Excavation Definition | Types of Excavation | Excavation Hazards & Safety
What is Excavation/Excavation Definition?
Excavation can be defined as the process of moving earth, soil, rock, or other materials from areas where there are unwanted using tools, equipment, or explosives. The excavation process uses different tools and techniques to move soil, rock, and other material to form a cavity and prepare the area for construction. Excavation is an important part of any construction project.
Cutting is when material is removed from an area in order to reduce its height, while filling is when material is added to an area in order to increase the height
Key Steps of Excavation
Clearing means cleaning the site, which includes removing the obstacles from the sites such as roots of plants, poles, hard rocks, etc
It should be in accordance with the excavation plan and should be marked along the surface with thread and lime
It is the process of breaking the material for removing by drilling, blasting, shipping, ripping, pounding or cutting with the help of rams, pounder explosive fusion cutter, swinging, rotary drill, etcetera,
Digging and Hauling,
Digging and means to excavate and hauling means the horizontal movement of that dug material.
Digging efficiency depends upon factors such as capacity and size of the container, proper choice of methods, how fast equipment operates, number and size of hauling equipment, minimum swing, optimum travel path during dumping and delivery.
It is the process of filling back the excavated trench pit with the excavated material. After the completion of work, backfilling material should ensure the following properties adequate strength in compress ability, stability against volume change, durability.
Spreading and leveling
Spreading and leveling give the advantage of improved appearance, maintaining proper drainage patterns and soil, not interfering in surveying work.
Compacting is the process in which the air voids are removed from the soil, making it denser, and this could be done by rolling, tamping, and vibrations.
Permission and Precaution for Excavation.
Permission is required for excavation When:
- Any gas, water, telephone line, or electricity lines are passing through the excavation site, then it is important to obtain permission to move them to another location.
- Proper permission should be obtained for cutting of trees or storing materials on private property
- Remove debris that may slide, roll, or fall on the worker.
- Dewatering arrangements for removing water from the excavation.
- All utilities located should be shut off or disconnected before excavation activity begins.
- Protect yourself by making proper and safe arrangements for entry and exit into the excavation site.
- Be aware of nearby vehicles, all mobile equipment causing soil to vibrate
- Also, ensure vehicle movements are at least 1 m away from the edges of excavation walls.
- Test for low oxygen does it is fumes and toxic gasses etc. are to be done.
- Soil strength and stability is to be checked to ensure shoring requirements
- Railing of a least 1-meter height should be provided for the normal depth of excavation and 2.4 m or more for excavations exceeding 8 ft depth.
- There should be proper space available for work around the excavated area.
- Backfield soil should be stored 1.5 m away from the edge of the excavated pit.
- Black cotton soil is not preferred for construction; hence it is to be removed before carrying out construction work.
- A minimum of 600 millimeters wide road with railing should be kept near the trench.
Types of Earth and Soil for Excavation.
Classifications of earth could be done into:
Clay contains particles of diameter less than 0.2 millimeters Specification range for backfilling for clay lies between 15% to 25%.
Silt contains particles of diameter between 0.2 to 0.5 millimeters and its specifications range for backfilling lies between 35% to 50%.
Fine sand contains particles of diameter between 0.50 point 10 millimeters, with specifications, range 30% to 40% for backfilling.
Coarse sand contains particles of diameter between 0.25 to 2.0 millimeters, with specifications range 30% to 40% for backfilling.
Gravel has particles of diameter size between 2.0 to 75.0 millimeters and specifications range less than 10%.
Rock contains particles of diameter greater than 75.0 millimeters with no specifications.
Good for backfilling.
Classification of Soil
Soil can be classified as
- Black Soil
- Red Soil
- Shadu Soil
- Murram Soil
It is grayish-black in color, with heavy glade contents up to 40 to 50%, and has adhesive property.
It is subjected to excessive volumetric changes and is considered poor soil for foundations.
This soil comes between sand and clay and is also known as loamy soil. It is slightly sticky in nature and also water absorbs.
It turns to grey on drying.
It is yellowish or whitish, brown and color containing moisture when wet and possesses appreciably cohesion on drying.
It is considered good soil for foundations.
Murram is red or brown in color and a gritty material found in lumps layers when excavated.
It is good for backfilling
Rock is generally found in the lowermost strata and can be black or red in color.
It is very hard and cannot be excavated with the pickaxe and is considered good for foundations.
Excavation hazards include;
- Falling into trenches or excavations.
- Tripping over equipment, debris, and soil
- Excavated material or other objects falling on workers
- Exposure to underground services or overhead electrical poles.
- Unstable adjacent structures,
- Mishandled or poorly placed materials.
- Hazardous atmosphere, noxious gasses
- Lack of oxygen
- Incidents involving vehicles and other mobile equipment.
Excavation Hazards and Its Control.
The Collapse of sides
This is one of the main hazards in the excavation type of soil structure is an important factor.
What might appear to be a safe soil structure can change dramatically with changes in the weather.
- Materials falling onto people working in the excavation people and vehicles falling into the excavation.
- People being struck by machinery undermining nearby structures.
- Contact with underground services.
- Access to excavation.
- Chemical hazards like fumes from vehicles, plant CO, to methane, other gasses.
- Contaminated land.
- Previous use of biological hazards.
- Previous used, for example, hospitals drain, sewers, rubbish and waste
- Tier ladder provides safe access.
- Guard rails to prevent falls
- Poling boards extend above the edge to act as two boards
- supported by timbering and props.
To avoid collapse of sides
- Batter sides and end
- Support with timber sheeting or proprietary support systems.
- Use 1.2 m as a guide for support but assess conditions at all times.
- Even work and shallow trenches can be dangerous, especially if bending or kneeling
To avoid materials falling into excavations.
- Do not store, spoil, or other materials close to excavation.
- They could fall in nor conscious eyes to collapse.
- Provide guard rails and toe boards where necessary.
- Where hard hat at excavations sites.
People and vehicles falling into excavations
- Provide guard rails and toe boards (2m)
- Use stop blocks to prevent vehicles from overrunning.
- Keep vehicles away from excavations wherever necessary.
People being struck by plant
- Keep workers separate from moving equipment where possible.
- Plant operators should be trained and competent, undermining nearby structures.
- Make sure excavations do not affect the footings of scaffolds or foundations of nearby structures. Provide temporary support for structure if necessary.
- Surveys of foundations and advice of a structural engineer may be necessary.
Avoiding underground services.
- Look around for obvious signs of underground services for example, drains patching of surface etcetera.
- Use cable locators to trace any services. Mark the ground accordingly.
- Use Service plan Dig Trial holes by hand
- Hand dig If in doubt, particularly for plastic cables which cannot be detected.
- Have emergency procedures contact in place.
Safe Access and Egress
- Create steps and excavation.
- Provide good ladder access or other safe ways of getting in and out of the excavation
Do not site petrol or diesel engine equipment, such as generators or compressors in or near the edge of an excavation, unless fumes can be ducted away or the area could be ventilated.
Protecting the public
- Barrier all fall Excavations in public places to prevent falls
- Where people may get onto the site out of hours, backfill or cover excavations to reduce risks.
- A competent person must supervise the installation, alteration or removal of excavation support.
- People working in excavations should be given clear instructions on how to work safely.
- A competent person must inspect at the start of the shift after any event likely to have affected the strength or stability of excavation.
- And after an accidental fall of rock, Earth, and other material, a written report should be made after most inspections
- Stop work If inspection shows excavation to be unsafe
Types of Excavation
Construction companies use several different types of excavation in construction. Whether you want to construct a residential or commercial building, roadways, bridges, or install pipes and underground utility lines, the land needs to be inspected and prepared to ensure it provides a strong foundation by excavating.
The type of excavation used depends on the material used and the purpose. Below are common types of excavations
This type of excavation involves the removal of the exposed layer or the top-most area of the earth’s surface.
This process refers to removing soil from beneath the surface, with the purpose of building foundations or embankments. The excavation method removes vegetation, soil (commonly black cotton soil, red soil) and any other decaying material that could make the soil compressible and unfitting to bear structural loads
This type of excavation involves the removal of the rock that might obstruct construction projects. Rock excavation is the most complex as compared to the other types. It can b done by blasting, ripping, or breaking rock. A bulldozer can be used to supply the force. Blasting is using explosives placed in drill holes and then detonate.
To ensure that buildings, bridges, and any other structures do not sink or collapse, they need support. This excavation is fairly more precise than other types of excavation as footing concrete is poured and left to set.
This involves the removal of various layers of earth allows a construction company to lay a foundation for buildings and bridges or to construct drainage ditches. Earth excavation involves the removal of soil, a layer below the topsoil, for construction.
Cut and Fill Excavation
Also known as stripping excavation, this type of excavation is used to clear large areas before construction or engineering projects. The process involves the removal of broad and shallow layers of topsoil, rocks, sand, and other unwanted materials. The procedure may also include grading the land.
The choice of technique and plant for excavating, supporting, and backfilling the trench depends on factors such as; the purpose of the trench, the ground conditions, the trench location, the number of obstructions, and so on
Sediment deposits can build up over time underwater making construction, as well as the passage, difficult. The process of dredging involves excavating and removing sediments and debris from underwater to allow boats and ships to pass easily and for other construction purposes.
Excavation Tools and Equipment
Types of tools and equipment.
Manuel Excavation Tools
Manuel Excavation Tools is used for smaller depths of excavations in small areas.
Excavation Machinery Equipment: Machinery is operated by mechanical force used for the larger depths of excavations
- Excavator or Diggers.
- Loading Shovel
- Hauling Excavation Tools.
Manual Excavation Tools
Spade has a metal plate with sharp edges to dig soil easily.
Shovel is used for the purpose of lifting excavated or loose soil.
Pickaxe with pointed on one side and wide blade on the other side. Used for cutting of hard soil,
Mattock is look like a pickaxe. Generally, it is used as a lifting tool Because of its curved shapes.
Hoe has a metal plate, having a long handle attached to it, having acute tangle and sharp edges. Used for small work of excavation, it is widely preferred to excavation
Excavation Machinery and Equipment’s
- It consists of a boom, stick, bucket, and cab on a rotating platform.
- All movement and functions of the hydraulic excavator are accomplished through the use of hydraulic fluid.
- It used for digging underneath the surface of the ground
- Can have a clamp shell attachment to carry loose soil or vertical excavation beyond reach of a boom
- It is equipped with a metal plate used to push soil, sand rubble for grading, cutting of small trees, and for removal of vegetation and hard surface
- Typically equipped in the rear with a claw-like device known as a ripper to loosen densely compacted materials.
- Loading shovel is a vehicle with a power-operated shovel for scooping up material and carrying it short distances.
- Compactors are used to compact soil, gravel, asphalt, and concrete.
- Roller uses self-way for compaction. The width of contact between roller and surface is 75 millimeters. Depth of loose soil should not exceed 250 millimeters. If more material is to be consolidated, it should be done in layers.
- Vibrations generated using shaft inside the wheel, depth of loose soil should not exceed 600 millimeters.
- Each pass should overlap not less than one-third of track made in the proceeding pass
- Number of passes should be determined by the actual tested site.
- Certain amount of moisture, not more than 10% should be present to get better results.
- Grading is the function of grading equipment says to bring the earthwork to the desired shape and elevation.
- Grader is not used for excavation, but it is used to flatten the land and grades loose soil
- Scraper works as a grader, but it has a soil container that is used for backfilling soil.
- Hauling is the function of grading equipment says to bring the earthwork to the desired shape and elevation should be adequate.
What is Over excavation?
Over excavation occurs when excavation extends beyond the depth required for the creation of a below-ground structure due to the existence of inappropriate material that must be removed.
The term ‘Overexcavation’ as it applies to the area of reclamation can be defined as ‘ Excavation beyond specified or directed excavation.