# 15: Mass Wasting (Exercises)

### Q15.1 Sand and water

*Responses will vary*

### Q15.2 Classifying Slope Failures

### Q15.3 How Much Does a House Weigh and Can It Contribute to a Slope Failure?

*A typical 150 m ^{2} (approximately 1,600 ft^{2}) wood-frame house with a basement and a concrete foundation weighs about 145 t (metric tonnes). But most houses are built on foundations that are excavated into the ground. This involves digging a hole and taking some material away, so we need to subtract what that excavated material weighs. Assuming our 150 m^{2} house required an excavation that was 15 m by 11 m by 1 m deep, that’s 165 m^{3} of “dirt,” which typically has a density of about 1.6 t per m^{3}.*

*165 m ^{3} of excavated soil x 1.6 t/m^{3} = 264 t – thus the excavated material weighs about 1.8 times as much as the house. In this case weight has been removed from the slope by building the house.*