Demolition Risks and Safety Standards: A Comprehensive Guide

Posted on May 10, 2024 in Technology

Risks in Demolition Unit 13

Difference Between Demolitions and Demolition

– Break down, as opposed to building, means undoing the built.
– Tear down, undo the shot, break materials, components, and subcomponents of a construction system generally.

Types of Demolition

Total Demolition

A total demolition is one in which the whole building system is demolished. It means a complete collapse of the entire building system.

Partial Demolition

A partial demolition is one that affects part or whole systems or constructive elements of a building. This type of demolition is usual in rehabilitation work, as it does not affect the entire building.

Other Demolition Scenarios

There are cases where an activity is demolition work, e.g., removing a slab or foundation due to poor performance. The grounds for demolition can be of several kinds: legal, financial, urban, etc.

Demolition Systems

Manual Demolition

  • Demolition Hammer: Manual chopper and groundbreaking tools operate on percussion, delivering a quick succession of blows at regular intervals to break the material. The major drawbacks are noise and vibration.
  • Cutting and Drilling: A method for activities involving grooves, deep cuts, and drilling holes in horizontal and vertical walls. The most commonly used tools are saws, drills, and machines that act by abrasion on the construction element.

Mechanical Demolition

  • Pull Demolition: This process involves passing a cable around the item to be demolished and using a winch or tractor to pull it up, producing the break.
  • Demolition Drive: This procedure is usually done with the blade of a bulldozer or the more common hydraulic bucket shovel or backhoe loader. In the first case, the debris falls into the backhoe, while in the second case, it falls into the building.
  • Impact Demolition: This method uses a steel ball suspended from a crane cable, a power shovel transformed into a crane, a hydraulic excavator, or a dragline.

Other Demolition Methods

  • Blasting: Demolition with explosives is a controlled explosion of building systems. Small holes are placed in strategic locations and plugged with inert materials that generate large strains, causing a network of fissures. The advantage of blasting over traditional systems is the speed, as the demolition is done in a few minutes. Non-explosive demolition agents exist, based on inorganic lime mixed with clean water, which causes expansive stress.
  • Cutting and Drilling: This method involves deep cuts and drilling holes in horizontal walls. The most used tools are saws, drills, and abrasive machines.
  • Thermal Processes: These include heating systems and flame cutting, which produce a jet of gas flame or high temperature capable of melting steel and construction materials containing silica, such as concrete.
  • Experimental Processes: These methods are still under development and research.

Demolition Process

Complete Study of the Building

  • Recognition of drawings, original drafts of the work, and existing reforms.
  • Control of outbuildings.
  • Identification and assessment of electrical, telephone, and distribution systems.
  • Understanding the building’s use to plan escape routes for staff and debris.

Preliminary Work and Preparation

The objective of preliminary work is mainly the establishment of generic security measures prior to the implementation of the demolition.

Tasks Prior to Preparation

  • Notice to Potentially Affected Agencies: Communicate the intention to carry out the work to public or private bodies concerned.
  • Special Treatment of Premises: Special treatment is required for premises that have stored toxic or polluting products. Isolate the generated material for treatment or deposit in a suitable location. Disinfect areas with parasite nests, rodents, etc.
  • Cancellation of Existing Facilities and Emptying of Fuel Tanks: Do not start demolition until utility companies have canceled service connections for water, electricity, gas, etc. Even if services are no longer necessary, ensure they are adequately protected.
  • Shoring: During deconstruction, the stress state of building elements changes significantly faster than during construction. Common changes are caused by:
    • The accumulation of overloads in certain parts of the slabs.
    • The entry load of items that are not part of the building structure.
    • The removal of elements.
  • Provision of Scaffolds: Scaffolds should be placed on all facades of the building, serving as a platform for deconstruction work.
  • Forecast of Collective Means of Protection: Install protective measures for workers before work begins. Take appropriate measures to protect pedestrians and nearby buildings.
  • Means for Disposal of Materials and Recovered Items: Plan for the disposal of materials and the recovery of reusable items.
  • Forecast of Personal Protection: Personal security is a priority. Provide required personal protection means and observe safety requirements and standards.

Stages in a Demolition of Elements

  1. Phase One: Removal of recovered architectural elements that are not part of the building structure and do not support other elements.
  2. Phase Two: Removal of recyclable materials that do not have a support function.
  3. Step Three: Dismantling of architectural elements that are part of the structure or support other elements, with pre-shoring.
  4. Fourth Step: Removal or demolition of the building structure, using techniques and methods that facilitate the site selection of materials for recycling and easier retrieval.

Safety Standards in Demolition

Safety Standards in the Removal of Debris

  • For debris removal, consider the location of holes, which should be made approximately every 200 square meters (200 m2) in the building area. These gaps must increase in diameter on each lower floor.
  • If the height is greater than 5 floors, debris dumping should be done using prefabricated ducts, called elephant trunks.

Protection and Access to the Work

  • Use a fence, wall, or any adequate protection system to frame the work enclosure. The height should be no less than 2.00 meters and a maximum distance of 1.50 meters from the building.

Most Common Risks

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Falls of people at different levels: This risk may be on the edge of the floors, on the scaffolding, etc.
Falls of persons at the same level: This risk may be taken for items left on the ground, especially in transit areas.
Falls: it could be the possibility of collapse of retaining structures, freeing objects, tools fall of senior workers
Knocks and blows against stationary objects: it can be by blows or collisions with protruding parts of structures, facilities or equipment, narrowing of passageways, stairs, etc.
Projection of fragments: This risk may be small fragments or particles of material projected by a machine tool or mechanical action.
Electrical contacts. This risk may be risk of injury to electrical installations of any kind.