Tag: Material

Natural materials – silt

In this blog post we will characterize the natural material silt. We will try and answer some of the most important questions in relation to silts such as; What is silt? What is silt used for? What is the difference between silt, sand and clay? Does silt pollute water? What is siltation?

Definition of silt

Silt is a characteristic soil whose grain size lies between that of clay and sand with sizes ranging between 0.002 mm and 0.063 mm.

Silt is a detritus material meaning that it stems from weathered rock material and you can actually feel the individual particles between your fingers if rubbed gently. The physical properties of silt is hard to make general characterizations about as the individual properties depend on its ability to adhere to water and drain. An example of possible explanatory properties is the Atterberg limits.

Atterberg limits

The silty soils adherence to water makes is hard to accurately characterize. This means that the defining characteristic when it comes to soil dynamics is the ability to describe the Atterberg limits of silty soil. Atterberg limits are used to describe cohesive materials for their strength and water limit, see source.

The Atterberg limits are a simple way of describing the bearing capacities of wetted silt and clayey soils. These Atterberg limits are some of the defining limit states behind the soil characteristics and are used to accurately describe the water content and corresponding soil behavior in a simple manner.

Individual soil states

The Atterberg limits are described in four different manners called states. These states are given from silty and clayey soils and includes; Solid, Semi solid, Plastic and Liquid.

The definition of each of the subzones varies based on the type of clay and silt being investigated. Here the defining property is the ability to adhere and keep water content within the soil. Generally speaking, as the silty soils water content increases, it transforms its characteristics from that of a solid towards a liquid.

Atterberg limits visualized

The key defining characteristic behind the definitive behavior of silts and clays is their ability to keep water within the substrate. This is best illustrated from the resulting stress-strain curves usually employed when defining solid state materials bearing strengths. An illustration of the different characteristic states of the material alongside the bearing capacity of each state is outlined in Figure 1.

Figure 1: Illustration of Atterberg limits with different strength characteristics shown versus different states of the material. This includes the stress-strain curves of the material which describe the material properties through the SL, PL and LL states

With this initial explanation of the Atterberg limits, it quickly becomes evident the importance of defining each of these limits in an accurate manner.

Thought process behind silty\clayey soils bearing capacity

To set the stage for the upcoming explanation of why these limits are important, lets try and imagine a scenario where a large infrastructure project is trying to be built.

Firstly one may investigate the initial area visually ensuring that there are no immediate obstacles needing to be removed before geotechnical investigations might be performed.

Second, a set of initial tests have examined the cross-section of the earth and found out that the initial state of the underground consists of a mixture of clay and silty soil.

Third, now one may wonder what the initial strength of such soils might be and if at all the soil exhibits sufficient capacity for bearing the load of the structure proposed for the site in question.

In conclusion, it becomes evident that the bearing capacity of silty clayey soils must be understood properly for the construction of larger infrastructures to be feasible.

As we now understand, it is important to estimate the limiting behavior of soils when subjected to loads and therefore we need to calculate the Atterberg limits. In the following sections we dive deeper into the calculation of the different types of Atterberg limits. Starting of with the liquid limit, LL.

The Casagrande cup experiment

The Casagrande cup experiment is used for the determination of the soil water content based on a standardized number of blows until a small valley created through use of specialized instruments collapses. See Figure 2 for an illustration of the equipment and resulting collapse of the valley.

Figure 2: Casagrande cup filled with substrate. Top left: valley and filled cup before number of blows. Bottom left: Collapsed valley after x number of blows. Right: Illustration describing the specialized equipment used for creating the valley and material used as shock absorption.

When the valley starts to fall together the number of blows is numbered on a piece of paper. The soil sample is then weighed and dried with the resulting weight before and after measured carefully. This way you can determine the number of blows before failure mechanisms of the substrate are activated as a function of the water content of the sample.

A relationship between the number of blows and the water content can then be drawn and theoretical distributions for the soil strength can be inferred through careful regression techniques. An example of a given relationship between water content and number of blows is outlined in Figure 3. The predetermined liquid limit is theoretically defined for 25 number of blows to the sample.

Figure 3: Water content versus number of blows within the Casagrande cup experiment before the collapse of the shear walls. The liquid limit of the Casagrande experiment corresponds to the straight line interception at 25 blows.

The liquid limit described by this test allows for an easy and fast interpretation of the liquid limit of silty clayey soils.

Now in order to try and estimate the plastic limit of the soil we need another test measure technique called the rolling test.

Rolling tests determining plasticity level

In order to determine the plastic limit of the soil, the limit where constant stress cause constant strain, we need to perform a rolling test on a sample of the substrate.

The methodology of performing a rolling test is in short to roll out a specific sample of the soil under assumptions of constant stress and cross section until the water content start to crack. When cracking is initiated the sample is quickly weighed before being dried out in the lab heaters for 24 hours.

Soil sample roll speed

When rolling the soil sample out you are actually drying out the sample therefore it is important to realize that the speed at which you are rolling out the sample influences the drying rate and correspondingly can result in errors as the sample is considered to contain a constant water content.

Faster speeds and pressure on the silty soil sample will cause inaccurate measurements of the water contents due to the pressure distribution on the soil pushing out water from underneath the soil sample.

Figure 4: Example of a rolled silt soil experiment. The silty soil is observed through use of the cracked and jagged sample

However, rolling out the soil sample slowly is neither a good option as the contents of the water sample is likewise going to dry out before being able to accurately predict the water contents.

A perfect roll out speed is necessary for the plastic limit of the soil to be accurately described. This speed depends and varies individually from the different soil samples and thus expert engineering judgement is needed for determination of the plastic limits.

Differentiating clay from silt

When trying to investigate soil properties and before determining and characterizing the difference qualitative parameters of the soil sample it is important to consider the distinctive behavior’s separating silt from clay. The distinction is easily made through use of two different test techniques. Firstly the ‘Elephant’ test technique is easily utilized

Elephant test technique

The elephant test technique for distinguishing soil behavior’s is quickly and accurately utilized even without expensive field laboratory equipment. The distinctive test is performed by creating an elephant like trunk shape of a small soil sample which is approximately 3 mm thick in shape.

The shape of the constructed elephant trunk is then examined and seen whether or not it is able to withstand the force underneath its own gravity. If the trunk easily upheld its own shape under its own weight, then the soil sample is considered to be clay.

However if the soil sample cannot easily withstand the force of gravity with deformed shapes and cracks on the surface then the soil sample is considered silt. This is an easy and inexpensive way of making sure that the soil sample in question is actually silt and not clay and visa versa.

Another commonly used methodology is to create a bended U-shaped sausage which is then utilized to check for cracks in a similar manner as the elephant. These inexpensive ways of determining whether or not a soil sample is consisting of clay or silt is invaluable.

With this being said, there also exist other methodologies to easily investigate whether a soil sample is clay or silt one of these is called a sedimentation test.

Sedimentation testing

The sedimentation test is a technique similar to that of the elephant test in that this specific version is likewise meant as an example to try and differentiate the soil sample into clay and silt respectively. The clay particles when settling in a tube will create a mixture of solid particles and liquids called a suspension while a silt sample will create a coarser sample.

Suspension definition and behavior

A suspension is particular interesting when trying to investigate the hydrodynamic properties of a fluid and when trying to investigate eco-systemic impacts of large infrastructure projects.

The ecosystem can easily be affected by suspensions in the sense that endangered species are affected by floating clay particles where gills of fish are clotted and marine fauna such as eelgrass are threatened by sedimentation layers stealing available sunlight.

The problems also arrives when considering the time spent on the settling particle velocities which for a given suspension can be extremely small, allowing individual particles to easily stay in the suspended water column for extended periods of time before it will be able to settle on the ground surface.

For clay the particles can stay in suspension for hours even days without settling in still water due to the water undulations within the water column causing the fine material to keep sculpting around.

Settling behavior of silt

The difference in settling between clay and silt is easily measured when conducting sedimentation experiments. As explained, the clay settling velocities are small allowing for the suspension to keep particles in the water column for extended periods of time corresponding to days.

For silt the suspension will fall out of the water column much faster than clays and thus when investigating soil samples and characterizing the sample into clay and silt, measuring the settling time and velocities would allow you to easily distinguish the soil sample into clay and silt.

The silts settling velocity is much larger than clay due to mainly two phenomena, the particle sizes of silt are an order of magnitude larger and flocculation effects are often quite significant for silty materials. The flocculation is when particles of different sizes clump together during settling resulting in increasing settling velocity of the entire joint lump of particles compared to the individual ones.

This particulate behavior leads to a common phenomena called siltation.

Siltation

Siltation is a phenomena common in river -streams and -mouths as a result of excavating, extreme rainfall events or pollution. The siltation of river streams poses environmental dangers to ecosystems as the consequent sedimentation strangles bottom feeding and living creatures, while simultaneously damaging eggs and larvae exposed to silted environments.

Some common example of siltation events occur during marine dredging where silted material is transported upwards in the water column. The upward momentum allows whirling of particles up into the undisturbed water column causing the individual particles to be transported large distances and spread out over potentially endangered areas.

Another example of siltation is during extreme rainfall events where soil banks are eroded away due to increased water volumes causing silt and clay rich banks to be eroded and washed into the water column.

When transported downstream and before settling down into more calmer waters this siltation of water streams can cause suffocation of fish and degradation of wildlife. It is therefore considered an environmental disaster when rivers are exposed to siltation events.

Tags Engineering, Material, Natural

Natural materials

Natural materials – clay

In this blogpost we will explore one of the most common natural materials in the world, clay.

What is clay?

Clay is a natural fine-grained material which smoothens out easily under pressure and is often filled with water.

The composition of clay is typically filled with minerals such as kaolinite, etc. these minerals are important for the beauty industry as most common type beauty products utilize some form of clay minerals. Additionally clay minerals are important in certain types of pharmaceutical industries as binders, lubricants, diluents, pigments and opacifiers.

History of clay in pharmacy

The use of clay in the pharmaceutical industry dates back to prehistorian eras where it has been used in pottery for containers of medicine and in 1600 BC a ‘book’ containing evidence that clay was used against hemorrhages and other types of diseases has been found. Underlining the fact that clay is a crucial part of human society for thousands of years.!

Another prehistorian example of clay as a pharmaceutical instrument is In the 400’s BC a book by Hippocrates called “On Airs, Waters and Places”. In this book they describe the Armenian bole and clays usage in healing dysentery and diarrhea. The Armenian bole is a special type of clay often used as medicine, as a pigment and gliding material. It is often red due to the presence of iron oxide.

The important compounds of clay in pharmacy is their mineral composition. In order to characterize clay it usually is subdivided into four main groups corresponding to the mineral content. These are:

Kaolinite
Smecticte
Illite
Chlorite

Where further subdivisions can be made of clay based on the mineral plate layering as outlined in Table 1.

S. No.	General Formula	Group	Layer Type
1	Al₂Si₂O₅(OH)	Kaolinite-Serpentine	1:1
2	Al₂Si₄O₁₀(OH)₂Mg₃Si₄O₁₀(OH)₂	Pyrophyllitetalc	2:1
3	Montmorillonate (Al_1.67Mg_0.33) Si₄O₁₀(OH)_2M + 0.33 Saponite:Mg₃(Si_3.67Al_0.33)O₁₀(OH)_2M + 0.33 Hectorite(MgLi)₃(SiAl)₄O₁₀(OH)_2M+	Smectite	2:1
4	(Mg,Fe,Al)₃(Al,Si)₄O₁₀(OH)_2.4H₂O	Vermiculite	2:1
5	KAl₂(Si₃Al)O₁₀(OH)₂	Mica/Illite	2:1
6	Al₄[Si₈O₂₀](OH)₄Al₄(OH)₁₂	Chlorite	2:1:1
7	(Mg,AL,Fe³⁺)₅(Si,Al)₈O₂₀(OH)₂(OH₂)_4.4H₂O Mg₈Si₁₂O₃₀(OH)₄(OH₂)_4.8H₂O	Palygoskite-sepiolite group

Table 1: Mineral compounds typically found in clay with subdivisions based on typical geometries and mineral composition.

Common use cases of clay

The usages of clay are plentiful and it has been used for various amounts of pottery throughout history. These types of pottery have played an important role when trying to establish a culture and society, as containers have been produced holding everything from water to spices.

In modern history after the industrialization it has been possible to mass produce pottery instead of individual people being employed full time with the occupation suddenly it was possible to free up time for individuals now focusing on something more productive such as innovation and rethinking new technologies.

Clay pottery as food storage

Meanwhile clay pottery is still used today to store all kinds of inventory such as food, spices and vegetables. With the advent of vegetarianism it might be reasonable to ask: Is clay vegan friendly? And to that the answer is a sounding yes! Clay is absolutely vegan friendly as the compounds making up clay pottery is entirely from non-animal origins meaning that anything vegan that you put in a clay bowl or pottery stays vegan.

Additionally clay pottery is able to withstand high temperatures and doesn’t decompose easily when burnt. Furthermore the trash from clay pottery is entirely natural and thus no need to worry about environmental hazards from trashed clay pottery.

Clay as a building material

Another usage of clays is as a building material for bricks, huts and similar. Here the clay is used to mold bricks in huge ovens allowing for hardening. When hardened and burned, the resulting bricks are capable of withstanding outside weather, rain and storms.

Clay bricks for building have been used for millennia and such the technology of creating bricks from ‘mud’ is something that has withstood the test of time. In a primitive manner, the recipe for creating clay bricks is simple; Mix water, clay, straw and heat until hardened in high temperatures.

Creating bricks with bare hands

An excellent resource for showcasing the simplicity and ancient technology associated with the clay brick creation is the Youtube channel ‘Primitive Technology’. A guy shows in simple steps how to create clay bricks from raw materials.

Video 1: Fired clay bricks as a primitive technology for brick creation

This way of creating bricks is simple yet effective and can be understood through the use of ancient technology.

The flow of liquids through clay

Unlike other materials such as sand, clay has quite an adherence to water. it is hydrophilic in the sense that most clays adsorb water in huge amounts leading to saturated soils. Additionally water passes extremely slowly through clay meaning that it acts as plug stopping all of the water trying to go through.

This property of plugging water and other liquid substances from flowing through clay is important in industries such as oil and gas. In fact clay functions as a lid under which oil and gas collects in huge amounts in large oil reservoirs and often times act as a necessary predisposition for the existence of oil fields.

The drainage of oil wells is a complicated process where high pressures are utilized for pumping water and oil mixtures up towards the surface from deep underground aquifers. Here impermeable layers help build up necessary pressures through overburden stresses allowing the transformation from organic material toward hydrocarbon fossil fuels.

The overburden stressors and impermeable layers can lead to another phenomena called artesian wells.

Artesian wells

An important consideration when trying to identify potential locations for water extraction is the overburden pressures or internal fluid pressures in underground aquifers. These aquifers allow the flow of liquids over large distances and are typically separated by impermeable clay layers. The impermeable clay layers impose stresses on underlying layers resulting in increased internal water pressures. When trying to extract water from such configurations the resulting pressures in the liquid lead to the establishment of artesian wells see Figure 1-2.

$An illustration of an artesian well, where the clay\impermeable layer is overlaying the aquifer layers.$

Figure 1: Cross-section diagram of an artesian well, USA. Illustration published in Physical Geology by Mytton Maury (University Publishing Company, New York and New Orleans) in 1894. Digitally restored.

Figure 2:The great artesian basin in Australia consisting of the largest artesian basin in the world spanning more than 1.7 million square kilometers.

The key defining characteristic between regular and artesian wells is the overburden stresses and internal fluid pressures. these allow for the easy extraction of liquids through since flow is automatic up to the surface meaning no need for pumping systems or otherwise extraction techniques.

Water in artesian wells

Artesian wells often contain water. This water is typically of high quality and easily drinkable as the aquifers functions as filtering material of harmful minerals and bacteria. Additionally water from artesian wells are often free from contaminant sources and thus often bottled as spring water more expensive than regular water from taps, examples of such include Fiji water among others.

Oil in artesian wells

In the beginning of the oil era, artesian wells played an important part for extraction of oil. The flowrate is large for aquifers allowing the extraction of huge amounts of oil and the artesian wells didn’t require expensive pumping instruments.

Additionally the locations of the artesian wells made extraction easily manageable as the land deposits at the time were full of oil. An example of such oil fields are displayed in GIF 1.

Meme 1: Example of an Artisian oil well being lit on fire

The land deposits were furthermore located in locations where large infrastructure existed making the pipeline laying easily manageable. This ensured that oil deposits kickstarted the production of oil in the United States within the first years of industrialization.

Clay for sculping

As a last addition clay is also fantastic for sculping sculptures. For the handy people around these sculptures are easily made utilizing a spinning wheel combined with sculpting clays such as monster sculpting clay.

The monster sculpting clay is exceptional for clay sculpting whether you are a beginner just trying it out for the first time or an experienced professional looking for a hard clay based mounding substrate to easily manipulate into beautiful structures or figures.

References

Mineral composition of clay, source.

Tags Clay, explanatory, Material, Natural

Natural materials

Soil characteristics – sand

Post author By joachimsbach
Post date 19th February 2023
No Comments on Soil characteristics – sand

In this blogpost we dive deeper into the soil characteristics of one of the most common construction materials – Sand. Throughout this blogpost we will try and characterize sand as a building and natural material.

Figure 1: Hand embracing desert sand

Why is sand called sand

Lets start of with a small history lesson of why sand is called sand in the first place. The word “Sand” comes from the old English word of “sund” which referred to the ground, soil or earth.

With the advent of time the meaning of sand have changed from loosely describing earth and ground, to the present day version describing a granular, particulate in-cohesive substance most commonly associated with the beach sands and backyard playing ground equivalents.

Common and professional usage of the word sand

Comparatively sand refers in professional terms to building material used in concrete mixing, as a pore-breaking material underneath foundations and walkway substrate in parks and forests. In contrary the layman term of sand refers more to the old English “sund” version.

What characterizes sand grains

One of the defining characteristics of sand is the granular size. The granular size of particles is important when trying to characterize sand properly. In geotechnical terms the governing common definition of sand is a substrate whose particle grain sizes varies between 0.063 and 2 millimeters.

Geotechnical definition of sand

The importance of this distinction lies in the physical properties of particles within this size range whose characteristics are particularly useful for construction, filtering, crafting and mixture purposes but more on that later.

Sand grain characteristics through a lens

While the size range is sharply defined in terms of radius, in reality the individual particles can vary in shape, size and form in three-dimensions. Microscopes allow researches and engineers to characterize differences between individual particles sharpness and skewness factors. The differences of individual sand particles are easily seen through a microscope, see Gallery 1 for examples of sand grains throughout the world.

Construction site sand under the microscope. — **Gallery 1:** *Collection of microscopic images of sand with origins from Australia’s outback, beaches of England till a construction site.*

Hawaiian beach sand under the microscope — **Gallery 1:** *Collection of microscopic images of sand with origins from Australia’s outback, beaches of England till a construction site.*

As we can see the color of sand varies greatly from location so one could be tempted to ask; what color is sand exactly?

What color is sand?

The color of sand varies greatly with the mineral content as the mineral composition determines the light refraction indices that make up color of solid particles. Typically the mineral composition of sand consists of quartz. Quartz is a hard, crystalline material composed of silica. The pure color of quartz is transparent which is perceived as white in large quantities.

Minerals found in sand

However the mineral composition of sand is far from regular as often times the deposition consists of a mixture of some of the following minerals:

Quartz: It is a hard, crystalline mineral that is often clear or white, although it can also be found in shades of pink, yellow, and gray.
Feldspar: It is a group of minerals that include orthoclase, plagioclase, and microcline. Feldspar is often white, pink, or gray in color.
Mica: Is known for their shiny, reflective surface and can be found in a range of colors, including white, brown, and black.
Olivine: This is a green, iron-rich mineral that is often found on beaches and in volcanic areas.
Calcite: This is a mineral that is often found in sandstone and limestone. It is typically white or colorless but can also be found in shades of yellow, green, and blue.
Magnetite: This is a black, iron-rich mineral.
Garnet: This is a red or brown mineral that is found on beaches and in riverbeds.
Rutile: This is a titanium mineral that is often found in coastal areas. It is typically reddish-brown or black in color and has a distinctive metallic luster.
Zircon: This is a mineral that is commonly found in beach and river environments. It is usually brown or reddish-brown in color and has a high refractive index, which gives it a brilliant luster.
Tourmaline: This is a mineral that is often found in beach environments. It can be found in a range of colors, including black, green, pink, and blue.
Gypsum: This is a mineral that is often found in sand dunes and other desert environments. It is typically colorless or white and has a soft, powdery texture.
Pyrite: This is a sulfide mineral that has a metallic luster and is typically a brassy yellow color.
Halite: This is a mineral that is commonly found in desert regions. It is also known as rock salt and is typically colorless or white.

This is not an exhaustive list of all the minerals which can be found in sand however it consists of some of the more common minerals found in beach sand, rivers and deserts.

As the composition of sand can vary greatly depending of the type of sand, location and weathering effects, the actual color of sand can vary greatly even within the same sample of grains! see Gallery 1 for examples. Although the composition of minerals differs within each of the sand grains one characteristic which is continuous is the adherence to water.

Why is sand attracted to water?

Sand is attracted to water or rather, water easily passes through sand. People often believe that sand is attracted to water in the sense that it is almost magnetic. However this is far from the truth. Sand is not attracted to water, in reality the composition and compactness of sand allow individual water molecules to easily fit between sand grains. This feature allows for sand to act as a porous substrate whereby the flow of water through the compacted medium is happening at a reasonable pace.

The flow of water through a medium

The flow of water through a medium and particularly a substrate is governed by the natural law which is Darcys law see below equation.

(1) $\begin{equation*} Q = - K \cdot A \frac{\delta H}{\delta l} \end{equation*}$

Where, Q, is the total discharge in [m³/s], K is the hydraulic conductivity in [m/s], A is the cross-sectional area in [m²], H, is the hydraulic head [m] and l is the length in [m].

This law in three-dimensions govern the flow of water through the underground for fully saturated soils assuming laminar flow. For sand in particular, the values for the hydraulic conductivity K, are high resulting in a relatively speaking geotechnical context fast paced flow patter through water.

Darcy flow experiment

In order to correctly estimate such flow rates through saturated soils, Darcy produced an experiment determining the pressure loss between points of interest based on flowrates of water. To investigate his hypothesis concerning the governing parameters of soil flow rates, he deviced an apparatus designed specifically to measure flow rates through solid medium, see Figure 2.

The results of typical Darcy flow experiments in modern time results in parameter estimates which coarsely have characteristic hydraulic conductivity values in the ranges presented in table 1, here considering sand substrates only.

Type of sand	Hydraulic conductivity [m/s]
Corse sand	9 * 10^-7 to 6 * 10^-3
Medium sand	9 * 10^-7 to 5 * 10^-4
Fine sand	2 * 10^-7 to 2 * 10^-4

Table 1: Typical values of sand hydraulic conductivity from source.

Darcy's original apparatus for determining the soil characteristics of sand — **Figure 2:** *The original Darcy apparatus with additional annotations for reading feasibility from source*.

The apparatus allows Darcy to study the change in pressure versus flowrate of saturated soils and is the basis for most groundwater flow models where advanced features like non-stationary gradients, rocks, unsaturated flow and varying water tables through aquifers can be incorporated, amongst other parameters.

How many types of sand exist?

There exist a plethora of sand types throughout the globe. The individual characterization of different sand compositions in minerals, weathering effects and similar arises from the differences in earths soil, climate and type of origination. A specific number of sand types is thus impossible to give a precise picture of. However if pressed one possible way of characterizing soils in general is through their grain size distributions.

Grain size distributions

The grain size distribution allow a characterization of soils and in particular sand through the use sieves throughout the soil sample. The grain size distribution is important to understand as the defining mechanical and physical behavior of the soil sample depend heavily on the grain size distribution, shape and sharpness of the individual grains.

Laboratory equipment

In order to characterize and calculate a grain size distribution one should utilize sieves with different mesh sizes. The sieving systems regularly used for commercial grain size characterizations are among others the following:

As any laboratorian would know, another part of the puzzle before you are set for producing your own grain size distribution analysis is the laboratory grade scales able to measure weights in the range from 0.01 grams into 5000 grams. You need this scale range in order to both capture sieves with and without soil and the percent finer settlement.

The last piece of the puzzle is the important test-equipment for performing a sieve analysis with resulting grain size distribution is the sieve stack shaker.

By utilizing this equipment and measuring the weight before and after, it is possible to perform a grain size distribution characterization of a given soil sample.

Procedure for production of a grain size distribution

The procedure for performing the a grain size distribution analysis has the following steps:

Weigh sample before sieving.
Weigh each individual sieves when they are empty
Note down individual mesh sizes
Stack sieves from coarsest to finest meshes in the shaker stack.
Pour soil sample from the top of the sieve stack
Start the stack soil shaking apparatus
Shake samples for approximately 24 hours
Split up shaker stack and weigh residual soil in each individual sieves
Subtract original sieve masses to obtain residual mass of soil
Calculate the percent finer from the original soil weight.
Plot mesh particle size versus the percent finer % from the soil sample
Perform the grain size distribution plot

By following the above steps you will be able to perform an analysis of the grain size distribution whose result will be in a similar form.

Figure 3: Example of a grain size distribution diagram after performing a sieve analysis of a soil sample here containing a mixture of rocks, gravel, sand, silt and clay.

This example allows you to characterize individual soil samples from around the globe. The distribution of particle sizes between soil samples vary greatly based on location of extraction but is an excellent way of characterizing sand.

What is the importance of sand

Sand is important for both industrial and domestic use cases. The industrial uses of sand are among other things construction, asphalt, cement, glass making, foundry casting, abrasives, filtration, manufacturing and fracking. Some of the domestic use cases of sand include; gardening, kitty litter, play sand and home décor.

Related read: Earthquake proofing buildings

To create concrete you need cement, sand, water and rock. One of the most important ingredients in concrete is sand as it serves as a binding agent between cement water and rock to create concrete. The usage of concrete is wide from large infrastructure projects such as dams, highways, skyscrapers and airports until smaller projects such as individual house building etc. In fact the consumption of concrete is enormous throughout the world and is estimated to be around 4.27 billion tons worldwide, see source. This puts sand in high demand across the globe.

Artificial islands

To build artificial islands you need a lot of sand. To build beach nourishments and land reclamation you also require a lot of sand. To incorporate changes in landscapes and road developments you require a lot of sand. These projects all require sand in vast amounts.

As an example consider the recreational beach built as an artificial island off the coast of Amager strand in Denmark. To realize this project contractors needed to use an estimated 1.000.000 m³ of sand. This allowed the creation of an entirely new island for recreational usage, see Figure 4.

A more famous example of built artificial islands is the “world” located in the northern part of Dubai’s coast. The world is a massive system of smaller artificial islands which when seen from afar correspond to a world map similar to the globe. Estimates show that the amount of sand utilized for building the artificial network of islands in Dubai is approximately 100.000.000 m³ see source and Figure 5.

Figure 4: Amager recreational beach is here seen as the elongated artificial island.

Figure 5: The ‘world’ as artificial islands in the northern part of the coast of Dubai. source.

All of these massive utilizations of sand makes one wonder, is there enough of it to go around?

Can we run out of sand?

Yes is the short answer, what type of sand is another answer. We can definitely run out of useable sand. In fact when asking the question: “Can we run out of sand” people often refer to the type of sand used for construction material and for this purpose the answer is: Yes absolutely we can run out of sand.

In fact, the useable kind of sand whose grain size distribution is exactly right is often times hard to come by. For the same reason, once we discovers a usable location for sand excavation we often build large quarries to ensure we get all of it. Furthermore we go as far as to expropriate people from their properties if they are in the way such that we ensure access and maximize the excavated amount of sand.

Now one might consider using sand from deserts as deserts, see Figure 6, cover a vast amount of the entire earths landmass. In factuality, experts believe that one-fifth of all landmasses on earth consists of deserts! See source.

Figure 6: Desert sand dunes typically found in deserts.

Therefore it seems absurd to ask questions like “Can we run out of sand” however the answer is that the vast majority of sand is unusable for practical purposes, unless you want to create a desert! The desert sand is useless for building any buildings, infrastructure or mixture in concrete due to its rounded shape and unfavorable grain size distribution. Furthermore desert sand is often times located in remote places where infrastructure doesn’t facilitate the usage of sand.

Conclusion

In this blogpost we have characterized one of the most common soil characteristics – Sand. We have described the name origin, grain size, most common mineral composition, color, hydraulic properties and common usages. Furthermore we have described and debunked common myths in relation to the excavation and usage of sand.

References

General information about sand and pictures Wikipedia

Darcy law equipment source.

Consumption of concrete in the world: finance.yahoo

Sand volume estimates source.

lab equipment – Amazon.com

Desert covering earth, from National Geographic education, source.

Tags Material, Natural, sand