NEBOSH CC Excavation & Ground Work Hazards 3

Question 1

What type of ground movement hazard involves soil suddenly losing its strength and behaving like a liquid?

Accepted Answer

Liquefaction

Answer

Liquefaction occurs when saturated, loose, granular soils lose their shear strength due to vibration or rapid loading, causing them to behave like a liquid. This can result in sudden and catastrophic excavation collapse.

Question 2

Which permit-to-work system is used for excavation work near live underground services?

Accepted Answer

Excavation permit

Answer

An excavation permit is used when working near live underground services. It records the checks carried out, identifies the services present, specifies the methods to be used and identifies who has authorised the work.

Question 3

What personal protective equipment is essential for all workers entering an excavation?

Accepted Answer

Hard hat, high-visibility clothing, and safety footwear

Answer

As a minimum, workers entering an excavation must wear a hard hat to protect against falling objects, high-visibility clothing so they can be seen by plant operators, and safety footwear to protect feet from sharp objects.

Question 4

What is the purpose of a trench box (also called a drag box) in excavation work?

Accepted Answer

To provide a pre-made support system that can be dragged along as the trench progresses

Answer

A trench box or drag box is a steel or aluminium pre-fabricated support system that is placed in the excavation and dragged forward as work progresses. It protects workers from collapse without the need for traditional timber shoring.

Question 5

What is 'heave' in the context of excavation hazards?

Accepted Answer

Upward movement of the excavation base due to stress relief or groundwater pressure

Answer

Heave is the upward movement of soil at the base of an excavation caused by stress relief when overburden is removed, or by groundwater pressure. It can destabilise the excavation and supporting structures.

NEBOSH Construction Certificate Practice Test

NEBOSH Construction Certificate Practice Test

NEBOSH CC Excavation & Ground Work Hazards 3