technical and economic adaptation of these to various applications are discussed.

Geological hazards in loess terrain, with particular reference to the loess regions of China

The considerable morphodynamic energy provided by the continuing tectonic evolution of Asia is expressed in high erosional potentials and very high rates of sediment production that make this continent unequalled as a terrestrial source of primary silt. Many of these environments are hazardous, threatening human occupation, health and livelihood, especially in regions of dense population such as the loess lands of north China. Dry loess can sustain nearly vertical slopes, being perennially under-saturated. However, when locally saturated, it disaggregates instantaneously. Such hydrocompaction is a key process in many slope failures, made worse by an underlying mountainous terrain of low-porosity rocks. Gully erosion of loess may yield very high sediment concentrations (>60% by weight). Characteristic vertical jointing in loess influences the hydrology. Enlarged joints develop into natural sub-surface piping systems, which on collapse, produce a “loess karst” terrain. Collapsible loess up to 20 m thick is common on the western Loess Plateau. Foundation collapse and cracked walls are common, many rapid events following periods of unusually heavy monsoonal rain. Slope failure is a major engineering problem in thick loess terrain, flow-slide and spread types being common. The results are often devastating in both urban and rural areas. An associated hazard is the damming of streams by landslides. The human population increases the landslide risk in China, notably through imprudent land-use practices including careless water management. A number of environmentally related endemic diseases arise from the geochemistry of loess and its groundwaters, including fluorosis, cretinism, Kaschin–Beck Disease, Keshan Disease and goitre. The Chinese desert margins also have a major atmospheric dust problem. The effect of such dust upon human health in these extensive regions, including many large cities, has yet to be evaluated, but pneumoconiosis is thought to affect several million people in north and west China.

Flintshire Bridge [Pont Sir Y Fflint], Wales: Design Aesthetics and Innovation

Acclaimed winning design of the competition to devise the new River Dee crossing, the landmark Flintshire Bridge in Wales, United Kingdom, opened on March 6, 1998, by Her Majesty the Queen, defines new levels of excellence in engineering design and technology. A long-span, cable-stayed asymmetric concrete structure, it represents a radical resolution of major environmental, aesthetic, and technological problems, resulting in significant advances in the techniques of modern bridge building. A demonstration of the state of the art in civil engineering, it has won local and national praise. The impact of the use of concrete in relation to aesthetics, engineering, and architecture is discussed, in particular the use of a project as a pilot scheme for the development of a new specification for internally grouted posttensioned concrete following the collapse of a bridge in Wales due to corrosion. The innovation relating to the inherent instability of parallel strands (stay cables) in rain and light wind is discussed, together with the resulting innovations to overcome associated problems.

“Optimum offset” seismic reflection mapping of shallow aquifers near Bangkok, Thailand

The “optimum offset” shallow seismic reflection technique was developed for geotechnical and groundwater applications in the early 1980s. The method was based on equipment that was “state of the art” at the time: a 10-bit engineering seismograph, a simple inhole shotgun source, and Apple II personal computers for data processing. In 1985 and 1986, this technique was successfully used in Thailand to assist in understanding the land subsidence problem around Bangkok, which is directly attributable to excessive groundwater withdrawal. The seismic sections acquired in this study were used to map subsurface structure to a depth of about 180 m, which includes several major aquifers beneath the Bangkok Clay. Much of Bangkok’s domestic water is pumped from the so‐called “second aquifer,” 80–130 m below surface, which proved to be an excellent seismic marker horizon showing lateral continuity over distances on the order of kilometers. This observation suggests that there may be good hydraulic connection within this aquifer over large areas. While the technique and equipment used in this study are dated now, the results provide a valuable demonstration of the application of inexpensive shallow reflection methods to a major engineering and groundwater problem that is of concern in many urban centers around the world. It is presented here for its societal relevance in this regard and for its historical aspect as perhaps the first application of shallow seismic reflection profiling in Southeast Asia.

Advanced Process for the Production of Clean Coal by Chemical Leaching Technique

If coal must be used in industry to replace oil that becomes scarce, the coal should be demineralized to get a clean, high-heating-value, noncorrosive, free flowing solid fuel. Alkali leaching of coal under ambient pressure followed by acid leaching under milder conditions affords a convenient process for cleaning coal up to a degree of demineralization of 75%. The conditions for alkali-acid leaching have been optimized. Toxic mineral microconstituents are removed to give a clean coal for burning in thermal power stations or in industries. The demineralized, clean, high-heating-value coal can be used for coal-water or coal-oil mixture combustion and in diesel engines as a noncorrosive clean fuel. The advanced bench scale process developed may be improved by scaling up the present work and undertaking further work on process economics and studies on the major engineering problems involved.

Depth profiles and retention of helium in amorphous alloy irradiated with helium ions

Radiation damage of material is one of the major technological problems in design of fusion reactors. Since the first wall is struck by α particles and 14 MeV neutrons created by D-T burning, thermal plasma and neutral atoms, study of the first wall radiation damage becomes very important. Radiation damage of the wall materials are divided into two aspects: bulk and surface damage. Surface damage of the first wall caused by α particle bombardment has already attrracted much attention in research of the fusion reactors.

International Convention Centre, Birmingham, England

The International Convention Centre, opened to the public in April 1991, comprises eleven halls on a site adjacent to the city centre. One of the eleven halls is a major new Symphony Hall for the City of Birmingham Symphony Orchestra which is also used for conferences and which enlivens the convention centre through usage by the public as well as conference delegates. While many smaller halls are rectangular, the larger halls are typically non-orthogonal in plan. The principal exhibition hall is octagonal, and the ends of the Symphony Hall are curved. The siting is ideal in that the building complex forms the closing end to a major new square built to celebrate the centenary of Birmingham. However, the site imposed major engineering and building problems due to adjacent road traffic and a main line railway tunnel underneath.

Land subsidence and sea level rise on the Atlantic Coastal Plain of the United States

Land subsidence due to decline in head in confined aquifers, related to municipal and industrial water pumpage, is widespread in the Atlantic Coastal Plain. Although not a major engineering problem, subsidence greatly complicates adjustment of precise leveling and distorts prediction of future sea-level rise. When preconsolidation stress equivalent to about 20 m of head decline is exceeded compaction of fine-grained sediments of the aquifer system begins, and continues until a new head equilibrium is attained between fine and coarse units. The ratio subsidence/head decline is quite consistent, ranging from 0.0064 in southeastern Virginia to 0.0018 at Dover, Delaware and Atlantic City, New Jersey. Higher values are related to the occurrence of montmorillonite as the predominant clay mineral present. Review of tide gauge records indicates that gauges not affected by land subsidence or other local secular effects have been sinking relative to sea level since 1940 at rates averaging about 2.5 mm/yr, of which 0.6 mm/yr is ascribed to glacio-isostatic adjustment to unloading of North America resulting from melting of late Pleistocene glaciers, and about 0.9 mm/yr is ascribed to steric sea-level rise related to ocean warming. The residual 1 mm/yr of relative sea-level rise is not well understood, but may be related to regional tectonic subsidence of the Atlantic coast.

Coastal erosion in the eastern half of Christchurch Bay

Abstract Christchurch Bay has a long history of shoreline recession and this has given rise to some major coastal engineering problems. An area of particular concern is Hurst Beach at its eastern end, where the maximum rate of recession has increased from 1.5 m a -1 (1867 to 1968) to 3.5 m a -1 (1968 to 1982). Hurst Castle itself is now subject to wave attack on part of its frontage. The littoral sediment movement was assumed to be essentially continuous around Christchurch Bay, but, in fact, a littoral drift sub-cell boundary (i.e. a partial barrier to littoral drift) is present in the vicinity of Hordle Cliff. Therefore, the increased recession of Hurst Beach is a local problem. Milford-on-Sea is situated on a thick sequence of Pleistocene Gravels, whose erosion contributed substantially to the maintenance of Hurst Castle Spit as a major physiographic feature. However, a series of coast protection works were constructed to protect Milford-on-Sea between 1936 and 1968, removing this important source of sediment. In the long term, without any further human interference, recession rates of up to 6 m a -1 will probably occur along Hurst Beach. A breach of Hurst Beach is a major concern, as it would create an island at Hurst Castle and expose the vulnerable, low-lying, northern coast of the West Solent, including the village of Keyhaven, to increased wave attack and tidal scour. Ecologically important saltmarshes would also be destroyed. Shingle renourishment is the only environmentally acceptable engineering solution. Limited renourishment has already commenced. Any cost benefit decisions must consider the wider implications of a breach in Hurst Beach, including environmental and ecological considerations. This case study demonstrates the importance of a detailed understanding of both the littoral and offshore sediment movement for the planning of coast protection.

The chemical engineering side of nuclear fusion power

AbstractIt is widely recognized that chemical engineering has important roles to play in the development of national and worldwide energy resources through optimal utilization of fossil fuel reserves. It is much less appreciated that there are crucial chemical engineering problems in the development of energy production from other sources. In particular, the successful development of nuclear fusion power generating systems will require the solution of many problems that are uniquely suited to chemical engineers.This paper presents a brief overview of the fusion development program for magnetically confined fusion power reactors and an identification of the major technological problems remaining to be solved.

MOVABLE BED TIDAL INLET MODELS

Stabilization of tidal inlets is a major engineering problem that is frequently encountered in the development of harbors. The planning, design, and modification of these inlets under the dynamic conditions that generally characterize their surroundings is, at best, a complex and uncertain undertaking. Prediction of the sedimentary response of an existing inlet to artificial improvements and to changing environmental conditions, or of a new inlet to the expected ambient conditions, and the optimization of the layout in order to minimize undesirable accretion or erosion are major elements in the design of tidal inlets. Because of the complexity of the problem, movable bed hydraulic models often are employed, despite the questions that surround their validity, to investigate these responses and to guide designs. The success of a movable bed hydraulic model depends upon the proper choice of similitude conditions and modeling criteria. Unfortunately, the conditions of similitude still are not well defined, as many of the phenomena constituent to the processes involved are yet to be elucidated adequately and formulated. Moreover, it is not possible to satisfy simultaneously all of the similitude conditions that arise. The required grain size and density of the model bed material, the current exaggeration that may be required, the effects of geometric distortion, etc. cannot be determined by straightforward computations. These must be chosen to obtain the most favorable balance between all relevant phenomena. The criteria of similitude generally are specified by experimenters who have previous experience with this type of model. The execution of a model studies of this type is, therefore, largely an "art" and entails major elements of subjectivity. The Iowa Institute of Hydraulic Research, under contract to Coastal Engineering Research Center, U.S. Army Corps of Engineers, is presently (1976) conducting a study to evaluate the reliability and effectiveness of movable bed, tidal inlet, hydraulic models as predictors of prototype behavior. The main emphasis of this study is on comparison of model predictions with observations made in the prototypes, and evaluation of model performance in the light of: (i) the criteria of similitude adopted; (ii) the sedimentary material and instrumentation utilized in the models; (iii) the experimental procedure followed; (iv) the quality of the prototype data utilized in verification of the models; and (v) the degree and accuracy of model verification. The scope of this study is limited to those models in which the area of interest is composed entirely of movable material and not of just a thin erodible layer placed over a fixed bathymetry.

A Critique of MHD Power Generation

Magnetohydrodynamic electrical power generation is a promising new technique for upgrading the efficiency of converting heat into electricity. The concept has been explored intensively but on a small scale during the past ten years, and the initial enthusiasm in it has been confirmed. Its utilization in base-load plants, in addition to increasing overall efficiency, can also lead to important reductions in the adverse environmental effects of thermal and air pollution. The projected efficiencies of large dual cycle systems are initially in the range of 47–50 percent, and improvements in technology could later increase this to 60 percent. In an MHD system, energy is extracted from a flowing electrically conducting fluid. The fluid may be either a seeded plasma or a liquid metal. Various MHD power cycles and systems are therefore under consideration. The status of these systems will be reviewed with emphasis on their application to large central-station commercial systems. The major technological problems and progress in the three major cycles (open cycle, closed-cycle plasma, and closed-cycle liquid metal) will be discussed in depth. In the open-cycle system, the engineering solutions that have been proposed for the major problems in the generator and auxiliary equipment will be detailed. In addition, the experience gained from the operation of a succession of generators will be summarized. In the case of the closed-cycle plasma system, the progress that has been made toward developing a generator with the requisite conversion efficiency will be cited. Recent cycle analyses that have established the conditions for matching these systems to current heat sources will also be reviewed and their implications noted. The potential of developing liquid-metal MHD systems for commercial application will be explored in the light of recently obtained experimental and analytical performance information. In particular, promising new techniques that can lead to improved efficiencies will be detailed.

Ultraviolet Astronomy

Ultraviolet astronomy is in a phase of very rapid development and any review of the new techniques involved is necessarily conditioned by the fact that most of the work is in a preparatory stage. This paper, therefore, will not be restricted to a discussion of those techniques which have undergone the ultimate test of their effectiveness, i.e., an actual space mission, but will include a consideration of those techniques which are still under development. Some omissions are therefore inevitable.The presentation is divided into three categories: (a) the vehicle and its stabilisation (if any), (b) the optics, and (c) detectors. Category (a) presents the major new technological problems and contributes the greater part of the total cost. Experience in the other categories of optics and detectors had, of course, reached an advanced and sophisticated level at the time of the advent of the rocket, but new and difficult problems have been posed mainly by their operation in a space environment, but also by their use in the ultraviolet region of the spectrum.

Economics and productivity in tomorrow’s arc furnace

The present technical position of the electric arc furnace is favorable for the production of large tonnages of mild steels. Furnaces can now operate in the 250 to 274-ton heat size range, and can be made even larger without encountering any major engineering problems. High power arc operation has been demonstrated in commercial practice, and will probably be economically attractive in many situations.

HURRICANE STUDIES FOR NARRAGANSETT BAY

Hurricane flooding has emerged as one of the major coastal engineering problems of the Atlantic and Gulf Coast areas of the United States. Engineering and scientific investigations have been made to determine the fundamental mechanics of the hurricane surges that cause inunda tion of coastal areas and to develop practical and economical protection. Mathematical models and large hydraulic models were used for the Narragansett Bay studies of two major projects. The discussions presented herein are limited to the hydraulic studies of barriers at the mouth of the bay, known as the Lower Bay Barri Plan, and a brief description of this plan and the Fox Point Hurricane Barrier which is now under construction.

Design of a multichannel magnetic recording system for frequency multiplication

This paper concerns a multichannel magnetic tape recorder/reproducer whose primary function is to provide stable, real-time multiplication (100 times) of all frequencies present at the input. This is accomplished by the use of rotating playback head assembly, located near and downstream of a conventional record station. This arrangement yields a short processing delay and, because of the iterative scans, makes possible time division multiplexing of other system components. System requirements and characteristics are presented along with a discussion of the major engineering problems that had to be solved.

Personal radio antennas

The trend toward personalizing vehicular radio sets has been accompanied by major engineering problems. Of these, one of the most challenging is that of designing an efficient antenna to occupy a small space. Due to these size limitations, personal radio antennas will be referred to as small antennas. This paper will describe a series of tests made under laboratory conditions followed by a coverage study made under service conditions in city streets to evaluate the relative performance of small antennas and accumulate propagation data for system design. The laboratory measurements included a study of the properties of ferrite loop antennas, coils, whips and short wire antennas. The field measurements covered actual recorded field strength data from personal carried transmitters using reference quarter-wave whips. It was concluded that ¾-wave whips even when working against as poor a ground plane as the set chassis offered the best performance. However, the 20 to 25 db of shadow loss found in city streets plus a 10 to 15 db antenna loss even with whips will severely restrict the coverage of personal transmitters. Other steps may be necessary if adequate areas are to be reliably covered.