Soil Instability
Toppling
In addition to sliding, tension cracks can cause toppling. Toppling occurs when the trench's vertical face shears along the tension crack line and topples into the excavation.
Subsidence and Bulging
An unsupported excavation can create an unbalanced stress in the soil, which, in turn, causes subsidence at the surface and bulging of the vertical face of the trench. If uncorrected, this condition can cause face failure that may trap or bury workers in the trench.
Knowledge Check Choose the best answer for the question.
3-4. What may occur when the trench's vertical face shears along the tension crack line?
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