The Invisibles

Split Tensile Strength Test (Brazilian Test)

The Brazilian Test is a laboratory test conducted in rock mechanics to indirectly determine the tensile strength of rocks. The tensile strength of rock materials is an important parameter in designing a geotechnical project since it is significantly lower than the rocks’ compressive strength. This phenomenon is also presented in concrete, a fact that led to the utilization of steel reinforcement to increase the tensile capacity of the material. Research has also shown that during compression, the tensile strength in the tips of microcracks is exceeded and those cracks tend to propagate through the specimen leading to failure.

Bentonite as Drilling fluid

Bentonite in Piling The most common use of bentonite is in drilling fluids. The bentonite in the flush fluid lubricates and cools the cutting tools while protecting against corrosion. As the drilling fluid generates hydrostatic pressure in the borehole, it hinders fluid and gas penetration. The drilling liquid conveys the drill cuttings to the surface. As a flushing fluid, bentonite seals the drilled shaft from water ingress downwards and at the sides of the shaft. The mineral forms a firm sludge cake on the bore wall, which provides the borehole with additional stability. The fine bentonite particles enter into the bore wall where they swell and harden. Depending on the constitution of the ground structure, fine and coarse particles are needed.

Soil Bearing Capacity Failure

Buildings are often held up by footings underneath the columns. If the soils are too weak or the column load too big, the footing plunges into the earth in a bearing capacity failure. This exercise demonstrates bearing capacity by identifying the three principal modes of failure using various arrangements of piles, foundations, loads, and the factors that contribute to increasing bearing capacity.

Plate Bending Experiment

Source channel- Engineering Models

In order for students to understand how plates carry load and where reinforcing is required in concrete slabs or composite plates, they must be able to visualize how plates deform. This model is designed so that students can see how real plates deform under their own weight, and learn through experimentation about the additional deformations caused by various external loads.

Effect of Gravity on Soil Strength

Source channel- ExpeditionWorkshed

This experiment demonstrates how deposition under gravity of soil particles, in lakes and rivers, affects how soils behave soils laid down under gravity form column structures within their mass, which makes these soils stronger vertically than horizontally. Gravity effects the strength of soil at different depths. This experiment shows that the more load a foundation carries, the further it will push into the soil before it reaches equilibrium. The conclusion is that soil strength increases with depth.

Illustration of Moments


Calculating reactions at supports is always the first step in analyzing a beam structure, and it is generally the easiest. It involves calculating the reaction forces at the supports (supports A and B in the below example) due to the forces acting on the beam. You will need to know this to progress through and calculate bending moment diagrams (BMDs) and shear force diagrams (SFDs)

Rock Bolting

Source channel- Practical Engineering

Tunnels play an important role in our constructed environment as passageways for mines, conveyance for utilities, and routes for transportation. Rock bolts are a type of reinforcement for stabilizing rock excavations, usually made from steel bars or bolts. This simple construction method dramatically reduces the cost of making tunnels through rock safe from collapse.

Dam Breach Flood Experiment

Source channel – USGS

Dam breach analyses are used to estimate the potential hazards associated with a failure of a project structure/feature. Dam failures or levee breaches can occur quickly and without much warning, causing severe flash flooding in the surrounding area and resulting in property damage and loss of life.The non-uniform and discontinuous dam material and the inconsistent water flow particularly complicate the failure process, and there are different failure modes such as the overtopping failure mode and slope failure mode. Dam breach prediction models are used to estimate the geometry and formation time of a dam breach. Typically, dam breach prediction models are based on empirical data derived from a number of mostly earth and rockfill dam failures case studies. The available empirical equations relate the dam breach parameters to properties of the dam and reservoir such as height, dam type and its erodibility, volume impounded, and shape of the reservoir. In support of risk informed decision making, a probabilistic approach to dam breach modeling may be considered.

Seven Bar Truss Experiment

Source Channel – STRUCOMP

Seven Bar Truss Experiment investigates the internal forces induced in a 7-bar truss from & application of
a pattern of point loads applied to free joints and/or the roller support, from evaluation of the
elongation/contraction of each model truss member and its nominal stiffness.

Quick Sand Condition

Quicksand condition occurs when seepage pressure, which acts in the upward direction, overcomes the downward direction pressure due to submerged weight of soil, and the sand grains are forced apart. The result is that the soil has no capability to support a load.
The soil that experiences quicksand condition would lose shear strength and bearing capacity.Quicksand cannot support the weight of man or animal and it behaves like a liquid with a unit weight about twice that of water. A person can easily float in it with about one-third of his body out of quicksand.

SandBox Experiment

Source channel- Marco Antonio

Sandbox modeling has been used extensively over the last decades to study the structural evolution to model shallow geological processes. A sandbox experiment model was designed to simulate how differences in rock strength and gravity between two blocks can influence the formation characteristics of thrusts. Layers are made of medium sand, clay (bentonite) and cement. The black layers are clay tinted with reused laser printer powder, just to add some contrast.


Source Channel- QuakeCoRE NZ

Liquefaction is a phenomenon in which the strength and stiffness of a soil is reduced by earthquake shaking or other rapid loading. Liquefaction and related phenomena have been responsible for tremendous amounts of damage in historical earthquakes around the world. Liquefaction occurs in saturated soils, that is, soils in which the space between individual particles is completely filled with water. This water exerts a pressure on the soil particles that influences how tightly the particles themselves are pressed together. Prior to an earthquake, the water pressure is relatively low. However, earthquake shaking can cause the water pressure to increase to the point where the soil particles can readily move with respect to each other.

Torsion Test on Mild Steel

Source- MTN Pro

Torsion testing is a type of mechanical testing that evaluates the properties of materials or devices while under stress from angular displacement. Torsion test on mild steel is performed to study the shear stress shear strain behavior of the material. To study the failure pattern of these materials in torsion. To determine the mechanical properties, e.g, Modulus of elasticity, Modulus of rigidity, Shear strength, shear strain and ductility in torsion.

Hydraulic Jump

Source channel- Alian S

Hydraulic jump is the jump or standing wave formed when the depth of flow of water changes from supercritical to subcritical state. When the slope of open channel decreases from steep to mild, the depth of flow of water increases toward the critical depth and a flow instability occurs at some point. The flow becomes turbulent until the new normal depth is attained in the downstream. This is called a hydraulic jump. The hydraulic jump is necessarily formed to reduce the energy of water while the discharge downfalls a spillway. It becomes necessary to reduce its energy and maintain stable velocities, that phenomenon is called energy dissipation in hydraulic structures.

Compaction Factor Test of Concrete

Sorce channel- Mr.Chiranjeevi Rahul

The compaction factor test is used for concrete which have low workability for which slump test is not suitable. The compacting factor test is performed to ascertain the workability of the concrete. The slump test does not give accurate results for low worability of concrete when slump is<50mm.The compaction factor test is a workability test for concrete conducted in the laboratory. It was developed by the Road Research Laboratory in the United Kingdom and is used to determine the workability of concrete.
The compaction factor is defined as the ratio of the weight of partially compacted concrete to the weight of fully compacted concrete.

Bernoullis Theorem

Source- Practical Guru

The Bernoulli’s theorem states that For a continuous, steady and frictionless flow the total head (which is the sum of pressure head, velocity head and elevation head) at any section remains constant. It is applied in Airplane wings, atomizers, chimneys and flying discs. 

Consistency Test of Cement

Source Channel- CE Quick Solution

The consistency test is to find the basic required percentage quantity of water to form a cement paste of uniform viscosity. The standard consistency of cement is that consistency, which permit the vicat plunger to penetrate to a point 5 to 7mm from the bottom of the vicat mould when tested.

Vibration Table test of Concrete

Source channel- Virtualwebs Servers Pvt. Ltd : Software and Web Design Company

The Vibrating is a critical step on many concrete construction projects. When concrete is poured, it might have hundreds or even thousands of air bubbles, which can substantially weaken the concrete structure. Most concrete is under-vibrated or improperly vibrated. The best technique with an internal vibrator is to withdraw the vibrator very slowly, at a rate of around 1 inch per second. As long as bubbles still emerge as the concrete vibrator is withdrawn, more vibration is necessary.

Hydrometer Method

Source Channel- engiNERDing

The hydrometer analysis of soil, based on Stokes’ law, calculates the size of soil particles from the speed at which they settle out of suspension from a liquid. Results from the test show the grain size distribution for soils finer than the No. 200 (75µm) sieve. However, when combined with a sieve analysis, offer a complete gradation profile of soils containing coarser materials. The hydrometer measures the specific gravity of the soil suspension at the center of its bulb. The specific gravity depends upon the mass of solids present, which in turn depends upon the particle size.

Flakiness Index Test of Aggregates

Source channel- Construction Technology And Management

The particle shape of aggregates is determined by the percentages of flaky and elongated particles contained in it. For base course and construction of bituminous and cement concrete types, the presence of flaky and elongated particles are considered undesirable as these cause inherent weakness with possibilities of breaking down under heavy loads. Thus, evaluation of shape of the particles, particularly with reference to flakiness and elongation is necessary. The Flakiness index of aggregates is the percentage by weight of particles whose least dimension (thickness) is less than three- fifths (0.6times) of their mean dimension. This test is not applicable to sizes smaller than 6.3mm. The Elongation index of an aggregate is the percentage by weight of particles whose greatest dimension (length) is greater than nine-fifths (1.8times) their mean dimension. This test is not applicable for sizes smaller than 6.3mm.


Source Channel- Practical Guru

The Tension test is performed on mild steel, tor steel and high tensile steel to determine the properties like Young’s modulus, ultimate strength, and the percentage elongation. In the tension test, a steel rod is subjected to tension load by the means of a Universal testing machine(UTM). The specimen is subjected to constant tension load and the extension caused in the steel rod is noted against the load within the elastic limit. The load values at yield point, breaking point, and ultimate point are carefully noted. With the obtained values, the stress and strain are calculated and plotted in a graph.

Izod Impact Test

Source Channel- Practical Guru

The Impact test signifies toughness of material that is the ability of material to absorb energy during plastic deformation.Toughness takes into account both the strength and ductility of the material.T here are two distinct type of toughness mechanism and in this case it is appropriate to consider notch as a very high local stress concentration. The first type of mechanism occurs in ductile material. This is because very high stresses at the end of the notch produce local yielding of the material and local plastic flow at the crack tip. This has a action of blunting the sharp tip of the notch and hence reduces the stress concentration effect.The second mechanism occurs in fibers, wood materials etc which have a weak interface. Local tensile stress developed at the front of a propagated crack opens up the interface and produces a crack sink i.e., blunts the crack by effectively increasing the radius of the crack tip. The stress-concentration at the notch increases with decreasing notch radius.

Flow Table Test of Concrete

Source Channel- Ahmed aboalliel

As Workability is a complex property of concrete which directly impacts on Concrete strength, quality and appearance and it also determines how easily freshly made concrete can be mixed, placed, compacted and finished with the minimum to no loss concerning homogeneity. As mentioned, its a complex property which involves many factors concerning the good workable concrete.The workability of concrete is determined by examining the flowing property of concrete. Flow table test of concrete also determines the Quality of Concrete concerning its consistency, cohesiveness and the proneness to segregation.

Unconfined Compression Test for Soil

Source Channel- Life_of_a _Civil_Engineer

It is used to determine the unconfined and undrained compressive strength of a cohesive soil in an inexpensive manner. Unconfined Compressive Strength (UCS) stands for the maximum axial compressive stress that a cohesive soil specimen can bear under zero confining stress. Unconfined compression test is one of the fastest and cheapest methods of measuring shear strength of soil.

Los Angeles Abrasion Test

Source- BPUT Digital Learning Resources

The Los Angeles (L.A.) Abrasion Test is widely used as an indicator of the relative quality of aggregates. It measures the degradation of standard gradings of aggregates when subjected to abrasion and impact in a rotating steel drum with an abrasive charge of steel balls. The drum is fitted with an internal shelf that lifts and drops the charge and sample with each revolution, generating impact forces. After the machine has completed the required rpm, contents are removed and percent loss is measured.

Hydraulic Flume Test

Source channel- JBA Trust

The mini flume shows the flow of water in a simple channel, driven by a system of recirculating pumps. It shows scale models of typical engineered structures such as weirs, bridges, culverts and debris screens. The mini flume is particularly useful in helping to understand some of the causes of flooding and how good design and maintenance of rivers and drainage channels can help to manage flood risk.

Penetration Test of Bitumen

Source Channel- NCTEL

The Penetration value test on bitumen is a measure of hardness or consistency of bituminous material. A 80/100 grade bitumen indicates that its penetration value lies between 80 & 100. Penetration value is the vertical distance traversed or penetrated by the point of a standard needle into the bituminous material under specific conditions of load, time and temperature. This distance is measured in one tenths of a millimeter. Penetration test is used for evaluating consistency of bitumen.