| 摘要 |
A mechanized unit that is moved through a trench in the ground for the purpose of placing a length or lengths of a utility or utilities by a guide device on the bottom of the trench, and then encasing the placed utility or utilities. The unit has at least one plow to sweep the material excavated from the ground to for m the trench back into the trench onto a screening member mounted to the unit. The screening unit has spaced screens one above another with progressively small er openings from top to bottom and the screening member is vibrated to deposit onto the one or more utilities layers of the excavated material having particle o f progressively larger size from the bottom to the top of the trench to protec t the utility or utilities from physical damage caused by large excavated particle s.
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