Although carpenters have very little to do with excavations, they may have to enter a trench for the purpose of fixing formwork for concrete etc. They should, therefore, realise the potential danger in entering an excavation that has not had its sides supported. Accidents have occurred, many fatal, when workmen were in trenches that collapsed for one reason or another. Vibrations from traffic moving nearby, overloading of the area near to a trench with materials, scaffolding etc., and penetration of the soil by rain or streams can all affect the stability of the trench sides.
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