Units & Conventions
Unit systems, sign conventions, and coordinate conventions used throughout JW Slope.
JW Slope uses a single, consistent set of SI units throughout. There is no unit-system selector, so you are responsible for entering all values in the expected units. This page summarizes the units, the analysis basis, and the sign and direction conventions.
Units
All quantities are SI. There is no imperial option and no per-field unit override.
| Quantity | Unit |
|---|---|
| Length / coordinates | m |
| Force | kN |
| Pressure / stress | kPa |
| Unit weight | kN/m³ |
| Cohesion | kPa |
| Angles (friction, dip, etc.) | degrees |
| Seismic coefficients | dimensionless |
Because there is no unit-system selector, JW Slope cannot detect inconsistent input. Enter every value in the units above. Mixing units (for example, entering a unit weight in lb/ft³) will silently produce incorrect results.
Analysis basis
Analysis is 2D plane-strain. All geometry is a single vertical cross-section, and all results are computed on a per-metre out-of-plane basis. Loads and forces are therefore expressed per metre of slope width (kN/m for line loads, kPa for distributed loads acting over the section).
Groundwater
| Parameter | Unit | Default | Description |
|---|---|---|---|
| Pore fluid unit weight | kN/m³ | 9.81 | Unit weight used to convert pressure head to pore pressure. |
Pore pressure at a point is computed from the pressure head and the pore fluid
unit weight (pore pressure = pore fluid unit weight × pressure head). The
default value, 9.81 kN/m³, corresponds to fresh water; adjust it if your pore
fluid differs.
Coordinate convention
Geometry is defined in a 2D Cartesian plane: the horizontal axis runs across the section and the vertical axis is elevation (up is positive). Slope profiles are typically drawn left to right across the section.
Failure direction
The Failure Direction setting tells the solver which way the slope fails:
| Setting | Meaning |
|---|---|
| Left to Right | The slope descends and fails toward increasing horizontal position (the default). |
| Right to Left | The slope descends and fails toward decreasing horizontal position. |
Set this to match the downslope direction of your section. The default is Left to Right. For non-circular block searches, the failure direction also controls which end of a surface is treated as the entry versus the exit.
Sign conventions
- Elevations increase upward.
- Seismic coefficients are pseudo-static and dimensionless; a positive horizontal coefficient drives the destabilizing direction consistent with the failure direction.
- Distributed and line loads are entered as magnitudes with a defined orientation in their respective dialogs.
See Loads & Support for the full load conventions and Groundwater for water modeling details.