Abstract

Analysis of the circumstances surrounding several cave-ins indicates that these incidents are caused by inadequate shoring and steep (approaching vertical) trench wall slopes. Operational considerations render the use of shoring mandatory. One of the major reasons that shoring is not widely used is the inability of most construction equipment to lift or manoeuvre the heavy caissons currently available. This project was undertaken at the request of construction companies to develop a shoring system which can be manoeuvred by backhoes used on construction sites or by the workers themselves. The project involved a definition of operational requirements, review of soil mechanics, characterization of the capacity of backhoes, and selection of shoring. The shoring selected is made of a polyester-rod-reinforced dual-sheet geotextile which is anchored at the surface of the pre-excavation trench and unrolled along its walls. The sheets are then secured to the trench walls by vertical metal supports erected at 3.5-metre intervals.