Concrete Pipe & Box Culvert Installation - Shaw Precast Solutions

SITE PREPARATIONEXCAVATIONTrenches should be excavated to the dimensionsand grade specified on the plans or as ordered bythe owner. The width of the trenches should be keptto the minimum required for installation of the boxsections (ASCE 26-97). The trench width shouldtake into account the machinery needed to properlyinstall the box section. Over excavated areasshould be backfilled with approved materials andcompacted to the Standard Proctor density specifiedfor the leveling course.Preparation of the site should establish a goodlevel grade, using fine to medium granular material.When ledge rock, compacted rocky, or otherunyielding foundation material is encountered, itshould be removed to the requirements shown onthe plans. The foundation should be moderatelyfirm to hard in-situ soil, stabilized soil or compactedfill material. If unstable or unsuitable material is encountered,it should be removed and replaced withstable material approved by the engineer.Stockpiling excavated material adjacent to thetrench could cause a surcharge load, which maycave-in the trench walls. The ability of the trenchwalls to stand vertically under this additional loaddepends on the cohesive characteristics of the particulartype of material being excavated. This surchargeload should be considered when evaluatingthe need to provide trench support. It may benecessary where deep or wide trenches are beingexcavated to haul away a portion of the excavatedsoil or spread the stockpile with a bulldozer or otherequipment. If the excavated material is to be usedas backfill, the stockpiled material should be visu-American Concrete Pipe Association • www.concrete-pipe.org 69