# Factors of Safety for Cantilevered Sheet Pile Walls

Courses > Foundation Analysis and Design > Sheet-pile Walls: Cantilevered and Anchored > Factors of Safety for Cantilevered Sheet Pile Walls

### Introduction

Methods to apply a factor of safety to the geotechnical design of a cantilevered sheet pile wall are described here. For types and design processes see Sheet Pile Walls Topic.

### Concepts and Formulas

There are usually three methods:

#### Factored depth of embedment

This is the method mostly used in practice due to its simplicity and easiness; calculate the value of the depth of embedment (D) using static equilibrium and the best estimate of strength parameters (φ, c). Then, calculated value of D is arbitrarily increased by 20 to 60%:

$D_{design}=(1.2\; to \; 1.6)D_{calculated}$

usually 1.2 - 1.4 for granular soils

usually 1.4 - 1.6 for cohesive soils

Round up D design to next whole foot.

#### Factored earth pressure

In this approach, use factored Kp (called K*p) in place of Kp to determine net pressure diagram:

$K^*_p=\frac{K_p}{SF}$

where

$1.5\leq SF\leq 2\; (usually)$

In this approach

$D_{design}=D_{calculated}$

#### Factored strength parameters

This approach is super conservative; in this approach, use factored strength parameters (φ*,c*) in place of (φ,c) to determine K*p and K*a.
Determine net pressure diagram using K*p and K*a in place of Kp and Ka:

$\phi^*=tan^{-1}(\frac{tan\phi}{FS})$

$c^*=\frac{c}{FS}$

where

$1.2\leq FS\leq 1.5\; (usually)$

In this approach

$D_{design}=D_{calculated}$