Code of safety for excavation work
1992 Edition

IS 3764 mandates distinct shoring and timbering protocols for various soil types, including hard soil, soils prone to cracking or crumbling, loose or sandy soils including previously excavated soils, and soils under hydrostatic pressure. Each category is addressed in dedicated tables (Tables 1 to 4) prescribing the dimensions and spacing of sheathing, wales, and struts to maintain trench stability. Timber used should be of adequate strength like sal wood, and for deep or wide excavations where slopes cannot be safely maintained, sheet piling systems using timber, concrete, or steel are recommended. Rectangular supports must be oriented with their longer dimension vertical for enhanced strength.

The standard requires that trenches remain free of dangerous gas concentrations by implementing continuous monitoring and ventilation. Mechanical ventilation must be provided when harmful gases or fumes are detected or anticipated. When ventilation alone cannot maintain safe air quality, respiratory protective devices supplying clean air should be used. For explosive gases, ventilation systems must reduce flammable gas content below 1.5% by volume before workers enter. These measures collectively prevent inhalation hazards and ensure worker safety in confined excavation spaces.

IS 3764 specifies that all personnel entering excavation sites should wear safety helmets, especially where there is risk from falling objects or after blasting operations. Additionally, protective footwear such as rubber boots must be worn when tasks involve foot hazards. In areas where ventilation is insufficient to ensure clean air, respiratory protective equipment must be provided to supply uncontaminated air to workers. Adhering to these PPE requirements minimizes injury risks during excavation activities.

The code requires provision of safe access and egress means for workers, including ladders positioned at intervals not exceeding 15 meters for hazardous work and 30 meters for less risky tasks. Ladders must extend at least one meter above excavation edges for secure handholds and comply with IS 3696 (Part 2) for design and maintenance. Excavation slopes within 1.5 meters of the bottom must be inspected and certified stable; where stability is uncertain, shoring is compulsory. Safety barriers such as fences or barricades are mandated to prevent accidental falls by workers or the public.

Excavated materials must be placed at a safe distance from trench edges, typically at least one-third of the final excavation depth to form a berm. If space constraints exist, a minimum berm width of one meter is acceptable provided the material is stable, shoring is designed to support the extra load, and toe-boards are installed to prevent soil sliding back into the trench. Additionally, loose stones and unstable earth near trenches should be cleared or securely braced, and shoring should extend at least 30 centimeters above any vertical excavation walls to prevent material from falling into the excavation.

IS 3764 recommends maintaining a minimum distance between heavy machinery and excavation edges equal to the trench depth, with a minimum of six meters if the trench is deeper than six meters. Materials should not be stacked or moved near excavation edges to avoid collapse or falling hazards. Tools should be properly sized and used with adequate spacing between workers to prevent accidents. Additionally, slopes formed by machinery operations should be promptly stabilized to prevent collapse, and workers should be prevented from occupying danger zones above or below unstable faces.

The standard prescribes a combination of training workers to recognize poisonous plants and vermin hazards, use of personal protective equipment such as boots, gloves, masks, and netting, and implementation of environmental controls like drainage, spraying, and nest destruction. Poisonous plants should be removed or destroyed where feasible, and protective ointments made available. Sanitation improvements and rodent extermination are essential. First-aid facilities and immunization must also be provided to ensure comprehensive protection against biological hazards.