# Groundwater Overview

The Groundwater modelling options in Slide3 allow you to define the method of calculating groundwater pore pressures for the materials in your slope. The pore pressures are used in the calculation of effective stress and shear strength which is required for the limit equilibrium stability analysis. Water Surfaces allow you to model ponded water and other hydraulic-related options.

## Groundwater Method

The Groundwater Method determines how pore pressure is modelled for a material. There are three main methods:

• Water Surfaces (e.g. water table or piezo surface)
• Ru Coefficients

The Groundwater Method in Slide3 can be specified independently for each material defined in the Material Properties dialog. See the Groundwater Method topic for details. A default groundwater method can be selected in Project Settings, to automatically set the initial default method for all materials.

## Water Surfaces

If the Groundwater Method = Water Surfaces then you can assign a water surface (e.g. water table, piezo surface) to calculate the pore pressure for a material. Pore pressure is proportional to the vertical distance from the water surface. Water surfaces are created with the Add Water Surface or Add Water by Location options, and may represent a water table, piezo surface or drawdown surface. Water surfaces can be used to define ponded water and other hydraulic-related options. See the Water Surfaces Overview topic.

## Ru Coefficient

If the Groundwater Method = Ru Coefficient, then a Ru Coefficient can be specified for a material in order to define pore pressure. The Ru coefficient models the pore pressure as a fraction of the vertical earth pressure. See the Ru Coefficient topic.

## Water Grids

If the Groundwater Method = Water Grids then you can assign a water grid (total head, pressure head or pore pressure) to a material. A water grid specifies pore pressure at a grid of x, y, z locations, from which the pore pressure at any point in the material can be interpolated. Water Pressure Grids are created with the Add Water Pressure Grid option. See the Water Pressure Grid Overview topic.