Excavation and Earthwork Safety Flashcards

What is 'shoring' in the context of excavation safety on Singapore construction sites?

Answer: A temporary support system using vertical and horizontal members to prevent the walls of an excavation from collapsing

Shoring systems use vertical sheets (sheet piles, timber, or steel) and horizontal supports (struts, walers) to hold back the soil and prevent cave-ins during excavation work.

What are the risks of working near excavations adjacent to existing buildings in Singapore?

Answer: Ground settlement affecting building foundations, undermining, and potential structural damage to adjacent buildings

Excavations near buildings can cause ground settlement, foundation undermining, and structural damage. Singapore requires protective measures including underpinning, monitoring, and maintaining safe distances.

What measures must be taken to prevent vehicles from falling into excavations on Singapore sites?

Answer: Physical barriers (stop blocks, guardrails), warning signs, designated traffic routes away from excavation edges, and banksmen for reversing vehicles

Physical barriers must be installed to prevent vehicles from driving into excavations. Additionally, traffic routes should be planned to keep vehicles away from edges, and banksmen should guide reversing vehicles.

What are the dangers of accumulated water in excavations on Singapore construction sites?

Answer: Water undermines soil stability, increases hydrostatic pressure on support systems, and creates drowning risks for workers

Water accumulation (from rain or groundwater) weakens soil, increases pressure on shoring systems, can cause sudden collapse, and creates drowning risks. Dewatering must be implemented promptly.

What is 'benching' or 'stepping' in excavation safety?

Answer: Cutting the sides of an excavation into a series of steps to reduce the risk of cave-in

Benching involves excavating the sides in a series of horizontal steps (like a staircase) rather than vertical walls. This reduces the effective height of unsupported soil and lowers the risk of collapse.

What atmospheric hazards can exist in deep excavations on Singapore construction sites?

Answer: Oxygen deficiency, toxic gases (hydrogen sulphide, methane), and carbon dioxide accumulation, especially in poorly ventilated excavations

Deep excavations can accumulate toxic gases from decomposing organic matter, sewage pipes, or contaminated soil. Oxygen levels can drop dangerously. Gas monitoring and ventilation are essential.