Site investigation is a process of site exploration consisting of boring, sampling and testing so as to obtain geotechnical information for a safe, practical and economical geotechnical evaluation and design. Generally it is an exploration or discovery of the ground conditions especially on untouched site.

In other words the main purpose of site investigation is to determine within practical limits, the depth, thickness, extent and compositions of each subsoil stratum, the depth and type of rock, the depth and composition of groundwater, the strength, compressibility and hydraulic characteristics of soil strata required by geotechnical engineers. Sometimes it is also known as geotechnical investigation.

The Importance of SI

• To study the general suitability of the site for an engineering project.
• To enable a safe, practical and economic design to be prepared.
• To determine the possible difficulties that may be encountered by a specific construction method for any particular civil project.
• To study the suitability of construction material (soil or rock).

Why Have To Perform SI?

SI is essential for every construction project. This sketch should do the trick...

Obviously, it is a part of geotechnical processes in preliminary stage.

Lack of geotechnical processes will lead to a:

• Failures where many case histories are available.
• Significant delay and increase in construction costs when the design has to be revised or amended.

Generally the elimination of the site investigation will not safe the cost of the project thus it only comprises from only 0.1% to 5% of the project cost. In fact most frequent claims in civil engineering contracts are on the basis of inadequate SI or obstructions resulting in extra costs which could not reasonably have been foreseen by an experience contractor.

Wok Procedure for SI
Steps of work involved in site investigation:

1. Desk study to collect all the relevant data and information,
2. Reconnaissance of site works,
3. Planning program after reviewing the above,
4. Ground or soil exploration includes boring, sampling and testing,
5. Laboratory testing (also field if necessary),
6. Preparation and documentation of SI report,
7. Engineering design stages,
8. Review during construction and monitoring.

Planning of SI Works
Surface Investigations:

• Site inspection to assess general site condition if there is any anticipated problems that might arise during the construction later on.
• Usually the engineer is required to inspect the site to appreciate actual site and ground problems with particular reference to terrain, vegetation, swamps, water runoff, stratigraphical formations where it is exposed.

Sub-surface Investigations:

• Ground or soil investigation by means of boring, sampling, testing, and etc. And also as to determine the stratigraphy and pertinent properties of soil underlying the project site.

Site Reconnaissance
A reconnaissance is a preliminary examination or survey of a job site. First step is to collect and study any pertinent information already available. After collecting and studying the data available, the engineers should visit the site in person, observe thoroughly and interpret what is seen. Results of reconnaissance help to determine the scope of subsequent soil exploration. It is important to locate any underground utilities to assist in planning and carrying out subsequent subsurface exploration.

A few generalizations of reconnaissance:

• Details on the ground surface for an early observation,
• Topographical characteristics, e.g. flatland, hilly, swamps or pit area,
• The possible location of the ground water tables (GWT),
• Interviewing the local residents for further information,
• Taking a lot of photographs of the proposed site.

Steps of Soil Exploration
Soil exploration in site investigation consists of:

• Boring: Refers to drilling or advancing a hole in the ground. The test would include hand auger, motorized hand boring (wash boring), deep boring (rotary drilling), and/or trial pits.
• Sampling: Refers to removing soil from the hole. The samples can be classified as disturbed or undisturbed sampling. Disturbed samples are usually used for soil grain-size analysis, determination of liquid limit, specific gravity of soil as well as compaction test and California bearing ratio (CBR). The undisturbed samples are collected at least every 1.5 m and if changes occur within 1.5 m intervals, an additional samples should be taken.
• Testing: Refers to determining the properties from the soil. The test can be perform either at laboratory or at field. Laboratory testing would normally be moisture content, sieve analysis, liquid limit, compaction test, CBR and so forth. Field test would include Standard Penetration Test (SPT), Cone Penetration Test (CPT) and Vane test.

One of SI method; Rotary wash boring...

Record of Soil Exploration
It is important to keep complete and accurate records of all data collected. Boring, sampling and testing are often costly but it is necessary in every site investigation. A good map giving specific locations of all boring should be available. All boring should be identified and its location documented by measurement to permanent features. And all pertinent data should be recorded in the field on a boring log sheet.

Soil data obtained from a series of test boring can best be presented by preparing a geologic profile:

• Arrangement of various layers of soil,
• Ground water table,
• Existing / proposed structures,
• Soil properties data (e.g., Standard Penetration Test values).

The profile was prepared with data obtained from the boring, sampling and testing of each borehole from selected points.

Geotechnical Report Guideline
Here is the comprehensive guidelines for Site Investigation report:

• Table of Contents: Summery of content details included in the geotechnical report.
• Executive Summary: Brief to the point summary not exceeding one page of findings and design recommendations.
• Terms of Reference: Outline terms of reference and scope, identify requesting source. Find out geotechnical requirements from the project manager, structural engineer or the geometric designer at the beginning of the assignment and keep track of changing requirements thus terms of reference.
• Background Information/Review of Existing Data: Provide site description. Describe, topography and geology (in terms of engineering significance and engineering properties), seismic ground motion data, lab data, ground water and drainage information. Provide location map, National Topographic Series 1:50,000 map reference, e.g. 92B/12, Longitude and Latitude, Universal Transverse Mercator coordinates if possible. Provide plan profile where applicable, site history if available.
• Site Investigation: Describe what is needed in light of existing information, provide specific rationale for the scope and methods of site investigation to make it possible for reviewers to assess the adequacy of the investigation. Describe what was carried out. Show location of test holes or pits or geophysical lines if any. Include field observations at the site, soils and existing conditions.
• Laboratory Testing: List the tests done and present the results using standard format.
• Evaluation and Analysis: Discussion of the site investigation and laboratory test results and their implications on the proposed facility or the stability of the site investigated. The seismic assessment should be provided. Describe analyzes performed, assumptions, parameters and methods used (use two methods for analyzing slope stability or calculating bearing capacities where practical). Provide foundation or slope design information in terms of both static and dynamic (seismic) design if required and state what safety factors are in place. Provide anticipated range of settlement for foundations and fills, and Factor Of Safety of fill. Apply your field observation of the site conditions and existing foundations if any, on your choice of foundation type.
• Sand and Gravel Sources / Disposal Areas: Provide legal description, status (Crown, lease, etc.). Describe potential sand and gravel sources, tested or estimated material properties and projected quantities. Describe investigation methodology. Provide recommendations on waste or surplus material disposal areas.
• Design Recommendations, Including the Design of Pavement Structures: Point out possible foundation and construction difficulties, effects on the existing adjacent structures and suggest methods of overcoming these difficulties, recommend the preferred type of foundation, describe why and suggest possible alternatives (value engineering) where possible. Refer to findings of field investigation, lab test findings and analyzes the results. Point out that the geotechnical engineer should be given appropriate opportunity to review the geotechnical aspects of the completed design prior to construction.
• Discuss Predicted Effects of The Recommended Work on The Environment (water quality, etc.): Provide recommendations on mitigation measures. Provide specifications and special provisions for construction contract. Provide cost estimates for the recommended work.
• Literature References: Provide a list of references used in the preparation of the report.
• Appendices: Correspondence Soils and rock core logs (make sure standard disclaimers are included with the logs in contract drawings), test hole location plan, design profile for new roads, pit development plan, drawings, plan and profile, and also photos.
• Quality Control of Work: Reports must be signed and stamped both by the author and the reviewer. It is the responsibility of the author and the reviewer to determine the appropriateness and accuracy of input data and the correctness of the computed results. Use of computer programs does not free the Professional Engineer or the Professional Geo-scientist from this responsibility.

Drilling a borehole at site...

Summarizing
Scope of site investigation works when planned by different engineers tend to be varied because there are an infinite number of conditions to be met and the process of planning also leaves many areas where individual judgment and experiences must be applied. It is also impossible to attempt to provide an exhaustive step by step guidelines applicable to all possible cases. It should be realized that there is a possibility that any site investigation may leave some area unexplored or overlooked. The main risk in foundation design is the uncertainty involving in predicting soil conditions which may change with environment. The more site investigation the more it will reduce the margin of uncertainty but the time and cost requirement will be exorbitant.

Therefore the extent and the cost of site investigation should be such that risk is at an established acceptable level to the designer and also comply to the accepted code of practice.

Read More Constructive Posts:

• Video: Geotechnical Investigation at Site
• Foundation In GeoTechnical Perspective

A structure that is composed of a number of bars pin connected at their ends to form a stable framework is called a truss. It is generally assumed that loads and reactions are applied to the truss only at the joints. A truss would typically be composed of triangular elements with the bars on the upper chord under compression and those along the lower chord under tension. Trusses are extensively used for bridges, long span roofs, electric tower, and space structures. The study of truss analysis shall be used in determination of the compression and tension reactions occurred in it.

Trusses are statically determinate when the entire bar forces can be determined from the equations of statics alone. Otherwise the truss is statically indeterminate. A truss may be statically (externally) determinate or indeterminate with respect to the reactions (more than 3 or 6 reactions in 2D or 3D problems respectively). The support reactions and related diagrams covered in previous post…

Members subjected to forces; Tension and Compression.

For the truss analysis, it is assumed that:

• Bars are pin-connected.
• Joints are frictionless hinges.
• Loads are applied at the joints only.
• Stress in each member is constant along its length.

The objective of analyzing the trusses is to determine the reactions and member forces. The methods used for carrying out the truss analysis with the equations of equilibrium and by considering only parts of the structure through analyzing its free body diagram to solve the unknowns.

Method of Joints

The first to analyze a truss by assuming all members are in tension reaction. A tension member is when a member experiences pull forces at both ends of the bar and usually denoted as positive (+ve) sign. When a member experiencing a push force at both ends, then the bar was said to be in compression mode and designated as negative (-ve) sign.

In the joints method, a virtual cut is made around a joint and the cut portion is isolated as a Free Body Diagram (FBD). Using the equilibrium equations of ∑ F_x = 0 and ∑ F_y = 0, the unknown member forces could be solve. It is assumed that all members are joined together in the form of an ideal pin, and that all forces are in tension (+ve) of reactions.

An imaginary section may be completely passed around a joint in the truss. The joint has become a free body in equilibrium under the forces applied to it. The equations ∑ H = 0 and ∑ V = 0 may be applied to the joint to determine the unknown forces in members meeting there. It is evident that no more than two unknowns can be determined at a joint with these two equations.
CCS: Figure 1: A simple truss model supported by pinned and roller support at its end. Each triangle has the same length, L and it is equilateral where degree of angle, θ is 60° on every angle. The support reactions, R_a and R_c can be determine by taking a point of moment either at point A or point C, whereas H_a = 0 (no other horizontal force).

Here are some simple guidelines for this method of truss analysis:

1. Firstly draw the Free Body Diagram (FBD),
2. Solve the reactions of the given structure,
3. Select a joint with a minimum number of unknown (not more than 2) and analyze it with ∑ F_x = 0 and ∑ F_y = 0,
4. Proceed to the rest of the joints and again concentrating on joints that have very minimal of unknowns,
5. Check member forces at unused joints with ∑ F_x = 0 and ∑ F_y = 0,
6. Tabulate the member forces whether it is in tension (+ve) or compression (-ve) reaction.

CCS: Figure 2: The figure showing 3 selected joints, at B, C, and E. The forces in each member can be determine from any joint or point. The best way to start by selecting the easiest joint like joint C where the reaction R_c is already obtained and with only 2 unknown, forces of F_CB and F_CD. Both can be evaluate with ∑ F_x = 0 and ∑ F_y = 0 rules. At joint E, there are 3 unknown, forces of F_EA, F_EB and F_ED, which may lead to more complex solution compare to 2 unknown values. For checking purposes, joint B is selected to shown that the equation of ∑ F_x is equal to ∑ F_y which leads to zero value, ∑ F_x = ∑ F_y = 0. Each value of the member’s condition should be indicate clearly as whether it is in tension (+ve) or in compression (-ve) state.

Trigonometric Functions:
Taking an angle between member x and z…

• Cos θ = x / z
• Sin θ = y / z
• Tan θ = y / x

Method of Sections

The section method is an effective method when the forces in all members of a truss are being able to determine. Often we need to know the force in just one member with greatest force in it, and the method of section will yield the force in that particular member without the labor of working out the rest of the forces within the truss analysis.

If only a few member forces of a truss are needed, the quickest way to find these forces is by the method of sections. In this method, an imaginary cutting line called a section is drawn through a stable and determinate truss. Thus, a section subdivides the truss into two separate parts. Since the entire truss is in equilibrium, any part of it must also be in equilibrium. Either of the two parts of the truss can be considered and the three equations of equilibrium ∑ F_x = 0, ∑ F_y = 0, and ∑ M = 0 can be applied to solve for member forces.

CCS: Figure 3: Using the same model of simple truss, the details would be the same as previous figure with 2 different supports profile. Unlike the joint method, here we only interested in finding the value of forces for member BC, EC, and ED.

Few simple guidelines of section truss analysis:

1. Pass a section through a maximum of 3 members of the truss, 1 of which is the desired member where it is dividing the truss into 2 completely separate parts,
2. At 1 part of the truss, take moments about the point (at a joint) where the 2 members intersect and solve for the member force, using ∑ M = 0,
3. Solve the other 2 unknowns by using the equilibrium equation for forces, using ∑ F_x = 0 and ∑ F_y = 0.

Note: The 3 forces cannot be concurrent, or else it cannot be solve.

CCS: Figure 4: A virtual cut is introduce through the only required members which is along member BC, EC, and ED. Firstly, the support reactions of R_a and R_d should be determine. Again a good judgment is require to solve this problem where the easiest part would be consider either on the left hand side or the right hand side. Taking moment at joint E (virtual pint) on clockwise for the whole RHS part would be much easier compare to joint C (the LHS part). Then, either joint D or C can be consider as point of moment, or else using the joint method to find the member forces for F_CB, F_CE, and F_DE. Note: Each value of the member’s condition should be indicate clearly as whether it is in tension (+ve) or in compression (-ve) state.

Graphical Method (Maxwell’s Diagram)

The method of joints could be used as the basic for a graphical analysis of trusses. The graphical analysis was developed by force polygons drawn to scale for each joint, and then the forces in each member were measured from one of these force polygons.

The number of lines which have to be drawn can be greatly reduced, however, if the various force polygons are superimposed. The resulting diagram of truss analysis is known as the Maxwell’s Diagram.

In order to draw the Maxwell diagram directly, here are the simple guidelines:

1. Solve the reactions at the supports by solving the equations of equilibrium for the entire truss,
2. Move clockwise around the outside of the truss; draw the force polygon to scale for the entire truss,
3. Take each joint in turn (one-by-one), then draw a force polygon by treating successively joints acted upon by only two unknown forces,
4. Measure the magnitude of the force in each member from the diagram,
5. Lastly, note that work proceed from one end of the truss to another, as this use for checking of balance and connect to other end.

CCS: Figure 5: A simple triangle truss with degree of angle, θ is 60° on every angle (a equilateral) and same member’s length, L on 2 types of support. Yet again, evaluating the support reaction plays an important role in solving any structural problems. For this case, the value of H_b is zero as it is not influence by any horizontal forces.
CCS: Figure 6: The procedure for solving this problem could be quite tricky and requires our imagination…sort of. It starts by labeling the spaces between the forces and members with an example shown above; reaction R_a and applied force, P labeled as space 1 and continue moving clockwise around the truss. For each member, take example between space 1 and 5 would be the member AC and so forth. Note: Choose a suitable scale for drawing the Maxwell diagram.

In conclusion, the truss internal reaction as well as its member forces could be determine by either of this 3 methods especially in mechanics of structures. Nonetheless, the methods of joints becomes the most preferred method of truss analysis when it comes to more complex structures…

Read More Constructive Posts:

• Shear Force and Bending Moment as Structural Basics
• The Basic Principles in Structural Mechanics

The most important and essential scope in rock mechanics is measuring and determination of rock properties and behavior by using the recommended testing methods, procedures, and specifications. These include the engineering characteristics of rock such as its strength, mode of deformation, mode of failure, and modulus of elasticity.

A study upon rock in rock mechanics is one of civil subject disciplines which describe as oath-to-know or important as the rest of other mechanics related subject; soil, fluids, materials, and structures. Rocks are naturally occurring material where it is inhomogeneous and anisotropic, and also even-though it came from the same class or collected from the same spot, it still exhibit variations.

Generally there are two common category for testing of rock samples:

• Laboratory testing which is done at the lab with the rock samples obtained from the selected locations,
• Field or In-situ testing which is done by operating directly at the site itself.

Laboratory Testing of Rocks

* Recap: The testing of rock conducted for measuring and evaluating the changes of rock properties as well as its properties by applied loading or force. The properties will include physical, index and strength whereby the behavior include deformation and failure mode.

As stated before, the two most common methods of laboratory testing for rock are: 1) Index test, and Indirect Strength test; 2) Direct or Strength test. The types are generally based on the methods of testing and the nature or type of data obtained.

Index Test and Indirect Strength Test

Point-Load Index Test

Index test is relatively simple and rapid to conduct, but it does not provide fundamental property. The data obtained is just an indicator on property that being tested. The apparatus used are normally simple and portable which also allows the test to be conduct at site.

The tests may not require some detailed sample preparation where certain tests are non-destructive type and does not involve failure of samples (cost saving for sample could be reused). The data also not suitable for detailed design purposes but it is useful and valuable for preliminary or pre-feasibility assessments.

The tests for Index and Indirect Strength test include:

• Point-load index test
• Scmidt or Rebound hammer test
• Slake durability index test
• Sonic wave velocity test
• Uniaxial compressive strength test
• Brazilian or Inderect tensile strength test

Point-Load Index Test
It is a quick and simple test to conduct where the rock sample can be in core or irregular block. The equipment is easy to use and handle as test could be perform directly on site.

Scmidt or Rebound Hammer Test

Scmidt or Rebound Hammer Test

It normally test on surface hardness of rock sample using the L-type as it is also easy to use and handle. The sample can be in core or block shape and it is non-destructive type of test where the sample can be reused again.

Slake Durability Index Test

Slake Durability Index Test

This test is to assess the resistance of rock sample throughout weakening and disintegration when subjected to drying and wetting process, known as weathering process.

Sonic Wave Velocity Test

Sonic Wave Velocity Test

This test is non-destructive and the equipment is portable. The test involves transmitting of primary-wave through core rock sample and the data obtained is wave propagation velocity.

Brazilian or Indirect Tensile Strength Test

Brazilian or Indirect Tensile Strength Test using the UTM equipment.

The objective of this test is to measure uniaxial tensile strength of rock sample indirectly using Brazilian test.

Direct Test or Strength Test
The test procedure requires detailed preparation of sample in terms of standard shapes and finishing. The sample preparation process is equipment related and it is costly. The testing itself involving sophisticated and large equipment significant to the detailed testing procedures and may require complex analysis and this is also costly.

However, the data obtained is the fundamental property and would be the direct presentation of property being evaluated. The numbers of tests were limited due to its cost of operation and with this the data obtained can be use for detailed design.

The tests for Direct or Strength test include:

Hook's Cell used for Triaxial Compressive Strength Test

• Permeability of rock
• Modulus of deformation
• Uniaxial and Triaxial compressive strength test
• Shear strength test

Uniaxial Compressive Strength Test
It requires a preparation of sample as accordance to ISRM (International Society of Rock Mechanics). Uniaxial compressive strength (UCS) of rock material and deformation behavior under loading is verify by applying compressive load until failure using high capacity Universal testing machine (UTM).

Triaxial Compressive Strength Test
Triaxial compressive test is a 3 dimensional compression which used to evaluate the strength of rock under confinement condition; example rock samples obtained from deep seated rock mass.

Shear Strength Test

Shear Strength Test
Shear test is to evaluate shear strength and shear behavior of weakness plane in rock which is not shearing of the intact rock material. This is the most expensive laboratory strength tests, as it requires special kind of method for acquiring the samples from the site as fracture plane to be tested and utmost relatively complex testing procedures. The weakness planes shear strength, fractures and joints in rock mass is important for project which involves excavation in rock such as slope and tunnel.

Field or In-situ Testing of Rocks

* Recap: The testing approach is to access the rock properties at the site scene where it is found. It will include large-scale of direct strength test on site as the preparation and the equipment could be expensive, complex, and time-consuming.

In-situ strength tests are undertaken when properties of rock is very critical to the design and detailed assessment under the actual environment is consider essential. The cost involved in undertaking the test can be seen in the anticipated behavior of the unstable block with regards to nature of the project and the surrounding of rock mass.

The main advantages of field full-scale test are:

• It involves larger size of sample as inclusive of large-scale discontinuities,
• In-situ sample is undisturbed and more representative of the actual field condition.

In conclusion, the results obtained from either laboratory or field is very useful for projects involving excavation of tunnels, stability of slopes, and foundation of structures. Photos of equipment; credit to: Matest.

Read More Constructive Posts:

• Rocks in the Forms of Minerals
• The Three Groups of Rock
• Rock Mechanics in Civil Engineering

Before constructing any desired road, there are few factors that need to be consider carefully in choosing the right and yet convenient location of the new road. This is very important as proper planning with systematic approach needed in terms of time, budget, resources, safety, and eco-friendly to environment.

There are six main factors for road construction at certain location which is topographic condition, soil characteristics, environmental aspect, economical aspect, historical site, and political influence.

For the above matters, a scenario developed to support the consideration factors in building a new road. In CCS: Figure 1, there are two country namely as country A and country B with two different profiles.

Topography Condition
The Earth’s profile or topography condition of certain section will eventually influence the capacity of the road, the exact purpose yet convenient to built it, and the total cost for the whole project. The surface profiles will not always flat and sometimes there is an area with greater elevation such as hilly area or highland. This will ultimately increase the cut and fill of earthworks, and the operation cost as a whole plus developing a road with low capacity due to low of design speed.

First let’s take a look at CCS: Figure 2 as some part of country A is covered with hilly area at western side. A road builds to connect the cityscape and the industrial zone on the other side. The industrial zone is vital for country A economic growth and significantly upgrade its status as powerhouse.

As per CCS: Figure 3, the secondary bridge build crossing the river to connect the cityscape with the town (as 2nd city) as well as connector to outside country.

Soil Characteristic
The soil characteristic plays an important role as it relatively related with the earthworks costing and of course the whole road construction cost. In general, suitable soil required mostly as filing materials and normally the weaker ones should not be use (example; pit soil), thus should be replace. Nonetheless, the moderate type of soil which consider can be taken into use due to lack of resources, should be treat properly before use in construction.

Environmental Aspect
Significantly, road construction relatively will give an impact to the surrounding of environment and it should be create as part of the local surrounding. The impact or effect upon the environmental should be study first (also by research) with positive outcomes which is to make sure the road project would not have any negative measures upon natural habitat of wildlife, plants, and human community. Besides that, the project progress should be properly planned so that pollution upon environment as a result of the construction can be prevent or minimize.

In CCS: Figure 4 showing the sustainable development is important for preserving natural resources such as forest and could still make progress in development without jeopardizing the environmental aspect.

Economical Aspect
When it comes to economy, financial would be the number one priority of any country or nation and it is the factor most likely to be consider with deep analytical studies. Before commencing any project, an economic study will determine the cost versus the benefit that involves. Normally the main road of connecting two places is constructed from the Government funding and the alternative roads constructed mostly from the private sector funding. Any proposed road project would offer an effective connection and may bring development to the connected place (between rural and urban area) which will increased the socio-economy and lifestyle of the local residents.

Showing in CCS: Figure 5 where country B projected its economy mostly from agricultural sector as the land structure is mostly flat with good soil quality for planting activities. As shown, the planting of paddy and corn as the source of food, and also can be export to country A. The local villager residents would not be left behind as development also needed at rural area, example the education aspect.

Historical Site
It is best to make sure the selected pathway will not ruin the historical places such as ancient cemetery, old building structures, monuments, landmarks, and so forth. Any proposed road that runs through this sacred place should be diverting and this will help to preserve our national treasure.

One of the local attractions of country B would be its historical place, as shown in CCS: Figure 6. The tourist will not only limit to country A but also from other countries. Hmm…the Stonehenge and Easter Statue combines…

Political Influence
This factor seldom becomes a big issue unless a road project which involves several countries or nations. A mutual agreement between these countries or nations in that particular road project must be archived before it could become a reality. The internal politics of certain country (upon location) would most likely given deep impact or effect upon the level of interest as a result of the project, take example in terms of import and export which benefit both parties.

The main bridge becomes a mutual connector between country A and country B (shown in CCS: Figure 7) as well as road to outside country from country A in CCS: Figure 8. Both will benefit a lot from the political agreement and will strengthen their alliance especially when comes to the economical agenda.

Constructing any new road is not an easy task as most people thought it would be. Lots of effort and brainstorming were put into the action in order to make it happen. The figure above modeled with Google Sketchup where the terrain, road and bridges designed by me and the props ‘borrowed’ from the 3D Warehouse. Thanks and cheers…

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• Subgrade, An Important Road Surface

Water as we know it, very-very important and vital for our survival on this blue planet. An adequate supply of water (quantity) alone would not guarantee our well-being as the quality of water would be a serious measure. One most comprehensive explanation of this is whether the water safe for the use of our body (through drinking) and clear of harmful diseases which effect our health.

The objective of this particular engineering field is to supply clean and safe water for public usage. Clean in physical terms as colorless, odorless, tasteless, and no suspended solids whereas safe from harmful microorganism, pathogen, dangerous organic or inorganic, and with lesser mineral substances.

Water, one of nature's most precious treasure.

Water quality measurements would include the physical, chemical, and biological parameters. [Image via: Extension.usu.Edu]

Physical Parameters

Physical characteristics relate to the quality of water for domestic and usually associated with the general appearance of the water.

Odor and Taste
It is the most common observation in water quality. The sources would be from organic compounds such as degradation of organic matters or petroleum, and inorganic compounds such as minerals, metals, salts which gives the taste. In addition, certain types of algae, especially the blue-green algae, can also impact foul tastes and odors. The significant effect of this would be upon our health, example gases like chlorine (Cl₂) and feeling aesthetic.

pH
pH is a term used to indicate the alkalinity or acidity of a substance as ranked on a scale from 1.0 to 14.0. Normally it is caused by the balance of positive hydrogen ions (H+) and negative hydroxide ions (OH-) in water. The water will becomes acid if the scale falls below than 7 and alkaline if more than 7.

Turbidity
Turbidity is a measure of the amount of particulate matter that is suspended in water. It normally measured in Nephelometric Turbidity Units (NTU) or Formazin Turbidity Units (FTU). The sources would be from organic compounds such as plant fiber, human waste, etc. and inorganic compounds such as clay or sand. Beside of feeling aesthetic and effect upon health, the adsorption point or centre for chemicals and micro-organism would also effected.

Temperature
Water temperature affects the ability of water to hold oxygen, the rate of photosynthesis by aquatic plants and the metabolic rates of aquatic organisms. The sources would normally be the effect from changes of weather or heat and industrial activities such as cooling system. The temperature effects would be upon the disturbance of biological activities (aquatic life and micro-organism) and the chemical properties such as the degree of gas solubility, density and viscosity.

Dissolved Oxygen (DO) in water:

• In cold water, oxygen would be less, and in hot water, oxygen content would be more.
• When the temperature is risen, the dissolved oxygen will decrease and eventually will make the bacteria becomes active…ready to rumble…

Total Suspended Solid
Total suspended solids (TSS) or minerals is a measure of the amount of sediment moving along in a stream. The sources would be from organic compounds such as plant fiber, human waste, etc. and inorganic compounds such as clay or sand. Beside of feeling aesthetic and effect upon health, the adsorption point or centre for chemicals and micro-organism would also effected. (It measured in mg/L)

Chemical Parameters

The chemical characterization of drinking water would includes the identification of its components and its concentration of water. Water treatment plants normally monitor for a variety of inorganic and organic components.

Alkalinity
Alkalinity is a total measure of the substances in water that have “acid-neutralizing” ability and is not a pollutant. In other words, it is the quantity of ions in water which responsible in neutralizing the acid. The main constituents are bicarbonate (HCO₃^-), carbonate (CO₃^2-), and hydroxide (OH^-) ions.

Normally the sources from mineral dissolved in water and air, and also from human activities such as detergent (in wastewater), fertilizers, pesticide, so forth. The effects would caused non pleasant taste and reaction between alkaline constituent and cation (positive ion), produces precipitation in pipe.

Hardness
Defined as a measure of multi-valent cations in water such as Ca²⁺, Mg²⁺, Fe²⁺, Mn³⁺. Ca²⁺ and Mg²⁺ are very important and usually present in water. Natural mineral from Earth is the source and effects of hardness would be excessive usage of soap, precipitate form on hardware and in pipelines which increased temperature and pH.

Two kinds of hardness:

• Carbonate hardness; Temporary in character such as Ca(HCO₃)₂ and Mg(HCO₃)_{2; precipitated through heating (boiling).}
  
• Non-Carbonate hardness; Permanent in character such as CaCl₂, CaSO₄, MgCl₂, MgSO₄; eliminated through chemical softness method or ion exchange.

Inorganic Compounds
When placed in water, the inorganic compounds will dissociate into an electrically charged atoms referred as ions and classified as metal or non-metal.

Metal Inorganic Compounds:

1. Non-toxic Metal
   • Among dangerous metal if the concentration is high such as Na⁺, Ca²⁺, Mg²⁺, Fe²⁺, Mn²⁺, Cu²⁺, Zn²⁺, Al³⁺.
   • The source normally readily available from nature and have effects on color, odor, and turbidity as well as deteriorate health at high concentration.
2. Toxic Metal
   • Normally it is stored in the food chain, such as As²⁺, Ba²⁺, Cd²⁺, Cr²⁺, Pb²⁺, Hg²⁺.
   • The source of this is from our own doing, through mining and industries which will promote dangerous diseases such as cancer, abortion, and deformation of the new born baby (abnormal).

Non-Metal Inorganic Compounds:

1. The source is from mineral such as Si⁴⁺, Cl^-, NO₃^-.
2. The effects of non-metal:
   • Diseases which caused blue baby syndrome (with less oxygen supply) due to heavy metal such as NO₂^-.
   • Aesthetic due to Si⁴⁺.
   • Fluoride (F^-) which is not good for health if taken in high concentration, and excessive amount will caused teeth color changed and problem in bone growth.

Organic Compounds
All the organic compound contains carbon in combination with one or more elements.

The sources came from:

• Nature such as fibers, vegetable, animal oils and fats, cellulose, starch, and sugar.
• Synthesis of wide variety of compounds and materials prepared by manufacturing processes such as polyvinylchloride and DDT.
• Fermentation of alcohols, acetone, glycerol, antibiotics, acids, etc.

The effects would be:

• Depletion of the dissolved oxygen (DO) in the water that would eventually reduces its percentage and concentration, thus destroying aquatic life and damaging the ecosystems.
• Upon our health where some organics can caused cancer which contains Trihalomethane (THM-carcinogenic compound) produced in water and waste-water treatment plants. This occurred as a result of natural organic compound combined with chlorine (Cl₂) for disinfection purposes.

Nutrients
It is a crucial elements needed by living things especially animals and plants to live and survive. Important elements are carbon, nitrogen, and phosphorus. Carbon can be easily obtained from carbon dioxide (CO₂) and nitrogen is an important element for protein, chlorophyll and biological compounds. Phosphorus exists in a form of orthophosphate, condensed phosphate, and organic phosphate which it is readily present in soil, fertilizers, human waste and domestic waste.

Total Dissolved Solid
The total dissolved solids (TDS) in water consist of inorganic salts and dissolved materials. In other words, solid left in water after it was filtered and dried. The sources would be from organic compounds such as product from degradation of organic matters or gas and inorganic compounds such as minerals, metals and gases. The effect would cause the taste, color, and odor problems as well as our health, plus water would becomes corrosive to attain equilibrium due to small amount of TDS matter.

Note: It measured in either mg/L for organic and inorganic or mS/m for conductivity measurement.

Biological Parameters

For biological aspect, microbiological agents are important to public health and may also be significantly modified the physical as well as chemical characteristics of water. Water for drinking and cooking purposes must be free from any disease-producing organism called pathogen. This group quantities are very small compared to other micro-organism. The experiment to determine the presence of all pathogens takes a long time and often very expensive as it is only carried out for very specific cases. The presence of pathogenic micro-organisms is shown by indicator microorganisms.

Indicator Micro-organisms
Their presence shows that popularization has occurred and suggests the type and level of pollution. The typical indicators used are the coliform groups, Fecal coliforms (E-coli) and Total coliforms (Fecal coliforms and any others).

The Indicators Properties:

• Can be used for all types of waters,
• Always present when pathogen is present,
• Always absent when pathogen is absent,
• Easily experimented and give reliable results.

These are the parameters used when sampling of water taken from various resources where the data recorded and further tested in certified laboratory. Understanding of these parameters could be useful to assure the quality of water being safely use by the public.

Read More Constructive Posts:

• Introductory of Fluid Mechanics Properties
• Insight Fundamentals of Hydrology

Basic structural learning begins with an analyzing of a simply supported beam. A beam is a structural member (horizontal) that is design to support the applied load (vertical). It resists the applied loading by a combination of internal transverse shear force and bending moment. An accurate analysis required in order to make sure the beam is construct without any excessive loads which affect its strength.

Types Of Load and Support

The Men-at-Work in construction...

Two types of typical loadings:

• Concentrated load is one which can be considered to act at a point although of course in practice it must be distributed over a small area (normally vertical or incline loads). (Unit in kN)
• Distributed load is one which is spread in some manner over the length or a significant length of the beam. It is usually quoted at a weight per unit length of beam and it may either be uniform or varying loading from point to point. (Unit in kN/m)

Three types of support:

• Namely as Pinned support, Roller support and Fixed or Built-in support.
• Covered in previous post together the reactions explained in diagrams.

The Sign Conventions

The general sign convention of a beam.

The sign convention depends on the direction of the stress resultant with respect to the material against which it acts. It is used for both shear force and bending moments in analyzing the directions. Positive (+ve) shear forces always deform right hand face downward with respect to the left hand face and negative (-ve) would be the other way round. Positive (+ve) bending moments always elongate the lower section of the beam and negative (-ve) would elongate the mid-section upward of the beam.

Shear Force and Bending Moment in Simply Supported Beam
For a simply supported beam, the reactions are generally simple forces. When the beam is built-in, the free body diagram will show the relevant support point as a reaction force and a reaction moment. It is normal practice to produce a free body diagram with the shear force diagram and bending moment diagram position.

A simply supported beam with brief details.

The unknown forces (generally the support reactions) are then determined using the Equation of Equilibrium:

• Horizontal reaction respect to x-axis; ΣF_x = 0
• Vertical reaction respect to y-axis; ΣF_y = 0
• Bending reaction (clockwise or anti-clockwise), ΣM = 0

Shear Force and Bending Moment Diagrams
The shear force diagram indicates the shear force withstood by the beam section along the length of the beam. The bending moment diagram indicates the bending moment withstood by the beam section along the length of the beam.

Shear Force and Bending Moment Diagrams in simply supported beam with two different loads.

Simple calculation of determine the reactions:
* Take example the 1st one with point load, W…
ΣM_c = 0 (taking clockwise as +ve at point C)
(R_a x L) – (W x L/2) = 0
So, R_a = W/2 [in kN]

ΣF_y = 0 (taking vertical ↑ as +ve)
R_a + R_c – W = 0
W/2 + R_c – W = 0
So, R_c = W/2 [in kN]

The shear force diagram (SFD) is simply constructed by moving a section along the beam from the left origin and summing the forces to the left of the section. The equilibrium condition states that the forces on either side of a section balance and therefore the resisting shear force of the section is obtained by this simple operation.

On the other hand, bending moment diagram (BMD) is obtained in the same way except that the moment is the sum of the product of each force and its distance of x from the section either left or right. Distributed loads are calculated buy summing the product of the total force (to the left of the section) and the x distance of the distributed load centroid.

Shear Force and Bending Moment Diagrams in cantilever beam with two different loads.

The basic procedure for determining the shear and moment is to determine the values of V and M at various sections along the beam and plotting the results from point to point. By doing so, we will be able to determine critical sections within the beam where a critical or maximum stress might occurs:

• Section of Maximum Shear – Since the shear, V, at any transverse section of the beam is the algebraic sum of the transverse forces to the left of the section, the shear, in most cases can be estimated at a glance.
• Section of Maximum Moment – It can be obtained mathematically, that when the shear force is zero or changes sign; the bending moment, M will be either a maximum or relative maximum.

In conclusion, we could obtained the reactions value at the supports by using the equation of equilibrium. The shear force and bending moment diagram used for determine both of force, V and moment, M maximum values. Both of this reactions are the fundamental forces which becomes available in mechanics of structures.

Read More Constructive Posts:

• 3 Methods for Truss Analysis
• The Basic Principles in Structural Mechanics