CITB Excavation and Groundworks 2 — Questions and Answers
Question 1: What is 'benching' in the context of excavation safety?
- Installing horizontal timber supports
- Cutting stepped horizontal platforms into the excavation sides (Correct answer)
- Placing concrete at the trench base
- Creating a barrier around the excavation perimeter
Correct answer: Cutting stepped horizontal platforms into the excavation sides
Benching involves cutting steps or terraces into the sides of an excavation to reduce the height of unsupported face and improve stability, particularly in cohesive soils.
Question 2: What should be done if groundwater begins to seep into an excavation at a significant rate?
- Continue work until water reaches ankle level
- Immediately stop work and reassess stability (Correct answer)
- Add extra spoil to the trench sides
- Install more lighting
Correct answer: Immediately stop work and reassess stability
Groundwater ingress significantly increases the risk of collapse by reducing soil stability; work must stop immediately and a competent person must reassess the excavation before any re-entry.
Question 3: Which regulation primarily governs the safety of excavation operations on UK construction sites?
- Work at Height Regulations 2005
- Lifting Operations and Lifting Equipment Regulations 1998
- Construction (Design and Management) Regulations 2015 (Correct answer)
- Manual Handling Operations Regulations 1992
Correct answer: Construction (Design and Management) Regulations 2015
The Construction (Design and Management) Regulations 2015 (CDM 2015) set out duties for managing health and safety on construction projects, including requirements for safe excavation work.
Question 4: What is the purpose of a 'toe board' at the edge of an excavation?
- To direct surface water away from the trench
- To prevent tools and materials from falling into the excavation (Correct answer)
- To mark the edge of the safe working zone
- To support the shoring system
Correct answer: To prevent tools and materials from falling into the excavation
Toe boards (or kick boards) are fixed at ground level at the edge of excavations to stop loose materials, tools, or equipment from rolling or being kicked into the trench.
Question 5: How should workers access and egress a deep excavation safely?
- By climbing the shoring timbers
- Via a secured ladder or purpose-built access stairway (Correct answer)
- By jumping from the excavation edge
- Using a rope attached to a crane hook
Correct answer: Via a secured ladder or purpose-built access stairway
Workers must use a secured ladder or purpose-built stairway for safe access and egress, ensuring the access point does not compromise the shoring system.
Question 6: What color are gas pipes typically marked in the UK for identification purposes?
- Blue
- Red
- Yellow (Correct answer)
- Green
Correct answer: Yellow
Gas pipes in the UK are identified by yellow coloring or yellow marker tape, helping excavation workers recognize and avoid striking gas supply pipes.
Question 7: Which type of excavation support uses hydraulic or mechanical jacks to push steel or aluminum plates against trench walls?
- Sheet piling
- Trench box (drag box)
- Hydraulic trench strut system (Correct answer)
- Timber close boarding
Correct answer: Hydraulic trench strut system
Hydraulic trench strut systems use adjustable struts or props fitted with spreader plates to apply outward pressure against the trench walls, providing adjustable and efficient lateral support.
CITB Excavation and Groundworks 2
What is 'benching' in the context of excavation safety?