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SAFETY IN DEMOLITION ANDUNDERPINNING WORKNational Safety Council , Hqs.98-A,Institutional Area, Sector 15,CBD Belapur , MaharashtraNaviMumbai – 400615.India www.nsc.org.inContact no : 022- 27579924 /25

SAFETY IN DEMOLITION & UNDERPINNING WORK1. DEMOLITIONIt is general experience that far less regard and consideration is given to the demolitionor dismantling of structures then to erection, construction and maintenance; althoughthe problems, hazards and uncertainties can be much greater as the demolition isfrequently carried out by the unskilled workers. The design engineers have theresponsibility not only for the safe design and construction but also for the safedemolition of the structure at the end of its designed life. Necessary measures neededfor a safe and smooth demolition can be incorporated at the design / construction stage.I.Legal requirements for Demolition II.Common Safety Hazards and Environmental Aspects in Demolition The Building And Other Construction Workers (Regulation Of Employment AndConditions Of Service) Act, 1996 And BOCW Central Chapter XII Rules ,1998The Hazardous Wastes (Management, Handling and Transboundry Movement)Rules, 2008, (amended 2010)The Noise Pollution (Regulation & Control ) Rules, 2000 (amended 2010)The Environmental (Protection) Act, 1986 (amended 1991)The Environment (Protection) Rules, 1986 (amended 2010)The Municipal Solid Waste (Management & Handling) Rules, 2000.IS CODE:IS 4130:1991 Demolition of buildings - Code of Safety .Unintentional collapse of structure or part of it.People and objects falling from heights.Striking overhead or underground services.Manual handling activities associated with demolition and material movement.Generation of Demolition debris.Hazardous substances in debris.Dust emission.Generation of noise.Effect on micro- climate.Segregation of the generated debris due to demolition activity is requiredbetween hazardous and non-hazardous debris.National Safety Council, India

III.Methodology for Safe DemolitionThe methods of demolition include hand or manual demolition; mechanicaldemolition by pusher arm, demolition ball and wire rope pulling; explosives;demolition by hydraulic busters and the thermic lance. These methods of demolitionare suitable for particular types of buildings and structures such as houses, largebuildings, bridges, arches, independent chimneys, steel and concrete structures,spires, pylons and masts, petroleum tanks etc. Demolition process in all types ofstructure is not same and all debris and waste generated during demolition shouldn’tbe used for landfilling.IV.Actions to be taken before any demolition work is taken up: V.It should be preceded by a site survey which should be comprehensive andcover the position of screens, scaffolds etc.Protection of the public shall be ensured and also methods to ensure thestability of surrounding buildings/structures from the danger of collapse due towithdrawal of support or undermining of the foundations shall be paid attention.The electric power to all services within the structures to be demolished shouldbe shut off or discontinued at outside the building.All gas, water and steam service lines should be shut off or otherwise controlledoutside the structure to the demolished.The structure to be demolished should be adequately fenced and cordoned offand suitable board shall be prominently displayed to warn the public.Measures for dust suppression / control shall be in place.Safety measures in demolition of the buildings:Demolition operations should begin with by removing glass in doors and windows,loose objects and projecting parts. Workers should not be deployed at differentlevels unless adequate precautions are taken to ensure safety of those deployedlevels. Demolition work should begin at the top of the structure and processdownwards. Masonry concrete and other dismantled materials should not beallowed to accumulate in quantities which may endanger the stability of any floor orstructural support. Part of the structures, where necessary should be adequatelyshored, braced or otherwise supported. If the structure is to be demolished byexplosives, all safety measures pertaining to explosives such as transport, storage,handling, loading firing etc. should be strictly adhered to. Foundation walls servingas retaining walls to support of adjoining structures should not be demolished untilthe adjoining structure have been under pinned or braced or earth supported bysheet pilling.Stairs with hand railing should be kept in place as long as practicable to provideaccess and egress.If the work of demolition is continued at height, allNational Safety Council, India

passageways, stairs and other parts of the structure where the workers have to passand work, should be adequately lit. Workers should strictly wear safety harness /belts, safety helmets, hand glove and goggles.If the demolition is carried out by machines such as power shovels, bulldozers etc.the safety measures relevant to operation and use of such machines should beadhered to. If swinging weight such as ball is used for demolition, a safety zonehaving a width of at least 1.50 times the height of the building or structure should bemaintained.Scaffolds used for demolition operations should be independent of the structure tobe demolished. If ladders are used for demolition, only travelling type mechanicalladders should be used, except that ordinary ladders may be used as means ofaccess to the scaffolds. The hoists or chutes, whenever it is practicable, should beused to lower the materials. Materials chutes should have a gate at the bottom withsuitable means for regulating the flow of materials. The safest way to transport thedebris generated at different levels in demolition is by material hoist or chutes.Whenever the condition demands, suitable catch platforms (at least 1.50 M. wide)should be provided along the outside of the exterior walls so as to prevent dangerfrom falling objects. The catch platforms should be moved downward as the level ofdemolition operation gets lowered. The catch platforms should be inclined such thatthe outer edge is higher than the inner edge for arresting fall of material duringdemolition.VI.Safety measures in demolition of structural steelworks:The steel structures should be demolished from top tier by tier. There should be adefinite plan and sequence of removing the various members of the steel structure.All precautions should be taken to prevent danger from any sudden twist, spring orcollapse of steel parts / work when it is cut or released. Removed parts should becarefully lowered and not to be dropped from a height. Safety precautions of gascutting of should be adhered to.VII.Safety measures in demolition of tall chimneys, minars, pylons etc.Tall chimneys, minars, pylons, etc., should not be demolished by overturning orblasting unless a protected area of an adequate dimension can be established inwhich the chimney or the structure can fall safely. If the demolition of the tallstructure is resorted to by blasting with explosives, the services of the specialistengineer should be requisitioned for the pattern of drilling, the size of the holes todrilled, the charge of the explosives & the entire sequence of the firing of theexplosives etc. The entire operation should be under supervision and control of thecompetent person. The whole area shall remain out of bounds for public.VIII.Safety measures in demolition of Industrial Structures:National Safety Council, India

Required safety measures, in addition to some of the relevant safety measuresstated herein before, should be observed in removing heavy and bulky machinery,plant and equipment. For example, If the industrial structure such as a nuclearpower station is to be demolished, the services of the specialist expert in the field ofradio-activity and radiation should be requisitioned for the operation of the demolitionof the structures which has radiation hazards. The entire operation of the demolitionis to be planned by the specialist engineer, in consultation with the demolitionengineer. Segregate and dispose hazardous waste separately as per applicable law.Worker getting struck by excavator during Demolition Activity2. UNDERPINNINGIn construction, underpinning is the process of strengthening and stabilizing thefoundation of an existing building or other structure. Underpinning may be necessary fora variety of reasons: The original foundation is simply not strong or stable enough.The intended usage of structure has changed.The properties of the soil supporting the foundation may have changed (possiblythrough subsidence) or were mischaracterized during planning.The construction of nearby structures necessitates the excavation of soilsupporting existing foundations.It is more economical, due to land price or otherwise, to work on the presentstructure's foundation than to build a new one.The existing foundations of the building have moved – this is caused by poor soilor changes to the soil conditions (e.g. subsidence has occurred).There has been a decision to add another storey to the building, either above orbelow ground level, and the depth of the existing foundations is inadequate tosupport the modified building or load (weight) of it.Underpinning is accomplished by extending the foundation in depth or in breadth sothat it either rests on more supportive soil stratum or distributes its load across agreater area. Use of micro piles and jet grouting are common methods inunderpinning. An alternative to underpinning is the strengthening of the soil by theNational Safety Council, India

introduction of a grout. All these processes are generally expensive and elaborate.Underpinning work requires very careful planning and execution. An initial step,before substantial commencement of the work, will generally be to dig a trial holenext to the existing footings/foundation to make an assessment of the conditions byan expert engineer.It is a messy, noisy and traumatic operation for buildings and their occupants alike.Unless sophisticated and expensive jacking systems are incorporated, theunderpinning will almost inevitably promote some additional subsidence as theworks settle in. If a structure is partially underpinned, then future damage may recuras the rest of the non-underpinned structure continues settling. For these reasons,underpinning should be avoided if at all possible.National Safety Council, India

Fig. 1 Underpinning the foundations of a railway bridge. A completed concrete padunderpinning can be seen at the bottom right.IX.Safety measures – UnderpinningMost types of underpinning involve digging holes under buildings in confined spaces.The existing structure is expected to defy gravity and temporarily arch over theexcavation. Collapses can occur and the following related risks must be identifiedand managed accordingly Investigate services before starting excavationAlways do excavation at angle greater than angle of response of soilCheck that underpinning pits cannot get flooded or be gassedStrengthen superstructure before diggingCheck that walls above are strong enough to support themselves over pitsSupport sides of excavationsEnsure that workers can escape from pits easilyUse threaded couplers instead of dowel bars to connect reinforcement rodsbetween sections of shallow mass concrete underpinningEnsure strengthening of nearby surrounding structuresProvide all required PPE’s (Safety Harness, Safety Helmet, Safety Shoes,Mask, Safety Goggles, Safety JacketEnsure safe access and ventilation to pits****National Safety Council, India