Piles · Rischio

Rischio's deep foundation tool: what it checks on a single pile or a pile group in axial compression, what it leaves out and how a model is built.

Rischio’s deep foundation tool checks the axial compressive capacity of a single pile or a rectangular pile group in layered soil. It adds the shaft resistance, stratum by stratum, to the toe resistance, and for a group it compares the piles on their own with the group as one block. It checks static axial capacity only: lateral loads, uplift (tension), pile settlement, negative skin friction, seismic loading and the structural design of the piles and the cap are outside it.

What it checks

Check	Rule	Limit
Pile group The group's axial capacity, as piles or as one block $FS = \frac{Q_g}{Q}$	$FS = \frac{Q_g}{Q}$	$\ge 3.0$
Single pile One pile's axial capacity against its load, when there's only one $FS = \frac{Q_u}{Q}$	$FS = \frac{Q_u}{Q}$	$\ge 3.0$

Check

Limit

Pile group

The group's axial capacity, as piles or as one block

$FS = \frac{Q_g}{Q}$

\ge 3.0

Single pile

One pile's axial capacity against its load, when there's only one

$FS = \frac{Q_u}{Q}$

\ge 3.0

The limit of 3.0 is Rischio’s default; each result shows its margin, $\mathrm{FS}/3.0 - 1$ , negative when the check fails; and a group is checked only as a group, against the whole load.

How a model is built

One pile, or a rectangular group of $n_x \times n_y$ identical piles at a centre-to-centre spacing $s$ ; a 1 × 1 group is a single pile. Piles are circular or square, bored or driven, and the load is one vertical force on the cap.

The soil is a stack of horizontal strata from the ground surface down; the last one may have no thickness, and then extends down. Each stratum is undrained, with its undrained shear strength $c_u$ , or drained, with its friction angle $\phi'$ , and that sets the method: α for undrained, β for drained. Each has its unit weight $\gamma$ ; one that reaches below the water table, if there is one, also needs $\gamma_{sat}$ .

In these pages

Inputs: every field a model takes, with its unit and its limits.
Method and assumptions: units and conventions, the key assumptions, and the method in order, with a page for each part:
- Shaft resistance: the α method in clay, the β method in sand, and the critical depth.
- Toe resistance: Meyerhof, in sand and in clay.
- Pile groups: a single pile, the group as piles or as one block, and the group efficiency.
Equations: every step of the calculation report, in its order, with its equation.
Warnings: what each warning means.
Verified examples: worked examples from Das & Sivakugan (2017) that Rischio is tested against, with the book’s answer and Rischio’s.