Technical Booklet N Drainage·Page 23·3.8
Protection for flexible pipes with shallow cover
Flexible pipes with insufficient depth of cover require either concrete paving slabs bridging for non-vehicular areas or reinforced concrete slabs for vehicular areas to protect against ground loads.
Where a flexible pipe has less than 300 mm depth of cover under an area other than a vehicular area, it should have concrete paving slabs laid as bridging on granular or other flexible filling at least 75 mm above the top of the pipe. Where a flexible pipe has less than 600 mm depth of cover under a vehicular area it should have a reinforced concrete slab laid as bridging in a similar manner (see Diagram 3.5).
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