Soil and Soil Mechanics

The word “Soil” is derived from the Latin word “solum” which, according to Webster’s dictionary, means ‘the upper layer of the earth that may be dug or plowed specifically, the loose surface material of the earth in which plants grow’. The term ‘Soil’ has different meanings in different scientific fields. To an agricultural scientist, it means ‘‘the loose material on the earth’s crust consisting of disintegrated rock with an admixture of organic matter, which supports plant life’’. To a geologist, it means the disintegrated rock material which has/has not been transported from the place of origin.

But, to a civil engineer, the term ‘soil’ means, the loose unconsolidated inorganic material on the earth’s crust produced by the disintegration of rocks, overlying hard rock with or without organic matter. Foundations of all structures have to be placed on or in such soil, which is the primary reason for its engineering behaviour.

In general, soils are formed by weathering of rocks. The formation of soil happens over a very long period of time. The physical properties of soil are dictated primarily by the minerals that constitute the soil particles and, hence, the rock from which it is derived. The mineral grains that form the solid phase of a soil aggregate are the product of rock weathering. The size of the individual grains varies over a wide range. Many of the physical properties of soil are dictated by the size, shape and chemical composition of the grains.

Soils are formed over thousands of years through the weathering of parent rocks, which can be igneous, sedimentary or metamorphic rocks. Igneous rocks (e.g., granite) are formed by the cooling of magma (underground) or lava (above the ground). Sedimentary rocks (e.g., limestone, shale) are formed by gradual deposition of fine soil grains over a long period. Metamorphic rocks (e.g., marble) are formed by altering igneous or sedimentary rocks by pressure or temperature or both. Soils are quite different from other engineering materials, which makes them interesting and at the same time challenging.

Soil Mechanics

Karl Terzaghi (an Austrian geotechnical engineer, and geologist known as the "father of soil mechanics and geotechnical engineering) defined Soil Mechanics as follows:

“Soil Mechanics is the application of the laws of mechanics and hydraulics to engineering problems dealing with sediments and other unconsolidated accumulations of solid particles produced by the mechanical and chemical disintegration of rocks regardless of whether or not they contain an admixture of organic constituents.”

The term Soil Mechanics is now accepted quite generally to designate that discipline of engineering science which deals with the properties and behavior of soil as a structural material. All structures have to be built on soils. The application of the principles of soil mechanics to the design and construction of foundations for various structures is known as ‘‘Foundation Engineering’’. ‘‘Geotechnical Engineering’’ may be considered to include both soil mechanics and foundation engineering.

History and Development of Soil Mechanics

The use of soil for engineering purposes dates back to prehistoric times. Soil was used not only for foundations but also as construction material for embankments. The knowledge was empirical in nature and was based on trial and error, and experience. The hanging gardens of Babylon were supported by huge retaining walls, the construction of which should have required some knowledge of earth pressures. The large public buildings, harbours, aqueducts, bridges, roads and sanitary works of Romans certainly indicate some knowledge of the engineering behaviour of soil. This has been evident from the writings of Vitruvius, the Roman Engineer in the first century, B.C. Mansar and Viswakarma, in India, wrote books on ‘construction science’ during the medieval period.

The Leaning Tower of Pisa, Italy, built between 1174 and 1350 A.D., is a glaring example of a lack of sufficient knowledge of the behaviour of compressible soil, in those days. Coulomb, a French Engineer, published his wedge theory of earth pressure in 1776, which is the first major contribution to the scientific study of soil behaviour. He was the first to introduce the concept of shearing resistance of the soil as composed of the two components— cohesion and internal friction. Poncelet, Culmann and Rebhann were the other men who extended the work of Coulomb. D’ Arcy and Stokes were notable for their laws for the flow of water through soil and settlement of a solid particle in liquid medium, respectively. These laws are still valid and play an important role in soil mechanics.

Rankine gave his theory of earth pressure in 1857; he did not consider cohesion, although he knew of its existence. Boussinesq, in 1885, gave his theory of stress distribution in an elastic medium under a point load on the surface. Mohr, in 1871, gave a graphical representation of the state of stress at a point, called ‘Mohr’s Circle of Stress’. This has an extensive application in the strength theories applicable to soil. Atterberg, a Swedish soil scientist, gave in 1911 the concept of ‘consistency limits’ for a soil. This made possible the understanding of the physical properties of soil.

The Swedish method of slices for slope stability analysis was developed by Fellenius in 1926. He was the chairman of the Swedish Geotechnical Commission. Prandtl gave his theory of plastic equilibrium in 1920 which became the basis for the development of various theories of bearing capacity. Terzaghi gave his theory of consolidation in 1923 which became an important development in soil mechanics. He also published, in 1925, the first treatise on Soil Mechanics, a term coined by him. Thus, he is regarded as the Father of modern soil mechanics’. Later on, R.R. Proctor and A. Casagrande and a host of others were responsible for the development of the subject as a full-fledged discipline.

Application of Soil Mechanics

1) Foundations

The loads from any structure have to be ultimately transmitted to a soil through the foundation for the structure. Thus, the foundation is an important part of a structure, the type and details of which can be decided upon only with the knowledge and application of the principles of soil mechanics. A foundation is termed shallow foundation when it transmitted the load to upper strata of earth. A foundation is called deep foundation when the load is transmitted to strata at considerable depth below the ground surface. Pile foundation is a type of deep foundation.

Shallow Foundation

Deep Foundation

2) Earth-Retaining Structures

When sufficient space is not available for a mass of soil to spread and form a safe slope, a structure is required to retain the soil. An earth retaining structure is also required to keep the soil at different levels on its either side. The retaining structure may be rigid retaining wall or a sheet pile which is relatively flexible. Such as retaining walls can be designed and constructed only by using the principles of soil mechanics and the concept of ‘soil-structure interaction’.

Retaining Wall

Sheet Pile

3) Stability of Slopes

If soil surface is not horizontal, there is a component of weight of the soil which tends to move it downward and thus causes instability of slope. The slopes may be natural or man-made. Soil engineering provides the methods for checking the stability of slopes.

Embankment Slope

4) Underground structures

The design and construction of underground structures, such as tunnels and conduits, require evaluation of forces exerted by the soil on these structures.

Tunnel

5) Pavement Design

Pavement Design may consist of the design of flexible or rigid pavements. Flexible pavements depend more on the subgrade soil for transmitting the traffic loads. Problems peculiar to the design of pavements are the effect of repetitive loading, swelling and shrinkage of sub-soil and frost action. Consideration of these and other factors in the efficient design of a pavement is a must and one cannot do without the knowledge of soil mechanics.

Pavement

6) Excavations, Embankments and Dams

Excavations require the knowledge of slope stability analysis; deep excavations may need temporary supports such as ‘timbering’ or ‘bracing’, the design of which requires knowledge of soil mechanics. Likewise the construction of embankments and earth dams where soil itself is used as the construction material requires a thorough knowledge of the engineering behaviour of soil especially in the presence of water.

Earth Dam

7) Miscellaneous Soil

The geotechnical engineer has sometimes to tackle miscellaneous problems related with soil. Such as soil heave, soil subsidence, frost heave, shrinkage and swelling of soils.

Read More

Fine aggregate/Sand

Aggregate is the granular material used to produce concrete or mortar. Sand is a form of silica (quartz) and may be of argillaceous, siliceous or calcareous according to its composition. Natural sands are formed from weathering of rocks (mainly quartzite) and are of various size or grades depending on the intensity of weathering. The sand grains may be of sharp, angular or rounded. Aggregates passing through 4.75mm sieve and retained on 75micron sieve is termed as fine aggregate.

Fine aggregate sand is important ingredient of mortar and cement concrete. Sand particles consist of small grains of silica. It is formed by decomposition of sand stone due to various effects of weather. River sand is widely used as fine aggregate. Fine aggregates are classified as follows: 

1. Source of Origin 
2. Grain Size 
3. Composition

I) Classification according to Sources of Origin

Sand particles consist of small grains of silica (Si02). It is formed by the decomposition of sand stones due to various effects of weather. The following are the natural sources of sand.

1) Pit Sand

This sand is found as deposits in soil and it is obtained by forming pits to a depth of about 1m to 2m from ground level. Pit sand consists of sharp angular grains, which are free from salts for making mortar. Clean pit sand free from organic matter and clay should be used.

Pit Sand

2) River Sand

This sand is obtained from beds of rivers. River sand consists of fine rounded grains. Colour of river sand is almost white. As the river sand is usually available in clean condition, it is widely used for all purposes.

River Sand

3) Sea Sand

This sand is obtained from sea shores. Sea sand consists of rounded grains in light brown colour. Sea sand consists of salts which attract the moisture from the atmosphere and causes dampness, efflorescence and disintegration of work. Due to all such reasons, sea sand is not recommendable for engineering works. However be used as a local material after being thoroughly washed to remove the salts.

Sea Sand

The natural product which is obtained as river sand & pit sand is called sand.

II) Classification Fine Aggregate According to Grain Size

Fine aggregate	Size variation (mm)
Coarse Sand	0.5 – 2.0
Medium sand	0.25 –  0.5
Fine sand	0.060 – 0.25
Silt	0.0020 – 0.06
Clay	<0.002

III) Classification Fine Aggregate According to Composition 

1) Clean Sand 

These are well-graded sand containing quartz particles in a wide range of grain sizes. 

2) Silty Sand 

These are poorly graded, having a considerable proportion of silt and other non-plastic fines. 

3) Clayey Sand 

There is poorly graded sand that has a prominent clay fraction and also plastic fines.

Requirement of good sand

1. It should be hard
2. It should be chemically inert
3. It should be free from salts
4. It should free from organic matters
5. It should be well graded

Uses of sand

1. It is used in mortar
2. It is used in concrete
3. It is used for the filling the gaps between the building blocks
4. It is used as binding materials in the form of paste
5. It prevents the shrinkage of cementing materials.

Alternatives to river sand

Sand is a vital ingredient in making two most used construction materials viz. cement concrete and mortar. Traditionally River sand, which is formed by natural weathering of rocks over many years, is preferred as fine aggregate. The economic development fuelling the growth of infrastructure and housing generates huge demand for building materials like sand. The indiscriminate mining of sand from riverbeds is posing a serious threat to environment such as erosion of riverbed and banks, triggering landslides, loss of vegetation on the bank of rivers, lowering the ground water table etc. Demand for sand is increasing day by day and at the same time mining threats cannot be ignored. Hence, sand mining from riverbeds is being restricted or banned by the authorities like National Green Tribunal, State Environmental Impact Assessment Authority and Pollution Control Board. Hence it is necessary to find and use the alternative for river sand.

Some of the Alternatives to River sand are:

• Manufactured sand
• Processed quarry dust
• Processed crushed rock fines
• Offshore sand
• Processed glass
• Aluminum saw mill waste
• Granite fines slurry
• Washed soil (filtered sand)
• Fly ash (bottom ash/ pond ash)
• Slag sand
• Copper slag sand
• Construction Demolition waste

Manufactured Sand (M-Sand)

Manufactured sand is an alternative for river sand. Due to fast growing construction industry, the demand for sand has increased tremendously, causing deficiency of suitable river sand in most part of the word. Due to the depletion of good quality river sand for the use of construction, the use of manufactured sand has been increased. Another reason for use of M-Sand is its availability and transportation cost. Since manufactured sand can be crushed from hard granite rocks, it can be readily available at the nearby place, reducing the cost of transportation from far-off river sand bed. Thus, the cost of construction can be controlled by the use of manufactured sand as an alternative material for construction. The other advantage of using M-Sand is, it can be dust free, the sizes of M sand can be controlled easily so that it meets the required grading for the given construction.

M-Sand

Advantages of Manufactured Sand

• It is well graded in the required proportion. It does not contain organic and soluble compound that affects the setting time and properties of cement, thus the required strength of concrete can be maintained. 
• It does not have the presence of impurities such as clay, dust and silt coatings, increase water requirement as in the case of river sand which impair bond between cement paste and aggregate. Thus, increased quality and durability of concrete.

Read More

Types of Drawings

Drawing

A drawing is a graphic representation of an object, or a part of it and is the result of creative thought by an engineer or technician. Graphic communication involves using visual materials to relate ideas. Drawings, photographs, slides, transparencies and sketches are all forms of graphic communication. One of the most widely used forms of graphic communication is the drawing.

Technically, it can be defined as “a graphic representation of an idea, a concept or an entity which actually or potentially exists in life”. Drawing is one of the oldest forms of communicating, dating back even farther than verbal communication. The drawing itself is a way of communicating all necessary information about an abstract, such as an idea or concept or a graphic representation of some real entity, such as a machine part, house or tools. There are two basic types of drawings: Artistic and Technical drawings.

1) Artistic Drawings

Artistic Drawings range in scope from the simplest line drawing to the most famous paintings. Regardless of their complexity, artistic drawings are used to express the feelings, beliefs, philosophies and ideas of the artist. In order to understand an artistic drawing, it is sometimes necessary to first understand the artist. Artists often take a subtle or abstract approach in communicating through their drawings, which in turn gives rise to various interpretations.

Artistic drawing

2) Technical Drawings

The technical drawing is not subtle, or abstract. It does not require an understanding of its creator, only an understanding of technical drawings. A technical drawing is a means of clearly and concisely communicating all of the information necessary to transform an idea or a concept in to reality. Therefore, a technical drawing often contains more than just a graphic representation of its subject. It also contains dimensions, notes and specifications.

                      Technical drawing

Purpose of Technical Drawings

To appreciate the need for technical drawings, one must understand the design process. The design process is an orderly, systematic procedure used in accomplishing a needed design. Any product that is to be manufactured, fabricated, assembled, constructed, built or subjected to any other types of conversion process must first be designed. For example, a house must be designed before it can be built.

Application of Technical Drawing

Technical drawings are used in many different applications. They are needed in any setting, which involves design and in any subsequent forms of conversion process. The most common applications of technical drawings can be found in the fields of manufacturing, engineering and construction. For instance, surveyors, civil engineers, sanitarians use technical drawings to document such works as the layout of a new subdivisions or the marking of the boundaries for a piece of property. Construction personnel use the technical drawings as their blue prints in converting architectural and engineering designs into reality.

Read More

History of Surveying

Surveying had its origins in ancient Egypt. The Great Pyramid of Khufu at Giza was built in 2700 BC, 755 feet long and 480 feet high. Its nearly perfect square and north-south orientation affirm the ancient Egyptian’s knowledge of surveying. Evidence of some form of boundary surveying (as early as 1400 BC) has been found in the fertile valleys and plains of the Tigris, Euphrates and Nile rivers. Clay tablets of the Sumerians show records of land measurement and plans of cities and nearby agricultural areas. Boundary stones marking land plots have been preserved. There is a representation of land measurement on the wall of a tomb at Thebes in Egypt (1400 BC) showing head and rear chainmen measuring a grain field with what appears to be a rope with knots or marks at uniform intervals. Two are of high estate, according to their clothing, probably a land overseer and an inspector of boundary stones.

There is some evidence that, in addition to a marked cord, wooden rods were used by the Egyptians for distance measurement. The Egyptians had the groma, which was used to establish right angles. It was made of a horizontal wooden cross, pivoted at the middle and supported from above. A plumb bob was hung from the end of each of the four arms. A plumb bob is a shaped weight that hangs from a string. Because of the weight, the string will always be vertical. By sighting along each pair of plumb bob cords in turn, the right angle could be established. The device could be adjusted to a precise right angle by observing the same angle after turning the device approximately 90°. By shifting one of the cords to take up half the error, a perfect right angle would be obtained.

                                                                                             Egyptian groma

There is no record of any angle-measuring instruments of that time, but there was a level consisting of a vertical wooden A-frame with a plumb bob supported at the peak of the ‘A’ so that its cord hung past an indicator, or index, on the horizontal bar. The index could be properly placed by standing the device on two supports at approximately the same elevation, marking the position of the cord, reversing the ‘A’, and making a similar mark. Halfway between the two marks would be the correct place for the index.

                                                                                              A - frame

Thus, with their simple devices, the ancient Egyptians were able to measure land areas, replace property corners lost when the Nile covered the markers with silt during floods, and build the huge pyramids to exact dimensions. The Greeks used a form of log line for recording the distances run from point to point along the coast while making their slow voyages from the Indus to the Persian Gulf about 325 BC.

The Greeks introduced the astrolabe, which is an instrument to measure the altitude of stars above the horizon, in the 2nd century BC. It took the form of a graduated arc suspended from a hand-held cord. A pivoted pointer that moved over the graduations was pointed at the star. The instrument was not used for nautical surveying for several centuries, remaining a scientific aid only.

During their occupation of Egypt, the Romans acquired Egyptian surveying instruments, which they improved slightly and to which they added the water level and the plane table. About 15 BC, the Roman architect and engineer Vitruvius mounted a large wheel of known circumference in a small frame, in much the same fashion as the wheel is mounted on a wheelbarrow; when it was pushed along the ground by hand it automatically dropped a pebble into a container at each revolution, giving a measure of the distance travelled. It was, in effect, the first odometer.

                                                                                 Vitruviu's first odometer

The water level consisted of either a trough or a tube turned upward at the ends and filled with water. At each end there was a sight made of crossed horizontal and vertical slits. When these were lined up just above the water level, the sights determined a level line accurate enough to establish the grades of the Roman aqueducts. In laying out their great road system, the Romans are said to have used the plane table. It consists of a drawing board mounted on a tripod (a three legged stand (similar to that used by photographers) or other stable support.

It also consists of a straightedge ruler, usually with sights for accurate aim (the alidade) to the objects to be mapped, along which lines are drawn. It was the first device capable of recording or establishing angles. Later adaptations of the plane table had magnetic compasses attached. Arab traders brought the magnetic compass to the west in the 12th century AD. Plane tables were in use in Europe in the 16th century. Surveyors practiced the principle of graphic triangulation and intersection.

                                                                                            Plane table

In 1615 Willebrord Snell, a Dutch mathematician, measured an arc of meridian by instrumental triangulation. In 1620 the English mathematician Edmund Gunter developed a surveying chain, which was superseded only by the steel tape in the beginning of the 20th century. A surveyors chain consists of a series of links, each link about 0.2m long, used to measure distances accurately. Every 10 links (about 2m) has a small disc hanging from the chain, so that the position can be accurately measured.

                                                                                    Surveyors chain/Gunters chain

The study of astronomy resulted in the development of angle-reading devices that were based on arcs of large radii, making such instruments too large for field use. With the publication of logarithmic tables in 1620, portable angle measuring instruments came into use. They were called topographic instruments, or theodolites. They included pivoted arms for sighting and could be used for measuring both horizontal and vertical angles. Magnetic compasses may have been included on some. The vernier, an auxiliary scale permitting more accurate readings (1631), the micrometer microscope (1638), telescopic sights (1669) and spirit levels (about 1700) were all incorporated in theodolites by about 1720.

The development of the circle-dividing engine about 1775, a device for dividing a circle into degrees with great accuracy, brought one of the greatest advances in surveying methods, as it enabled angle measurements to be made with portable instruments far more accurately than had previously been possible.

By the late 18th century modern surveying can be said to have begun. One of the most notable early feats of surveyors was the measurement in the 1790s of the meridian from Barcelona, Spain, to Dunkirk, France, by two French engineers, Jean Delambre and Pierre Méchain. This was to establish the basic unit for the metric system of measurement. Many improvements and refinements have been incorporated in all the basic surveying instruments. These have resulted in increased accuracy and speed of operations and have opened up possibilities for improved methods in the field.

During the nineteenth century, the combination of a hot air balloon and a camera were used to produce maps and plans. It was difficult to survey large areas because the balloons were slow moving and a new photographic negative had to be loaded into the camera after each photograph was taken. In 1862 union soldiers used cameras mounted in hot air balloons to map behind the confederate lines.

It was not until the turn of the twentieth century, with the developments of the aircraft and invention of the roll of photographic film, that aerial photographs started to be used extensively within the survey industry. The first light wave Electronic Distance Measurement instrument was developed in 1943 to measure the velocity of light. Once the velocity of light was known, it was then possible to reverse the process so that a distance could be measured. In 1954, the light wave was replaced by a radio wave to increase the distance that could be measured. In the late 1960s, lasers were first used with EDMs.

In the mid to late 1970s, the United States of America sent their first Global Positioning System satellites into space. The final development was the extensive use of computers to perform most common data processing and recording of survey data.

Read More

Water Resources Engineering

Water is an essential ingredient for sustenance of life. The total quantity of water available on earth is estimated to be about 1400 million cubic kilometer, which is enough to cover the earth with a layer 3 km deep. However, 97.3% of this is saltwater in oceans, thereby leaving only 2.7% freshwater. Again, about 75% of the freshwater lies frozen in the Polar Regions and about 22.6% are groundwater- some of it very deep to be economically extractable. The surface freshwater is thus only about 0.007% of the total water occurring on earth. With increasing population, while the demand for water increases, anthropogenic pressures are rendering many water sources unfit for use because of the high level of pollution. Development and management of water resources is thus one of the important aspects of development at the present time. 

Water Resources Engineering is the science of designing, developing and managing projects and systems to protect and use water resources in a sustainable and efficient manner. This includes the design, construction and operation of water supply systems, flood control, water quality and water resources management. This engineering field is closely related to hydrology and the science of studying the properties of water and how it is distributed and used by humans. It can include the study of watersheds, rivers, lakes and coastal areas. 

Water Resources Engineering is a huge field which involves managing available water resources from the standpoint of both water quantity and water quality to meet the water needs of humanity and habitats at the local, regional, national or international level. It is the study and management of equipment, facilities and techniques that are used to manage and preserve life’s most plentiful resource - water. In addition to assessing how and the best ways to control water as it pertains to water-related activities – such as irrigation, waste disposal and canal development. Water resource engineers are also frequently involved in water management to ensure that it’s safe to drink both for humans, plants and animal usage. 

Managing water requires a sound understanding of water distribution systems such as rivers, canals, pipelines, culverts, ground water wells and water storage systems such as reservoirs, retention-detention ponds and aquifers. Water resources engineers must also have knowledge of various structures that are used to manage the conveyance of water such as sluice gates, emergency spillways and structures that are used to store water such as dams and dikes. In addition, water resources engineers must know techniques to assess future water demand as well as the quantity and quality of the available water resources in water bodies such as rivers, lakes and groundwater. Water resources engineers should also be familiar with the transport processes such as evaporation, transpiration, runoff and infiltration which are used by nature to move water globally.

History 

Water resources engineering has its roots in the ancient world, with evidence of its use in the Middle East, India and China since 3000 BC. Ancient civilizations used water engineering techniques to irrigate their agricultural land and store water for long-term use. In the middle ages, water engineering was used to build dams and canals for the purpose of flood control and agricultural irrigation. In the 16th and 17th centuries, water engineering began to be used for other purposes such as water supply and sewage systems, as well as providing a source of energy through the use of water wheels. In the 19th century, advances in engineering and technology have allowed engineers to design and build more complex water resource projects such as aqueducts and irrigation canals.

Water resources engineering has evolved over the past 9000 to 10,000 years as humans have developed the knowledge and techniques for building hydraulic structures to convey and store water. Early examples include irrigation networks built by the Egyptians and Mesopotamians and by the Hohokam in North America. The world’s oldest large dam was the Sadd-el-kafara dam built in Egypt between 2950 and 2690 B.C. The oldest known pressurized water distribution (approximately 2000 B.C.) was in the ancient city of Knossos on Crete. There are many examples of ancient water systems throughout the world.

The importance of water resources engineering includes the following: 

1. It is essential to managing our water resources, helps to ensure the availability of clean drinking water, efficient use of water for agricultural purposes and protect our water sources. 
2. It helps improve water quality to meet human and environmental needs. It can also help to reduce water pollution and to conserve water resources. 
3. It is also important for infrastructure development and management of water systems. This includes the construction of dams, reservoirs, canals, pipelines and other water-related infrastructure. 
4. It is essential for flood prevention and management, helps to identify possible areas of flooding, design and construction of dams and other flood control structures. 
5. It is important for agricultural production and also helps develop irrigation systems, drainage systems and erosion control systems that improve crop yields and reduce the risk of crop loss due to drought and other environmental factors. 
6. It is important for coastal zone management. They help to identify risk zones for coastal erosion and flooding and develop solutions to reduce these risks. 

Examples of water resources engineering projects include the following: 

• Construction of artificial reservoirs 
• Groundwater recharge 
• Drip irrigation systems 
• Desalination plants
• Flood Control Systems

Read More

Fluid Mechanics

Fluid mechanics is the branch of science that deals with the study of fluids (liquids and gases) in a state of rest or motion. Fluid mechanics is a science concerned with the response of fluids to forces exerted upon them. A fluid is a substance which deforms continuously under the application of a shear stress. The applications of fluid mechanics is enormous: breathing, blood flow, swimming, pumps, fans, turbines, airplanes, ships, rivers, windmills, pipes, missiles, icebergs, engines, filters, jets and sprinklers etc. It is an important subject of civil, mechanical and chemical engineering. 

From the point of view of fluid mechanics, all matter consists of only two states, fluid and solid. The difference between the two is perfectly obvious. The technical distinction lies with the reaction of the two to an applied shear or tangential stress. A solid can resist a shear stress by a static deflection; a fluid cannot. Any shear stress applied to a fluid, no matter how small, will result in motion of that fluid. The fluid moves and deforms continuously as long as the shear stress is applied. As a corollary, we can say that a fluid at rest must be in a state of zero shear stress.

Fluid

A substance that flows is called as fluid. All liquid and gaseous substances are considered to be fluids. Water, oil and others are very important in our day-to-day life as they are used for various applications. For instance water is used for generation of electricity in hydroelectric power plants and thermal power plants, water is also used as the coolant in nuclear power plants, oil is used for the lubrication of automobiles etc.

Whether the fluid is at rest or motion, it is subjected to different forces and different climatic conditions and it behaves in these conditions as per its physical properties. Its various branches are fluid statics, fluid kinematics and fluid dynamics. 

Fluid Statics 

The fluid which is in state of rest is called as static fluid and its study is called as fluid statics. 

Fluid Kinematics 

The fluid which is in state of motion is called as moving fluid. The study of moving fluid without considering the effect of external pressures is called as fluid kinematics. 

Fluid Dynamics 

The branch of science which studies the effect of all pressures including the external pressures on the moving fluid is called as fluid dynamics.

Liquid and Gases

A fixed amount of a liquid has a definite volume which varies only slightly with temperature and pressure. If the capacity of the containing vessel is greater than this definite volume, the liquid occupies only part of the container and it forms an interface separating it from its own vapour, the atmosphere or any other gas present.

A fixed amount of a gas, by itself in a closed container, will always expand until its volume equals that of the container. Only then can it be in equilibrium. In the analysis of the behaviour of fluids an important difference between liquids and gases is that, whereas under ordinary conditions liquids are so difficult to compress that they may for most purposes be regarded as incompressible, gases may be compressed much more readily. Where conditions are such that an amount of gas undergoes a negligible change of volume, its behaviour is similar to that of a liquid and it may then be regarded as incompressible. If, however, the change in volume is not negligible, the compressibility of the gas must be taken into account in examining its behaviour.

The continuum

An absolutely complete analysis of the behaviour of a fluid would have to account for the action of each individual molecule. In most engineering applications, however, interest centres on the average conditions of velocity, pressure, temperature, density and so on. Therefore, instead of the actual conglomeration of separate molecules, we regard the fluid as a continuum that is a continuous distribution of matter with no empty space. This assumption is normally justifiable because the number of molecules involved in the situation is so vast and the distances between them are so small. The assumption fails, when these conditions are not satisfied as, for example, in a gas at extremely low pressure.

Read More

Mechanics of Solids

Solid mechanics (also known as mechanics of solids) is the branch of Continuum Mechanics that studies the behavior of solid materials, especially their motion and deformation under the action of forces, temperature changes, phase changes and other external or internal agents. The application of the principles of mechanics to bulk matter is conventionally divided into the mechanics of fluids and the mechanics of solids. The entire subject is often called continuum mechanics.

Solid mechanics is also defined as a branch of applied mechanics that deals with behaviours of solid bodies subjected to various types of loadings. Solid mechanics is concerned with the stressing, deformation and failure of solid materials and structures.

The various bodies on which engineers are interested to apply laws of mechanics may be classified as Solids and Fluids.

Solids

The bodies which do not change their shape or size appreciably when the forces are applied are termed as solids. It can support normal forces.

Example: stone, steel, concrete etc.

Fluids

The bodies which change their shape or size appreciably even when small forces are applied are termed as fluids.

Example : water, gases etc.

History 

Solid mechanics developed in the outpouring of mathematical and physical studies by the Newton laws of motion. The need to understand and control the fracture of solids in structural member seems to have been a first motivation. Leonardo da Vinci sketched in his notebooks a possible test of the tensile strength of a wire. Galileo had investigated the breaking loads of rods under tension and concluded that the load was independent of length and proportional to the cross section area, this being a first step toward a concept of stress. He also investigated the breaking loads on beams that were suspended horizontally from a wall into which they were built.

Solid mechanics is usually subdivided into further two streams i.e Mechanics of rigid bodies or simply Mechanics and Mechanics of deformable solids. 

Rigid body 

Rigid bodies do not deform (stretch, compress or bend) when subjected to external loads. Rigid body is basically defined as a body where changes in the distance between any two of its points are negligible.

In actuality, no physical body is completely rigid, but most bodies deform so little that this deformation has a minimal impact on the analysis. For this reason, we usually assume that bodies in the statics and dynamics are rigid. 

Deformable body 

Deformable bodies deform (stretch, compress or bend) when subjected to external loads. Deformable body is basically defined as a body where changes in the distance between any two of its points could not be neglected.

Read More

Urban Planning

Urban planning, also known as town planning, is a technical and political process that is focused on the development and design of land use and the built environment, including air, water and the infrastructure passing into and out of urban areas, such as transportation, communication and distribution networks and their accessibility. (Urban planning is similar to town planning but done on a much larger scale). Urban planning is the design and regulation of the uses of space that focus on the physical form, economic functions and social impacts of the urban environment. Urban planning concerns itself with both the development of open land and the revitalization of existing parts of the city, thereby involving goal setting, data collection and analysis, forecasting, design, strategic thinking and public consultation. Increasingly, the technology of geographic information systems (GIS) has been used to map the existing urban system and to project the consequences of changes. 

Urban planning is an interdisciplinary field that includes aspects of civil engineering, architecture, geography, political science, environmental studies, design science and other sciences. Practitioners of urban planning are concerned with research and analysis, strategic thinking, engineering architecture, urban design, public consultation, policy recommendations, implementation and management. 

The modern origins of urban planning lie in a social movement for urban reform that arose in the latter part of the 19th century as a reaction against the disorder of the industrial city. Many visionaries of the period sought an ideal city, yet practical considerations of adequate sanitation, movement of goods and people and provision of amenities also drove the desire for planning. Contemporary planners seek to balance the conflicting demands of social equity, economic growth, environmental sensitivity and aesthetic appeal. The result of the planning process may be a formal master plan for an entire city or metropolitan area, a project plan, or a set of policy alternatives. Successful implementation of a plan usually requires entrepreneurship and political astuteness. 

Traditionally, urban planning followed a top-down approach in planning the physical layout of human settlements. The primary concern was the public welfare, which included considerations of efficiency, sanitation, protection and use of the environment, as well as effects of the master plans on the social and economic activities. Over time, urban planning has adopted a focus on the social and environmental bottom-lines that focus on planning as a tool to improve the health and well-being of people while maintaining sustainability standards. Sustainable development was added as one of the main goals of all planning endeavors in the late 20th century when the detrimental economic and the environmental impacts of the previous models of planning had become apparent.

Urban

The concrete technical aspects defining ‘urban’ are: 

• Population size 
• Population density 
• Economic base
• Presence of a municipal body

There must be a minimum number of people residing in the place for it to be called urban; these people must be concentrated in a particular area and not scattered; there should be a minimum number of people in one unit area of land; they should be engaged in economic activities other than primary ones such as agriculture or animal rearing etc. and there must be a municipality or town committee or a planning and governing body to take care of the services and planning of that place. There is no common minimum number that can be put against these aspects, as no numbers are universally applicable all over the world. All countries have their own specifications for each of these aspects and they vary considerably.

In India, the Census defines an urban area as one with: 

• Population more than 5000 
• Population density over 400 persons per sq.km 
• 75% of the male population engaged in non-agricultural occupations

Read More

Construction Engineering

Construction Engineering is a professional discipline that deals with the designing, planning, construction and management of infrastructures such as roads, tunnels, bridges, airports, railroads, facilities, buildings, dams, utilities and other projects. Construction engineering is similar to civil engineering, which also focuses on infrastructure design and development, but with more emphasis on managing the construction process on project sites. It is an important field because it ensures structures are safe, well-made and dependable. It also makes sure construction projects get finished by a set date and according to strict plans and building codes.

Construction engineers are involved in nearly every step of a construction project, from its design to its implementation. They manage building projects and maintenance, often being present to oversee workers and activities on-site. Projects and infrastructure that construction engineers might work on include:

• Roads and highways
• Bridges
• Tunnels
• Railroads
• Housing projects
• Airports
• Energy sources like dams
• Facilities such as wastewater treatment plants
• Utilities
• Drainage and sewage systems
• Public buildings such as hospitals and sports stadiums

The typical duties of a construction engineer include:

• Calculating the cost of inspections, testing, materials, equipment and labor to create a budget for each project
• Managing funds appropriately to stay within budget
• Using computer software and simulations to create project designs and 3D models
• Performing risk analysis
• Surveying potential construction sites and planning their layouts
• Preparing bids from contractors and managing the contracting firms they hire
• Choosing and acquiring materials and equipment
• Hiring and overseeing workers and setting their schedules
• Making sure projects follow environmental laws, government regulations and building codes
• Designing and overseeing the construction of temporary structures needed on-site
• Using engineering and business skills to solve any problems that might occur during construction
• Staying up-to-date on the latest technology, building laws and construction processes 

Successful construction projects require a highly coordinated team effort. Builders and skilled trade’s people are required to lay brick, construct frames, install plumbing and electrical systems and ensure completion of a long list of other elements. With a large-scale construction project, construction engineers play an essential role in designing and implementing complicated building plans. They may also oversee the development or maintenance of critical infrastructure, ranging from roads and bridges to dams and water supplies.

Read More

Environmental Engineering

Environmental Engineering is a branch of civil and chemical engineering that is concerned with natural resource management, the use of water, environmental pollution and human health. It is the study of problems associated with soil, air and water pollution. Environmental engineering is the development of processes and infrastructure for the supply of water, the disposal of waste and the control of pollution of all kinds. The aim is to protect public health by preventing disease transmission and to preserve the quality of the environment by averting the contamination and degradation of air, water and land resources. It was traditionally a specialized field within civil engineering and was called sanitary engineering until the mid-1960s and then the more accurate name Environmental Engineering was adopted.

As per ASCE, Environmental engineering is a profession that applies mathematics and science to utilize the properties of matter and sources of energy in the solution of problems of environmental sanitation. These include the provision of safe, palatable and ample public water supplies; the proper disposal of or recycle of wastewater and solid wastes; the adequate drainage of urban and rural areas for proper sanitation; and the control of water, soil and atmospheric pollution and the social and environmental impact of these solutions. Furthermore it is concerned with engineering problems in the field of public health, such as control of arthropod-borne diseases, the elimination of industrial health hazards, and the provision of adequate sanitation in urban, rural and recreational areas and the effect of technological advances on the environment. 

Projects in environmental engineering involve the treatment and distribution of drinking water, the collection, treatment and disposal of wastewater, the control of air pollution and noise pollution, municipal solid-waste management and hazardous-waste management, the cleanup of hazardous-waste sites and the preparation of environmental assessments, audits and impact studies. Mathematical modeling and computer analysis are widely used to evaluate and design the systems required for such tasks. Chemical and mechanical engineers may also be involved in the process. 

Environmental engineering applies scientific and engineering principles to improve and maintain the environment to protect human health, protect nature's beneficial ecosystems and improve environmental related enhancement of the quality of human life. Environmental engineers devise solutions for wastewater management, water and air pollution control, recycling, waste disposal and public health. This will design municipal water supply and industrial wastewater treatment systems and design plans to prevent waterborne diseases and improve sanitation in urban, rural and recreational areas. 

Environmental engineers study the effect of technological advances on the environment, addressing local and worldwide environmental issues such as acid rain, global warming, ozone depletion, water pollution and air pollution from automobile exhausts and industrial sources. An environmental engineer is responsible for improving the quality of the environment and public health and developing solutions to minimize the degradation of natural resources. They devise ways to control pollution, treat wastewater, distribute safe drinking water, manage hazardous waste, etc.

History

The earliest examples of environmental engineering date back thousands of years to when people moved away from a nomadic lifestyle and began living in semi-permanent settlements. This change required people to access clean water supplies and dispose of waste including sewage. As settlements grew and large-scale agriculture took hold, people also began to tackle challenges around air quality and soil contamination.

Evidence of environmental engineering can be seen from many different ancient civilizations around the world, including the Indus Valley Civilization, Mesopotamian Empire, Mohenjo Daro, Crete, Rome, Egypt and the Orkney Islands in Scotland. These civilizations included aqueducts, sewer systems, drinking water systems, irrigation systems and even public baths.

Despite these earliest examples of environmental engineering, nothing much changed in the field until the middle of the 19th Century, when Joseph Bazalgette was tasked with overseeing the construction of London’s first large-scale municipal sanitary sewer system following a series of cholera epidemics and the ‘great stink’ that was caused by the discharge of raw sewage into the river Thames. This "great stink," which was so noxious that it caused Parliament to evacuate Westminster, gave then-Prime Minister Benjamin Disraeli grounds to ask for 3.5 million pounds to improve the city's sewage disposal system.

Growing concerns over environmental degradation as well as air and water pollution in the middle of the 20th Century led to environmental engineering becoming its own academic discipline. These concerns were accentuated by new technologies such as pesticides like DDT that had detrimental effects on the environment. 

The goal of environmental engineering is to ensure that societal development and the use of water, land and air resources are sustainable. This goal is achieved by managing these resources so that environmental pollution and degradation is minimized. Environmental engineers study water, soil and air pollution problems and develop technical solutions needed to solve, attenuate or control these problems in a manner that is compatible with legislative, economic, social and political concerns. Civil engineers are particularly involved in such activities as water supply and sewerage, management of surface water and groundwater quality, remediation of contaminated sites and solid waste management. 

The activities of such engineers include, but are not limited to, the planning, design, construction and operation of water and wastewater treatment facilities in municipalities and industries, modeling and analysis of surface water and groundwater quality, design of soil and remediation systems, planning for the disposal and reuse of wastewaters and sludges and the collection, transport, processing, recovery and disposal of solid wastes according to accepted engineering practices.

Read More