Preparing the Backfill Layer

Free O4 questions: Preparing the Backfill Layer

These questions are in the practice set above. Answer them there to see the correct option and the explanation for each.

• Under SROH, whereabouts across a road is the most heavily stressed area usually found?
• Scenario: a gang opens a trench in a footway close to the carriageway and finds a band of material running along under the footway that is plainly holding the road edge up. Under SROH, what is that band most likely to be, and is it the only form this support can take?
• Scenario: the surround to a gas service includes fine unbound granular material and a run of protective tiles. The ganger intends to pick the compaction plant for the surround from whatever will bring the backfill above it up to density quickest. Under SROH, is that the right basis for the choice, and if not, what should drive it?
• Scenario: a job opens a trench in a cycle track running alongside a carriageway. The nearest face of the excavation is 500 mm from the edge of the road surface, and the apparatus is expected to have 750 mm of cover over it. Under SROH, what should the crew expect to meet alongside the excavation, and what tells them so?
• Under SROH, in what circumstances would a bituminous sub-base be expected to be selected?
• Scenario: an opening has been backfilled and the exposed surface of the backfill compacted, ready for bituminous material to be placed directly onto it. The crew plans to leave it as it stands overnight and bring the first layer of bituminous material in the following morning, with the excavation sheeted over in the meantime. Under SROH, what is wrong with that plan?
• Scenario: a load of sub-base material is on site and the gang is not satisfied with the condition it has arrived in. Under SROH, which assessment does the Code's guidance name for checking it before any of the load goes in?
• Scenario: material dug out of a trench is identified as a high silt content material by the Code's own field identification test for fine material. Under SROH, how must it be compacted?
• Scenario: the first layer of bituminous material is down over the backfill and is being rolled, and pore water pressure is building up in the backfill beneath it. Under SROH, what should happen next?

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