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High Resolution 1:10,000 scale Mapping Strategy of Multi ... - NDMA

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normal stress in Eq 1). It is represented by the following equation:<br />

μ = γw mzcosβcosβ (Eq 3)<br />

γzsinβ<br />

Potential failure<br />

Plane<br />

Figure App 5.2: Geometry <strong>of</strong> the vector components <strong>of</strong> gravity. Unit width <strong>of</strong><br />

the block is assumed; block length is infinite in the infinite slope model and is<br />

dropped from the equation.<br />

The driving force is shear stress (τ), the slope parallel component <strong>of</strong> Shear strength<br />

is given by the following equation<br />

τ =γz cosβ sinβ (Eq 4)<br />

Slope stability is typically evaluated in terms <strong>of</strong> a safety factor, also referred to as a<br />

factor <strong>of</strong> safety and denoted as SF. As it applies to the infinite slope model, the SF is<br />

a ratio between resisting and driving forces as shown in Equations 5 and 6.<br />

Resisting Force Shear Strength S<br />

SF= = = (Eq 5)<br />

Driving Force Shear Stress τ<br />

γz<br />

Z<br />

γzcosβ<br />

41

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