What material is preferred for bedding in a trench installation?

The preferred material for bedding in a trench installation is stone-free earth. This choice is favored because stone-free earth provides a stable, supportive base that minimizes the risk of damage to buried utility lines such as electrical cables. The absence of large rocks or stones reduces the likelihood of punctures or abrasion on the protective insulation of these cables. Additionally, stone-free earth can conform better to the shape of the utility, ensuring a snug fit and reducing the chances of movement or displacement over time.

Using clay soil or a sand or gravel mix can present challenges. Clay soil tends to retain water and can expand and contract, which may lead to shifting and potential stress on the buried utilities. A sand or gravel mix, while it allows for good drainage, can sometimes contain larger particles that may not adequately cushion the utilities or may shift too much under load. Pebbles are generally too large and can create gaps that do not provide sufficient support or protection, failing to ensure a solid bedding material. Therefore, stone-free earth strikes the right balance of support, compression resistance, and adaptability for a trench installation.