A trench is being dug in granular fill material with an excavated depth of 2.5 metres. The soil type is classified as Type 3 (loose sandy soils, high moisture). What is the maximum allowable slope angle for an unsupported excavation of this type, according to CSA Z275.5 or similar guidelines?

Question: A trench is being dug in granular fill material with an excavated depth of 2.5 metres. The soil type is classified as Type 3 (loose sandy soils, high moisture). What is the maximum allowable slope angle for an unsupported excavation of this type, according to CSA Z275.5 or similar guidelines?

Answer options:

• 1 horizontal to 1 vertical (45 degrees)
• 1.5 horizontal to 1 vertical (33.7 degrees) ✅ 2 horizontal to 1 vertical (26.6 degrees)
• 3 horizontal to 1 vertical (18.4 degrees)

Correct answer: 2 horizontal to 1 vertical (26.6 degrees)

Explanation: For Type 3 soil conditions (e.g., loose sandy soils), standard trenching and excavation safety guidelines often require a maximum slope of 2 horizontal to 1 vertical (26.6 degrees) for unsupported excavations to prevent collapses.