NEBOSH CC Excavation and Demolition Safety 2

Question 1

What is the minimum distance from the edge of an excavation that heavy plant and materials should be kept to prevent surcharge loading causing collapse?

Accepted Answer

Materials and plant should be kept as far back as practicable; a common guideline is at least equal to the depth of the excavation

Answer

Surcharge loading from heavy plant, vehicles, and stored materials near excavation edges can cause collapse. While the exact safe distance depends on soil conditions, a common guideline is to keep loads at least as far back from the edge as the excavation is deep. A competent person should assess the specific conditions and set exclusion zones.

Question 2

What protective measures should be in place around an open excavation to prevent people and vehicles from falling in?

Accepted Answer

Substantial barriers or guardrails, clear warning signage, and edge protection

Answer

Open excavations must be protected by substantial barriers (not tape alone) to prevent persons and vehicles from falling in. Guardrails should meet the same standards as for work at height (950mm top rail, toe board, intermediate rail). Clear warning signs, lighting for night-time, and vehicle stop blocks should also be provided.

Question 3

What is the correct sequence for demolishing a multi-storey building using the top-down method?

Accepted Answer

Remove hazardous materials first, then demolish storey by storey from the top downwards, ensuring structural stability at each stage

Answer

Top-down demolition is the reverse of construction: remove hazardous materials (asbestos, chemicals), soft strip internal fittings, then demolish floor by floor from the top. Structural stability must be maintained at each stage. This method is common in urban areas where controlled collapse is not possible due to proximity of other buildings.

Question 4

An excavation is being dug near an existing building. What is the primary structural risk to the adjacent building?

Accepted Answer

Undermining the building's foundations, causing settlement or collapse

Answer

Excavating near existing buildings can remove the soil supporting their foundations, leading to settlement, cracking, or structural collapse. A structural assessment must determine the depth and proximity of existing foundations. Underpinning or sheet piling may be required to protect the adjacent structure.

Question 5

How often must excavations be inspected under the CDM Regulations 2015?

Accepted Answer

At the start of each shift, after any event likely to affect stability, and after any accidental fall of material

Answer

CDM 2015 Schedule 3 requires excavation inspections at the start of every shift before work commences, after any event likely to have affected strength or stability (such as heavy rain, frost, or nearby vehicle movement), and after any accidental fall of rock or earth. A competent person must carry out and record inspections.

NEBOSH Construction Certificate Practice Test

NEBOSH Construction Certificate Practice Test

NEBOSH CC Excavation and Demolition Safety 2