Development of Soft Excavation Techniques. Phases of 1, 2, 2A, 2B, and 2C

摘要

The information in this report covers work accomplished in Phases I, II, IIA, IIB and IIC of the subject contract. A rotary excavator and a rotating spring capable of keeping a vacuum excavation hose clear of clogs were fabricated and tested. The rotary excavator was successful in loosening a wide variety of soils and to a lesser extent those that were frozen. The rotating spring did prevent soil buildup in the vacuum hose but sharp rocks could damage or destroy the spring. Alternate soil removal methods were studied but none were deemed equal to the existing vacuum systems providing hose clogging could be reduced significantly. A dual wall pipe mockup and an improved method of vacuum excavation were built and tested. Fluidizing the wall of the inner pipe by injecting air through orifices along the inner wall reduced clogging but it was tested only in the lab because it was cumbersome to handle. A vacuum truck, loaned to the program, was rebuilt to accept a moveable hopper for field testing which was successfully accomplished in cooperation with a local utility. Ten rotary excavators and portable power supplies were built and tested by 33 utilities throughout the country. Although early results were mixed, there was enough interest to justify and support commercialization.