What is Iron?

What is Iron?

Iron ore in rock form
iron ore on a rocky base

Did you know that iron is a healthy nutrient for our bodies as well as the main ingredient in the manufacture of steel?

Before we venture into the types of iron, let’s first examine its properties. Iron is a mineral with the symbol Fe and atomic number 26. On the periodic table, it belongs to the first transition series, which reflects a change in the inner layer of electrons, but we’ll leave that for the chemists since the chemical compound of this material is beyond the scope of this article; however, if you’d like to learn more about a material’s transition series, click here.

Iron is the most common element on Earth when referenced by mass and is very prominently found in the Earth’s outer and inner cores. It is the fourth most common element in the Earth’s crust, but the process to extract it requires kilns or furnaces capable of reaching a temperature of 2,730 °F or higher.

A Little Bit of Iron History

The Bronze Age (c. 3300–1200 BC) is characterized by the use of bronze as the metal of choice to create art, tools, and weapons and was the first time metals were used for these purposes. Prior to this period, the stone was used as tools and weapons; hence, the Stone Age.

Interestingly enough, the Bronze Age also brought us the first writing systems and the invention of the wheel. Indeed, an intriguing period of creative thought for sure.

Enter Iron

Say goodbye to bronze and hello to iron; hence, the Iron Age, which started around 1200 BC, but before the Iron Age was coined, there are occasions when iron was found to be used much earlier. One of the most ancient iron historical accounts was that of ancient Egyptians where iron beads dating back to 3200 B.C. were found to be made from meteorites as iron is abundant in outer space also.

Iron for Nutrition

OK so iron is a mineral rock, but it is an important nutrient for our bodies as well. If you have an iron deficiency, you can possibly acquire anemia and also fatigue that affects the ability to perform physical work in adults.

So how much iron do you need on a daily basis? For most people, an adequate amount of iron is consumed daily via the foods that we eat, but to determine your specific iron needs you can see a chart and information here. One person told us that he eats yogurt and raisins every day. Raisins contain a certain amount of iron. 

Red Blood Cells
“Red blood cells” by rpongsaj is licensed under CC BY 2.0

Do you know why our blood is red?  It is because there is an interaction between iron and oxygen within the blood creating a red color. Learn more about red blood cells and iron here.

To be sure you have enough iron, check with your doctor to confirm you are not deficient.

Iron for Infrastructure

Once we enter the 19th century, we come upon new uses for iron besides artifacts and weapons. It was discovered that this mineral can be used for building purposes and with the advent of the industrial revolution, where items were being mass-produced, the manufacture of iron became very economical.

Iron in its pure form is not used for building construction, but when other elements are mixed in with it, it becomes an acceptable form for building bridges and buildings.

Cast Iron

Cast iron is an alloy of pure iron, containing 2 to 4% carbon and other impurities, such as sulfur and phosphorus, but it still lacks good tension capabilities, as it maintains a brittleness; however, it does have relatively good compressive strength and hence, it was used during the 18th and 19th centuries for infrastructure.

The_Iron_Bridge
WikipediaCommons William Williams The Iron Bridge, Coalbrookdale, Shropshire

Cast iron structures were initially found in the UK, where The Iron Bridge in Coalbrookdale, Shropshire, England was built in 1781 was the first large-scale cast-iron structure to be constructed.

Cast iron was used in the 19th and 20th-century buildings as well. In fact, there is a whole section in New York City that is called the Cast Iron District, also known as SOHO.

Wrought Iron

Wrought iron is also an iron alloy with a much lower carbon content than cast iron.  It is a tougher material than cast iron and is also malleable, ductile, and corrosion-resistant.

Wrought iron was a step above cast iron and since it was malleable, it was given the name wrought since it could be hammered into shape while it remained hot. It is a prerequisite to mild steel, also called low-carbon steel, the first of the steel alloys. 

Early on, wrought iron was refined into steel. In the 1860s, as ironclad warships and railways were built with these iron alloys, but with the advent of the Bessemer process, making steel became less costly to make, wrought iron was eventually halted to make way for the even less expensive and stronger iron alloy called steel.

Conclusion

Besides being an essential component for healthy blood in our bodies, iron became an essential component for weapons and later, building materials.

As such, numerous bridges and buildings have been constructed during the 18th, 19th, and 20th centuries, but as the industrial revolution advanced and the making of materials became automated, new alloys of iron were created, specifically, steel and this, along with concrete led to the construction of buildings, bridges, and skyscrapers we see today all over the world.

6 Longest Non-Polar Glaciers Around the World

Photo of a glacier
Photo by leaf – yayimages.com

Glaciers, large masses of dense ice, are formed in high altitude regions where the accumulation of snow is far greater and faster than the melting process. Over time, the layers of snow crystallize and form ice. The process of formation of glaciers takes centuries and even millennia. Surprisingly, glaciers are not just a unique feature of the polar caps but they are also found in many non-polar regions of the world. High mountain ranges in the former USSR, Pakistan and the Americas are also home to some of the world’s largest non-polar glaciers. Below is a list of the seven longest non-polar glaciers in the world.   

Fedchenko Glacier, Tajikistan 

The world’s longest glacier outside the polar world is the Fedchenko glacier situated in the Central Asian country of Tajikistan. The glacier is around 45 miles long and covers an area of 350 square miles. The Fedchenko Glacier flows north from the ice field of Revolution Peak and receives ice from dozens of other smaller glaciers. The thickness of ice in the middle of the Fedchenko glacier is approximately 3,280 feet. The giant mass of ice can cover a distance of up 26 inches every day and forms the headstream of River Surkhab and the Amu Darya. 

It was discovered in 1871 by a Russian expedition and is named after the Russian explorer A.P Fedchenko. Parts of this iceberg were explored later in 1928. Over time, the glacier has experienced a significant loss of ice. Climate change and global warming have dramatically reduced its size since the second half of the last century. 

Siachen Glacier, Indo-Pak Border 

The Siachen is the second-longest non-polar glacier in the world lying in the Karakoram Range near the border of India and Pakistan. It is 47 miles long and covers an area of 270 square miles. The region is home to many smaller glaciers and a number of fast-flowing surface streams.  

Climate change has significantly affected almost every part of the world and the Siachen glacier is no exception. Between the years 1989 and 2009, this area of ice was reduced by 2.2 square miles. Human presence in the region has further accelerated the melting, as this mountain of ice has been a source of conflict between military conflict for decades. The highest battlefield on Earth provides freshwater which enters the River Indus of Pakistan and the Ganges in India.

Biafo Glacier, Pakistan 

The Biafo Glacier is another long non-polar glacier located in the Karakoram range in Pakistan. The 40-mile long mountain in Gilgit-Baltistan meets Hispar Glacier, another 30-mile long glacier and forms the largest glacial system outside the polar region. This ice formation acts as a bridge between the two ancient kingdoms of the mountains; The Nagar and Baltistan. The Biafo glacier provides a trek with spectacular sights and traces of wildlife all along.  

The glacial system is largely affected by the changing global climate. The rising temperature has destabilized the movement of these ice formations and have altered the level of rain and snowfall in the region; consequently, these changes have resulted in flooding and intense heat waves not only in Pakistan but in other neighboring countries as well. 

Bruggen Glacier, Chile 

The Bruggen Glacier, also known as the Pio XI Glacier, is located in southern Chile. With a length of 40 miles, it is the fourth largest glacier in the non-polar region and the longest glacier in the Southern hemisphere.  The glacier continued to advance towards the sea and covered a distance of more than three miles between 1945 and 1976. 

Despite being one of the largest glaciers in the nonpolar region of the world, the Bruggen glacier is one of the least studied glacial areas in the world. However, considering its pattern of movement, it can be concluded that the glacier experienced periods of enhanced movement followed by retreat periods. This effect is in addition to climate change which is negatively affecting the glaciers around the world. 

Baltoro Glacier, Pakistan 

The Baltoro glacier is located in the mountain range of the Karakoram in the Baltistan region of northern Pakistan. It covers an area of 23 square miles and the length of the centerline is more than 35 miles. The second highest mountain in the world, K2 is located around 7 miles north of the tongue of the main glacier. 

Despite its location in a remote and politically unstable region of Pakistan, this glacier is extensively studied by geologists. This glacier is of unique importance to geologists because of extensive debris cover. 38% of the area of the glacier is covered with debris. When it comes to these types of ice formations, debris accumulation follows a certain pattern of increasing thickness. Ongoing landsliding and mud flow has led to an increase in the thickness of debris in the Baltoro glacier. As of now, the debris thickness in Baltoro glacier has reached almost 10 feet, which is a major concern for geologists. 

South Inylchek Glacier, Kyrgyzstan and China 

Another tourist-friendly destination, the South Inylchek Glacier is located on the borders of Kyrgyzstan and China. With a length of over 60 miles and more than 300 square miles, the Inyichek glacier is the sixth-longest nonpolar glacier. It is divided into two sections and covers more than 100 peaks of varying height with snow and ice. 

It is a place of incredible natural beauty where climbers around the world can enjoy the trek along with breathtaking aerial views. 

 

Acid Rain and the Effect on the Environment

Oil Refinery
Photo: Graphic Stock

Although arguments have surfaced about how much climate change is affecting our environment during these politically contentious years, one thing is for certain:  The burning of fossil fuels, the eruption of volcanoes and rotting plants all release harmful gases. When these gases react with water, oxygen, and other substances in the environment, it results in the production of acid. As the winds blow, this acidic content may spread over hundreds and thousands of miles.

Like the domino effect, the acid then falls from the atmosphere and enters the water system. This results in contamination of the water and subsequently, it affects fish and other species in the water,  which can result in contamination of the entire food chain.

When the water is used by other animals or for the cultivation of crops, both the animals and human beings bear the consequences. Acid rain also corrodes away the trees and affects their ability to absorb nutrients from the soil and take up water.

Most of the acid rain today is a result of human activities. And since everything in the environment is closely linked to each other, if something harms one part of the environment, everything else gets affected. Let’s have a detailed look at how acid rain affects the environment. But first, it is important to understand what acid rain is.

What is Acid Rain?

Some natural activities such as rotting vegetation and volcanic activities result in the release of harmful gases. Human activities such as the burning of fossil fuels also result in the release of compounds like sulfur dioxide and oxides of nitrogen. When these gases are released into the air, they react with other substances such as water and oxygen. This reaction results in the formation of acidic pollutants and can easily become a part of the rain, snow and fog.

Normal rain has a pH value between 5.0 and 5.5. So it is slightly acidic. But when acidic pollutants become a part of the rain, it becomes more acidic than normal and is known as acid rain.

Effects of Acid Rain on the Environment 

Nature depends on balance. There is a certain percentage of acidic content present in the environment, which is normal, but as one noble writer put it quite eloquently and to the point: “Too much of anything is not good for you”; hence, an overabundance of acidic content will have a negative impact on the environment with which we live.

Effects on Plants and Trees

Acid rain affects plants and trees in multiple ways. When the acidic pollutants are absorbed in the soil, it removes the essential minerals and nutrients. As a result, plants and trees do not get adequate nutrition. Acid rain also allows aluminum to seep into the soil. This affects the ability of the trees to absorb water which is essential for their growth.

Another way through which acid rain affects the trees is by hindering their ability to absorb sunlight. The acidic fog and air do not allow the absorption of sunlight through the leaves. Since the basic requirements for the growth of plants are not met, the trees eventually die.

Effects on Marine and Wildlife

Photo of the ocean
Photo: Graphic Stock

The effects of acid rain are most obvious on the marine ecosystem. As the contaminated water flows through the soil, it can bring along soil that is rich in aluminum to the streams and lakes. Thus, the streams and lakes develop more acidic water along with a higher content of aluminum.

Some marine plants and animals are more resistant to acidic water. However, species that are sensitive to high acidic content suffer greatly due to acid rain. The eggs of most species of fish cannot hatch in an acidic environment. Also, some species of adult fish can actually die.

In cases where the fish can tolerate acidic water, most of the other animals and plants they feed on might not survive in that environment. As a result, the fish die due to inadequate nutrition.

While acid rain directly affects marine species, it indirectly affects birds and other animals as well. Acid rain is known to be the biggest reason for the decline of the population of some species of birds including wood thrush. It also affects animals that depend on marine life for survival. Mammals including bears which heavily depend on fish need to find an alternate source of food due to the decreasing population of these types of fish.

Effects on Humans

The presence of sulfuric and nitric acid in the environment can make the air hazy. This is the reason why acid rain is a primary contributor to the formation of fog and smog. As far as the effect on humans is concerned, walking in acid rain is no more damaging than walking in normal rain. However, the presence of pollutants in the air can have a harmful effect on human health. The presence of acidic pollutants affects the quality of air. The sulfate and nitrate particles in the air can affect the function of the heart and lungs. Thus, acid rain is one of the major causes of increasing respiratory problems in humans including asthma, bronchitis and pneumonia.

Conclusion

Apart from living things, acid rain is known to affect non-living things as well. It can corrode buildings, statues and other man-made structures. Though sulfur dioxide and nitrogen oxide are not greenhouse gases, they definitely have an important effect on the recent climate change as both these gases have serious effects on the environment. Since the primary source of these gases comes from burning fossil fuels, by reducing the reliance on fossil fuels, we can control the damaging effects of acid rain.

 

Life in Outer Space – A Mathematical Approach

Milky Way Galaxy
Photo by Arnaud Mariat on Unsplash

Is There Really Intelligent Life Out There?

One of our previous articles discussed the minerals of Star Trek, giving rise to the hope that there is extraterrestrial life out there, but the real discussion about ET’s existence is a loaded subject. 

For this article, we are going to focus on what the mathematical formulas tell us. The ones developed by astrophysicists; in other words, what are the odds that there really is intelligent life on other planets?

As difficult it is to comprehend that the sun fuses hydrogen and helium every second, resulting in the power of 100 billion atomic bombs, we need to go even further and try to comprehend the immense size of our universe.

It is estimated that there is an average of 1 – 2 billion stars in any recorded galaxy and there are over 2 trillion galaxies in the universe. If 10% of each galaxy contains a solar system, that is, it contains a star with planets revolving around it, then we can estimate that each galaxy has between 100 – 200 million solar systems.

Outer Space Ailen
Photo by Stephen Leonardi on Unsplash

If 1% of the stars in each solar system has a planet just distant enough from their sun where life could evolve, we could have 1 – 2 million possible planets that could contain life. And if 1% of these planets have the right ‘ingredients’ to build intelligent life. then there is the possibility that there exist 10,000 stars that could have planets with intelligent life in each galaxy.

Cutting the odds even further, let’s take 10% of this result, which would equate to the possibility of 1,000 stars with intelligent life in each galaxy.

That would mean that there could exist 1,000 x 100,000,000,000,000 (galaxies) = 1,000,000,000,000,000,000 (1 Quadrillion) planets with intelligent life. How many is that? Take a look at this numerical comparison.

If we use the estimate of 200,000,000 galaxies in the universe, well, that would mean ET lives in over 2 quadrillion planets in our universe.

Don’t even try to comprehend how many fusion reactions occur in the universe every second. Fuhgeddaboudit!

What About the Scientific Formulas?

The above calculations were based on a general assumption, but have the experts really gave this serious thought? Of course!

American astronomer and astrophysicist Dr. Frank Drake developed a formula that he presented at a meeting in Virginia in 1961 and it is called the Drake Equation, which calculates the possibilities of life on other worlds within our own Milky Way galaxy.

Drake Equation
Nasa Photo

We won’t go into the particulars, but in a general sense, it is based on calculating our assumptions above but uses trigonometry to formulate a much more explicit and precise determination of ET’s existence. For you, science and math connoisseurs, feel free to give it a shot!

Just maybe Men in Black had it right!

 

What is Concrete?

What is Concrete?

Concrete Blocks
Photo by uve sanchez on Unsplash

Ever notice that just about every building has a concrete foundation?  There is a very good reason for this and it is not about aesthetics. Concrete has enormous compressive strength, meaning that it is an excellent material for holding up the weight that is above it. 

Concrete is not just used for foundations, but also for columns, beams. slabs and just about anything where there is a load-bearing issue. Load bearing meaning an element that supports the weight above it. The amount of weight that the load-bearing element would support would depend upon how many concrete columns (or other concrete supporting materials) are available to support the whole load.

For example, a 30-story building has 10 supporting columns on the ground. That would mean that the weight is evenly distributed across each of the 10 columns or mathematically speaking, each concrete column would support 0.333 (10/30) of the load (building).

Another probably more identifiable example is the load-bearing walls in a house. If you live in a house, you have probably come aware of where your load-bearing walls are. These are the walls that actually hold up the house; however, for frame houses, concrete is not the usual load-bearing material, but heavy wood or steel instead. 

A concrete column
Concrete column supporting the highway above. Photo by SS

In short, concrete is an excellent source for withstanding the heavy forces that are above it or more formally stated as an excellent compression material.

Did you know that concrete also gains more strength as it ages? With that said, let’s take a look at just what this compressive material is actually made of.

What is Concrete Made Out of?

Concrete is a mixture of air, water, sand and gravel and the percentages of these elements are usually 20% air and water, 30% sand called fine aggregates and 40% gravel, with 10% being the cement; that is, 10% being the ‘glue’ that keeps all those other materials together. Remember, from our article on cement, it is just the binding material for the assembly of concrete. When the cement is mixed with water, it is called paste

This proportion is called the 10-20-30-40 Rule; however, the exact percentages of the materials can vary depending on the combination of the concrete mixture, including the type of cement and other factors that we will explain in this article.

How are the Proportion of Materials that Form Concrete Determined?

So we know that concrete is a mixture of paste and aggregates and sometimes rocks. The paste coats each of the aggregates and as it hardens (the process is called hydration), concrete is born until it becomes a rock-solid mass, capable of withstanding a load much heavier than itself, but if the proportion of water and paste is not correct, this rock-solid mass can deteriorate causing unwanted and potentially dangerous consequences.

The trick is to carefully proportion the mix of the ingredients and much of it depends on the ratio of water to cement and this ratio is calculated by the weight of the water divided by the weight of the cement. A low water-content ratio yields high-quality concrete, so it is best to lower the ratio as much as possible without sacrificing the integrity of the concrete.

If the ratio results where there is too much water in the mixture, the aggregates become thinned out, resulting in weakening the concrete and we can figure out what that would mean.

Conversely, If there is not enough water in the mix, the water will evaporate too fast, comprising the integrity of the concrete and resulting in it being weak as well.

What is the Strongest Concrete Mixture Ratio?

1:3:5 which is cement and aggregates (in this case, the aggregate is broken into sand (3) and gravel (5) and this is considered the ratio that would create the strongest concrete.

How Much Time is Allocated Before the Finished Concrete is Used at the Construction Site?

There is a limit to how long the concrete can be poured after it is mixed. In the US, the limit is 60 minutes from the time the water mixes with the cement to the time of delivery to the construction site. 

A safe time frame is up to 90 minutes, then the integrity of the concrete will start to deteriorate. That is why we see concrete mixers right at the construction site as no time is lost between the mixture and the pouring.

What About Reinforced Concrete?

As the name applies, when steel (usually using steel bars, called rebars) is placed inside the slab where the concrete is going to be poured, it reinforces the strength of the concrete.

How Does it Reinforce the Concrete?

We have been discussing compression strength; that is, how strong the material is when a heavy load is placed on it, but we haven’t discussed tensile strength, which is the opposite of compression.

Tensil strength represents the strength material can endure when a force tries to pull on it. The reason why compression is so important when using concrete is that that is its main purpose – to hold up heavy loads, but concrete does have a limit on how much pull can be leveled on it and there are situations where the tensile strength of concrete is put to the test. The weather being one factor, but there are more.

Enter Steel

Reinforced Steel Slab
A construction worker working on a reinforced steel slap where the concrete will be poured. Photo by SS.

By integrating the rebars inside the concrete, the concern about stretching the concrete is greatly minimized. The combination of concrete and its accompanying reinforcing steel bars successfully manages these situations, because of steel’s high tensile strength; hence, you have a perfect storm of compressive and tensile strength in reinforced concrete (RC).

What Happens if the Reinforcing Steel is Not Inside the Concrete?

Cracking of the concrete surfaces can occur, subsequently causing aesthetic issues, but if the tensile yield is really great, (e.g. a strong pull on the concrete) the situation can become unsafe, so without the steel rods to compensate for this pull, you will find cracks in the concrete or worse.

Conclusion

Concrete is a mixture of sand, water, aggregates and cement. The amount of any of these elements will determine the strength of the concrete. Timing also plays a role as the concrete must be readily mixed within 90 minutes max, but 60 minutes is the usual requirement before being poured into its foundation or another element such as a column or slab.

By placing steel bars which is a mesh of steel wires (rebar) inside the concrete, the tension issue is resolved by aiding the concrete under tension.

So the next time you are walking in a building, especially a large structure such as a skyscraper, give thanks to the materials that allow you there, as well as the people who created allowed it to happen!

 

How Cement is Made?

What is Cement?

Solider pouring the fine powdery cementIf you were to say “I tripped on a cement block”, would you be wrong?

The answer is yes because there is technically no such thing as a ‘cement’ block, but there are concrete blocks; that is, the cement is nothing more than the ‘glue’ that binds the materials that collectively make the concrete block, which is usually sand and gravel. So if you were to say “I tripped on a concrete block”, you would then be correct.

According to Wikipedia, cement sets, hardens and adheres to other materials to bind them together.In simple terms, cement is the centerpiece of what keeps the concrete intact. 

What Materials is Cement Made of? 

The sand and gravel are called aggregates, and it is these materials that are bound together but remember, cement is not the material, it is the glue. So what makes up the cement? 

The ingredients are mainly limestone and clay, which are extracted from quarries from around the world. Of course, the process of making cement is not that simple. The limestone is heated with clay to 2,640 °F in a kiln (an insulated chamber). This process is called calcination, which liberates molecules of carbon dioxide from the calcium carbonate (the main ingredient of limestone) to form calcium oxide, commonly referred to as quicklime

It is here where the quicklime chemically combines with the other materials to make a hard substance, called ‘clinker‘. Gypsum is then added to make Portland cement, the most popular type of cement used, which is referred to in the industry as OPC. 

How does the Limestone Mixture Process Work?

The limestone rock is crushed in a machine appropriately called a crusher which reduces the limestone to a size of about six inches maximum. It is then fed into the second crusher where it is further reduced to under three inches. The mix is conveyed and then sent to a raw mill bin to be ground down even further.  

In these bins are two chambers. One that dries the limestone and clay mix and the other that grinds it via hot gasses. Then, once all dry, it is moved to the grinding chamber called a ball mill.  Here there is a cylinder that contains steel balls and rotates which causes the balls to fall back into the cylinder and onto the limestone mix; hence, grinders. 4 to 20 revolutions per minute is the general rotation of the cylinder, which is dependent upon the diameter of the ball mill.

A Newcome Engine

What’s left when the grinding process is done is a product of fine and coarse material. The coarse material is useless in that state and is called reject where it is returned back to the ball mill for additional grinding. A machine called a separator does this part. 

Having the limestone and clay grounded down to a fine powder is still not enough to complete the cement process. The mixture must then enter a device called a cyclone which is used to separate the fine grounded material from existing gases that still exist in it.

Then, the hot gas and fine materials enter a multistage “cyclone”. This is to separate the fine ground materials from the gases.

The result – a clean, fine powdery material and is renamed kiln feed. 

Next, the feed is heated via a process called sintering, which is when the chemical bonds of the material are broken down using heat and once complete, a new substance is formed called clinker.

Clinker nodules for the production of cement
Clinker nodules produced by sintering at 1450 °C. This is the intermediate process for the production of cement

The clinker is initially very hot and contains small, dark gray nodules from 1mm to 25mm in size where it is placed into a grate cooler for cooling from approximately 2550 °F to approximately 240 °F via the use of cooling fans.

And voila! You have cement!

Final Note

Other elements are added to the clinker depending upon what the cement is going to be used for. In the case of Portland cement, gypsum is the additive.

And you thought that making cement was just adding powder and water. We hope you gained some good knowledge as to how cement is actually created.

 

 

 

How Buildings are Constructed Along Earthquake Fault Lines

Transamerica Pyramid San Francisco
Earthquake resistant Transamerica Pyramid, San Francisco. Photo Wikimedia CC

One of the first structures built to withstand an earthquake was the Transamerica Pyramid, also called the Transamerica Tower. In this seismically active region, no engineering was spared to keep the building safe from earthquake tremors.

Located on 600 Montgomery Street, it rises 853 feet and 48 floors and was the eighth tallest building in the world in 1972. On the highest floor, 48, there is a conference room that has unobstructed 360-degree views of the San Francisco Bay area.

The building has a wide base that narrows upwards, much like the churches and buildings of antiquity, which is designed to give the structures their stability. No doubt this is an optimum method for buildings that reside along earthquake fault lines. From an environmental perspective, the pyramid design (hence the name), allows natural light to filter down to the streets below.

Looking to limit the degree by which the structure would twist and shake during an earthquake, engineers used a unique truss system with built-in steel, reinforced concrete, precast quartz aggregate and glass. It has two angular setbacks working their way up to the top of the tower and a 212-foot spire. There are two angular concrete structures on the east and west sides that protrude from the 29th floor rising upwards called wings. The wings are part of the structural engineering that went in to keep the building sturdy during an earthquake, but they also have a function. The eastern wing serves as an elevator and the western wing includes a staircase.

To reinforce the building even more, there is a truss system on the ground and lower floors which are designed to support both vertical and horizontal stresses. Truss designs are cross beams engineered to perfectly distribute the weight of a structure in order to withstand tension (pulling) and compression (pulling) forces.

Modern building with external truss system
Buildings with external truss systems are able to manage torsional (twisting) forces generated by seismic events. Photo by Ricardo Gomez Angel on Unsplash

Under the truss, beams are X beams over the ground floor, designed to brace the building against any type of torque movement.

This torque and stress reinforcement was tested in 1989 during the .71 magnitude Loma Prieta earthquake. The building successfully withstood the quake with no damage and no injuries.

 

In addition to above-ground stress reinforcement, there is an additional basement from earthquake tremors, consisting of a 9-foot deep concrete mat foundation, which lies on top of a steel and concrete block that goes 52 feet underground. This foundation contains 16,000 cubic yards of reinforced concrete, including over 300 miles of steel reinforcing rods. This concrete assists with the additional support of Compressive stress and tensile stress.

The Pyramid is a self-contained structure, which has its own 1.1-megawatt power system. Construction began in the fall of 1969 with the first tenant moving in in 1972 and is still standing gracefully today as a monument to earthquake building construction.

 

The 2 Methods to Building a Subway

Subway tunnel construction in NYC
Subway tunnel construction in NYC  (Photo: wirestock – www.freepik.com)

For those who love big cities (and even smaller ones), there’s no doubt you have ridden on one of their mass transit lines. With that said, have you ever wondered about the amount of engineering that has gone into building one? Well, here we will give you some basic information as to how they are constructed.

There are two basic methods to subway construction: “cut and cover” and the other is called “deep bore.”  Cut and cover refers to the complete opening of the street, down to where the subway would be built and deep bore refers to the burrowing strategy previously discussed in our Tunnel Boring article.

To determine which method is going to be used, an engineering and environmental review is necessary, which includes logistics, underground water determination, earth material, demographics and of course, costs, not to mention the bureaucracy of working with the different city agencies to determine where all the utility lines, water pipes and potential other tunnels are located. 

This bureaucracy alone could take months or even years, And if any of these factors become obstacles, then additional planning would be required. The bottom line is that this whole procedure is a great undertaking and can get very complex. 

So with this introduction, let’s delve into describing the engineering process by which each of these methods would be used.

Cut and Cover Method of Building a Subway

Tunnel cut and cover method of construction of the Paris Metro
Tunnel cut and cover method of construction of the Paris Metro – Wikipedia Public Domain

This method is found in the building of some of the older subway systems, such as the Paris Metro, London Underground and the NYC subway. With this method, the pavement of the street is completely removed and then a hole is dug down into the ground. 

“Cut and cover” is considerably cheaper than the “deep bore” method; however, the dig must parallel the street, so there is no room for more sophisticated planning, like curved tracks that fork off to some desired locations, unless the street above does the same.

Another undesirable factor is that “cut and cover” results in large holes in the street significantly causing traffic nightmares, as well as major inconveniences for store owners along the route.

Deep Bore Method 

The boring machine is a sophisticated and expensive apparatus that cuts through the underground dit by using circular spinning blades. The advantage this has over “cut and cover” is that they do not have to follow the street grid above, allowing much greater flexibility in the design of the subway lines, as well as not have to dig big holes along the route. The boring method is slow, but efficient and cuts through the earth at a rate of about fifty feet per day

The disadvantages are that the costs are significantly higher than cut and cover, where $150 million would be a medium price. 

How the Subway Construction Method Is Decided

As mentioned, there are so many factors to consider when building a subway line, but the number of subway lines and the cost factors involved would be the major considerations.

For example: After extensive analysis of which method would be better to construct the Second Ave Subway in Manhattan, it was decided that the TBM would be more efficient, based upon the fact that cut and cover would cause so much economical damage, the boring method would be more practical, even though it is more expensive.

Preparation for TBM cutting head to be lowered into a tunnel
Cutting Head of a boring machine being lowered into the hole where a tunnel is to be constructed. Photo by david carballar on Unsplash

Just lowering this giant machine into the tunnel is a major task, not to mention expense, but it is worth it in the case of big-city construction.

Another major consideration was the amount of interruption and financial damage the cut and cover method would have caused, especially on a congested and commercial road like Second Ave. where the upper east side and midtown Manhattan would be commercially interrupted.

Considering how often there would have been complaints, especially in this time period, where community demonstrations are the norm, more and more TBM usage is becoming the preferred method, so as not to disturb life above ground. However, cut and cover construction may still be considered if the soil conditions are not up to standard.

Building the Second Ave Subway NYC
TBM in action during the building of New York’s Second Ave Subway (Google CC Flicker)

An example of how the political consequences of cut and cover road disruptions can escalate, take a look at Vancouver B.C.’s recently opened Canada Line. A lawsuit was taken against the city of Vancouver and the plaintiff, a retailer with a store along the subway route where won C$600,000 after cut and cover caused major financial hardship. Following that lawsuit, an additional 41 plaintiffs have taken legal action to recover financial damages. 

What the Future Holds

We are now in the 21st Century and with technology streaming at a rocket pace (e.g. artificial intelligence, at home video conferencing, sending a man to Mars) it will only be time before new engineering technologies will lead to faster, lighter and much less expensive boring machines. Then if you think some cities have excellent transportation facilities now, wait till these new machines come along and open the door to even more elaborate and reduced financial expense.  

 

 

Understanding the Geology of Silver

10 Gram Silver Bar
10 Gram Silver Bar

Silver – Overview 

This soft, white, precious metal is valued for its beauty and industrial uses. It has a history that goes back as far as 4,000 B.C. Around the same time, techniques to refine silver and separate it from other metals were identified and practiced. As research on natural elements progressed, silver got its chemical name and secured its position in the periodic table in group 11 and period 5. For our science enthusiasts, this malleable metal has the following element properties: 

    • Atomic Number – 47
    • Atomic Weight – 107.8
    • Melting Point – 1,861.4oF
    • Boiling Point – 4,014oF
    • Specific Gravity – 10.5
    • Luster – Metallic
    • Mohs Hardness – 2.5 to 3 

Because of its rarity and high industrial demand, silver is considered a precious metal with a high economic value. Its physical properties make it the best possible metal for various uses in a wide variety of industries. 

For starters, it has electrical and thermal conductance that is higher than any other metal, which makes it valuable in the electronic industry.  Silver is also sort after because of its exceptional ability to convert ethylene into its oxide, a prerequisite of many organic compounds. However, it is the least reactive of the transition elements.

Moreover, it has better reflectivity at most temperatures. Finally, its color and attractive finish make it a desirable choice for coins, tableware, jewelry and many other objects.

Given its uses and properties, silver is often the material of choice. However, unlike other precious metals, the value of silver is often not reflected in the price, which makes it one of the most underrated precious metals.

Let’s take a closer look at how silver is found in nature.  

The Geology of Silver 

The precious metal occurs in nature as one of the four following forms.

  • as a natural element; 
  • as an essential component of silver minerals; 
  • as an alloy with other metals; and 
  • as a trace element in the ores of other metals. 

Below we intend to understand the geology of the precious metal better.

Silver as a Natural Element 

Silver rarely occurs as a natural element. Instead, it is often found with other metals, including gold, copper, quartz and sulfides and other metals’ arsenides. In placer deposits, silver is rarely discovered in significant amounts. Because it does not oxidize readily, silver can also be found above the ores of other metals in its natural state. However, the precious metal reacts with hydrogen sulfide that results in a discolored surface, including silver sulfide, also known as acanthite. Researchers have found many specimens as a natural element that have been exposed and reacted with hydrogen, and have an acanthite coating.

Silver in this form is often associated with hydrothermal activity. In areas of abundance in this activity, silver can be found as cavity fillings. Some of these deposits are rich enough to support mining. However, mining for silver alone is often not feasible. Therefore, the economic viability of silver extraction depends upon the presence of other valuable minerals. For extraction of such deposits, an underground operation is undertaken that follows the veins and cavities where silver in its natural state is found. 

As an Essential Component of Silver Minerals

Close up of Silver CoinsThere is a surprisingly high number of minerals that contain silver as an essential component. There are over 35 different distinct silver minerals which include but are not limited to the following. 

  • Acanthite, 
  • Berryite, 
  • Chlorargyrite, 
  • Dyscrasite,
  • Empressite, 
  • Fettelite, 
  • Petzite, 
  • Samsonite

Each of the silver minerals is distinct and rare, however, a few silver minerals exist in quantities that warrant mining. Silver minerals can be found as silicates, sulfides, iodates, carbonates, oxides, nitrates and bromates. 

Alloys and Amalgams of Silver 

If you take a closer look at the placer deposits of gold, you will find gold alloyed with small quantities of silver. When the ratio between gold and silver reaches at least 20% silver, the alloy is called “electrum” which is a combination of silver and gold. When gold is refined and purified, that leads to the production of a significant amount of silver. Interestingly enough,  most of the silver available on the market today is a byproduct of gold extraction and purification.

The metal can also be found as a natural alloy of mercury, which is found in the oxidation zones of silver deposits. This amalgam of silver is also associated with cinnabar, which is a toxic mercury sulfide mineral. 

As a Trace Element in the Ores of Other Metals

The other most common source of silver is its occurrence as a trace element in the ores of other metals. It is often found along with other commonly extracted metals, including copper, lead and zinc and can be found as an inclusion within the ore. Moreover, it can be found as a substituted metal ion within the ore’s atomic structure. However, there is a possibility that the value of silver may exceed the value of the primary metal within the ore.

Silver – Extraction and Production Around the World 

Silver is found all around the world. Over 50% of its production comes from North, Central and South America. Other contributors of silver outside America include Russia, China and Australia. 

Silver deposits are usually associated with magmatic and hydrothermal activity. Major mineral deposits are therefore found in these regions. The association between geothermal activity and silver deposits is more pronounced in the Americas, where the silver production follows the Andes Mountain Range. In other parts of the world, the production of silver is related to igneous activity regardless of its geologic age, but a different trend has been observed in Europe, where silver production is associated with historic volcanic activity. 

Conclusion 

Silver is a precious metal with various industrial and commercial uses. While its worth is often not reflected in its economic value, silver still remains a rare, precious metal, given how it is found in nature. 

How Tunnel Boring Machines Work

NYC subway tunnel with tracks crossing
NYC Subway Tunnel. Note the concrete slabs, called rings on the sides and ceiling of the tunnel Photo by wirestock – freepik.com

Did you ever wonder how a tunnel is created?  Well, you’ve come to the right place.

Human ingenuity has taken us from the industrial revolution to space exploration, but it has also taken us underground, from the giant Bagger 293 bucket wheel excavator for mining to machines that crush through the dirt to make tunnels deep below the surface.

A Little Tunnel History

In the earlier days, boring through the underground required many hours of tedious labor. It was not just the dig that was time-consuming but buttressing the area around the tunnel so that it stayed safe was also tedious.

Men would create concrete rings and secure them along the top of the tunnel and alongside the walls.  This would ensure that the tunnel didn’t weaken and collapse.

Greathead-tunnelling-shield
Assembling concrete rings were previously done with manual labor

The process of securing the tunnel by hand was the normal way of doing things back in the day, but now, all that hard, unhealthy labor is a thing of the past. Why? Enter the tunnel boring machine (TBM).

The Tunnel Boring Machine

Tunnel Boring Machine

Power Saw
Photo by Greyson Joralemon on Unsplash

If there was ever a device that one would call a machine, the TBM would be just that. Large, noisy but effective, it is used to cut through soil and rock much like a power saw is used on wood. As the saw’s steel blade spins, it cuts right through the wood, which is similar to the job of the boring machine, only larger. Much larger!

How Does the TBM Work?

The machine consists of three major parts (actually, a lot more, but we’ll keep it simple so that we don’t bore (pun intended) you with all the intricate details). 

The Three Parts are: 

  • Cutter-head (front)
  • Tunnel shield (middle)
  • Trailing gear (rear)

Of course, each of these sections is made up of smaller parts and together they comprise the boring machine.

The Cutting Head

Preparation for TBM cutting head to be lowered into a tunnel
Preparation for TBM cutting head to be lowered into a tunnel. Photo by david carballar on Unsplash

We spoke about the saw, but what does this saw have that cuts the wood so precisely? It is a circular piece of steel with cutting blades.

For the TBM, they are called disc cutters and are integrated onto the edges of a round piece of steel. For the TBM, the cutting head is located at the very front of the machine. 

As the boring machine’s cutter-head rotates, it breaks through the rock and/or soil at a rate of 2.7 revolutions per minute and at a pace of about 50 feet per day. 

The machine looks like a giant worm, expanding about 272 feet in length. It is this long because after the soil is extracted, it is sent down long conveyor belts where it is extracted to the surface and carted away.  See these videos below, which provide expert explanations about how the Tunnel Boring Machine operates. 

The Tunnel Shield 

A tunneling shield is a cylindrical protective structure that is located just behind the cutting head and is used to shelter the workers from the dangers of falling dirt and debris and/or actual collapse of the tunnel.

The shield is used as a temporary support structure until the tunnel is secured with concrete (see Tunnel Rings below).  The first shield was designed by Marc Isambard Brunel and was rectangular in design with iron scaffolding and consisting of three levels. Then it was later modified into a cylindrical form, which is what is used today.

What are Tunnel Rings?

Tunnel Ring
Tunnel rings. From HerrenknechtAG video above.

The tunneling shield is designed to be used only until the tunnel is safely secured with a more permanent process; as such, prefabricated concrete rings are secured along the roof and sides of the tunnel to stabilize it and turn it into a permanent structure. The process begins when the cutting head stops spinning, synchronized to do so each time a new set of rings are needed to be installed. 

A robot called an erector lifts each ring and sets it in place along the tunnel lining, resulting in a solid cylindrical wall of concrete at the top and along the sidewalls, subsequently maintaining the structural integrity of the tunnel.  

The rings are assembled as segments from above-ground factories. They are transported from the factory to the tunnel location, moved down into the tunnel and onto the boring machine where the erector lifts them and secures them inside the tunnel.

Precast molded lining sections were first patented in 1874 by James Henry Greathead, a mechanical and civil engineer famous for his work on the London Underground. Greathead also improved the tunnel shield from its rectangle form into its current form of cylindrical steel.

This process of cutting through the dirt then stopping so that the rings can be installed alternates every 5–7 feet. The cutting heads spin, evacuating the earth in front of it, then stops and the erector builds the supporting rings and then the cutting head begins to spin again, moving forward at its slow but efficient pace.

Trailing Gear

How Does the Evacuated Dirt and Rock Get Taken Out from Underground?

Tunnel Boring Machine
Tunnel Boring Machine trailer section. Screenshot from video HerrenknechtAG

Enter the trailing mechanisms. They include a conveyor belt that removes the soil that was excavated from the cutter head. As the cutter pulls dirt out, it places it onto a belt conveyor which consists of a machine belt, cross belt and a tunnel belt. The tunnel belt is dynamic, in that it expands as the machine digs forward. The tunnel belt can expand up to 18 miles back to the extraction point where the soil is lifted to the ground.

The first two belts, the machine and cross belt are located at the very front of the TBM and the tunnel belt is the conveyor that moves the debris through the TBM to the area where it is taken out of the tunnel. 

Summary

The engineering that goes into the assembly of a tunnel boring machine is quite sophisticated, but fascinating as well. 

In this article, we simplified the process so that it can be easily understandable and we hope you were able to gain a good understanding of how tunnels are created, so the next time you drive through a tunnel or ride through the subway, you can be grateful for the ingenuity and hard work of the people who built it. 

 

Howard Fensterman Minerals