Details of landfills methods

Landfill means an engineered site where waste is separated from the atmosphere underneath the ground or on top unless it is secured and entirely dissolute biologically, chemically and naturally.

Benefits of landfilling:

a. Burying can lead to energy formation with the conversion of landfill gas as for instance methane and CO2.
b. Landfill byproducts are utilized as direct/indirect fuel for combustion.
c. Easy observation because of particular location.
d. It can be reprocessed as well as applied as parks or farming land.
e. All the reusable materials are utilized prior to closing.
f. Organic material is segregated and applied for compost or formation of natural gas.
g. Considerably inexpensive.

Different types of landfills methods :-

1. Area method (over ground level)

a. It is suitable for flat ground or terrain and not suitable for the excavation of trenches.
b. Prior to actual land filling, an earthen levee is built up against which waste are arranged in thin layers and compressed.
c. Depth of layer attains a height of 200 to 300 cm.
d. Cover material with 15 to 30 cm deepness is arranged after every layer.
e. A complete lift along with the cover is defined as a cell.
f. This method is effective for the disposition of huge amounts of solid waste.

2. Trench Method (Underneath ground level)

a. It is suitable where cover material is present at construction site and the water table is located under the surface.
b. Waste are arranged in trench and compressed in thin layers.
c. After the compression of layer, height attains design height and the cover material is arranged over the compressed layer.
d. Some trench is then sustained and filled correspondingly.
e. It is perfect for the areas where the waste is considerably minimum.

3. Depression/Valley Method

a. It is suitable for the areas where natural or artificial depressions remain and these are utilized for land filling.
b. It is based on the geometry of the site as well as geography of the site and entry to site.
c. The general method is to arrange in such a way that the water should not be stored behind the landfill.

4. Slope Method

a. It is effective for hilly areas since flat ground is not available for land filling.
b. Waste is arranged along the sides of current hill slope.
c. Managing incoming water from hill side slopes is a crucial factor for creating the design of such landfills.
d. It is generally applied for flat or little undulating regions.
e. Alteration of both the area and the trench method and employs specific technique of both.

Details of landfills methods

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Details of top down construction method

Under top down construction method, the basement concrete slabs function as lateral bracing toward the perimeter wall system. Ground level and first basement slabs are poured, with access holes left to facilitate excavation below. Since every succeeding sub-grade level is finished, the floors perform as lateral bracing toward the perimeter wall system.

Top-down method is mostly suitable for two types of urban structures, tall buildings containing deep basements and underground structures like car parks, underpasses and subway stations. In such a circumstance the basement floors are built up as the excavation steps forward.

The top/down method is utilized for deep excavation projects where tieback installation can’t be done and soil movements should be reduced. Top-down construction method saves the entire construction time. So, it is mainly implemented for some major projects where time is a key factor.

The sequence construction starts with retaining wall set up and then load-bearing elements to support the future super-structure. The basement columns (generally steel beams) are built up prior to starting of excavation and rest on the load bearing elements. These load bearing elements normally belong to concrete barrettes constructed under slurry (or caissons).

Construction method: Given below, the detail construction method for top down construction :-

• Built up the retaining wall.
• Build up piles. Arrange the steel columns or stanchions where the piles will be developed.
• Carry on the first phase of excavation.
• Cast the floor slab of first basement level
• Start to build up the superstructure
• Carry on the second phase of excavation; cast the floor slab of the second basement level.
• Reiterate the similar method unless the required depth is attained.
• Develop the foundation slab and ground beams, etc. Finish the basement work.
• Continue constructing the superstructure unless it is completed.

To learn the step-by-step process in detail, go through the following video presentation.

Video Source: geobuuk

Details of top down construction method

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Commonly used joints in sewer pipes

The following types of sewer joints are generally found :-

1. Bell and Spigot Joints.
2. Collar Joints.
3. Flexible Joint.
4. Expansion Joint.
5. Flanged Joint.

Bell and Spigot joints: This joint is also termed as socket and spigot joint. This type of joint is mostly found in cast iron pipes containing different sizes and concrete pipes under 60 cm in diameter.

The pipes which should be attached with this joint are built up in such a manner that one end is expanded and the other end is normal. The expanded end is defined as socket or bell and the normal end is spigot. The spigot end is placed into the bell end and the void of the joint is stuffed with molten lead or bitumen or cement mortar.

Collar joints: In this type of joint, the ends of sewer are plain.

Prior to attach, the pipes are carried face to face at the equivalent level and a collar of marginally larger diameter is arranged over the joint. Then the annular gap among the pipes and the collar is stuffed with cement mortar (1:1). The collar joints are utilized for sewers of big diameter.

Flexible joint: This joint is utilized at such areas where settlement is subject to happen as soon as the pipe is arranged. With this type of joint, one pipe contains spigot end and other pipe contains socket end. The spigot is set up into the socket and the annular space developed among the socket and spigot is stuffed with bitumen.

Expansion joint: This joint is adopted at places where pipes expands or contracts due to variation in atmospheric temperature. Here the socket end is cast flanged and the spigot end is plain. A flanged ring and a rubber gasket are arranged in place on the spigot end. Then the spigot end is entered into the socket end nut and bolts are secured.

Flanged joint: This joint is frequently utilized for temporary work. The pipe applied in this type of joint contains flanges on both ends. At the time of joining the pipes, a rubber gasket is entered among the flanges and nut bolts are secured.

To get more information, go through the following link civilnoteppt.com

Commonly used joints in sewer pipes

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Impact of impurities in water on concrete properties

If the water applied for concrete preparation contain impurities, the properties of concrete is influenced in the following manner:

a) The strength & longevity of concrete is decreased because of the existence of the impurities in the mixing water. It is found that water with extreme amount of dissolved salts weakens the compressive strength by 10 to 30% as compared to potable water.
b) The setting time of cement is modified. Existence of Zinc chlorides delays the setting of concrete to significantly so that no strength test can be done at 2 and 3 days.Contrary, the existence of calcium chloride speeds up the setting and hardening.
c) Existence of extreme chlorides leads to dampness, surface efflorescence & raise the corrosion of reinforcing steel.
d) Existence of algae in water decreases the bond among aggregate & comet paste & as a result the strength of concrete is reduced significantly.

e) Existence of sugar up to 0.15% by weight of cement delays the setting of cement and the early strength is decreased. When the quantity of sugar is raised to 0.2% by weight of cement ,setting is expedited.
f) The existence of vegetable oils provides detrimental effect on the concrete strength, specifically at later ages.

Name of Impurities – Allowable limit
1.Organic matter – 200 mg/lit
2.Inorganic matter – 3000 mg/lit
3.Sulfates ( as SO2 ) – 400 mg/lit
4.Chlorides (as Cl)
a) For plain concrete – 2000 mg/lit
b) For R. C. C. – 500 mg/lit
5.Suspended matter – 2000 mg/lit

Impact of impurities in water on concrete properties

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Bar Bending Schedule For Floor Slabs

Bar bending schedule is an important structural working document that rightly gives the disposition, bending shape, total length, and quantity of all the reinforcements that have been provided in a structural drawing.

It is often provided in a separate sheet (usually A4 paper) from the structural drawing.

The bar marks from structural detailing drawing are directly transferred to the bar bending schedule. We normally quantify reinforcements based on their total mass in tonnes or kilograms. For smaller projects, you can quantify based on the length needed.

Unit mass of rebars

The unit mass of the reinforcements is obtained from the density of steel. The density of steel provided for this purpose is 7850 kg/m3.

Suppose, there is a bar with 12mm dia;

The area is calculated by (πd2)/4 = (π × 122)/4 = 113.097mm2 = 0.0001131m2

Based on a unit length of the bar, it is established that the volume of a metre length of the bar is 0.0001131m3.

Density = Mass/Volume = 7850 kg/m3 = Mass/0.0001131

So, the unit mass of 12mm bar = 7850 × 0.0001131 = 0.888 kg/m

So, for any diameter of bar;

Basic weight = 0.00785 kg/mm2 per metre

Weight per metre = 0.006165 ϕ2 kg

Weight per mm2 at spacing s(mm) = 6.165ϕ2/s kg

Here;
ϕ denotes diameter of bar in millimetres
Bending Shapes
There exist some basic standard shapes with specific shape codes in the code of practice.
The length of reinforcement bars can be determined with the following relation;

Length of bar = Effective Length + Width of Support – Concrete cover (s) – Tolerances
The standard values of tolerances (deductions) are provided in the table below;

To get more details, go through the following link structville.com

Bar Bending Schedule For Floor Slabs

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Method of constructing post tension RCC slab

In this construction video tutorial, you will learn how post tension RCC slabs are built up as well as how post tensioning is performed and benefits of post tensioning process.

POST TENSION SLAB: It refers to the slab that is tensioned as soon as the slab is developed. Reinforcement is arranged to avoid the compression.

In Post tension slab, cables or steel tendons are utilized to substitute the reinforcement. Post-tensioning offers a solution to get rid of the natural weakness of concrete in tension as well as optimize its strength in compression.

In concrete structures, this is obtained by arranging high-tensile steel tendons/cables in the element prior to start the casting. If the concrete attains the required strength, the tendons are pulled with special hydraulic jacks and retained in tension with specially designed anchorages which are attached at each end of the tendon.

It creates compression at the edge of the structural member that increases the strength of the concrete for resisting tension stresses.

If tendons are correctly curved to a specific profile, they will exert, other than compression at the perimeter, a useful ascendant set of forces (load balancing forces) that will neutralize applied loads, alleviating the structure from a portion of gravity effects.

In this type of concrete slab, cables are affixed in place of reinforcement. In Steel reinforcement the gapping among bars is 4inch to 6inch while in Post tension slab the gapping is in excess of 2m.

Go through the following video tutorial, to get more details on post tension slab.

Video Source: F&U-FORYOU

Method of constructing post tension RCC slab

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How soil cement is used in earthfill dams & embankments

Now-a-days soil cement as a facing material for earthfill dams is considered very cost-effective where proper riprap is unavailable near the site.

A fairly rigid foundation is suitable in order that deformation after disposition of soil-cement is not vital; however, no uncommon design features should be integrated into the embankment.

Normal embankment construction methods are followed, with perhaps proper precaution to make sure a minimum of embankment consolidation and foundation settlement once the construction is completed.

The soil-cement is normally arranged and compacted in stair-step horizontal layers. It provides greater construction efficiency and operational potency. With standard embankment slopes of 2:1 and 4:1, a horizontal layer with 8 feet width will set least protective thicknesses of about 2 and 3l/2 feet correspondingly, measured normal to the slope.

It starts at the lowest layer of soil-cement, each subsequent layer is stepped back a distance equivalent to the product of the compacted layer thickness in feet times the embankment slope.

As for instance, if the compacted thickness is 6 inches and the slope is 2:1, the step back is = 0.5(2) = 1 foot. The normal compacted layer thickness is 6 inches. Soil-cement layers of this dimension is positioned efficiently and compressed with standard highway equipment.

A plating system that develops a single soil-cement layer parallel to the slope is often applied in less critical areas for slope protection. If the soil-cement facing does not start at natural ground level, the lower part of the embankment should remain on a flatter slope than the part safeguarded by the soil-cement; or a beam is arranged at the lowest elevation of the facing. It is necessary that the soil-cement expand underneath the minimum water level and over the maximum water level.

The top of the facing should contain a freeboard allowance of minimum 1.2 times the projected maximum wave height, or 5 feet, whichever is higher. The edges of the finished soil-cement layers should not be cropped since the rounded starstep effect allows retard wave runup. Soil-cement is produced with different types of soils.

The main standard for finding out the soil type is gradation. Coarse sandy or gravelly soils having about 10 to 25 percent material passing the No.200 sieve are perfect (American Society for Testing and Materials Standard Sieve Series). These soils are sufficiently stabilized with from 3 to 5 sacks of cement per cubic yard of compacted soil cement.

Standard compaction and placement control for soil-cement is recommended. If the amount of material smaller than the No.200 sieve surpasses 35 percent, some effort to determine a coarse material is appropriate from a processing cost standpoint. Soils with 50 percent or more material passing the No.200 sieve are not suggested for being applied in their natural state.

To get more details, go through the following link aboutcivil.org

How soil cement is used in earthfill dams & embankments

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Segregation of concrete – Causes and Remedies

Segregation means the partition of course materials (cement, sand, aggregates) from other mass. When the water quantity in the concrete mix is increased, the greater sized aggregates are detached thus results in segregation.

Therefore, concrete should be free from segregation as concrete not only gets weak but lack of consistency also brings unwanted properties in the hardened state. The segregation can be avoided with the choice of proper grading and careful handling.

Reasons for segregation :

Carrying concrete mixes for long distance.

Imperfectly proportioned mix where adequate matrix does not exist to unite the aggregates.

Dropping concrete from height places (underground foundation & rafts).

Vibrating concrete for long time.

Segregation is available in two types – Initially (in too dry mixes), the coarse aggregate is segregated or settling down from the rest of the matrix, secondly ( in too wet mixes ), the paste or matrix is detached away from coarse aggregate. In case of segregation, remixing for a short time may transform concrete again homogeneous.

The following precautions should be taken to get rid of concrete segregation :-

The concrete mix should be perfectly designed with best possible quantity of water i.e. not too wet nor too dry.

The proportion of the mix should be correct.

Ensure the concrete is mixed perfectly at the proper speed in a transit mixture for minimum two minutes.

Concrete should not become excessively wet or dry.

Refrain from arranging concrete from long height.

There should be proper transportation of concrete through shortest route.

Air entraining admixture and pozzolanic materials should be used in mix.

Select coarse and fine aggregate with approach specific gravity.

The vibrator should be used for exact time period (not too long or short).

Don’t permit concrete to flow.

The formwork should be firm.

The formwork should not be vibrated.

Video Source: Civil Engineers

Segregation of concrete – Causes and Remedies

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Bridge pile cap construction details

This construction video is based on pile cap construction process for building up a bridge. The video is specifically designed for bridge engineer.

The video throws light on the following topics :-

a. Pile Head Breaking
b. Granular laying
c. CC work
d. Rebar Fabrication

The construction method of bridge is segregated into two parts :-

Substructure (pile foundation, pile cap, pier, pier cap)

Superstructure (bearing, girder, slab)

Definition of pile cap: It belongs to a structural member that is positioned and generally attached on the top of a pile or a group of pier to transfer the loads into the pile or group of piles to relate them into a bent.

Functions of pile cap
To disperse a single load evenly over the pile group as well as over a larger area of bearing potential.

To laterally strengthen separate piles and enhance complete durability of the group.
To arrange the required combined resistance to stress organized by the super structure and ground movement.
To transfer the loads of the building to the foundations and the ground soil layers despite the loads are vertical or inclined.
To facilitate the column or superstructure to stay on a consistent and solid core foundation rather than staying directly on ground.

To learn the detail pile cap construction process for a bridge, go through the following video tutorial.

Video Source: Construction Methodology

Bridge pile cap construction details

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Pundit Lab – Ultrasonic Pulse Velocity Tester

To check the quality and strength of in-situ concrete in structural members, ultrasonic pulse velocity test is most recommended.

It is applied for the following purposes :-

The uniformity of a material

The existence of voids, cracks or other inner flaws or defects.

Changes in the concrete in due course because of the cement hydration, damage from fire, frost or chemical attach.

The durability or modulus of a material.

The quality of the concrete with regard to specified standard requirements.

It comprises of a pair of transducers (probes) with various frequencies, electrical pulse generator, electrical timing devices and cables.

It is supported with the through-transmission method. It comes with size 180 x 110 x 160 mm. It’s weight is 3 Kg.

Digital display with precision +_0.1 microseconds.

The following testing method is used with the machine :-

Direct transmission

Pulse velocity is estimated in concrete with the arrangement of transducers across the member perfectly opposite to each other.

This method is considered as most perfect & authentic to determine the quality & strength of concrete. If there does not exist any other method, then this method will be suitable.

Semi Direct Transmission

Pulse velocity is estimated in concrete with the arrangement of transducers in planes perpendicular to each other.

This method is not so authentic to determine the quality/strength of concrete.

Process for estimation of pulse velocity :-

Velocity = (Distance travelled/path length)/Time taken

Pulse velocity in concrete will be demonstrated with Km/sec.

Proper correction factors should be used on the basis of site condition & factors which impact the velocity of pulse.

Pundit Lab - Ultrasonic Pulse Velocity Tester

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